cargo systems and operating manual lng lerici

MANUAL CONTENTS

LIST OF CONTENTSGENERAL ARRANGEMENTINTRODUCTION (INCLUDING SNAM SAFETY PROCEDURES ANDINSTRUCTIONS)SYMBOLS AND COLOUR SCHEMEISSUE AND UPDATE CONTROL

PART 1: LNG, NITROGEN AND INERT GAS1.1 Physics of Gases

1.1.1 Gas Laws

1.1.2 Definitions

1.2 Properties of LNG1.2.1 Physical Properties, Composition,

and Characteristics of LNG

1.2.2 Flammability of Methane, Oxygen and Nitrogen Mixtures

1.2.3 Supplementary Characteristics

1.3 Properties of Nitrogen and Inert Gas1.3.1 Nitrogen

1.3.2 Inert Gas

ILLUSTRATIONS AND TABLES1.1.1a Graph - Boyle’s Law

1.1.1b Graph - Charles’ Law

1.2.1a Table - Physical Properties of LNG Components

1.2.1b Table - Composition of North African LNG

1.2.1c Table - Properties of Methane

1.2.1d Graph - Methane Saturated Vapour:

Pressure - Temperature Equilibrium

1.2.1e Graph - Relative Density of Methane and Air

1.2.2a Graph - Flammability of Methane, Oxygen, and Nitrogen Mixtures

1.2.3a Double Hull and Compartments

Temperatures

1.2.3b Structural Steel Grades Plan

1.3.1a Structural Steel Ductile to Brittle Transition Curve

PART 2: CARGO SYSTEM DESCRIPTION 2.1 Containment System

2.1.1 Gas Transport System Construction

2.1.2 Deterioration or Failure

2.2 Cargo Piping System2.2.1 Description

2.2.2 Pipeline Identification System

2.2.3 Pressure Control2.2.4 Anti-Surge Operation

2.3 Cargo Pumps2.3.1 Main Cargo Pumps

2.3.2 Stripping/Spray Pumps

2.3.3 Emergency Cargo Pumps

2.4 Compressor House2.4.1 Description

2.5 Gas Heaters2.5.1 Boil-Off / Warm-Up Gas Heaters

2.5.2 Vent Gas Heater

2.6 Vaporisers2.6.1 General Description

2.6.2 Main Vaporiser

2.6.3 Forcing Vaporiser and Demister

2.7 Gas Compressors2.7.1 HD Compressors

2.7.2 LD Compressors

2.8 Vacuum Pumps2.8.1 Vacuum Pumps

2.9 Inert Gas and Dry Air Systems2.9.1 Inert Gas and Dry Air Plant

2.10 Nitrogen Production Systems2.10.1 Nitrogen Production Plant

2.11 Ballast System2.11.1 Ballast System Description

2.11.2 Cargo and Ballast Valves Hydraulic System

2.12 Deck Salt Water Cooling System

2.13 Air Systems2.13.1 General Service and Control Air

System

2.14 Deck Steam System2.14.1 Deck Steam Description

ILLUSTRATIONS AND TABLES2.1.1a Cargo Tank Lining Reinforcement

2.1.1b Construction of Containment System - Flat Area

2.1.1c Construction of Containment System - Securing of Insulation Boxes

2.1.1d Construction of Containment System - Longitudinal Dihedral

2.1.1e Construction of Containment System - Corner Part

2.1.1f Man Hole Arrangement

2.1.1g Man Hole Cover Arrangement

2.1.2a Hull Steel Grades

2.2.1a Cargo Piping System

2.2.4a Gas Compressors Surge Control System

2.3.1a Main Cargo Pump

2.3.2a Spray Pump

2.3.3a Emergency Pump

2.5.1a Boil-Off/ Warm-Up Gas Heater

2.5.2a Vent Gas Heater

2.6.2a Main Vaporiser

2.6.3a Forcing Vaporiser and Demister

2.7.1a HD Gas Compressors

2.7.1b Table - HD Alarm and Trip Settings

2.7.2a LD Gas Compressors

2.7.2b Table - LD Alarm and Trip Settings

2.8.1a Vacuum Pumps

2.9.1a Inert Gas and Dry Air Systems

2.10.1a Nitrogen Production Systems

2.11.1a Ballast System

2.11.2a Cargo Valves Hydraulic System

2.11.2b Ballast Valve Hydraulic System

2.11.2c Cargo and Ballast Valve Control

2.12 Deck Salt Water Cooling System

2.13.1a Deck Instrument and General Service Air Systems

2.14.1a Deck Steam System

PART 3: CONTROLS ANDINSTRUMENTATION3.1 Integrated Monitoring System

3.2 Cargo Control Room, Cargo Consoleand Panels

3.3 Custody Transfer System3.3.1 Custody Transfer System

3.3.2 Independent Very High Level Alarm System

3.3.3 Failure of CTS Computer

ILLUSTRATIONS3.1.1a IMS System Overview

3.1.1b Typical System Screen Shots

3.1.1c Typical System Screen Shots

3.2.1a Control Room Layout

3.3.2a CTS Measurement

3.3.2b Cargo Tank Temperature Measurement

3.3.3a Cargo Record Sheet

PART 4: CARGO OPER ATIONS4.1 Overview Operating Procedures

4.2 Normal In-Service Operations4.2.1 Loading4.2.2 Gas Freeing with Other Tanks In Service

Cargo Tank Stripping with Other Tanks In Service

4.2.3 Gas Freeing with Other Tanks In ServiceCargo Tank Warming with Other Tanks In Service

4.2.4 Gas Freeing with Other Tanks In ServiceCargo Tank Gas Freeing (Version 1 & 2)Initial Insulation Space Inerting (Steps 1 & 2)

4.2.5 Insulation Space Inerting During Normal Service

4.2.6 Loaded Voyage with (Normal & Forced) Boil-Off Gas Burning

4.2.7 Discharging with Gas Return from Shore4.2.8 Ballast Voyage

List of Contents - Issue: 1

Cargo Systems and Operating Manual LNG LERICI

4.3 Out of Service Operations4.3.1 Drying and Inerting Tanks

4.3.2 Displacing Inert Gas with LNG Vapour

4.3.3 Tank Cool Down

4.3.4 Tank Warm Up

4.3.5 Gas Freeing

4.3.6 Aerating

4.4 Emergency Operations andProcedures4.4.1 Cargo Discharging without Gas Return

from Shore

4.4.3 Use of Emergency Cargo Pump

4.4.4 In Service Repairs to Tanks

4.4.5 Jettisoning of Cargo

4.4.6 Cargo Spillage on Deck and Piping Leakage

4.4.7 Over-filling of Cargo Tanks

4.4.8 Structural Failure of Inner Hull

4.4.9 Ship Shore Operations in Event of Fire or Emergency

4.4.10 Personnel Contact with LNG

4.4.11 Fire Control Procedure for Main Vent Mast (Nitrogen Injection)

4.4.12 Cargo Piping Valve Freeze-up Procedure

4.4.13 Cargo and Ballast Valve Failure Procedure

4.4.14 Primary Membrane Failure

4.4.15 Punching Device

4.4.16 Loaded Voyage without Gas Burning

ILLUSTRATIONS4.1 Basic Cargo Operations Sequence Chart

4.2.1a Cargo Lines Cool down

4.2.1b Loading with Vapour Return to Shore Via Ship HD Compressor

4.2.1c Loading with Vapour Return to Shore Via Shore Compressor

4.2.1d Nitrogen Setting Up During Loading4.2.2a Cargo Tank Stripping with Other Tanks

In Service4.2.3a Cargo Tank Warm Up with Other Tanks

In Service4.2.4a Cargo Tank Freeing with Other Tanks

In Service (Version 1)4.2.4b Cargo Tank Freeing with Other Tanks

In Service (Version 2)

4.2.4c Initial Insulation Space InertingEvacuation of Insulation Spaces (First Step)

4.2.4d Filling from Liquid Nitrogen (Second Step)

4.2.5a Insulation Space Inerting During Normal Service

4.2.6a Loaded Voyage with Normal Boil-Off Gas Burning

4.2.6b Loaded Voyage with Forced Boil-Off Gas Burning

4.2.7a(i) Discharging with Gas Return from Shore

4.2.7a(ii) Stripping Cargo Tanks with Gas Return from Shore

4.2.8a Ballast Voyage with Normal Boil-Off Gas Burning

4.3.1a Drying Cargo Tanks

4.3.1b Inerting Tanks Prior to Gas Filing

4.3.1c Drying and Inerting Cargo Tanks using Nitrogen from Shore

4.3.2a Displacing Inert Gas (Gassing Up) with LNG Vapour

4.3.3a(i) Tank Cool Down With Return Through LNG Header

4.3.3a(ii) Tank Cool Down With Return Through

Vapour Header

4.3.4a Tank Warm Up

4.3.4b One Tank Warm Up

4.3.5a Gas Freeing

4.3.6a Aerating

4.4.1a Cargo Discharge without Gas Return from Shore

4.4.3a Emergency Cargo Pump Fitting Sequence

4.4.5a Jettisoning of Cargo

4.4.7a Over-filling of Cargo Tanks

4.4.8a Secondary Barrier Space De-Watering

4.4.15a Barrier Punch

4.4.16a Loaded Voyage without Gas Burning

PART 5: SAFETY SYSTEMS5.1 Deck Salt Water Systems

5.1.1 Spray System

5.1.2 Firemain System

5.1.3 Air Locks

5.1.4 Dry Powder System

5.1.5 Ship Side Water Curtain Spray

5.1.6 CO2 Protection in Cargo and Motor Compressor Rooms

5.1.7 Vent Mast Extinguishing

5.2 Emergency Shut Down System5.2.1 ESD System

5.3 Gas Detection System5.3.1 Infrared Gas Analyser System

5.3.2 Catalytic Gas Analyser

5.3.3 Hand Held Gas Analyser (O2, CO2, CO, Dew point, CH4)

5.4 Inner Hull Failure5.4.1 Leakage Detection

5.5 Fire Detection System5.5.1 Fire Detection System

5.6 Gas-Dangerous Spaces and Zones

5.7 Glycol Heating System5.7.1 Description

5.7.2 Glycol Heating for LNG Dual Purpose Heaters

5.8 Insulation and Barrier Systems5.8.1 Leakage Detection

5.8.2 Damage to Primary Insulation Space - Gas in Interbarrier Space

5.8.3 Damage to Primary Insulation Space - Emergency Discharge of LNG

5.8.4 Primary Insulation Space Drainage - Barrier Punch Systems

5.9 Ventilation of Ballast and Trunk Void5.9.1 Ventilating a Double Hull Ballast Tank

5.9.2 Ventilating the Trunk Deck Void Space

5.9.3 IMO Code for Existing Ships Carrying Liquefied Gases in Bulk

ILLUSTRATIONS5.1.1a Deck Water Spray System

5.1.2a Deck Fire Main System

5.2.1a Emergency Shut-down System

5.3.1a Gas Detection Systems

5.4.1a De-Watering Pump Arrangement

5.5.1a Fire Detection System

5.5.1b Fire Sensor Control Panel

5.6.1a Gas-Dangerous Zones

5.7.1a Glycol Heating System

5.7.2a Cofferdam Heating System

5.8.1a Nitrogen Sweeping with Gas

Concentration Below Alarm Point

5.8.2a Evacuation of Damaged Insulation Spaces

5.8.4 Primary Insulation Space Drainage- Barrier Punch Systems

5.9.1a Ventilating the Ballast Tanks

5.9.2a Ventilating the Trunk Void Spaces

PART 6: INNER HULL AND COLD SPOT INSPECTION PROCEDURES

6.1 Introduction

ILLUSTRATIONS6.1a No 1 CofferdamPerspective

6.1b No 1 Port Ballast Tank Perspective

6.1c No 1 Stb’d Ballast Tank Perspective

6.1d No 1 Above Tank Void Space Perspective

6.1e No 2 Cofferdam Perspective

6.1f No 2 Port Ballast Tank Perspective

6.1g No 2 Stb’d Ballast Tank Perspective

6.1h No 2 Above Tank Void Space Perspective

6.1i No 3 Cofferdam Perspective

6.1j No 3 Port Ballast Tank Perspective

6.1k No 3 Stb’d Ballast Tank Perspective

6.1l No 3 Above Tank Void Space Perspective

6.1m No 4 Cofferdam Perspective

6.1n No 4 Port Ballast Tank Perspective

6.1o No 4 Stb’d Ballast Tank Perspective

6.1p No 4 Above Tank Void Space Perspective

6.1q No 5 Cofferdam Perspective

6.1r Fore Peak Ballast Tank

(Port Side Perspective View)

6.1s Fore Peak Ballast Tank

(Stb’d Side Perspective View)



PART 7: STRESS AND DAMAGE S TABILITY CASES

7.1 Introduction7.1.1 Loading Stability Computer

7.2 Cases7.2.1 Case 1 Damaged Compartments 41 and 214

7.2.2 Case 2 Damaged Compartments 41, 214, 213, 49, 34, 400 and 500

7.2.3 Case 3 Damaged Compartments 34, 35, 49, 51, 401 and 500




7.2.7 Case 7 Damaged Compartments 37, 55, 201, 404 and 500


7.2.9 Case 9 Damaged Compartments 200, 201 and 207



7.2.12 Case 12 Damaged Compartments 206 and 1










7.2.22 Case 22 Damaged Compartments 55, 56, 12 and 500







General Arrangement of LNG Lerici - Page 1Issue: 1


Length Overall 216.14mLength Between Perpendiculars 205.00mExtreme Breadth 33.90mExtreme Depth 21.26mSummer Draught 9.52mCorresponding Deadweight 35761.00 tonnesLight Displacement 17099.00 tonnesLoaded Displacement (Summer) 52860.00 tonnesCargo Tank Cubic Capacity (100% Full) 65299.00 m3

Distance From KeelTo Highest Point 53.25mAir Draught 44.10m

General Arrangement of LNG Lerici

INTRODUCTIONGeneralAlthough the ship is supplied with Shipbuilder’s plans andmanufacturer’s instruction books, there is no singlehandbook which gives guidance on operating completesystems, as distinct from individual items of machinery.

The purpose of this manual is to fill some of the gaps andto provide the ship’s officers with additional informationnot otherwise available on board. It is intended to be usedin conjunction with the other plans and instruction booksalready on board and in no way replaces or supersedesthem.

In addition to containing detailed information of the Cargoand related systems, the CARGO OPERATING MANUALcontains safety procedures, and procedures to beobserved in emergencies and after accidents. Used inconjunction with the SNAM SMS MANUAL, thisinformation is designed to ensure the safety and efficientoperation of the ships. Quick reference to the relevantinformation is assisted by division of the manual into Partsand Sections, detailed in the general list of contents on thepreceding pages.

Reference is made in this book to appropriate plans orinstruction books.

For other information refer to:

1) Books and Publications contained in the

SMS Directory

2) SMS MANUAL

In many cases the best operating practice can only belearned by experience. Where the information in thismanual is found to be inadequate or incorrect, detailsshould be sent to the Snam LNG Operations Office so thatrevisions may be made to manuals of other ships of thesame class.

Safe OperationThe safety of the ship depends on the care and attentionof all on board. Most safety precautions are a matter ofcommon sense and good housekeeping and are detailedin the various manuals available on board. However,records show that even experienced operators sometimesneglect safety precautions through over-familiarity and thefollowing basic rules must be remembered at all times.

1 Never continue to operate any machine orequipment which appears to be potentially unsafeor dangerous and always report such a conditionimmediately.

2 Make a point of testing all safety equipment anddevices regularly. Always test safety trips beforestarting any equipment. In particular, over-speedtrips on auxiliary turbines must be tested beforeputting the unit into operation.

3 Never ignore any unusual or suspiciouscircumstances, no matter how trivial. Smallsymptoms often appear before a major failureoccurs.

4 Never underestimate the fire hazard of petroleumproducts, whether fuel oil or cargo vapour.

5 Never start a machine remotely from the controlroom without checking visually if the machine isoperating satisfactorily.

In the design of equipment and machinery, devices areincluded to ensure that, as far as possible, in the event ofa fault occurring, whether on the part of the equipment orthe operator, the equipment concerned will cease tofunction without danger to personnel or damage to themachine. If these safety devices are neglected, theoperation of any machine is potentially dangerous.

DescriptionThe concept of this Cargo Operating Manual is based onthe presentation of operating procedures in the form ofone general sequential chart (algorithm) which gives astep-by-step procedure for performing operations requiredfor the carriage of LNG.

The manual consists of introductory sections whichdescribe the systems and equipment fitted and theirmethod of operation related to a schematic diagramwhere applicable. This is then followed where required bydetailed operating procedures for the system orequipment involved.

The overview of cargo operations, as detailed in 4.1,consists of a basic operating algorithm which sets out theprocedure for cargo handling operations from dry dock tofirst loading and from first loading through the normalcargo operating cycle. The relevant illustration andoperation Section number is located on the right hand sideof each box.

Each cargo handling operation consists of a detailedintroductory section which describes the objectives andmethods of performing the operation related to theappropriate flow sheet which shows pipelines in use anddirections of flow within the pipelines.

Details of valves which are OPEN during the differentoperations are provided in-text for reference.

The ‘valves’ and ‘fittings’ identifications used in thismanual are the same as those used by Snam.

IllustrationsAll illustrations are referred to in the text and are locatedeither in-text where sufficiently small or above the text, sothat both the text and illustration are accessible when themanual is laid face down. When text concerning anillustration covers several pages the illustration isduplicated above each page of text.

Where flows are detailed in an illustration these are shownin colour. A key of all colours and line styles used in anillustration is provided on the illustration. Details of colourcoding used in the illustrations are given in the colourscheme.

Symbols given in the manual adhere to internationalstandards and keys to the symbols used throughout themanual are given on the following pages.

NoticesThe following notices occur throughout this manual:

! WARNINGWarnings are given to draw reader’s attention tooperation where DANGER TO LIFE OR LIMB MAYOCCUR.

! CAUTIONCautions are given to draw reader’s attention tooperations where DAMAGE TO EQUIPMENT MAYOCCUR.

NOTE:

Notes are given to draw reader’s attention to points ofinterest or to supply supplementary information.

Introduction - Page 1Issue: 1


Symbol and Illustration Colour SchemeIssue: 1


ELECTRICAL SYMBOLS KEY INSTRUMENTATION IDENTIFIERS & SYMBOLS KEY

Circuit breaker

Moulded case air current breaker

Fuse

Fused switch

Switch

Normally open contact

Normally closed contact

Contact with pushbutton

Changeover switch/contact

Two-way switch with ÔoffÕ position

Limit switch normally open

Pressure switch (closed by pressure)

Temperature switch (closed)

ÒOff loadÓ disconnect links

Connection for portable cables

Relay coil

Rectifier

Transformer

MotorM

A C generator

3 phase generator

Signal lamp

Capacitor

Overload release (magnetic)

Overload release (thermal)

Motor starter S

& AND Gate (both inputs must bepresent in order for there to be anOutput).

1 OR Gate (any one input will result in an output)

AmmeterA

VoltmeterV

Frequency meterHz

KilowattkW

Synchroscope

Latching device

Syn

Battery

Double junction of conductors vertically in line

Conductors crossing but not joining

Junction of conductors

Single contact pushbuttonnormally closed

Locally MountedInstrument

Remotely MountedInstruments

Letters outside the circleof an instrument symbolindicate whether high (H),high-high (HH), low (L)or low-low (LL) function is involvedO = OpenC = Closed

L

Trip Automatic Trip

I Interlock

AI Analyser indicatorAT Analyser transmitterFC Flow controllerFI Flow indicatorFIC Flow indicator controlFS Flow switchHY High adjustHIC High indicator controlHSS High switch selectorHS High selectorHTS High temperature selectorLA Level alarmLC Level controllerLG Level glassLIA Level indicatorLS Level switchLT Level transmitterLPS Low pressure selectorOdA Oil detection alarmOC Oxygen contentPA Pressure alarmPC Pressure controllerPCV Pressure control valvePdA Pressure differential alarmPdI Pressure differential indicatorPdS Pressure differential switchPdC Pressure differential controlPdT Pressure differential transmitterPI Pressure indicatorPS Pressure switchPT Pressure transmitterQA Quality alarmQI Quality indicatorQT Quality transmitterSA Salinity alarmSI Speed indicatorST Speed transmitterTA Temperature alarmTC Temperature controllerTCS Temperature control sensorTdA Temperature differential alarmTE Temperature elementTI Temperature indicatorTIC Temperature indicating controllerTR Temperature recorderTRC Temperature recording controllerTS Temperature switchTT Temperature transmitterVA Vacuum alarmVS Vacuum SwitchVIC Viscosity indicating controller HS High selectorXA Group alarmYT Vibration transmitterZS Movement switchZI Position indicatorZT Movement transmitterZA Position alarm

COLOUR SCHEME

Glycol Cold Water

Sanitary FW

LNG Liquid

LNG Vapour

Combustion Air

Warm LNG Vapour

Gas Burning Supply

Glycol Hot Water

Fire Main Sea Water

Electrical Distribution

Diesel Oil

Liquid Nitrogen

Primary Space Nitrogen

Gaseous Nitrogen

Ballast Water

SW

Lub - Oil

Freon

Secondary Space Nitrogen

Inert Gas

DSH Steam 8 Bar

Condensate

Dry Air

Deck Spray Water

Instrument Air

Hydraulic Oil

FW Cooling

Wet Air

Electrical

Instrumentation

List of SymbolsIssue: 1


L. C.

L. O.

L

T

M

E

H

P

T

C

C

M

M

P

PE

P

M

Bursting disc

Flexible hose

Alarm Klaxon

Flame Trap

Screw LiftValve Chest

Locked ClosedValve

Removable pipe Length (Spoolpiece)

Screw Down NRValve Chest

Locked OpenValve

Trace Heating And Insulated Pipe

InsulatedPipe

Pump

Non-return valve (N R)

Screw down N R valve

MECHANICAL SYMBOLS KEY

Pneumatic electrical Convertor

Flow control valve

Solenoid operated valve

Needle valve

Ball valve

Globe valve

Quick closing valve

Valve with limit switch

De superheater

Gate valve

Pneumatic orHydraulic Switch

Piston operated valve

Diaphragm operated valve(indicates close or open in the event of air supply failure)

Diaphragm operated valvewith built-on positioner

Valve with gland sealing

Suction bell mouth

Duplex filter

Automatic drain

Orifice or restriction

Globe valve (screw lift)

Vent Pipe

Diaphragm

Adjustable flow rotary displacement pump

Emergency remote quick closing valve

Self-closing test valve

Relief or safety valve

Two-way cock

PressureRelief Valve

Lever operated cock

Three-way cock (T or L signifies plug form)

Ball float valve

Valve with hose connection

Sea waterchest

Straight NRvalve

Sea water chestwith grid

Straight globe valve

Angle globe valve

3 way globe valve

T branch pipe

Cross branch pipe

Crossing pipe

Valve of any type

Angle NRvalve

Straight swing type NR valve

Angle swing typecheck valve

Spring loaded NR valve

3 way Ð plug valve2 plug port1 per bottom

3 way Ð plug valve2 plug ports

3 way Ð plug valve3 plug ports

Straight automatic shut off valve

Angle automatic shut off valve

Quick opening valve

Quick closing valve

Needle valve

Funnel with sieve

Earth

Diaphragm valve

Straight safety valve

Bib cock

Straight fire type valve

Angle fire type valve

Manifold with screw down swing valves

Manifold with lift check valves

Angle safety valve

Manual control

Remote manualcontrol

Pneumaticcontrol

Hydraulic control

Electriccontrol

Motorizedcontrol

Blind flange

Spectacleflange

Bleeding plug

Strainer

Straight sludge box

OpenClosed

Funnel

Remotely controlledvalve (2 or 3 way)

Ball or plug valve

Suction bellmouth

Air moistureeliminator

Watertrap

Lubricator

Pressure reducing valve

Angle sludge box

Basket strainer

Sieve strainer

Straight venting checkvalve with flame arrestor

Angle venting checkvalve with flame arrestor

Venting box with flame arrestor

Sounding and filling cap

Automatic shut off sounding cap

Angle venting check valve

Sight glass

Vacuum breaker

Straight anti-siphon vacuum breaker

Angle anti-siphonvacuum breaker

Ejector/ Eductor

Straight tubeexchanger

Air fan heater

Pressure reciever

Air eliminator

Electric heater

Turbine

Condenser

Vaporiser

Centrifugalcompressor

Reciprocatingcompressor

A C motor

D C motor

Gutterway orDrip-pan

Back flow preventer for continuous pressure

Constant flow rotary displacement pump

Reciprocating pump

U tube exchanger

Ignitor

Jack

Heater

Cooler

Rotarypump

Butterfly valve

Trip valve

Strainer

Filter

Cock

Tee

Bend

HydraulicOil Filter

HydraulicCheckValve

Motor

Issue and Update Control - Page 1Issue: 1


ISSUE AND UPDATE CONTROLThis manual is provided with a system of issueand update control. Controlling documentsensures that:

• documents conform to a standard format;

• amendments are carried out by relevantpersonnel;

• each document or update to a document isapproved before issue;

• a history of updates is maintained;

• updates are issued to all registered holders ofdocuments;

• sections are removed from circulation whenobsolete.

Document control is achieved by the use of thefooter provided on every page and the issue andupdate table below.

In the right hand corner of each footer or headerare details of the page’s section number and titlefollowed by the page number of the section. Inthe left hand corner of each footer is the issuenumber.

Details of each section are given in the firstcolumn of the issue and update control table.The table thus forms a matrix into which the datesof issue of the original document and anysubsequent updated sections are located.

The information and guidance contained herein isproduced for the assistance of certificated officerswho by virtue of such certification are deemedcompetent to operate the vessel to which suchinformation and guidance refers. Any conflictarising between the information and guidanceprovided herein and the professional judgementof such competent officers must be immediatelyresolved by reference to SNAM, Head Office,Milan.

This manual was produced by:

WRIGHT MARINE TECHNOLOGY LTD .

For any new issue or update contact:

The Technical DirectorWMT Technical OfficeThe Court House15 Glynne WayHawardenDeeside, FlintshireCH5 3NS, UK

E-Mail: [email protected]

Issue 1 Issue 2 Issue 3 Issue 4List of Contents November 98General Arrangement November 98Introduction (Including November 98SNAM Safety Proceduresand Instructions)

Symbols and November 98Colour Scheme

Text November 981.1 November 981.1.1 November 981.1.2 November 981.2 November 981.2.1 November 981.2.2 November 981.2.3 November 981.3 November 981.3.1 November 981.3.2 November 98

Illustrations1.1.1a November 981.1.1b November 981.2.1a November 981.2.1b November 981.2.1c November 981.2.1d November 981.2.1e November 981.2.2a November 981.2.3a November 981.2.3b November 981.3.1a November 98

Text2.1 November 982.1.1 November 982.1.2 November 982.2 November 982.2.1 November 98



Issue 1 Issue 2 Issue 3 Issue 4Text3.1 November 983.2 November 983.3 November 983.3.1 November 983.3.2 November 983.3.3 November 98

Illustrations3.1.1a November 983.1.1b November 983.1.1c November 983.2.1a November 983.3.2a November 983.3.2b November 983.3.3a November 98

Text4.1 November 984.2 November 984.2.1 November 984.2.2 November 984.2.3 November 984.2.4 November 984.2.5 November 984.2.6 November 984.2.7 November 984.2.8 November 984.3 November 984.3.1 November 984.3.2 November 984.3.3 November 984.3.4 November 984.3.5 November 984.3.6 November 984.4 November 98

Issue 1 Issue 2 Issue 3 Issue 4Text4.4.1 November 984.4.3 November 984.4.4 November 984.4.5 November 984.4.6 November 984.4.7 November 984.4.8 November 984.4.9 November 984.4.10 November 984.4.11 November 984.4.12 November 984.4.13 November 984.4.14 November 984.4.15 November 984,4.16 November 98

Illustrations4.1 November 984.2.1a November 984.2.1b November 984.2.1c November 984.2.1d November 984.2.2a November 984.2.3a November 984.2.4a November 984.2.4b November 984.2.4c November 984.2.4d November 984.2.5a November 984.2.6a November 984.2.6b November 984.2.7a(i) November 984.2.7a(ii) November 984.2.8a November 98



Issue 1 Issue 2 Issue 3 Issue 4Illustrations4.3.1a November 984.3.1b November 984.3.1c November 984.3.2a November 984.3.3a(i) November 984.3.3a(ii) November 984.3.4a November 984.3.4b November 984.3.5a November 984.3.6a November 984.4.1a November 984.4.3a November 984.4.5a November 984.4.7a November 984.4.8a November 984.4.15a November 984.4.16a November 98

Text5.1 November 985.1.1 November 985.1.2 November 985.1.3 November 985.1.4 November 985.1.5 November 985.1.6 November 985.1.7 November 985.2 November 985.2.1 November 985.3 November 985.3.1 November 985.3.2 November 985.3.3 November 985.4 November 98

Issue 1 Issue 2 Issue 3 Issue 4Text5.4.1 November 985.5 November 985.5.1 November 985.6 November 985.7 November 985.7.1 November 985.7.2 November 985.8 November 985.8.1 November 985.8.2 November 985.8.3 November 985.8.4 November 985.9 November 985.9.1 November 985.9.2 November 985.9.3 November 98

Illustrations5.1.1a November 985.1.2a November 985.2.1a November 985.3.1a November 985.4.1a November 985.5.1a November 985.5.1b November 985.6.1a November 985.7.1a November 985.7.2a November 985.8.1a November 985.8.2a November 985.8.4 November 985.9.1a November 985.9.2a November 98



Issue 1 Issue 2 Issue 3 Issue 4Text6.1 November 98

Illustrations6.1a November 986.1b November 986.1c November 986.1d6.1e6.1f November 986.1g November 986.1h November 986.1i November 986.1j November 986.1k November 986.1l November 986.1m November 986.1n November 986.1o November 986.1p November 986.1q November 986.1r November 986.1s November 98

Text7.1 November 987.1.1 November 98

Illustrations7.2.1 November 987.2.2 November 987.2.3 November 987.2.4 November 987.2.5 November 987.2.6 November 98

Issue 1 Issue 2 Issue 3 Issue 4Illustrations7.2.7 November 987.2.8 November 987.2.9 November 987.2.10 November 987.2.11 November 987.2.12 November 987.2.13 November 987.2.14 November 987.2.15 November 987.2.16 November 987.2.17 November 987.2.18 November 987.2.19 November 987.2.20 November 987.2.21 November 987.2.22 November 987.2.23 November 987.2.24 November 987.2.25 November 987.2.26 November 98

Part 1LNG, Nitrogen and Inert Gas

PART 1: LNG, NITROGEN AND INERT GAS1.1 Physics of GasesThis chapter provides some basic information onchemistry of gases in general. It is expected to give anoutline of the important physical and chemical propertiesof liquid gases.

1.1.1 Gas LawsAlthough strictly speaking a perfect gas is an ideal whichcan never be realised in practice, the behaviour of manyreal gases is very similar to the behaviour of a perfect gas.Two of the laws describing the behaviour of perfect gasesare Boyle’s Law and Charles’ Law.

Boyle’s LawThis law may be stated as follows:Provided the temperature T of a perfect gas remainsconstant, then the volume V of the gas is inverselyproportional to its pressure P, ie.

P x V = constant

if the temperature remains constant.

If a gas changes from a state 1 to a state 2 during aconstant temperature process (isothermal), then

P1 x V1 = P2 x V2 = constant

If the process is represented on a graph having axes ofpressure P and volume V, the result will be as shown inthe figure above. The curve is known as a rectangularhyperbola, having the mathematical equation

xy = constant

Charles’ Law (Gay Lussac’s Law)Provided the pressure P of a given mass of gas remainsconstant, then the volume V of the gas will be directlyproportional to the absolute temperature T of the gas, ie.

V = constant x T.

Therefore = constant for constant pressure P.

If a gas changes from state 1 to 2 during a constantpressure process, then

= = constant

If the process is represented on a P - V diagram, the resultwill be as shown in the figure above.

Combination of the Laws of Boyle and CharlesThe pressure, volume and temperature of a gas may allchange at once from P1 V1 and T1 to P2 V2 and T2. Inthis case, because pressure changes, Charles’ Law willnot apply and because the temperature changes, Boyle’sLaw will also not apply.

This change of state may therefore be regarded as takingplace in two stages:

a) By a change according to Boyle’s Law;

b) A change according to Charles’ Law.

By doing this it will be found that the following will apply

This result may be expressed thus: The product of thepressure and volume of a quantity of gas divided by itsabsolute temperature is a constant and this may bewritten as

where C is a constant.

Dalton’s Law of Partial PressuresThe sum of the partial pressure of the constituent gases ofa mixture of gases is equal to the total pressure of the gasmixture.

P = P1 + P2 + Pn

1.1.2 Definitions

Absolute PressureThe total pressure of a gas called Absolute Pressure is thesum of gauge pressure plus the barometric oratmospheric pressure.

Absolute TemperatureThe fundamental temperature scale with its zero atabsolute zero and expressed in degrees Kelvin. Onedegree Kelvin is equal to one degree Celsius or one degreeCentigrade. For the purpose of practical calculations inorder to convert Celsius to Kelvin add 273. It is normal forthe degree Kelvin to be abbreviated in mathematicalformulae to ‘K’ with the degree symbol being omitted.

Absolute ZeroThe temperature at which the volume of a gastheoretically becomes zero and all thermal motion ceases.It is generally accepted as being -273.16°C.

Activated AluminaA desiccant (or drying) medium which operates byadsorption of water molecules.

AdiabaticDescribes an ideal process undergone by a gas in whichno gain or loss of heat occurs.

Aerating Aerating means the introduction of fresh air into a tankwith the object of removing toxic, flammable and inertgases and increasing the oxygen content to 21% byvolume.

Airlock A separation area used to maintain adjacent areas at apressure differential. For example, the airlock to an electricmotor room on a gas carrier is used to maintain pressuresegregation between a gas-dangerous zone on the opendeck and the gas-safe motor room which is pressurised.

Approved Equipment Equipment of a design that has been type-tested andapproved by an appropriate authority such as agovernmental agency or classification society. Such anauthority will have certified the particular equipment assafe for use in a specified hazardous atmosphere.

Auto-Ignition TemperatureThe lowest temperature at which a solid, liquid or gascombusts spontaneously without initiation by spark orflame.

Avogadro’s Law Avogadro’s Hypothesis states that equal volumes of allgases contain equal numbers of molecules under thesame conditions of temperature and pressure.

Avogadro’s Law Avogadro’s Hypothesis states that equal volumes of allgases contain equal numbers of molecules under thesame conditions of temperature and pressure..

BLEVEThis is the abbreviation for a Boiling Liquid ExpandingVapour Explosion. It is associated with the rupture, under fireconditions, of a pressure vessel containing liquefied gas.

Boil-offBoil-off is the vapour produced above the surface of aboiling cargo due to evaporation. It is caused by heatingress or a drop in pressure.

Boiling PointThe temperature at which the vapour pressure of a liquidis equal to the pressure on its surface (the boiling pointvaries with pressure).

Booster PumpA pump used to increase the discharge pressure fromanother pump (such as a cargo pump).

British Thermal UnitThe quantity of heat required to raise 1 pound of waterthrough one degree Fahrenheit, expressed in Btu.

Bulk CargoCargo carried as a liquid in cargo tanks and not shippedin drums, containers or packages.

1.1 Physics of Gases - Page 1Issue: 1


PVT

P1V1

T1

P2V2

T2

=

P

V0

1 2

1.1.1b Charles Law

P2

V1 V2

P1

P

V

1

2

1.1.1a Boyle's Law

VT

= C or PV = CT

V1

T1

V2

T2

CalorieThe quantity of heat required to raise 1 gramme (1g) ofwater through 1°C. A kilo calorie is equal to 1000 calories.In the ISO system, the unit used is the JOULE (J).

1 calorie (cal) 4.185J1 thermie (th) = 106 cal

Calorific ValueThe calorific value or heat of combustion is defined as theamount of heat released when a unit quantity of gas isburned at atmospheric pressure and at ambienttemperature (25°C). The gross value is obtained when thecontribution from the latent heat of condensation of thewater vapour formed is recovered; the net calorific valueis a more realistic parameter pertaining to practicalconditions when flue gases are usually maintainedabove 100°C. However, the gross heating value is thestandard adopted almost universally for the calculation ofthermal efficiencies of fuel burning appliances.

Canister Filter RespiratorA respirator consisting of mask and replaceable canisterfilter through which air mixed with toxic vapour is drawn bythe breathing of the wearer and in which the toxicelements are absorbed by activated charcoal or othermaterial. A filter dedicated to the specific toxic gas mustbe used. Sometimes this equipment may be referred to ascartridge respirator. It should be noted that a canister filterrespirator is not suitable for use in an oxygen deficientatmosphere.

CarcinogenA substance capable of causing cancer.

Cargo AreaThat part of the ship which contains the cargocontainment system, cargo pumps and compressorrooms, and includes the deck area above the cargocontainment system. Where fitted, cofferdams, ballasttanks and void spaces at the after end of the aftermosthold space or the forward end of the forwardmost holdspace are excluded from the cargo area. (Refer to the GasCodes for a more detailed definition).

Cargo Containment SystemThe arrangement for containment of cargo including,where fitted, primary and secondary barriers, associatedinsulations, interbarrier spaces and the structure requiredfor the support of these elements. (Refer to the GasCodes for a more detailed definition).

Cascade Reliquefaction CycleA process in which vapour boil-off from cargo tanks iscondensed in a cargo condenser in which the coolant is arefrigerant gas such as R 22. The refrigerant gas is thencompressed and passed through a conventional seawater-cooled condenser.

CavitationA process occurring within the impeller of a centrifugalpump when pressure at the inlet to the impeller falls belowthat of the vapour pressure of the liquid being pumped. Thebubbles of vapour which are formed collapse with impulsiveforce in the higher pressure regions of the impeller. Thiseffect can cause significant damage to the impeller surfacesand, furthermore, pumps may loose suction.

Certificate of FitnessA certificate issued by a flag administration confirming thatthe structure, equipment, fittings, arrangements andmaterials used in the construction of a gas carrier are incompliance with the relevant Gas Code. Such certificationmay be issued on behalf of the administration by anapproved classification society.

Certified Gas FreeA tank or compartment is certified to be gas-free when itsatmosphere has been tested with an approved instrumentand found in a suitable condition by an independent chemist.This means it is not deficient in oxygen and sufficiently freeof toxic or flammable gas for a specified purpose.

CofferdamThe isolating space on a ship between two adjacent steelbulkheads or decks. This space may be a void space orballast space.

Compression RatioThe ratio of the absolute pressure at the discharge from acompressor divided by the absolute pressure at the suction.

CondensateReliquefied gases which collect in the condenser andwhich are then returned to the cargo tanks.

Critical DensityDensity at critical temperature and pressure.

Critical Pressure The pressure at which a substance exists in the liquidstate at its critical temperature. (In other words it is thesaturation pressure at the critical temperature).

Critical Temperature and PressureThe critical temperature of a gas is the temperature abovewhich the substance cannot be liquid however great thepressure.

The critical pressure of a gas is the pressure required tocompress a gas to its liquid state at its criticaltemperature.

Cryogenics The study of the behaviour of matter at very lowtemperatures.

Dalton’s Law of Partial Pressures This states that the pressure exerted by a mixture of gasesis equal to the sum of the separate pressures which eachgas would exert if it alone occupied the whole volume.

Dangerous Cargo Endorsement Endorsement issued by a flag state administration to acertificate of competency of a ship’s officer allowingservice on dangerous cargo carriers such as oil tankers,chemical carriers, or gas carriers.

DensityThe density of a substance is the weight per unit volumeat standard temperature of 15°C. This is usually quoted inkg/m3 or g/cm3 or kg/dm3.

Deepwell Pump A type of centrifugal cargo pump commonly found on gascarriers. The prime mover is usually an electric orhydraulic motor. The motor is usually mounted on top ofthe cargo tank and drives, via a long transmission shaft,through a double seal arrangement, the pump assemblylocated in the bottom of the tank. The cargo dischargepipeline surrounds the drive shaft and the shaft bearingsare cooled and lubricated by the liquid being pumped.

Dewpoint The temperature at which condensation will take placewithin a gas if further cooling occurs.

Endothermic A process which is accompanied by the absorption of heat

EnthalpyThe enthalpy of a mass of a substance is a measure of itsthermodynamic heat content whether the substance isliquid or vapour or a combination of the two. Enthalpy (H)is defined as:

H = U + PV

where U is the internal energyP is the absolute pressure

and V is the total volume of the system(liquid + vapour)

EntropyThe entropy of a liquid or vapour is its enthalpy divided bythe absolute temperature. It is expressed as kilocaloriesper kilogramme per degree Celsius (kcal/kg/°C) andremains constant while the liquid or vapour volumechanges without absorption or release of heat. However,entropy increases or decreases if the material receives orsurrenders heat from or to its surroundings. Over aninfinitely small change in temperature, the increase ordecrease of entropy, when multiplied by the absolutetemperature, gives the heat absorbed or lost by the fluid

Explosive LimitsThe limits of the explosive range, that is, the rangebetween the minimum and maximum concentrations ofhydrocarbon vapour in air which form explosive(flammable) mixtures: usually abbreviated to LEL (LowerExplosive Limit) and UEL (Upper Explosive Limit).Sometimes referred to as LFL (Lower Flammable Limit)and UFL (Upper Flammable Limit).

Explosion-Proof/Flameproof EnclosureAn enclosure which will withstand an internal ignition of aflammable gas and which will prevent the transmission ofany flame able to ignite a flammable gas which may bepresent in the surrounding atmosphere.

Flame ArrestorA device fitted in gas vent pipelines to arrest the passageof flame into enclosed spaces.

Flame ScreenA device incorporating corrosion resistant wire meshes. Itis used for preventing the inward passage of sparks (or,for a short period of time, the passage of flame), yetpermitting the outward passage of gas.



Flash PointThe lowest temperature at which a liquid gives offsufficient vapour to form a flammable mixture with air nearthe surface of the liquid or within the apparatus used. Thisis determined by laboratory testing in a prescribedapparatus.

Gas-Safe SpaceA space on a ship not designated as a gas-dangerousspace.

Hard ArmAn articulated metal arm used at terminal jetties toconnect shore pipelines to the ship’s manifold.

HeelThe amount of liquid cargo retained in a cargo tank at theend of discharge. It is used to maintain the cargo tankscooled down during ballast voyages by recirculatingthrough the sprayers. On LPG ships such cooling down iscarried out through the reliquefaction plant and on LNGships by using the spray pumps.

Hold Space The space enclosed by the ship’s structure in which acargo containment system is situated.

Hydrates The compounds formed by the interaction of water andhydrocarbons at certain pressures and temperatures.They are crystalline substances.

Hydrate Inhibitors An additive to certain liquefied gases capable of reducing thetemperature at which hydrates begin to form. Typical hydrateinhibitors are methanol, ethanol and isopropyl alcohol.

IACS International Association of Classification Societies.

IAPH International Association of Ports and Harbours.

lCSInternational Chamber of Shipping.

IMO International Maritime Organization. This is the UnitedNations specialised agency dealing with maritime affairs.

Incendive Spark A spark of sufficient temperature and energy to ignite aflammable gas mixed with air.

Inert Gas A gas, such as nitrogen, or a mixture of gases containinginsufficient oxygen to support combustion.

Inerting Inerting means:(i) the introduction of inert gas into an aerated tank with

the object of attaining an inert condition suited to asafe gassing-up operation.

(ii) the introduction of inert gas into a tank after cargodischarge and warming-up with the object of:

(a) reducing existing vapour content to a levelbelow which combustion cannot be supportedif aeration takes place

(b) reducing existing vapour content to a levelsuited to gassing-up prior to the next cargo

(c) reducing existing vapour content to a levelstipulated by local authorities if a special gas-free certificate for hot work is required.

Insulation FlangeAn insulating device inserted between metallic flanges,bolts and washers to prevent electrical continuity betweenpipelines, sections of pipelines, hose strings and loadingarms or other equipment.

Interbarrier SpaceThe space between a primary and a secondary barrier ofa cargo containment system, whether or not completely orpartially occupied by insulation or other material.

Intrinsically SafeEquipment, instrumentation or wiring is deemed to beintrinsically safe if it is incapable of releasing sufficientelectrical or thermal energy under normal conditions orspecified fault conditions to cause ignition of a specifichazardous atmosphere in its most easily ignitedconcentration.

ISGOTTInternational Safety Guide for Oil Tankers and Terminals

IsothermalDescriptive of a process undergone by an ideal gas whenit passes through pressure or volume variations without achange of temperature.

Latent HeatThe latent heat of a liquid is the quantity of heat absorbedon vapourisation at normal boiling point, or conversely, itis the amount of heat given out when the vapour iscondensed at atmospheric pressure. As the heat contentof the liquid increases with temperature, the latent heatdecreases.The value of latent heat data lies in calculatingthe quantity of gas that will be vapourised at a given liquidtemperature by a specific heat input.

Latent Heat of VaporisationQuantity of heat to change the state of a substance fromliquid to vapour (or vice versa) without change oftemperature.

Liquefied GasA liquid which has a saturated vapour pressure exceeding2.8 bar absolute at 37.8°C and certain other substancesspecified in the Gas Codes.

Liquefied Natural Gas (LNG)Liquefied Methane and mixtures of other hydrocarbongases in which Methane predominates.

Lower Flammable Limit (LFL)The concentration of a hydrocarbon gas in air below whichthere is insufficient hydrocarbon to support combustion .

LPGThis is the abbreviation for Liquefied Petroleum Gas. Thisgroup of products includes propane and butane which canbe shipped separately or as a mixture. LPGs may berefinery by-products or may be produced in conjunctionwith crude oil or natural gas.

MARVSThis is the abbreviation for the Maximum Allowable ReliefValve Setting on a ship’s cargo tank as stated on theship’s Certificate of Fitness.

mlcThis is the abbreviation for metres liquid column and is aunit of pressure used in some cargo pumping operations .

Molar VolumeThe volume occupied by one molecular mass in grams(g mole) under specific conditions.For an ideal gas atstandard temperature and pressure it is 0.0224 m3/gmole.

MoleThe mass that is numerically equal to the molecular mass. Itis most frequently expressed as the gram molecular mass (gmole) but may also be expressed in other mass units, suchas the kg mole. At the same pressure and temperature thevolume of one mole is the same for all ideal gases. It ispractical to assume that petroleum gases are ideal gases.

Mole FractionThe number of moles of any component in a mixturedivided by the total number of moles in the mixture.

Mollier DiagramA graphic method of representing the heat quantitiescontained in, and the condition of, a liquefied gas (orrefrigerant) at different temperatures.

NGLsThis is the abbreviation for Natural Gas Liquids. These arethe liquid components found in association with naturalgas. Ethane, propane, butane, pentane and pentanes-plus are typical NGLs.

NPSHThis is the abbreviation for Net Positive Suction Head.This is an expression used in cargo pumping calculations.It is the pressure at the pump inlet and is the combinationof the liquid head plus the pressure in the vapour space.

OCIMFOil Companies International Marine Forum.

Oxygen AnalyserInstrument used to measure oxygen concentrations inpercentage by volume.

Oxygen-Deficient AtmosphereAn atmosphere containing less than 21% oxygen by volume.

Partial PressureThe individual pressure exerted by a gaseous constituentin a vapour mixture as if the other constituents were notpresent. This pressure cannot be measured directly but isobtained firstly by analysis of the vapour and then bycalculation using Dalton’s Law.

PeroxideA compound formed by the chemical combination of cargoliquid or vapour with atmospheric oxygen or oxygen fromanother source. In some cases these compounds may behighly reactive or unstable and a potential hazard.



PolymerisationThe chemical union of two or more molecules of the samecompound to form a larger molecule of a new compoundcalled a polymer. By this mechanism the reaction canbecome self-propagating causing liquids to become moreviscous and the end result may even be a solid substance.Such chemical reactions usually give off a great deal of heat.

Primary BarrierThis is the inner surface designed to contain the cargowhen the cargo containment system includes a secondarybarrier.

Other refrigerant gases listed in the IGC Code are shown inAppendix 2 although many are now controlled with a viewto being phased out under the Montreal Protocol (1987).

Relative Liquid DensityThe mass of a liquid at a given temperature comparedwith the mass of an equal volume of fresh water at thesame temperature or at a different given temperature.

Relative Vapour DensityThis is the relative weight of vapour compared with theweight of an equal volume of dry air at standard conditionsof temperature and pressure, ie 15°C and atmosphericpressure of 760mm Hg.

Restricted GaugingA system employing a device which penetrates the tankand which, when in use, permits a small quantity of cargovapour or liquid to be expelled to the atmosphere. Whennot in use, the device is kept completely closed.

Rollover The phenomenon where the stability of two stratifiedlayers of liquid of differing relative density is disturbedresulting in a spontaneous rapid mixing of the layersaccompanied in the case of liquefied gases, by violentvapour evolution.

Saturation TemperatureThe saturation temperature is that at which boiling occurs.At this temperature bubbles of vapour form in the liquidand break through the surface to occupy the space aboveit as a vapour. Supply of heat at this temperature causesfurther generation of vapour but does not increase thetemperature until all the liquid has been converted into avapour. Another definition of saturation temperature is thatit is the temperature at which the two phases, liquid andvapour, can exist in equilibrium with each other. As thepressure is increased so is the saturation temperature,until the critical point is reached.

Saturated Vapour PressureThe pressure at which a vapour is in equilibrium with itsliquid at a specified temperature.

Secondary BarrierThe liquid-resisting outer element of a cargo containmentsystem designed to provide temporary containment of aleakage of liquid cargo through the primary barrier and toprevent the lowering of the temperature of the ship’sstructure to an unsafe level.

Sensible HeatHeat energy given to or taken from a substance whichraises or lowers its temperature.

Shell and Tube CondenserA heat exchanger where one fluid circulates through tubesenclosed between two end-plates in cylindrical shell andwhere the other fluid circulates inside the shell.

Silica GelA chemical used in driers to absorb moisture.

Sl (Systeme International) UnitsAn internationally accepted system of units modelled onthe metric system consisting of units of length (metre),mass (kilogram), time (second), electric current (ampere),temperature (degrees Kelvin), and amount of substance(mole).

SIGTTO Society of International Gas Tanker and TerminalOperators Limited.

Slip Tube A device used to determine the liquid-vapour interfaceduring the ullaging of semi and fully pressurised tanks.

SOLAS International Convention for the Safety of Life at Sea,1974; as amended.

Span GasA vapour sample of known composition and concentrationused to calibrate gas detection equipment.

Specific Gravity SGThe specific gravity of a gas is normally defined as theratio of its density to that of air at the same temperatureand pressure (taken as unity).

Specific gravity of liquids expresses the relative weight ofthese hydrocarbon liquids at their boiling point ascompared to water at 4°C.

Specific HeatThis is the quantity of energy in kilo Joules required tochange the temperature of 1kg mass of a substance by1°C. For a gas the specific heat at constant pressure isgreater than that at constant volume.

Specific VolumeThis is the volume occupied by one kg of the substance at15°C and 760mm Hg pressure.

Spontaneous CombustionThe ignition of material brought about by a heat-producingchemical reaction within the material itself withoutexposure to an external source of ignition.

Static ElectricityStatic electricity is the electrical charge produced ondissimilar materials caused by relative motion betweeneach when in contact.

Submerged PumpA type of centrifugal cargo pump commonly installed ongas carriers and in terminals in the bottom of a cargo tank.It comprises a drive motor, impeller and bearings totallysubmerged by the cargo when the tank contains bulkliquid.

Superheated VapourVapour removed from contact with its liquid and heatedbeyond its boiling temperature.

Surge PressureA phenomenon generated in a pipeline system whenthere is a change in the rate of flow of liquid in the line.Surge pressures can be dangerously high if the change offlow rate is too. rapid and the resultant shock waves candamage pumping equipment and cause rupture ofpipelines and associated equipment

ThermThe therm is equal to 100,000 Btu.

Toxicity DetectorAn instrument used for the detection of gases or vapours. Itworks on the principle of a reaction occurring between thegas being sampled and a chemical agent in the apparatus.

TLVThis is the abbreviation for Threshold Limit Value. It is theconcentration of gases in air to which personnel may beexposed 8 hours per day or 40 hours per week throughouttheir working life without adverse effects. The basic TLV isa Time-Weighted Average (TWA). This may besupplemented by a TLV-STEL (Short-Term ExposureLimit) or TLV-C (Ceiling exposure limit) which should notbe exceeded even instantaneously.

Viscosity (Kinematic)The property of a liquid which determines its resistance toflow. The usefulness of viscosity data lies in specifyingpumps for liquid transfer and in predicting pressure lossesin pipe systems.

The unit used is the stoke (St) or centistoke (cSt).

Vapour DensityThe density of a gas or vapour under specified conditionsof temperature and pressure.

Void SpaceAn enclosed space in the cargo area external to a cargocontainment system, other than a hold space, ballastspace, fuel oil tank, cargo pump or compressor room orany space in normal use by personnel.



1.2 Properties of LNG1.2.1 Physical Properties, Composition and

Characteristics of LNGNatural gas is a mixture of hydrocarbon which, whenliquefied, forms a clear colourless and odourless liquid;this LNG is usually transported and stored at atemperature very close to its boiling point at atmosphericpressure (approximately –160°C).

The actual composition of North African LNG will varydepending on its source and on the liquefaction process,but the main constituent will always be methane; otherconstituents will be small percentages of heavierhydrocarbons, e.g. ethane, propane, butane, pentane,and possibly a small percentage of nitrogen.

A typical composition of LNG is given in Table 1.2.1b, andthe physical properties of the major constituent gases aregiven in Table 1.2.1a.

For most engineering calculations (eg. piping pressurelosses) it can be assumed that the physical properties ofpure methane represent those of LNG. However forcustody transfer purposes when accurate calculation ofthe heating value and density is required, the specificproperties based on actual component analysis must beused.

During a normal sea voyage, heat is transferred to theLNG cargo through the cargo tank insulation causingvapourisation of part of the cargo, ie. boil-off. Thecomposition of the LNG is changed by this boil-offbecause the lighter components having lower boiling

points at atmospheric pressure vapourise first; thereforethe discharged LNG has a lower percentage content ofnitrogen and methane than the LNG as loaded, and aslightly higher percentage of ethane, propane and butane,due to methane and nitrogen boiling off in preference tothe heavier gases.

The flammability range of methane in air (21% oxygen) isapproximately 5.3 to 14% (by volume). To reduce thisrange the air is diluted with nitrogen until the oxygencontent is reduced to 5% prior to loading after dry dock. Intheory, an explosion cannot occur if the O2 content of themixture is below 13% regardless of the percentage ofmethane, but for practical safety reasons, purging iscontinued until the O2 content is below 5%. This safetyaspect is explained in detail later in this section.

The boil-off vapour from LNG is lighter than air at vapourtemperatures above -110°C or higher depending on LNGcomposition (see graph 1.2.2a), therefore when vapour isvented to atmosphere, the vapour will tend to rise abovethe vent outlet and will be rapidly dispersed. When coldvapour is mixed with ambient air the vapour-air mixturewill appear as a readily visible white cloud due to thecondensation of the moisture in the air. It is normally safeto assume that the flammable range of vapour-air mixturedoes not extend significantly beyond the perimeter of thewhite cloud.

The auto-ignition temperature of methane, ie. the lowesttemperature to which the gas needs to be heated to causeself-sustained combustion without ignition by a spark orflame, is 595°C.

Table 1.2.1b Composition of North African LNG

Table 1.2.1c Properties of Methane

1.2 Properties of LNG - Page 1Issue: 1


Formula

Molecular Weight

Boiling Point at 1 bar absolute

Liquid Density at Boiling Point (kg/m3)

Vapour SG at 15°C and 1 bar absolute

Gas volume/liquid volume Ratio atBoiling Point and 1 bar absolute

Flammable Limits % in air by Volume

Auto - Ignition Temperature

Gross Heating Value at 15°C (kJ/kg)

Vaporisation Heat at Boiling Point(kJ/kg)

Methane

CH4

16.042

-161.5°C

426.0

0.554

619

5.3 to 14

595°C

55500

510.4

Ethane

C2H6

30.068

-88.6°C

544.1

1.046

431

3 to 12.5

510°C

51870

489.9

Propane

C3H8

44.094

-42.5°C

580.7

1.54

311

2.1 to 9.5

510/583°C

50360

426.2

Butane

C4H10

58.120

-5°C

601.8

2.07

311

2 to 9.5

510/583°C

50360

385.2

Pentane

C5H12

72.150

36.1°C

610.2

2.49

205

3 to 12.4

?

49010

357.5

Nitrogen

N2

28.016

-196°C

808.6

0.97 kg/m3

694

Non flammable

-

0

199.3

Methane

Ethane

Propane

Butane

Pentane

Nitrogen

Average molecular weight

Temperature at atm press (°C)

Density (kg/m3)

Formula

CH4

C2H6

C3H8

C4H10

C5H12

N2

Arzew

88.00

7.95

2.37

1.05

0.03

0.60

18.35

-162.04

464.34

Skikda

92.55

5.37

0.59

0.24

1.25

17.21

-164

456

Libya

71.40

16.00

7.90

3.40

1.30

22.66

-159

531

Boiling point 1 bar absolute

Liquid density at boiling point (kg/m3)

Vapour SG at 15°C and 1 bar absolute

Gas volume/liquid volume ratio at -161.5°C at 1 bar absolute

Flammable limits % in air by volume

Auto-ignition temperature

Gross Heating Value kJ at 15°C

Critical temperature

Critical pressure

-161.5°C

426.0

0.554 kg/m3

619

5.3to 14

595°C

55500

-82.5°C

43 bar a

Table 1.2.1a Physical Properties of LNG Components

Variation of Boiling Point of Methane with PressureSee Fig 1.2.1d Variation of Boiling Point of Methane withPressure.

The boiling point of methane increases with pressure, andthis variation is shown in the diagram for pure methaneover the normal range of pressures on board the vessel.The presence of the heavier components in LNGincreases the boiling point of the cargo for a givenpressure.

The relationship between boiling point and pressure ofLNG will approximately follow a line parallel to that shownfor 100% methane.



+20

0

– 20

– 40

– 60

1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5

– 80

–100

–120

–140

–160

Lighter than air

Ratio =Density of Methane vapourDensity of Air

(Density of air assumed to be 1.27 kg/m3 @ 15°C)

Methane vapourtemperature °C

1.2.1e Relative Densitiy of Methane and Air

Heavier than air

700

800

900

1,000

1,100

1,060

1,200

1,300

-165 -164 -163 -162 -161-161.3

-160 -159

Temperature 0C

Pressure (mbar abs)

1.2.1d Methane Saturated Vapour:Pressure - Temperature Equilibrium

1,050

950

Atmospheric Pressure Range

Cargo Tank Pressure Set Point Range

Usual Cargo Tanks Pressure Set-Point

1.2.2 Flammability of Methane, Oxygen andNitrogen Mixtures

The ship must be operated in such a way that flammablemixture of methane and air are avoided at all times. Therelationship between gas/air composition and flammabilityfor all possible mixtures of methane, air and nitrogen isshown on the diagram above.

The vertical axis A-B represents oxygen-nitrogen mixtureswith no methane present, ranging from 0% oxygen (100%nitrogen) at point A, to 21% oxygen (79% nitrogen) atpoint B. The latter point represents the composition ofatmospheric air.

The horizontal axis A-C represents methane-nitrogenmixtures with no oxygen present, ranging from 0%methane (100% nitrogen) at point A, to 100% methane(0% nitrogen) at point C.

Any single point on the diagram within the triangle ABCrepresents a mixture of all three components, methane,oxygen and nitrogen, each present in specific proportionof the total volume. The proportions of the threecomponents represented by a single point can be read offthe diagram.For example, at point D :

Methane : 6.0% (read on axis A-C)Oxygen : 12.2% (read on axis A-B)Nitrogen : 81.8% (remainder)

The diagram consists of three major sectors:

a) The Flammable Zone Area EDF. Any mixture whosecomposition is represented by a point which lies withinthis area is flammable.

b) Area HDFC. Any mixture whose composition isrepresented by a point which lies within this area iscapable of forming a flammable mixture when mixedwith air, but contains too much methane to ignite.

c) Area ABEDH. Any mixture whose composition isrepresented by a point which lies within this area is notcapable of forming a flammable mixture when mixedwith air.

Using the DiagramAssume that point Y on the oxygen-nitrogen axis is joinedby a straight line to point Z on the methane-nitrogen axis.If an oxygen-nitrogen mixture of composition Y is mixedwith a methane-nitrogen mixture of composition Z, thecomposition of the resulting mixture will at all times berepresented by point X, which will move from Y to Z asincreasing quantities of mixture Z are added.

Note that in this example point X, representing changingcomposition, passes through the flammable zone EDF,that is, when the methane content of the mixture isbetween 5.5% at point M, and 9.0% at point N.

Applying this to the process of inerting a cargo tank priorto cooldown, assume that the tank is initially full of air atpoint B. Nitrogen is added until the oxygen content isreduced to 13% at point G. The addition of methane willcause the mixture composition to change along the lineGDC which, it will be noted, does not pass through theflammable zone, but is tangential to it at point D. If theoxygen content is reduced further, before the addition ofmethane, to any point between 0% and 13%, that is,between points A and G, the change in composition withthe addition of methane will not pass through theflammable zone.

Theoretically, therefore, it is only necessary to addnitrogen to air when inerting until the oxygen content isreduced to 13%. However, the oxygen content is reducedto 5% during inerting because, in practice, completemixing of air and nitrogen may not occur.

When a tank full of methane gas is to be inerted withnitrogen prior to aeration, a similar procedure is followed.Assume that nitrogen is added to the tank containingmethane at point C until the methane content is reducedto about 14% at point H. As air is added, the mixturecomposition will change along line HDB, which, as before,is tangential at D to the flammable zone, but does notpass through it. For the same reasons as when inertingfrom a tank containing air, when inerting a tank full ofmethane it is necessary to go well below the theoreticalfigure to a methane content of 5% because completemixing of methane and nitrogen may not occur in practice.

The procedures for avoiding flammable mixtures in cargotanks and piping are summarised as follows:

a) Tanks and piping containing air are to be inerted withnitrogen before admitting methane until all samplingpoints indicate 5% or less oxygen content;

b) Tanks and piping containing methane are to be inertedwith nitrogen before admitting air until all samplingpoints indicate 5% methane.

It should be noted that some portable instruments formeasuring methane content are based on oxidising thesample over a heated platinum wire and measuring theincreased temperature from this combustion. This type of

analyser will not work with methane-nitrogen mixtures thatdo not contain oxygen. For this reason, special portableinstruments of the infrared type have been developed andsupplied to the ship for this purpose.



M

Oxygen %

Area ABEDHnot capable of formingflammable mixturewith air

Mixtures of air and methanecannot be produced above line BEFC

0 10

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21B

E

F

20 30 40 50 60 70 80 90 100C

Methane %

A H

X

N

Area EDFEflammable

D

G

Area HDFCcapable of forming flammable mixtures with air, but containingtoo much methane to explode

!This diagram assumes complete mixingwhich, in practice, may not occur

CAUTION

1.2.2a Flammability of Methane, Oxygen and Nitrogen Mixtures

Y

Z



Emergency Procedures - Methane

THE MAIN HAZARDFLAMMABLE.

METHANEFORMULA CH4

U.N. NUMBER 2043

FAMILY Hydrocarbon

APPEARANCE Colourless

ODOUR Odourless

EMERGENCY PROCEDURES

FIRE Stop gas supply. Extinguish with dry powder, Halon or CO2. Cool surrounding area with water spray.

LIQUID DO NOT DELAY. Flood eye gently with clean fresh/sea water. Force eye open if necessary.

IN EYE Continue washing for 15 minutes. Obtain medical advice/assistance.

LIQUID DO NOT DELAY. Treat patient gently. Remove contaminated clothing. Immerse frostbitten area

ON SKIN in warm water until thawed (see Chapter 9). Obtain medical advice/assistance.

VAPOUR Remove victim to fresh air. If breathing has stopped, or is weak/irregular, give mouth-to-mouth/nose

INHALED resuscitation.

SPILLAGE Stop the flow. Avoid contact with liquid or vapour. Flood with large amounts of water to disperse spill andprevent brittle fracture. Inform Port Authorities of any major spill.

EFFECT OF LIQUID

EFFECT OF VAPOUR

Frostbite to skin or eyes. Not absorbed through skin.

Asphyxiation - headache, dizziness, drowsiness. Possible low temperature damage to lungs, skin. Nochronic effect known.

PHYSICAL DATA

FIRE AND EXPLOSION DATA

BOILING POINT @ ATMOSPHERIC -161.5˚CPRESSUREVAPOUR PRESSURE See graphskg/cm 2 (A)

SPECIFIC GRAVITY 0.42

COEFFICIENT OF CUBIC EXPANSION 0.0026 per ˚C @ -165˚C

RELATIVE VAPOUR DENSITY 0.554

MOLECULAR 16.04WEIGHT

ENTHALPYLiquid Vapour

(kcal/kg)7.0 @ -165˚C 130.2 @ -165˚C

68.2 @ -100˚C 140.5 @ -100˚CLATENT HEAT OF VAPOURISATION See graphs(kcal/kg)

FLASH POINT -175˚C (approx) FLAMMABLE LIMITS 5.3 -14% AUTO-IGNITION TEMPERATURE 595˚C

HEALTH DATE

TVL 1000 ppm ODOUR THRESHOLD Odourless

“fire damp”“marsh gas”LNG

REACTIVITY DATA METHANE

AIR

WATER(Fresh/Salt)

OTHER LIQUIDS/GASES

No reaction.

No reaction. Insoluble. May freeze to form ice or hydrates.

Dangerous reaction possible with chlorine..

CONDITIONS OF CARRIAGE

NORMALCARRIAGECONDITIONS

SHIP TYPE

Fully refrigerated.

2G.

GAUGING

VAPOUR DETECTION

Closed, indirect.

Flammable.

MATERIALS OF CONSTRUCTION

UNSUITABLE SUITABLE

Stainless steel, aluminium, 9 or 36% nickel steel, copper.

SPECIAL REQUIREMENTS

Mild steel.



Emergency Procedures - Nitrogen

THE MAIN HAZARDFROSTBITE.

NITROGENFORMULA N2

U.N. NUMBER 2040

FAMILY Noble Gas

APPEARANCE Colourless

ODOUR Odourless

EMERGENCY PROCEDURES

FIRE Non-flammable. Cool area near cargo tanks with water spray in the event of fire near to them.

LIQUID DO NOT DELAY. Flood eye gently with clean sea/fresh water. Force eye open if necessary.

IN EYE Continue washing for 15 minutes. Seek medical advice/assistance.

LIQUID DO NOT DELAY. Handle patient gently. Remove contaminated clothing. Immerse frostbitten area

ON SKIN in warm water until thawed (see Chapter 9). Obtain medical advice/assistance.

VAPOUR Remove victim to fresh air. If breathing has stopped, or is weak/irregular, give mouth-to-mouth/nose

INHALED resuscitation.

SPILLAGE Stop the flow. Avoid contact with liquid or vapour. Flood with large amounts of water to disperse spill andprevent brittle fracture. Inform Port Authorities of any major spillage.

EFFECT OF LIQUID

EFFECT OF VAPOUR

Frostbite to skin or eyes.

Asphyxiation. Cold vapour could cause damage.

PHYSICAL DATA

FIRE AND EXPLOSION DATA

BOILING POINT @ ATMOSPHERIC -195.8˚CPRESSUREVAPOUR 2 @ -190˚C PRESSURE 10 @ -170˚Ckg/cm 2 (A)

SPECIFIC GRAVITY 0.9

COEFFICIENT OF CUBIC EXPANSION 0.005 @ -198˚C

RELATIVE VAPOUR DENSITY 0.967

MOLECULAR 28.01WEIGHT

ENTHALPYLiquid Vapour

(kcal/kg)7.33 @ -196˚C 54.7 @ -195˚C

34.7 @ -150˚C 52.0 @ -150˚CLATENT HEAT OF VAPOURISATION

47.5 @ -196˚C

(kcal/kg) 17.3 @ -150˚C

FLASH POINT Non-flammable FLAMMABLE LIMITS Non-flammable AUTO-IGNITION TEMPERATURE Non-flammable

HEALTH DATE

TVL 1,000 ppm ODOUR THRESHOLD Odourless

REACTIVITY DATA NITROGEN

AIR

WATER(Fresh/Salt)

OTHER LIQUIDS/GASES

No reaction.

No reaction. Insoluble.

No reactions.

CONDITIONS OF CARRIAGE

NORMALCARRIAGECONDITIONS

SHIP TYPE

Fully refrigerated.

3G.

GAUGING

VAPOUR DETECTION

Closed, indirect.

Oxygen analyser required.

MATERIALS OF CONSTRUCTION

UNSUITABLE SUITABLE

Stainless steel, copper, aluminium.

SPECIAL REQUIREMENTS

High oxygen concentrations can be caused by condensation and enrichment of the atmosphere in way of equipment at the lowtemperatures attained in parts of the liquid nitrogen system; materials of construction and ancillary equipment (e.g. insulation)should be resistant tot he effects of this. Due consideration should be given to ventilation in areas where condensation mightoccur to avoid the stratification of oxygen-enriched atmosphere.

Mild steel.

1.2.3 Supplementary Characteristics

When Spilled on Water:

1 Boiling of LNG is rapid due to the large temperaturedifference between the product and water,

2 LNG continuously spreads over an indefinitely largearea, it results in a magnification of its rate ofevaporation until vapourisation is complete,

3 No coherent ice layer forms on the water,

4 Under particular circumstances, with a methaneconcentration below 40%, flameless explosions arepossible when the LNG strikes the water. It resultsfrom an interfacial phenomenon in which LNGbecomes locally superheated at a maximum limit untila rapid boiling occurs. However, commercial LNG isfar richer in methane than 40% and would requireIengthy storage before ageing to that concentration.

5 The flammable cloud of LNG and air may extend forlarge distances downward (only methane whenwarmer than -100°C is lighter than air) because of theabsence of topographic features which normallypromote turbulent mixing.

Vapour Clouds

1 If there is no immediate ignition of an LNG spill, avapour cloud may form. The vapour cloud is long, thin,cigar shaped, and under certain meteorologicalconditions, may travel a considerable distance beforeits concentration falls below the lower flammable limit.This concentration is important, for the cloud couldignite and burn, with the flame travelling back towardsthe originating pool. The cold vapour is denser than airand thus, at least initially, hugs the surface. Weatherconditions largely determine the cloud dilution rate,with a thermal inversion greatly lengthening thedistance travelled before the cloud becomesnonflammable.

2 The major danger from an LNG vapour cloud occurswhen it is ignited. The heat from such a fire is a majorproblem. A deflagrating (simple burning) is probablyfatal to those within the cloud and outside buildingsbut is not a major threat to those beyond the cloud,though there will be burns from thermal radiations .

3 When loaded in the cargo tanks, the pressure of thevapour phase is maintained as substantially constant,slightly above atmospheric pressure.

4 The external heat passing through the tank insulationgenerates convecting currents within the bulk cargo,heated LNG rises to the surface and boils.

5 The heat necessary for the vapourisation comes fromthe LNG, and as long as the vapour is continuouslyremoved by maintaining the pressure as substantiallyconstant, the LNG remains at its boiling temperature.

6 If the vapour pressure is reduced by removing morevapour than generated, the LNG temperature willdecrease. In order to make up the equilibriumpressure corresponding to its temperature, thevapourisation of LNG is accelerated resulting in anincreased heat transfer from LNG to vapour.

ReactivityMethane is an asphyxiant in high concentrations because itdilutes the amount of oxygen in the air below that necessaryto maintain life. Due to its inactivity, methane is not asignificant air pollutant, and due to its insolubility, inactivity,and volatility it is not considered a water pollutant.

Cryogenic TemperaturesContact with LNG or with materials chilled to itstemperature of about -160°C will damage living tissue.Most metals lose their ductility at these temperatures;LNG may cause the brittle fracture of many materials. Incase of LNG spillage on the ship’s deck, the high thermalstresses generated from the restricted possibilities ofcontraction of the plating result in the fracture of the steel.The figure 1.2.3b shows a typical ship section with theminimum acceptable temperatures of the steel gradesselected for the various parts of the structure.



Illustration 1.2.3a Double Hull & Compartments Temperatures

Air Temperature = -180CWind = 5 knots

Air Temperature = -180CWind = 5 knots

LNG Within Secondary Barrier LNG Within Primary Barrier

Sea Water Temperature = 0oCAir Temperature Inside Compartment

Steel Plating Temperature

Sea Water Temperature = 0oC

-2

-3

No.

-2

-21

-23

-15

-59

-1

-20

-21

-13

-5

-25

-7

No.

-28

-18

-3

-22

-4

-23

-15

E (-30oC)

B (-10oC)

D (-20oC)

E (-30oC)

D (-20oC)

D (-20oC)

D (-20oC)D (-20oC)

E (-30oC)

D (-20oC)

E (-30oC)

E (-30oC)E (-30oC)

B (-10oC)

E (-30oC)

D (-20oC) D (-20oC)

Illustration 1.2.3b Structural Steel Grades Plan

Cofferdam(Without Heating) -63

-43Cofferdam(Without Heating)

-45

Insulation ThicknessSecondary = 0.300m

+ Primary = 0.250m---------------

0.550m

LNG CargoTemperature = -1630C

TYPICAL 65,000 m3

MID SECTION

Behaviour of LNG in the Cargo TanksWhen loaded in the cargo tanks, the pressure of thevapour phase is maintained substantially constant, slightlyabove atmospheric pressure.

The external heat passing through the tank insulationgenerates convecting currents within the bulk cargo,heated LNG rises to the surface and is boiled-off.

The heat necessary to the vapourisation comes from theLNG, and as long as the vapour is continuously removedby maintaining the pressure as substantially constant, theLNG remains at its boiling temperature.

If the vapour pressure is reduced by removing morevapour than generated, the LNG temperature willdecrease. In order to make up the equilibrium pressurecorresponding to its temperature, the vapourisation ofLNG is accelerated, resulting in an increased heat transferfrom LNG to vapour.

If the vapour pressure is increased by removing lessvapour than generated, the LNG temperature willincrease. In order to reduce the pressure to a levelcorresponding to the equilibrium with its temperature, thevapourisation of LNG is slowed down and the heattransfer from LNG to vapour, reduced.

LNG is a mixture of several components with differentphysical properties, particularly the vapourisation heat:the more volatile fraction of the cargo vapourises at agreater rate than the less volatile fraction. The vapourgenerated by the boiling of the cargo contains a higherconcentration of the more volatile fraction than the LNG.The properties of the LNG ie. the boiling point, density andheating value, have a tendency to increase during thevoyage.



1.3 Properties of Nitrogen and Inert Gas1.3.1 NitrogenNitrogen is used for the pressurisation of the inter barrierspaces, for purging of cargo pipe lines, fire extinguishingin the vent mast risers and for the sealing of the gascompressors. It is produced either by the vapourisation ofliquid nitrogen supplied from shore or by generatorswhose principle is based on hollow fibre membranes toseparate air into nitrogen and oxygen.

Physical Properties of NitrogenNitrogen is the most common gas in nature since itrepresents 79% in volume of the atmospheric air.

At room temperature, nitrogen is a colourless andodourless gas. Its density is near that of air: 1.25 kg/m3

under the standard conditions.

When liquefied, the temperature is -196°C underatmospheric pressure, density of 810 kg/m3 andvapourisation heat of 199 kJ/kg.

Properties of NitrogenMolecular weight 28.016Boiling point at 1 bar absolute –196°CLiquid SG at boiling point 1.81Vapour SG at 15°C and 1 bar absolute 0.97Gas volume/liquid volume ratio at –196°C 695Flammable limits Non Dew point of 100% pure N2 Below –80°C

Chemical PropertiesNitrogen is considered as an inert gas; it is non flammableand without chemical affinity. However, at hightemperatures, it can be combined with other gases andmetals.

Hazards

! WARNINGDue to the absence or to the very low content ofoxygen, nitrogen is an asphyxiant.

At liquid state, its low temperature will damage livingtissue and any spillage of liquid nitrogen on the ship’sdeck will result in failure as for LNG.

1.3.2 Inert GasInert gas is used to reduce the oxygen content in thecargo system, tanks, piping and compressors to preventan air/CH4 mixture prior to aeration post warm up beforerefit or repairs and prior to gassing up operation post refitbefore cooling down. Inert gas is produced on board usingan inert gas generator supplied by Navalimpianti, whichproduces inert gas at 6000m3/h with a -45°C dew pointburning low sulphur content gas oil. This plant can alsoproduce dry air at 6250m3/h and -45°C dew point (seesection 2.9 for more details).

The inert gas composition is as follows:

• oxygen <1% in vol.

• carbon dioxide <15% in vol.

• carbon monoxide <100 ppm by vol.

• hydrogen <100 ppm by vol.

• sulphur oxides (SOx) <2 ppm by vol.

• nitrogen oxides (NOx) <65 ppm by vol.

• nitrogen balance

• dew point < -45°C

• soot complete absence

• The inert gas is slightly denser than air: 1.35 kg/m3

abt at 0°C.

! WARNINGDue to its low oxygen content, inert gas is anasphyxiant.

1.3 Properties of Nitrogen and Inert Gas - Page 1Issue: 1


Avoidance of Cold Shock to MetalStructural steels suffer brittle fracture at low temperatures.Such failures can be catastrophic because, in a brittlesteel, little energy is required to propagate a fracture onceit has been initiated. Conversely in a tough material, theenergy necessary to propagate a crack will be insufficientto sustain it when it runs into sufficiently tough material.

Plain carbon structural steels have a brittle to ductilebehaviour transition which occurs generally in the range-50°C to +30°C. This, unfortunately, precludes their use asLNG materials (carriage temperature -162°C). The effectis usually monitored by measuring the energy absorbed inbreaking a notched bar, and a transition curve as shownin Illustration 1.2.3a, is typical for plain carbon steels.

For this reason materials which do not show such sharptransition from ductile to brittle fracture as the temperatureis lowered have found obvious application for use incryogenic situations in general and particularly liquidmethane carriers, for example, invar (36% nickelironalloy), austenitic stainless steel, 9% nickel steel and somealuminium alloys such as 5083 alloy. All of these materialsbehave in a ductile manner at -162°C, so that the chanceof an unstable brittle fracture propagating, even if thematerials were overloaded, is negligible.

In order to avoid brittle fracture occurring, measures mustbe taken to ensure that LNG and liquid nitrogen do notcome into contact with the steel structure of the vessel. Inaddition, various equipment is provided to deal with anyleakages which may occur.

The manifold areas are equipped with stainless steelspillways, which collects any spillage and drains itoverboard. The ship, in way of the manifolds, is providedwith a water curtain which is supplied by the deck firemain. The fire main must always be pressurised and themanifold water curtain in operation when undertaking anycargo operation. Additionally fire hoses must be laid out toeach liquid dome to deal with any small leakages whichmay develop at valves and flanges. Permanent drip traysare fitted underneath the items most likely to causeproblems and portable drip trays are provided for anyother needs.

During any type of cargo transfer, and particularly whilstloading and discharging, constant patrolling must beconducted on deck to ensure that no leakages aredeveloping.

In the event of a spillage or leakage, water spray shouldbe directed at the spillage to disperse and evaporate theliquid and to protect the steelwork. The leak must bestopped, suspending cargo operations if necessary.

In the event of a major leakage or spillage, the cargooperations must be stopped immediately, the generalalarm sounded and the emergency deck water spraysystem put into operation (refer to 5.1.1).

1.3 Properties of Nitrogen and Inert Gas - Page 2Issue: 1


Notchedbar testEnergy absorbed

T1 T2

Brittlefracture

Ductilefracture

For a typical mild steel:T1 might be –30;T2 might be +15. Although this depends on composition, heat treatment etc. the curve can shift to left or right.

Fracture transitionrange (mixed fractureappearance)

Illustration 1.3.1a Structural Steel Ductile to Brittle Transition Curve

Part 2Cargo System Description

2.1.1a Cargo Tank Lining ReinforcementIssue: 1

Key

Ballast

Void

Cofferdam

Duct Keel

Rei

nfor

ced

Are

a N

on R

einf

orce

d A

rea

Reinforced Area

Non Reinforced Area

Secondary boxes........... Type S

Primary boxes................ Type P

Secondary boxes........... Type RS

Primary boxes................ Type RP

Primary Insulation Boxes

Secondary Insulation Boxes

Secondary Membrane

Illustration 2.1.1a Cargo Tank Lining Reinforcement

Primary Membrane

Cofferdam

Void Area

Ballast Tank

Duct Keel


PART 2: CARGO SYSTEM DESCRIPTION2.1 Containment SystemGeneral DescriptionThe Cargo Containment System consists of 4 doubleinsulated cargo tanks encased within the inner hull andsituated in-line from forward to aft.

The spaces between the inner hull and outer hull are usedfor ballast and will also protect the tanks in the event of anemergency situation such as collision or grounding.

The cargo tanks are separated from other compartmentsand from each other by five transverse cofferdams whichare all dry compartments.

The ballast spaces around the cargo tanks are dividedinto two double bottom wing tanks, port and starboard foreach cargo tank. The double bottom tanks extend to theside of the cargo tanks as far up as the trunkways.

The LNG to be transported is stored in the 4 cargo tanksnumbered 1 to 4, from fore to aft. All cargo tanks have anoctagonal transverse section matching with the supportinginner hull.

Between the two transverse bulkheads, each tank iscomposed of a prism placed in a direction parallel to thekeel plate.

The boundaries of the tanks are as follows :

• One flat bottom, parallel to the keel plate raised alongthe ship’s plating by two inclined plates, one on eachside.

• Two vertical walls each extended at their upper partsby an inclined plate, in order to limit the liquid freesurface effect when the tanks are full.

• One flat top parallel to the trunk bottom.

Cargo tanks No. 1 and No. 2 are slightly different in shapedue to their position in the ship. They have a polygonalsection and the lengthwise walls are almost parallel to theship’s plating.

Cargo Containment System PrincipleThe cargo tanks are of double membrane, Gaz Transportdesign.

The inner hull, i.e. the outer shell of each of the cargotanks, is lined internally with the Gaz Transport integratedtank containment and insulation system. This consists ofa thin, flexible membrane called the primary membrane,which is in contact with the cargo, a layer of plywoodboxes filled with Perlite called the Primary insulation, asecond flexible membrane similar to the first one calledthe secondary membrane and a second layer of boxesalso filled with Perlite in contact with the inner hull calledthe Secondary insulation. The double membrane systemmeets the requirement of the relevant regulations on theCargo Containment System to provide two different“barriers” to prevent cargo leakage.

The tank lining thus consists of two identical layers ofmembranes and insulation so that in the event of a leak inthe primary barrier, the cargo will be contained indefinitelyby the secondary barrier. This system ensures that thewhole of the cargo hydrostatic loads are transmittedthrough the membranes and insulation to the inner hullplating of the ship.

The function of the membranes is to prevent leakage,while the insulation supports and transmits the loads andin addition, minimising heat exchange between the cargoand the inner hull. The secondary membrane, sandwichedbetween the two layers of insulation, not only provides asafety barrier between the two layers of insulation but alsoreduces the convection currents within the insulation.

The primary and secondary insulation spaces are under apressure controlled nitrogen atmosphere. The primaryspaces pressure must never exceed the cargo tankpressure to prevent the primary membrane fromcollapsing inwards. To avoid pollution of the secondaryinsulation space, in the event of leakage from the tank intothe primary insulation space, it is recommended that thepressure in the primary insulation space be maintained at2 mbar above the secondary insulation space pressure.

Construction of the Insulation and BarriersThe primary and secondary barriers are identical and arefabricated from cryogenic invar (a 36% nickel steel, with avery low coefficient of thermal expansion, 0.7 mm thick).

The composition of invar is :

Ni : 35 - 36.5%

C : < 0.04%

Si : < 0.25%

Mn : < 0.2 to 0.4%

S : < 0.003%

P : < 0.008%

S + P : < 0.02%

Fe : Remainder

Thermal expansion coefficient = 1.5 + 0.5 x 10-6between 0°C and -180°C(about ten times less than for stainless steel AISI 304type)

Charpy Test at -196°C, > 12 kg/cm2

The coefficient of thermal expansion is low enough toenable flat, rather than corrugated sheets to be used. Theentire surface area of the membrane is thus in contactwith the supporting insulation, so that the load which thesystem is able to carry is limited only by the load bearingcapacity of the insulation (refer to illustration 2.1.1b).

The primary and secondary insulation spaces are madeup of boxes fabricated from plywood and filled withexpanded Perlite. This insulation system allows freecirculation of nitrogen and therefore permits gas freeing orinerting to be carried out in the barrier spaces withoutdifficulty.

Perlite is obtained from a vitreous rock of volcanic originwhich, when heated to a high temperature (above 800°C),is transformed into very small balls. These balls havediameters that measure between a few hundredths to afew tenths of a millimetre. The cellular structure soobtained from the process gives the expanded perlite itslightness and thus its excellent insulation properties. Thewater repellency of the perlite is reduced by a silicontreatment.

The insulation is distributed over the hull in two specificareas :

1) Reinforced area located in the upper part of the tankand covering approximately 30% of the total tank wallsurface (including the tank ceilings). This area is fittedwith reinforced type boxes.

2) Standard area (or non-reinforced area) coveringapproximately 70% of the tank wall surface (includingthe tank bottom). This area is fitted with normal boxes(refer to illustration 2.1.1a).

The secondary and primary boxes in the reinforced areaare specially built with additional internal stiffeners toresist the impacts which can be created by the liquidsloshing inside the tanks. The primary reinforced boxeshave two 12mm thick plywood covers stapled on it.

The secondary insulation is 300mm thick whereas theprimary is 250mm thick. (The designed boil-off ratei.e. 0.18% of the total cargo tanks volume per day governsthe thickness).

2.1 Containment System - Page 1Issue: 1


Cargo TankVolume 100% Volume 98% Volume 10% L Volume 80% H

Tank No 1

Tank No 2

Tank No 3

Tank No 4

Volume m3

Volume m3

Volume m3

Volume m3

Innagem

Innagem

Innagem

Innagem

Total

11,217,642 20,740

20,740

20,740

20,740

19,972

20,103

20,083

20,101

2,568

3,462

3,462

2,866

16,592

16,592

16,592

16,592

19,132,409

19,107,477

15,841,630

65,299,158

10,993,289

18,749,761

18,725,327

15,524,797

63,993,175

1,324,448

3,168,435

3,166,899

2,128,549

9,788,331

9,627,966

16,179,078

16,170,094

13,395,685

55,372,823

Note! Innages refer to readings made by capacitive sensors

2.1.1b Construction of Containment System - Flat AreaIssue: 1

Epoxy RopeBearing Product

PerliteInsulation

InsulatingMaterial

InsulatingMaterial

InsulatingMaterial

Secondary Box

Primary Box

PlywoodBox Cover

Secondary Invar

Primary Invar

Illustration 2.1.1b Construction of Containment System - Flat Area

Insulating Material

Plywood Bridge

Wedge

Packing Washers


2.1.1c Construction of Containment System - Securing of Insulation BoxesIssue: 1

Setting Plate ForPrimary Box

Setting Plate Forthe Collar Stud

Plywood Bridge

Bearing Product

Setting Plate ForSecondary Box

Stainless Steel PlateSpot Welded To Nut Spring Washer

Packing Washers

Insulating Material

Bearing Product

Secondary Box

Primary Box

Fabric Seal

Secondary Box

Secondary Membrane

Double Hull Plating

Illustration 2.1.1c Construction of Containment System - Securing of Insulation Boxes


2.1.1d Construction of Containment System - Longitudinal DihedralIssue: 1

Position of Longitudinal Dihedral

Primary Box

Secondary Box

Primary Membrane

Secondary Membrane

Illustration 2.1.1d Construction of Containment System - Longitudinal Dihedral


2.1.1e Construction of Containment System - Corner Part Issue: 1

Position of Transverse Corner

Position of Transverse Corner 78.3°

Tra

nsve

rse

Bul

khea

d

Primary Box

Secondary Box

Primary Membrane

Primary Membrane

Secondary Membrane

Secondary Membrane

Illustration 2.1.1e Construction of Containment System - Corner Part

Tra

nsve

rse

Bul

khea

d

Invar Tube

Stainless SteelAnchoring Bars



Invar TubeStainless SteelAnchoring Bars


2.1.1f Man Hole ArrangementsIssue: 1


21

6

6050

354

3

7

10

16

71

14

18

16

22

10

1.5

1

1

1213

1215

1250

1253

1263

1270

1040

10

1.5

15

10

16

R1

20

31

18

20

3.9

Stainless Steel3 Spring Washers

40x20.4x1

Stainless Steel Rod10 L=580

32 Screws H. M16x60With Nuts H

Gasket Asbestos Elastomer 40x3

Washer Grower W16

Stainless Steel

Stainless Steel

LiquidDomeBox

Invar Th. 1.5mm

Stainless Steel60x60x6

Nut Locked BySpot Weld

The Dimension 3.9 Is Theoretically 6.9 mm.Each Spring Washer Is 2.3mm In Height And MustBe Compressed by 1mm

22

0.4

0.6

10

10

20

1256

1306

1250 0+1

0-1

PL 15

PL 30

PL 21

PL 15

(Outside Tank)

(Inside Tank)

Fibre GlassMatting + Resin

100

100

100

100

100

500

Flexible InsulatingMaterial Th. 10

1330

80

30Min

150

80

5

1450

Rigid InsulatingMaterial 55kg/m3

Rigid InsulatingMaterial 75kg/m3

14In Rigid InsulatingMaterial

Anchoring Flat Bar60x60x6Drilling 11

Stainless Steel Rod 10 L=580

Tank Ceiling

Glass Wool

Invar Duct Th. 1mmWelding JointOverlap 25mm

Invar Duct Th. 1.5mmWelding JointOverlap 25mm

Illustration 2.1.1f Man Hole ArrangementScale 1:5

Enlarged Detail Within CirclesScale 2:1

2.1.1g Man Hole Cover ArrangementsIssue: 1


10Stainless steel

150

R20

60

HandleScale 1:2

DetailScale 1:5

32 Holes 18Equally Spaced

2 Lifting Eyes

2 Handles

4 Handles

6 StaysEqually Spaced

Weld

Stainless SteelTh. 6mm

Stainless SteelTh. 16mm

1306

920

145

0

1410

Illustration 2.1.1g Man Hole Cover Arrangement

2.1.1 Gas Transport System ConstructionThe plywood boxes forming the secondary insulation arelaid on the ship’s inner hull through the transition of a hardplastic bearing product deposited on the box in the shapeof ropes by means of an automatic depositing machine.These ropes are of adjustable thickness and compensatefor the flatness defects of the inner hull. The boxes areheld in position by stainless steel coupler rods anchoredto the inner hull through their welded sockets. To absorbthe ship’s hull deformation, each coupler is fitted with anelastic coupling made up of several spring washerstightened down on the setting plates for secondary boxesby securing nuts (refer to illustration 2.1.1c). The numberof spring washers used depends on the location of thebox. Boxes on the ballast boundaries have a highernumber of spring washers (5) because the hulldeformation has the largest effect on this area.

A continuous invar tongue is held in slots running alongthe whole length of each secondary box cover. Thesecondary membrane strakes are resistance seamwelded with the continuous tongues in between.

The primary boxes are secured in position by collar studs.The collar studs are screwed into setting (clamp) platesfor collar studs linked to the setting plate for secondaryboxes by two securing screws. A plywood bridge isinstalled between the two setting plates to limit anythermal conduction through the box fixations.

To allow some flexibility, each collar stud is fitted with anelastic coupling similar to those on the secondary boxes.Each collar stud is fitted with a single spring washer andtightened down on the setting plate for primary boxes bysecuring nuts.

The primary insulation boxes have lipped invar tonguesstapled along slots running lengthwise. Continuous invartongues are positioned in the lip of the fixed tongues onthe boxes. The primary membrane strakes are resistanceseam welded with these tongues in between.

Each primary and secondary membrane strake terminateson an invar angle structure, 1.5mm thick, fitted around theperimeter of each transverse bulkhead and welded to it.Due to their superposition, the secondary and primarymembranes cross each other in both ways, forming asquare tube. This is prefabricated to allow an easiererection process and attached to the double hull by 4anchoring bars.

With this system, the membranes are directly connectedto the inner hull so that any membrane tension is directlyand uniformly taken by the ship’s structure (refer toillustrations 2.1.1d and 2.1.1e).

In the secondary and primary insulation spacesrespectively, the gaps between the secondary boxes andthe primary boxes are insulated with a combination of rigidinsulating materials and glasswool.

Cargo Tank OutfittingA vapour dome is located near the geometrical centre ofeach cargo tank ceiling. Each vapour dome is providedwith:

1) A vapour supply/return line to supply vapour to thetank when discharging, vent vapour from the tankwhilst loading and also vent the boil-off when the tankcontains cargo;

2) A spray valve arrangement for cooldown purposes;

3) Two pressure/vacuum relief valves set at 240 mbar gand -10 mbar vacuum, venting to the nearest mastriser, with tanks No. 3 & 4 via No. 3 vent mast riser;

4) Pick-up for pressure sensors;

5) Liquid line safety valves exhaust.

In addition, each cargo tank has a liquid dome locatednear the ship’s centreline at the aft part of the tank. Theliquid dome supports a tripod mast made of stainlesssteel(304L), suspended from the liquid dome and held inposition at the bottom of the tank by a sliding bearing toallow for thermal expansion or contraction depending onthe tank environment. The tripod mast consists of themain loading and discharging pipes in the form of a three-legged trellis structure and is used to support the tankaccess ladder and other piping and instrumentationequipment.

The instrumentation includes temperature and levelsensors, high and low level alarm sensors and cargopump electric cables. The two main cargo pumps aremounted on the base plate of the tripod mast, while thestripping pump is mounted on the pump tower support.The primary barrier punch device is also located nearby.An emergency pump column, float gauge column and thefilling line are also located in the liquid dome.

The four cargo tanks are connected with each other by theliquid, vapour and stripping/spray headers which arelocated on the trunk deck. The nitrogen mains supplyingthe primary and secondary insulation spaces and otherservices directly associated with the cargo system are

also located on the trunk deck together with the fire mainand deck spray main.



Cargo Handling Design

LNG Data- Chemical Composition 85.7% CH4,

8.5% C2H63.0% C3H8,1.4% N2

- Density 460 kg/m3

- Vaporisation Latent Heat 444 kJ/kg- Boil-off Gas 28,380 kJ/kg

Cargo Containment System- Natural Boil-Off Gas 2,342 kg/h- Total Fuel Gas Requirements 4,442 kg/h

at 100% MCR( 12,500 kW).- Cargo Tanks filling ratio. 98%- Pressure relief Valve Setting 240mbar gauge- Normal Operating Pressure 1,060mbar

absolute

Ship Operational Requirements- Insulation spaces inerting 36 hours

O2 content < 2% in volume.- Drying 20 Hours

dew-point < - 20°C.- Inerting 20 hours

O2 content < 2% in volume.- Natural gas filling 20 hours

CO2 content < 1% in volume.- Cooling-down 10 hours

temperature < - 130°C.- Loading

for loading flow rate 6,500m3/hand feeding pressure 1.96 bar gauge

- Voyage including approach 120 hoursand berthing.

- Unloading 12 hoursTanks simultaneously dischargingand shore back-pressure 4.2 bar gauge

- Warming up 30 hoursSecondary barrier > + 5°C.

- Inerting 20 hoursCH4 content < 1.5% in volume.

- (inert) Gas Freeing 20 hoursO2 content > 20% in volume.

Auxiliaries Main Specifications - Cargo pumps discharge head 145 mlc- High duty and low duty compressors

inlet / outlet pressure. 1.06 / 1.80 bar absolute

- Main vaporiser outlet temperatureNatural Gas / Nitrogen. -140°C/ + 20°C

- Forcing vaporiser outlet temperature. -40° C

- Heaters outlet temperatureswarming up / boil offgas heating. (0°C,+80°C)

/+20°C- Inert gas generator/ dry air

displacement cycles/ dew point. 2 cycles/-45°C

Cargo Handling Auxiliaries- Main cargo pumps, 2 per tank. 800m3/h- Stripping/spray pumps, 1 per tank. 35m3/h- Emergency cargo pump, 1 per ship. 300m3/h- H.D. compressor, 2 units equal size. 15,000m3/h- L.D. compressor, 2 units equal size. 4,000m3/h- Main vaporiser. 1,750kW

12,800kg/h- Forcing vaporiser. 675kW 3,450kg/h- Dual purpose heaters 750kW

13,500kg/h1 steam heated, 1 glycol heated.

- Vent mast heater, steam heated. 170kW 2,800kg/h- Inert gas generator. 6,500 Nm3/h- Nitrogen gas generators

2 equally sized units 57.5+57.5 m3/h- Vacuum pumps for insulation spaces

2 equally sized units. 817m3/h

Allowable Filling LimitIn compliance with RINA regulations, approved No. 43362778th March 1997Product which may be carried

• Nature: LNG

• Density: < 500kg/m3

• Temperature: > -163°C

Maximum allowable filling Limit:

• 98% of the volume of each tank

Set pressure of the Relief Valves:

• overpressure: 240mbar above atmospheric pressure

• vacuum: 10mbar below atmospheric pressure



96

96.25

96.5

96.75

97

97.25

97.5

97.75

-165 -164.75 -164.5 -164.25 -164 -163.75 -163.5 -163.25 -163 -162.75 -162.5 -162.25 -162 -161.75

Valve Setting Pressure 240 mbar GaugeValve Setting Pressure 240 mbar GaugeValve Setting Pressure 240 mbar Gauge

98

-161.5

Filling Limit %

Loading Temperature C °

2.1.2 Deterioration or FailureThe insulation system is designed to maintain the boil-offlosses from the cargo at an acceptable level, and to protectthe inner hull steel from the effect of excessively lowtemperature. If the insulation efficiency should deterioratefor any reason, the effect may be a lowering of the innerhull steel temperature, ie a cold spot and an increase inboil-off from the affected tank. Increased boil-off is of nodirect consequence to the safety of the vessel as anyexcess gas may be vented to the atmosphere via the ventmast heater line connected to No. 2 mast. The inner hullsteel temperature must, however, be maintained withinacceptable limits to prevent possible brittle fracture.

Thermocouples are distributed over the surface of theinner hull, but unless a cold spot occurs immediatelyadjacent to a sensor, these can only serve as a generalindication of steel temperature. To date, the only sure wayof detecting cold spots is by frequent visual inspection ofthe ballast spaces on the loaded voyage (see Section 6Inner Hull Inspection Route).

The grade of steel required for the inner hull of the vesselis governed by the minimum temperature this steel willreach at minimum ambient temperature, assuming thatthe primary barrier has failed, so that the LNG is in contactwith the secondary membrane.

With sea and air temperatures of 0°C and failure of theprimary barrier, the minimum temperature of the inner hullsteel will be about -8°C. For these conditions,Classification Societies require a steel grade distributionas shown in Fig 2.1.2a, where the tank top and toplongitudinal chamfer are in grade ‘D’ steel, and theremaining longitudinal steelwork grade ‘DH’, both gradeshaving a minimum operating temperature of -10°C. Thetransverse watertight bulkheads between cargo tanks areof grade ‘EH’ steel, having a minimum operatingtemperature of -20°C.

In addition to failure of the membrane, local cold spots canoccur due to failure of the insulation.

While the inner hull steel quality has been chosen towithstand the minimum temperature likely to occur inservice, prolonged operation at steel temperatures below0°C will cause ice build-up on the plating, which in turn willcause a further lowering of steel temperature due to theinsulating effect of the ice. To avoid this, glycol heatingcoils are fitted in the cofferdam spaces, of sufficientcapacity to maintain the inner hull steel temperature at 0°Cunder the worst conditions.

If a cold spot is detected either by the inner hulltemperature measurement system, or by visual inspection,the extent and location of the ice formation should berecorded. Small local cold spots are not critical, andprovided a close watch and record are kept as a checkagainst further deterioration and spreading of the iceformation, no further action is required. If the cold spot isextensive, or tending to spread rapidly, salt water sprayingshould be carried out. In the unlikely event that thisremedy is insufficient and it is considered unsafe to delaydischarge of cargo until arrival at the discharge port. Thefinal recourse will be to jettison the cargo via a spool piecefitted between liquid main and the aft jettison line by thestern nozzle using a single main cargo pump.



E

E

D

A

A

A

DH

DH

AE

D

DH A

E

D

A

Minimum Operating Temp 0C

Grade A -0 0C

Grade E -20 0C

Grade D -10 0C

Grade EH -20 0C

Grade DH -10 0C

Water Tight Bulkhead

Between Cargo Tanks

EH EH

Illustration 2.1.2a Hull Steel Grades

Duct Keel

2.2.1a Cargo Piping SystemIssue: 1


Key

Degassing line intoMain Cargo PumpCable Penetration

Illustration 2.2.1a Cargo Piping System

LNG Main Lines

LNG Stripping Lines

LNG Vapour

1

2

1

2

To EngineRoom

To InsulationSpaces

Inert Gas fromEngine Room

LD Compressor No. 1(Inboard)

Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser

HD Compressor No. 1(Inboard)

HD Compressor No. 2(Outboard)

LD Compressor No. 2(Outboard)

Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

101

161

162 114

116

115119

112

013

011

010110062

492

128126

125

124

127

485

482

483487

484

486129

170

120

122

022021

481 491

118

111

012

113117

403

160

171051

001003

053

173164

163

103

401

489

501

105

005 165

166

175055057

177168

167

107007

172152

151

102

052

002004

054

153

104

174

154

402

488

502156

106006

056

176

155

008

058178

158

157

108

023020

121

123

131

133

141

134

136

135139

132

033

031

030130

493

138

032

137

144

146

145149

142

043

041

040140

494

180

148042

000061

143

147

410

430FCV

FCV

FCV

FCV

451

453 460

452

FCV

FCV

FCV

FCV

TCV

TCV

TCV

TCV

470

190

090

480

404

405

063

454

450

420

455

456

440 411

431

AW/912

480421

441

400

406

2.2 Cargo Piping System2.2.1 DescriptionThe cargo piping system is illustrated in a simplifiedperspective drawing showing only the principal features ofthe system.

Liquid cargo is loaded and discharged via the twocrossover lines at midships and is delivered to and fromeach cargo tank liquid dome via the main liquid line whichruns fore and aft along the trunk deck. Each crossover lineat midships separates into two loading/dischargingconnections, port and stbd, making a total of fourloading/discharge connections on each side of the ship.

The cargo tank vapour domes are maintained incommunication with each other by the vapour mainrunning fore and aft along the trunk deck. The vapourmain also has a cross connection at the midship manifoldfor use in regulating tank pressures when loading anddischarging.

When loading, the vapour main and crossover, togetherwith the HD compressors are used to return the displacedgas from the tanks back to the shore installation. Whendischarging, the vapour main is used in conjunction witheither the vapour crossover, or a vaporiser, to supply gasto the tanks to replace the outgoing liquid cargo.

The stripping/spray line can be connected to the liquidcrossover lines and can be used to drain or to cool downeach cargo tank, and also to spray during discharging ifthe return vapour is insufficient.

The vapour main and stripping/spray lines are bothconnected to the vapour dome of each tank. The vapourdomes also house the tank safety valves, pressure pickup and three samples intake. The spray line on each tankconsists of two spray assemblies inside the tank at the topto distribute the incoming liquid into several spray nozzlesin order to assist in evaporation and thus achieve a bettercooldown rate.

The large spray assembly consists of a 40.0mm bore pipeequipped with spray nozzles of 19mm diameter whereasthe smaller spray assembly consists of a 40.0mm borepipe equipped with spray nozzles of 9.5mm diameter.

The number of spray nozzles in each tank is as follows :

The stripping/spray liquid line and vapour mains havebranches to and from the cargo auxiliaries room withconnections to the compressors, heaters and vaporiser forvarious auxiliary functions. Removable bends aresupplied for fitting where necessary to allow cross-connection between the various pipework for infrequentuses such as preparing for dry dock and recommissioningafter dry dock.

The vapour main connects the gas domes to each otherfor the venting of boil off gas to the vent gas heater, whichdischarges to atmosphere through vent mast riser No. 2.The vapour main also directs the boil off cargo vapour tothe engine room for gas burning, via the LD compressorsand boil off gas heaters.

The Inert Gas and Dry-Air System (section 2.9), located inthe Engine Room, is used to supply inert gas or dry air tothe cargo tanks via piping which connects with the maincargo system through a double non-return valve and aspectacle blank to avoid gas returning to the engine room.

All of the cargo piping is welded to reduce the possibilityof joint leakage. Flanged connections are electricallybonded by means of straps provided between flanges toensure that differences in potential due to static electricitybetween cargo and other deck piping, tanks, valves andother equipment are avoided.

Both liquid and vapour systems have been designed insuch a way that expansion and contraction are absorbedin the piping configuration. This is done by means ofexpansion loops and bellows on liquid and vapour pipingrespectively.

Fixed and sliding pipe supports and guides are providedto ensure that pipe stresses are kept within acceptablelimits.

All sections of liquid piping that can be isolated, and thuspossibly trapping liquid between closed valves, areprovided with safety valves which relieve excess pressureto the nearest vapour dome. This is a safety measure,although normal working practice is to allow anyremaining liquid to warm up and boil off before closing anysuch valves.

All major valves such as the midships manifold (Port andStbd) valves, also called ESDS Manifold Valves, andindividual tank loading and discharge valves are remotelypower-operated from the Cargo console, so that allnormal cargo operations can be carried out from theCentralised Control Room.

When an ESDS is activated, the closing of manifoldvalves is effected thus discontinuing loading or unloadingoperations.

A non-return valve is fitted at the discharge flange of eachcargo pump. A 5mm hole is drilled in the valve disc toallow the tank discharge lines to drain down and be gasfreed. Non-return valves are also fitted at the dischargeflange of the compressors.

A small 6mm diameter spray nozzle is also fitted at the topof each cargo pump discharge line inside the tank to cooldown the auxiliary pump tower leg in order to maintain acold temperature through the complete discharge.

Note : Electrical bonding by means of straps is providedbetween bolted flanges. Whenever a section ofpipe or piece of equipment is unbolted, the bondingstraps MUST be replaced when the flanged joint isremade.

2.2 Cargo Piping System - Page 1Issue: 1


Cargo TankSize

Large bore 8 11 11 10

Small bore 6 9 9 8

1 2 3 4

2.2 Cargo Piping System - Page 2Issue: 1


2.2.2 Pipe Identification System

PIPELINE IDENTIFICATION SYSTEM

PIPE CONTENTS BASIC COLOUR CODE BASIC COLOUR BASIC COLOUR CODE BASICCOLOUR INDICATION COLOUR INDICATION COLOUR

LIQUID NATURAL GAS YELLOW OCHRE DARK MAUVE YELLOW OCHRE

GAS NATURAL GAS YELLOW OCHRE PRIMROSE YELLOW OCHRE

LIQUID NITROGEN YELLOW OCHRE BLUE YELLOW OCHRE

GAS NITROGEN YELLOW OCHRE EMERALD GREEN YELLOW OCHRE

INERT GAS YELLOW OCHRE BLACK YELLOW OCHRE

BALLAST WATER GREEN PRIMROSE GREEN

FIRE SPRAY SYSTEM GREEN WHITE RED WHITE GREEN

FIRE EXTINGUISHING GREEN RED GREEN

GLYCOLED WATER GREEN BLUE CRIMSON BLUE GREEN

FRESH WATER GREEN WHITE AUXILIARY WHITE GREEN

BLUE

DRINKING WATER GREEN AUXILIARY BLUE GREEN

SEA WATER G R E E N

BILGE WATER GREEN BROWN GREEN

SANITARY WATER GREEN BLACK GREEN

FEED WATER GREEN CRIMSON WHITE CRIMSON GREEN

CONDENSATE GREEN CRIMSON EM. GREEN CRIMSON GREEN

FRESH WATER COOLING PLANT GREEN WHITE GREEN

FUEL OIL BROWN BLACK BROWN

DIESEL OIL BROWN WHITE BROWN

LUB OIL BROWN EMERALD GREEN BROWN

HYDRAULIC POWER BROWN SALMON PINK BROWN

CHEMICAL DRY POWDER BLACK RED BLACK

CO2 FLOODLINE BLACK RED EM. GREEN RED BLACK

DRAINS B L A C K

SUPERHEATED STEAM SILVER GREY RED SILVER GREY

DESUPERHEATED STEAM SILVER GREY RED SILVER GREY RED SILVER GREY

AUX. STEAM SILVER GREY RED SILVER RED SILVER RED SILVER GREY

GREY GREY

EXHAUST STEAM SILVER GREY BLUE SILVER GREY

COMPRESSED AIR L I G H T B L U E

ELECTRIC CONDUITS O R A N G E

2.2 Cargo Piping System Page 3Issue: 1


CL/ 128 VFCL/ 114 VRCL/ 119 VRCL/ 112 VRCL/ 117 VRCL/ 106 VRCL/ 111 VRCL/ 104 VRCL/ 109 VRCL/ 159 VRCL/ 155 VRCL/ 171 VRCL/ 167 VRCL/ 158 VRCL/ 154 VRCL/ 170 VRCL/ 166 VRCL/ 157 VRCL/ 153 VRCL/ 169 VRCL/ 165 VRCL/ 156 VRCL/ 152 VRCL/ 168 VRCL/ 164 VRCL/ 115 VFCL/ 118 VFCL/ 113 VFCL/ 116 VFCL/ 107 VFCL/ 110 VFCL/ 105 VFCL/ 108 VFCL/ 101 VFCL/ 150 VFCL/ 103 VFCL/ 102 VX

SHIPYARDNo.

000001002003004005006007008010011012013020021022023030031032033040041042043051052053054055056057058061062063090

SNAM No.

BUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

GATEGLOBEGLOBEGLOBEGATE

GLOBEGLOBEGLOBEGATE

GLOBEGLOBEGLOBEGATE

GLOBEGLOBEGLOBE

BUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

BALL

TYPE OFVALVE

TYPE OFOPERATION

POSITION

JETTISONLOADING/UNLOADING-PORTLOADING/UNLOADING-STB’DLOADING/UNLOADING-PORTLOADING/UNLOADING-STB’DLOADING/UNLOADING-PORTLOADING/UNLOADING-STB’DLOADING/UNLOADING-PORTLOADING/UNLOADING-STB’D

FILLING TO TANK 1DELIVERY CARGO PUMP 1DELIVERY CARGO PUMP 1

DELIVERY EM’G;Y CARGO PUMPFILLING SIDE TANK 3

DELIVERY CARGO PUMP 2DELIVERY CARGO PUMP 2





DELIVERY EM’G;Y CARGO PUMPDOUBLE VALVEDOUBLE VALVEDOUBLE VALVEDOUBLE VALVEDOUBLE VALVEDOUBLE VALVEDOUBLE VALVEDOUBLE VALVE

INTERCEPT LIQUID./JETTISONINTERCEPT LIQUID./GASINTERCEPT LIQUID./GAS

SERVICE

VALVE NUMBERS LIQUID LINECORRESPONDING SHIPYARD/SNAM NUMBERS

MANUALHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULIC

MANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUAL

STERNMANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDS

MANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDS

LIQUID DOME No1LIQUID DOME No 1LIQUID DOME No 1LIQUID DOME No 1LIQUID DOME No 2LIQUID DOME No 2LIQUID DOME No 2LIQUID DOME No 2LIQUID DOME No3LIQUID DOME No3LIQUID DOME No3LIQUID DOME No 3LIQUID DOME No 4LIQUID DOME No 4LIQUID DOME No4LIQUID DOME No4

MANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDSMANIFOLDS

LIQUID DOME No4VENT MAST 2

COMPRESSOR ROOM

CG/ 352 VRCG/ 309 VRCG/ 314 VRCG/ 374 VRCG/ 351 VRCG/ 373 VFCG/ 353 VRCG/ 354 VRCG/ 356 VRCG/ 355 VRCG/357 VRCG/ 358 VRCG/ 360 VRCG/ 359 VRCG/ 361 VRCG/ 370 VFCG/ 366 VRCG/ 367 VRCG/ 368 VFCG/ 369 VFCG/ 371 VFCG/ 372 VFCG/ 381 VFCG/ 301 VFCG/ 302 VFCG/ 304 VFCG/ 305 VFCG/ 306 VFCG/ 307 VFCG/ 318 VXCG/ 313 VXCG/ 308 VXCG/ 380 VFCG/ 379 VFCG/ 378 VFCG/ 377 VF

SHIPYARDNo.

400401402403404405406410411420421430431440441450451452453454460470480481482483484485486487488489491492493494

SNAM No.

BUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

BALLBUTTERFLY

BALLBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

BALLBALLBALL

BUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

TYPE OFVALVE

TYPE OFOPERATION

POSITION SERVICE

HYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULIC

MANUALHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULIC

MANUALHYDRAULICHYDRAULIC

MANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUAL

COMPRESSOR ROOMMANIFOLD-PORTMANIFOLD-STB’D

MIDSHIPCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOMCOMPRESSOR ROOM

VENT MAST 2VENT MAST 2VENT MAST 2VENT MAST 2VENT MAST 2VENT MAST 2

GAS DOME No1GAS DOME No2GAS DOME No3GAS DOME No4



CS/ 212 VFCS/ 226 VRCS/ 209 VRCS/ 223 VRCL/ 206 VRCS/ 220 VRCS/ 203 VRCL/ 217 VRCS/ 231 VRCS/ 239 VRCS/ 243 VRCS/ 288 VRCS/ 250 VRCS/ 254 VRCS/ 258 VRCS/ 262 VRCS/ 266 VRCS/ 285 VRCS/ 230 VRCS/ 238 VRCS/ 242 VRCS/ 287 VRCS/ 249 VRCS/ 253 VRCS/ 257 VRCS/ 261 VFCS/ 265 VFCS/ 284 VFCS/ 229 VFCS/ 237 VFCS/ 241 VFCS/ 244 VFCS/ 248 VFCS/ 252 VFCS/ 256 VFCS/ 260 VFCS/ 264 VXCS/ 283 VRCS/ 228 VRCS/ 236 VR

SHIPYARDNo.

101102103104105106107108110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141

SNAM No.

BALLBALLBALLBALLBALLBALLBALLBALL

GLOBEBALLBALLBALLBALLBALLBALLBALLBALLBALL



GLOBEBALL

TYPE OFVALVE

TYPE OFOPERATION

POSITION

LOADING/UNLOADINGLOADING/UNLOADINGLOADING/UNLOADINGLOADING/UNLOADINGLOADING/UNLOADINGLOADING/UNLOADINGLOADING/UNLOADINGLOADING/UNLOADING

DELIVERY STR. PUMP 1

SPRAY COOLING


SPRAY COOLING


SPRAY COOLING


SERVICE

VALVE NUMBERS LIQUID LINE CARGO STRIPPINGCORRESPONDING SHIPYARD/SNAM NUMBERS

MANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUAL

HYDRAULICMANUALMANUALMANUAL

HYDRAULICMANUALMANUALMANUALMANUALMANUAL





HYDRAULICMANUAL1

MANIFOLDMANIFOLDMANIFOLDMANIFOLDMANIFOLDMANIFOLDMANIFOLDMANIFOLD

LIQUID DOME No1LIQUID DOME No 1LIQUID DOME No1LIQUID DOME No 1

GAS DOME No1GAS DOME No1GAS DOME No1GAS DOME No1GAS DOME No1GAS DOME No1





LIQUID DOME No4LIQUID DOME No 1

CS/ 240 VRCS/ 286 VRCS/ 247 VFCS/ 251 VRCS/ 255 VRCS/ 259 VRCS/ 263 VRCS/282 VRCS/ 225 VRCS/ 224 VRCS/ 222 VRCS/ 221 VRCS/ 219 VFCS/ 218 VRCS/ 216 VRCS/215 VFCS/ 268 VFCS/ 213 VFCS/ 214 VFCS/ 210 VFCS/ 211 VFCS/ 207 VFCS/ 208 VFCS 204 VFCS/ 205 VFCS/ 269 VFCS/ 196 VXCS/ 200 VXCS/ 195 VXCS/ 199 VFCS/ 194 VFCS/ 198 VFCS/ 193 VFCS/ 197 VXCS/ 201 VXCS/ 202 VXCS/ 132 VXCS/ 131 VXCS/ 130 VXCS/ 129 VX

SHIPYARDNo.

142143144145146147148149151152153154155156157158160161162163164165166167168170171172173174175176177178180190XX1XX2XX3XX4

SNAM No.

BALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALLBALL

REG. VALVEREG. VALVEREG. VALVEREG. VALVE

TYPE OFVALVE

TYPE OFOPERATIO

POSITION

SPRAY COOLING

INTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPTINTERCEPT

INTERCEPTINTERCEPT STR. LIQUID/LINE1

SERVICE

MANUALMANUAL

HYDRAULICMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUALMANUAL

PNEUMATICPNEUMATICPNEUMATICPNEUMATIC

LIQUID DOME No1LIQUID DOME No 1




GAS DOME No1GAS DOME No2GAS DOME No3GAS DOME No4


VALVE NUMBERS BALLAST SYSTEMCORRESPONDING SHIPYARD/SNAM NUMBERS


AZ/ 001 VRAZ/ 028 VRAZ/ 027 VRAZ/ 029 VFAZ/ 033 VRAZ/ 020 VFAZ/ 032 VRAZ/ 039 VFAZ/ 057 VRAZ/002 VRAZ/ 003 VRAZ/ 010 VRAZ/ 004 VRAZ/ 005 VRAZ/ 026 VRAZ/ 006 VRAZ/ 007 VRAZ/ 059 VRAZ/ 008 VRAZ/ 009 VRAZ/ 025 VRAZ/ 044 VRAZ/ 022 VRAZ/ 058 VRAZ/ 037 VRAZ/ 066 VFAZ/ 034 VRAZ/ 067 VFAZ/ 023 VRAZ/ 065 VRAZ/ 196 VRAZ/ 021 VFAZ/ 011 VRAZ/ 012 VRAZ/ 013 VRAZ/ 056 VRAZ/ 014 VRAZ/ 015 VRAZ/ 038 VF

SHIPYARDNo.

200201202203204205205206210211212220221222230231232240241242250255260265270275280285290291300305310311312320321322330

SNAM No.

BUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

TYPE OFVALVE

TYPE OFOPERATION

POSITION

BALLAST FORE PEAKNO.1 BALLAST PUMP SUCTIONNO.2 BALLAST PUMP SUCTION

E.R BILGE SUCTIONNO.2 BALLAST PUMP

DISCHARGEE.R. BULKHEAD

NO.1 BALLAST PUMPDISCHARGE

TO I.G. SCRUBBERINTERCEPTION

BALLAST TANK No.1 PORTBALLAST TANK No.1 STARBOARD

MAIN INTERCEPTIONBALLAST TANK No.2 PORT

BALLAST TANK No.2 STARBOARDINTERCEPTION

BALLAST TANK No.3 PORTBALLAST TANK No.3 STARBOARD

INTERCEPTIONBALLAST TANK No.4 PORT

BALLAST TANK No.4 STARBOARDINTERCEPTION

BALLAST PUMP OVERBOARD INTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTIONINTERCEPTION

STRIPPING LINE INTERCEPTIONSTRIPPING BAL. TANK No.1

PORTSTRIPPING BAL. TANK No.1

STB’DINTERCEPTION

SERVICE

FORE PEAKFLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.PIPE TUNNELPIPE TUNNELPIPE TUNNELPIPE TUNNELPIPE TUNNELPIPE TUNNEL

FLOORING E.R.PIPE TUNNELPIPE TUNNEL


FLOORING E.R.E.R. FIRST DECKFLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.FLOORING E.R.PIPE TUNNELPIPE TUNNELPIPE TUNNELPIPE TUNNELPIPE TUNNELPIPE TUNNEL

FLOORING E.R.

AZ/ 016 VRAZ/ 017 VRAZ/ 040 VFAZ/ 018 VRAZ/ 019 VRAZ/ 045 VFAZ/ 043 VF

SHIPYARDNo.

331332340341342350355

SNAM No.

BUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLYBUTTERFLY

TYPE OFVALVE

TYPE OFOPERATION

POSITION

STRIPPING BAL. TANK No.3 PORTSTRIPPING BAL. TANK No.3

STB’DSTRIPPING LINE SUCTION

STRIPPING BAL. TANK No.4 PORTSTRIPPING BAL. TANK No.4

STB’DPIPE TUNNEL BILGE

EDUCTOR OVERBOARD

SERVICE

HYDRAULICHYDRAULIC

MANUALHYDRAULICHYDRAULIC

MANUALMANUAL

PIPE TUNNELPIPE TUNNEL


FLOORING E.R.E.R. FIRST DECK

HYDRAULICHYDRAULICHYDRAULIC

MANUALHYDRAULIC

MANUALHYDRAULIC

MANUALHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULIC

MANUALHYDRAULIC

MANUALHYDRAULICHYDRAULICHYDRAULIC

MANUALHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULICHYDRAULIC

MANUAL

2.2.3 Pressure Control

Methods of Maintaining the Cargo Tanks atAtmospheric PressureHeat transfer to the liquid cargo during cargo operationsor, during a voyage, will result in the generation of boil-offfrom the cargo.

Since some boil-off is generated at all times when liquidcargo is present in a tank, it would generate excessivepressure rises within the tank if allowed to accumulate. Itmust therefore be continuously removed to maintain thepressure in the tanks near atmospheric.

There are three methods of dealing with boil-off tomaintain the tanks at the required pressure:

1 On passage it is supplied to the boilers and burned asa fuel;

2 Alongside it is returned to shore through the vapourreturn line;

3 In unusual circumstances (eg. excessive boil-off ratesor failure of gas burning system) it may be heated andvented to atmosphere via vent mast No.2. Not onlydoes this method involve a substantial loss of cargobut precautions must also be taken for the releasedgases not to enter the accommodation and engineroom areas.

During cargo discharge it is necessary to replace thedischarged volume of cargo with cold vapour in order tomaintain a slight positive pressure in the tanks. This isnormally dealt with by supplying vapour from the shore viathe vapour return line. In case of failure of this system, itis possible to feed liquid cargo to the vaporiser whichproduces cold vapour for delivery to the cargo tanks, thusmaintaining the required pressure.

During certain cargo operations, ie drying, inerting,purging, heating and aerating, when there is no liquidcargo present, it is also necessary to regulate theatmosphere in the tanks to maintain a set pressure closeto atmospheric pressure. During heating (warming-up) ofcargo tanks, the extra vapours produced are normallyburned as fuel as much as possible, otherwise they arevented via the mast riser. Each individual cargo operationis described in detail under individual chapters on cargohandling procedures.Various safety devices are installed to prevent over andunder pressure of the cargo tanks in the event of amalfunction.

! WARNINGVenting to atmosphere is not recommended at alltimes but within harbour limits it is usually prohibitedby port authorities and consequently it must beensured that the venting system normally remainsshut off during port entry and departure.

! CAUTIONAll tanks should be kept common on the vapourheader in order to create a buffer; it is necessary toensure that the tank pressure is not above 1200 mbarabsolute when approaching or leaving port.

! CAUTIONThe pressure in the tanks must, at all times, bemaintained at least 10 mbar above atmospheric, and6mbar above the pressure in the insulation spaces.

2.2.4 Valve Designation



System Valve No.s

Liquid N.G. 000-090

Cargo Spray/Stripping 101-194

Ballast Installation 200-355

Vapour N.G. 400-494


ELECTRICMOTOR

PT1

Vapour In

Anti-Surge Line

Anti-SurgeValve

Vapour Out

TI

TT

TI

TT

FT1

FCSURGECONTROLLER

HD COMPRESSOR

Electric Motors Room Cargo Auxiliaries Room

Key

LNG Vapour

Electrical

CCRControl Panel

Illustration 2.2.4a Gas Compressors Surge Control System

TripTAHH

TA

HFIC

PT2

TT

2.2.4 Anti Surge OperationThere are four gas compressors, 2 high duty and 2 lowduty with the electric motors mounted in the motor room.The high duty compressors are driven by single speedelectric motors, while the low duty compressors are drivenby electric motors with a frequency speed-control system.The compressors are protected from damage by surging,by an anti-surge controller. This measures the differentialpressure across the compressor using pressuretransmitters PT1 & PT2, which outputs to the surgecontrol unit FIC. The output signal from FIC to anti-surgevalve FC controls the flow back to the compressor suction.Provided that the flow of gas rises when the differentialrises or vice versa, the surge valve will remain closed.

In the event that the differential pressure rises and timeflow drops, the output from the FIC rises and opens thesurge valve. This maintains the compressor below thesurge line.

The suction temperature must be closely monitored duringthis period as compressor energy is still being instilled inthe gas being pumped. The gas is now being recirculated,which will result in a rapid rise in the compressortemperature, and unless swift action is taken to reduce thethroughput, damage will occur to the compressor.

! CAUTION

Do not operate the compressor in surge.

Compressor surge is characterised by erraticcompressor inlet and discharge pressure and (usuallyaudible) flow pulsations.

There is no surge control protection whilst in themanualmode.



2.3.1a Main Cargo PumpIssue: 1

0 200 400 600 800 1000

300

400

Flow m3/h

InputCurrentAmps

6.0

7.0

DischargePress-Bar

Manufacturer JC. CarterPump model 60715-3468-127Rated flow (m3/h) 800Minimum flow (m3/h) 300Maximum flow (m3/h) 1100Rated head (m) 145Motor speed (rpm) 1780Rated motor power (kw) 275

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UpperBearing

Rotor andShaft

Pump Discharge

ElectricalTerminal Box

Stator

LowerBearing

Impeller

Inducer

Key

Liquid Flow

Lubrication Flow

Illustration 2.3.1a Main Cargo Pump

1200

500

200

0 200 400 600 800 1000 1200

8.0

9.0 Allowable Flow Range300 to 1100 m3/h

Flow m3/h


2.3 Cargo PumpsGeneral DescriptionThe ship is fitted with submerged, electric, single-stage,centrifugal cargo pumps manufactured by J.C. Carter.They are installed at the bottom of each tank.

Two sizes of pump, main cargo and stripping/spray pumpsare installed as fixed units, ie 2 main cargo pumps andone stripping/spray pump per tank.

In addition, provision is made at each tank to introduce anauxiliary (emergency) pump in case of total cargo pumpfailure. One auxiliary pump is available on each ship.

OperationThe cargo pumps are started and stopped from the CargoControl Room. The control being obtained through thedifferent mimics where the cargo pumps are present. Theywill also be automatically stopped in the event of variousshut-down trips being activated both in relation to the cargosystem and the pumps themselves. Starters are fitted withan auto-transformer to limit starting current torque. Eachcargo pump electric motor is protected from :

- Thermal overload (overcurrent)

- Under-current (no load operation)

- Imbalance between phases (single-phasing)

Due to high electrical load imposed on the cargoswitchboards by the running of main cargo pumps, thereis a limitation on the number of pumps that can be rundepending on the electrical power availability, ie :

• 8 main cargo pumps when at least 2 generators are inparallel.

• 4 main cargo pumps when only one generator is inuse and or both cargo switchboards are coupled.

The pumps should be started individually andsequentially, as required, with the pump discharge valveslightly open (approximately 15%).

If there is low liquid level, the discharge pipe of the maincargo pump must be filled by the stripping pump beforestarting the main pump.

The starting procedure for the main cargo pumps is asfollows :

1 Check to confirm that

- No pumps in starting phase (when cargoswitchboards are bus-tie connected, only one pumpis allowed in the starting phase)

2 Select the cargo pumps mimic display.

3 Choose the discharge valve symbol for the pump to bestarted.

The following information appears in the pop upwindow near the bottom of the screen.

Valve ’s reference% OPEN

% CLOSE

4 Open the discharge valve 15% maximum. If the valveposition does not correspond to the request, a time-out (valve failed) alarm is displayed.

5 Choose the pump symbol for starting the pump. Thefollowing information appears in the pop up windownear the bottom of the screen.

Pump ’s reference

STARTSTOP

Valve ’s referenceOPENSTOP

CLOSE

6 Start the associated main cargo pump.

Once the pump has started, OPEN the discharge valvegradually, using the Bailey key board control to set thevalve opening position to give the required flow-rate.

The discharge pressure and pump motor amperes aremonitored and adjusted to ensure the most efficientoperation as indicated on the pump performance graph,with due regard being taken of the head of liquid on thepump discharge flange.

The discharge pressure indications are on the mimicscreen itself whereas the ammeters are analog readingson the cargo console.

The manifold valves are ON-OFF valves and arecontrolled from the mimic screen, the states of which areindicated from limit switches.

Note : To avoid damage, three restarts are allowed with aminimum of five seconds delay between eachattempt. Then, a 15 minutes waiting period mustbe observed, after which another three restarts areallowed.

The starting procedure for stripping/spray pumps is asfollows:

1 Select the mimic display for the stripping/spray pumpsoperation.

2 Choose the pump symbol for the pump to be started.

The following information appears in the pop upwindow near the bottom of the screen.

Valve ’s reference% OPEN

% CLOSE

3 Open the discharge valve 15% (maximum). If thevalve position does not correspond to the request, atime-out (valve failed) alarm is displayed.

4 Choose the pump symbol for starting the pump. Thefollowing information appears in the pop up windownear the bottom of the screen

Pump ’s referenceSTARTSTOP

Valve ’s referenceOPENSTOP

CLOSE

5 Start the associated stripping/spray pump.

2.3.1 Main Cargo Pumps(See Illustration 2.3.1a)Each main cargo pump is rated at 800m3/h at 145m headof LNG. For optimum discharge results, bulk discharge willbe carried out with 8 pumps. The capacity of the dischargeterminal will regulate the discharge rate accordingly.

The pump discharge valves will be throttled to ensureoptimum performance as indicated by the pumpperformance graph.

During the course of discharge, changes in flow rate andtank levels will alter these readings and the dischargevalve will have to be re-adjusted accordingly.

Under normal conditions it should be possible to maintain fulldischarge rate until the tank level approaches approximatelyone metre above the the pump inlet. The current and pumpdischarge pressure should be monitored continuously andone pump stopped.

To prevent cavitation and loss of suction when dischargepressure and amperes start to fall, begin to close thedischarge valve whilst maintaining the discharge pressurewithin a range of 45% to 55% of design discharge pressure.The remaining pump is to be progressively throttled in tomaintain suction and to prevent operation of the lowdischarge pressure trip. In order to maintain the bottom of

cargo tanks in a cold condition, the levels should bereduced to the following levels in ballast for the trade routeLA SPEZIA / SKIKDA / ARZEW

Tank 1 Tank 2 Tank 3 Tank 447cm 30cm 30cm 30cm216m3 242m3 242m3 200m3

The cargo pumps may be run in closed circuit on their owntanks by opening the loading valve. This may be requiredif the discharge is temporarily halted when the tanks areat low level, thereby avoiding the problems of restartingwith low level and low discharge pressure.

The cargo pumps will be automatically stopped shouldany of the following occur:

a) Cargo tank pressure below or equal to primary spacepressure plus 5mbar (ESDS);

b) Vapour header pressure below or equal toatmospheric pressure plus 3mbar (ESDS);

c) Very high high level in cargo tank (99% volume)(ESDS);

d) Activation of Emergency shut down trip:

(8 push buttons and 8 fusible elements) (ESDS);

e) Activation of ship/shore pneumatic, or electrical shut-down (ESDS); (Shore Trip)

f) Motor single-phasing;

g) Low motor current;

h) High motor current (Electrical overload);

i) Low discharge pressure with time delay at starting;

j) Cargo Control Room stop.

ESDS signifies that all cargo plant is shut-down in additionto the pump(s) on the tank(s) in question.

Note: A megger test of all pumps is to be carried out afterleaving the loading port in order to establish that allpumps are operational and to allow time forinstallation of an auxiliary cargo pump should it benecessary.

!CAUTION

Do not allow the pump to run dr y. Even short periodsof dry running will result in motor or bearing failure.

2.3 Cargo Pumps - Page 1Issue: 1


2.3.2a Spray PumpIssue: 1

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UpperBearing

Rotor andShaft

ElectricalTerminal Box

Stator

LowerBearing

Impeller

Inducer

Key

Liquid Flow

Lubrication Flow

Illustration 2.3.2a Spray Pump

0 10 20 30 40 50

20

25

30

35

40

Flow m3/h

InputCurrentAmps

0 10 20 30 40 50

7.0

8.0

The Allowable Flow Range10 to 50 m3/h

DischargePress-Bar

Manufacturer JC. CarterPump model 6337-2119-138Rated flow (m3/h) 35Minimum flow (m3/h) 14Maximum flow (m3/h) 44Rated head (m) 145Motor speed (rpm) 3560Rated motor power (kw) 18


LNG LERICI


Cargo Systems and Operating Manual

2.3.2 Stripping/Spray Pumps(See Illustration 2.3.2a)A stripping/spray pump is installed in each tank for coolingpurposes and for forced vaporisation of LNG. It is rated at35 m3/h at 145 meters head of LNG.

The pumps are started and stopped from the CargoControl Room. In an emergency all pumps will be stoppedby activation of the Emergency Shut Down System trip.

The instances when these pumps can be used are:

i) To cool down the main liquid lines prior todischarging;

ii) To cool the tank membranes and insulation duringballast voyage prior to arrival at loading terminal bydischarging LNG to the spray header in the tanks;

iii) To pump LNG from the tanks to the forcing vaporiserwhen forced vaporisation of LNG in the boilers isrequired; and

iv) To enable each cargo tank to be stripped as dry aspossible for reasons such as technical requirementsinvolving cargo tank entry.

Whenever possible the stripping/spray pump should bestarted early enough to avoid possible starting problemsdue to very low tank levels (about 0.5m minimum).

The stripping/spray pumps will be stopped automaticallyshould any of the following occur:

a) Cargo tank pressure below or equal to primary spacepressure plus 5mbar (ESDS);

b) Vapour header pressure below or equal to atmosphericpressure plus 3mbar (ESDS);

c) Very high high level in cargo tank (99% volumeESDS);

d) Activation of Emergency Shut Down System trip: (8push buttons, and 8 fusible elements) (ESDS);

e) Activation of ship/shore pneumatic, or electrical shut-down (ESDS); (shore trip)

f) Motor single-phasing;

g) Low motor current;

h) High motor current (Electrical overload);

i) Low discharge pressure with time delay at starting;

j) Cargo Control Room stop.

Note: A megger test of all pumps is to be carried out afterleaving the loading port in order to establish that allpumps are operational and to allow time forinstallation of an auxiliary cargo pump should it benecessary.

2.3.3a Emergency PumpIssue: 1


0 100 200 300 400 500

100

125

150

Flow m3/h

InputCurrentAmps

DischargePress-Bar

Manufacturer JC. CarterPump model 6224-2740-599Rated flow (m3/h) 300 Minimum flow (m3/h) 120Maximum flow (m3/h) 360Rated head (m) 145Motor speed (rpm) 3560Rated motor power (kw) 108

Illustration 2.3.3a Emergency Pump

LubricationFilter

Inducer

Impeller

LowerBearing

MotorStator

Rotor andShaft Assembly

UpperBearing

DeliveryColumn

FootvalveOpening

Key

Liquid Flow

Lubrication Flow

175

200

0 100 200 300 400 500

6

7

8

Flow m3/h

9

2.3.3 Emergency Cargo Pump(See Illustration 2.3.3a)(Also see section 4.4.3 for installation and use ofemergency cargo pump).

Each cargo tank is equipped with an emergency pumpwell. This pump well has a foot valve which is held in theclosed position by highly loaded springs.

Should a failure of either one or both main cargo pumpsin one tank require the use of the emergency pump, theemergency pump is lowered into the pump well after thewell has been purged with nitrogen.

The weight of the emergency pump overcomes thecompression of the springs to open the foot valve.

A small flow of nitrogen should be maintained whilst thepump is being installed.

Note : Before undertaking this operation it is important toreduce the tank pressure near to atmosphericpressure and to keep at this level throughout theentire operation.

Electrical connections are made to the fixed junction boxwhich is located adjacent to each pump well.

A dedicated starter is available with one circuit breakerwhich can be placed in either of the port and starboardcargo switchboard depending on requirements.

All safety devices are transferred to the emergency pumpwhen the circuit breaker is engaged, as they are the sameas for the main pumps.

The control for the emergency pumps is the same as thestripping/spray pump through the mimic display. Aselection switch on the cargo control room console isswitched over to the required position. Indication is givenon the mimic display to show if the pump is selected ornot.

Note: A megger test of all pumps is to be carried out afterleaving the loading port in order to establish that allpumps are operational and to allow time forinstallation of an emergency cargo pump should itbe necessary.



2.4 Compressor House2.4.1 DescriptionA compressor house built on deck forward of theaccommodation block which houses the followingequipment.

2 X H.D. gas compressors. Cryostar type CM400/55 forcargo loading duties.

2 X L.D. gas compressors Cryostar type CM 300/45 forsupplying boil off gas to the E.R. for fuel.

2 X Vacuum pumps MPR industries type P.80 for reducingthe pressure in the inter barrier spaces.

The electric motors for the above machines are situated inthe adjacent motor room and drive through the bulkheadvia bulkhead seals.

Gas heaters. Glycol heated Cryostar Type 187-ST. 18/16- 2.75 used for heating boil off gas to the E.R under normalconditions and for supplying heated gas to the cargo tanksduring warm up operations. These are of the shell andstraight tube design.

The glycol plant (heaters and circulating pumps) aremounted in the motor room.

2 vaporisers (1 main, 1 forcing), which are steam heatedare provided for use where there is no gas return fromshore during discharge, and for vaporising LNG for usewhen purging tanks to remove inert gas prior to cooldownafter refit, for insulating spaces first inerting and for gasburning.

The forcing vaporiser will be used to maintain sufficientgas pressure in the system for gas burning when naturalheat leakage into the system is insufficient to maintainpressure.

Main vaporiser cryostar model 75-UT-25/21-3.6

Forcing vaporiser cryostar model 15-UT-25/21-4.2

There is a demister mounted down stream of the forcingvaporiser to ensure that any entrained droplets of LNGleaving the vaporiser are removed prior to the gasreaching the compressor suctions.Demister is a Cryostar VMS-10/12-700

The motor room has a supply fan with a natural exhaust,while the compressor room is natural supply with anexhaust fan.

The air lock for the motor room is supplied from the motorroom supply fan. A visual and audible alarm is providedadjacent to the air lock if both doors are open at the sametime.

In the starboard aft corner of the motor room there is anindependent CO2 flooding system for the protection of themotor room and compressor house (see section 5.1.4 fordetails).

An exhaust fan sited on the deck above the compressorroom is used to ventilate the CO2 room.

2.4 Compressor House - Page 1Issue: 1


2.5.1a Boil - Off / Warm - Up Gas HeaterIssue: 1


TemperatureControl

GlycolWaterOutlet Vent

FCV

TCV

A/M

LATripAlarm

VDU

To Liquidor VapourMain

GylcolWaterInlet

To EngineRoom Boilers

Master GasFuel Valve

YA/5141A/BWarming Up andBoil Off Heater

FromCompressor

T

TPI

>85H

L

c

PT LTT

TT TT

TI

KBD

SoftwareSwitch

SoftwareSwitch

Indic.A/M

Indic.A/M

Master GasFuel ValveShut Down-L.D.CompressorShut Down

TIC

ZIO

C

H

Key

LNG Vapour

Warm LNG Vapour

Glycol Water

Electrical

Instrument Air

A/MXL

HICHS

PIPI

HIC HS

XL

o

TI

(0 C)Lo

Illustration 2.5.1a Boil off / Warm up Gas Heater

T

LSS

HYInstrumentAir Supply

Manual Trip

TripAlarm

Manual Trip

TI

2.5 Gas Heaters2.5.1 Boil-off/ Warm Up Gas Heaters ( YA/5141 A/B)Two glycoled water heaters, installed in the compressorroom, are provided for dual purpose: heating the boil offgas for burning in the boilers and heating the gas forwarmup of the cargo tanks.

a) Warm-up (see section 4.3.6)

This is part of the preparations prior to refit work involvingtank entry. Cargo vapour is circulated in a closed cycle,from the tanks, through the high duty compressors,through both heaters in parallel, and back to the tanks.The heat input to the vapour in the heaters warms thecargo tank membrane and insulation. Initially, themaximum heating capacity of both heaters is required forthis operation, (see below), gradually decreasing as thewarm-up progresses.

b) Purge-drying (see section 4.3.3)

If the cargo tanks contain inert gas, e.g. after refit workinvolving tank entry, then immediately prior to cool-down,the inert gas is displayed by warm gas.

For both the above operations, the maximum heatingcapacity of the heaters is required, as follows:

Flow max 12700 kg/hHeat input Glycoled water inlet

temp. 80°C Vapour temperature inlet min -130°CVapour temperature outlet 0 to 80°C

! CAUTIONWhen returning heated vapour to the cargo tanks, thetemperature at the heater outlet should not exceed+85°C, to avoid possible damage to the cargo tankinsulation and safety valves.

c) Heating boil-off vapour for the boilers

Boil-off vapour is drawn from the tanks by the LDcompressor, which discharges it through one of the gasheaters and along the gas line to the boilers.

A reduced heat input is required for this operation, varyingfrom 10% to 100% of the maximum rating, as follows:

Flow max 12700 kg/hHeat input Glycoled water inlet

temp. 80°C Vapour temperature inlet min -130°CVapour temperature outlet 0 to 50°C

Manufacturer Cryostar

Model 187-ST-18/16-2.75.Shell and straighttube design

Heating medium Glycoled water

Inlet temp of the medium (°C) 80

Maximum gas flow (kg/h) 12700

Mini inlet gas temperature (°C) -130

Outlet gas temperature (°C) 0 to 50.

• The inlet gas valves are operated and the temperaturecontrol set locally or from the CCR.

• Alarms are provided on the outlet gas temperature.

Operation ProcedureTo Prepare Heaters for Use

Open glycol shut off valves inlet and outlets on heater andensure hot glycol supply. Open manual gas inlet and outletvalves.

Select sensor temperature

If in use, gas delivery to boiler select AF 663.01

Ensure set points of gas to engine are correct(approximately 20°C )

When E.R. gas security valve is open and compressorrunning ensure that temperature is being controlled.

On Completation

For warm-up - select by pop-up sel 1.01 - sel 1.02

(AF 661.01 Heater 1, AF 661.02 Heater 2) warm-uptemperature selectors.

Close manual gas inlet and outlet valves shut glycol inletand outlet ensure system is shut down from CCR.

Controls and Settings

Gas inlet temp

Gas outlet temp

Gas to E.R. temp low

Trips: Master gas fuel valve from L.D. gas compressor.

Alarm Low Low Low HighPoint

Boil off/warm up heater. AF 661.01 -116°C - +85°CGas out lettemperature. AF 661.02 -116°C - +85°CGas deliverytemperature. AF 663.01 - 5°C -Glycol heaterout let AF 653.01 - - +90°Ctemperature. AF 653.02 - - +90°CGlycol pump AF 657.01 +10°C - -suction AF 657.02 +10°C - -temperature. AF 657.03 +10°C - -

2.5 Gas Heaters - Page 1Issue: 1


2.5.2a Vent Gas HeaterIssue: 1


Illustration 2.5.2a Vent Gas Heater

Key

LNG Vapour

LNG Liquid

Warm LNG Vapour

Steam

Condensate

Electrical

Instrument Air

PB

ZA

ZLC

TI

ZLO

TT

Vent

SoftwareSwitch

Steam

AlarmValve Open

EmergencyClosing fromWheel House andCargo Control Roomby Push Buttons

Close

A/M ZS

PICA/MSET

A/MSETPIC

PI PI

LA TI TI

Drain

No.2VentingMast

VapourMain

Vent Gas Heater

FromCompressorRoom

Liquid Main

TH H

LL

TT

LS

TT

PI

TI PT PI

PT

PT

ZSC

LG

LT

LC

ZSO

PI

Steam ValveClosing

Trip SignalAlarms in

Wheel House andCargo Control Room

InstrumentAir Supply

ValveClosed

T

486

485

484

482481

487

483

062

YA5142

T

HC

<80°C

2.5.2 Vent Gas Heater (YA/5142)One steam heater, installed on deck in the vicinity of thevent mast No. 2, is used to raise the temperature of thevented vapour so that it is lighter than air and will dissipateclear of the ship.


Model 29-ST-38/34-2.4.Shell and straighttube design

Heating medium Saturated steam

Inlet temp of the medium (°C) 170 / 190


Mini inlet gas temperature (°C) -140

Mini outlet gas temp (°C) 0.

• Alarms are provided on the outlet gas temperature,high level and low temperature of the condensatedwater.

Operation

Gently warm through the deck steam supply line bycracking open steam supply valve and exhaust valves.Ensure that drain is clear and not contaminated (if theheater has been out of use for any length of time drain firstcondensate to deck).

Open gas inlet and outlet valves to heater and shut by-pass valve. Set control set point in Cargo Control Roomfor pressure at which vapour system is to vent.

When gassing or warming up and the liquid header is inuse for vapour, a removable bend is supplied to link liquidheader to gas control valve inlet.

Controls

Vapour Header/System Pressure Set

Alarm and trip which will shut steam supply valve in thecase of high condensate build up.

Gas Temp Outlet High/Low Indication

Emergency shut down of gas control valves from pushbuttons in Cargo Control Room and wheelhouse, ensuresgas venting ceases when atmospheric lightening ispresent.

Alarm Low Low Low HighPiont

Vent gas heater AF 669.01 -inlet gas temp.Vent gas heaterdischargetemperature. AF 670.01Vent gasheater trip. AF 668.01Vent gasheatercondensatehigh level. AF 670.03

2.5 Gas Heaters - Page 2Issue: 1


2.6.2a Main VaporiserIssue: 1


PI TI

TA

PT

PI

TI

HC

TI PI

Vent

Main VaporiserYA / 5151

Signal fromPrimary Space andGas HeaderPressureControllers

ToVapour Header

To Insulated Spaces

To MainHeater andFuel Gas Heater

Signalin CCR

VaporiserTripAlarm

L

Key

LNG Liquid

Warm LNG Vapour

Steam

Condensate

Liquid Nitrogen

Gaseous Nitrogen

Electrical

Instrument Air

OpenClosed

T

T

Strip/CoolHeader

TA

L

TI

High (>190mb)Tank Pressure

High Primary InsulatedSpace Pressure(>-50mbar)

XA

XA

TI

TA

LA

H

H

Steam Supply(See 2.14.1a)

TT

Supply ofN2 Liquid

Re-evaporation

Illustration 2.6.2a Main Vaporiser

Drain

Drain

xxxx xxxx

FCV01

470

063

xxxx

Instrument AirSupply

HIC

T7

HS

TT

HS ZSHY

HS ZS

HY

HIC

TIC

PICxxxx

xxxx

CondensateTo Gas ExchangersDrain Cooler

LineStrainer

456

To Tank No.4 Vapour Dome


To No.4Vapour Dome

LS

LT

LG

1

TCV

HC

LC

2.6 Vaporisers2.6.1 General DescriptionThe main vaporiser (YA/5151) is used for vaporising LNGliquid, to provide gas when displacing inert gas from thecargo tanks with LNG vapour, and for maintaining thepressure in the tanks when LNG is being discharged andvapour is not supplied from shore. This vaporiser can bearranged for vaporising liquid nitrogen for the initial fillingof the insulation spaces.

The forcing vaporiser (YA/5152) is used for vaporisingLNG liquid to provide gas for burning in the boilers tosupplement the natural boil off.

Both main and forcing vaporisers are situated in thecompressor room.

2.6.2 Main Vaporiser(See Illustration 2.6.2a)


Model 75-UT-25/21 - 3.6.

Shell and U tube design

Heating medium Saturated steam.



Inlet LNG temperature (°C) -163

Outlet gas temp (°C) -140 to 20.

• Alarms are provided on the outlet gas temperature,high level and low temperature of the condensatewater.

The main vaporiser is used for the following operations:

1 Discharging cargo at the design rate without theavailability of a vapour return from the shore.

If the shore is unable to supply vapour return, liquidLNG is fed to the vaporiser by using one strippingpump or by bleeding from the main liquid line. Thevapour produced leaves the vaporiser atapproximately -140°C and is then supplied to cargotanks through the main vapour header. Vapourpressure in the cargo tanks will normally bemaintained at 1100 mbar abs (minimum 1040 mbar)during the whole discharge operation. Additionalvapour is generated by the tank sprayer rings, theLNG being supplied by the stripping/spray pump.

If the back pressure in the discharge piping to shore isnot sufficient to have a minimum of 4 bar at the inlet tothe vaporiser, a stripping/spray pump will be used tosupply liquid to the vaporiser;

2 Purging of cargo tanks with GNG after inerting withinert gas and prior to cooldown. LNG is supplied fromthe shore to the vaporiser via the stripping/ spray line.The vapour produced at the required temperature+10°C is then passed to the cargo tanks;

Note: This operation is the normal procedure if the cargotanks have been inerted with inert gas containingcarbon dioxide.

3 Inerting could be carried out by evaporation of liquidnitrogen supplied from shore but the cost is veryexpensive. The vapour produced at the requiredtemperature +10°C is then passed to the cargo tanks.

4 Evaporation of liquid nitrogen from shore for insulationspaces inerting, after membranes in service tests.

Operating ProceduresSet the LNG or nitrogen pipelines as detailed for theoperation about to be undertaken. For vaporising liquidnitrogen a removable bend must be fitted at the inlet to thevaporiser.

A Main Vaporiser

To prepare the main vaporiser for use

1 Open the shell side vent valve.

2 Crack open the shell side drain valve.

3 Crack open steam supply manual valve (making suresteam to deck is available).

4 When all air is expelled from shell, shut the ventvalve.

5 When the correct level in condensate outlet isobtained, the drain valve is put on automatic control.

After about 30 minutes when pressures and temperatureshave stabilised on the vaporiser.

6 Slowly open fully the steam inlet manual valve.

7 Open the instrument air supply to the vaporisercontrols.

8 In the Cargo Control Room, set the controls for themain vaporiser on the Bailey IMS Mimic and select thecontrol loop required, ie for gas header or insulationspaces header.

9 Fill up the vaporiser with liquid using manual control.Check all flanges and joints for any signs of leakage.

10 When vapour is produced switch the control for liquidvalve to remote and automatic.

! WARNINGThorough checks around the main vaporiser andassociated flange connections must be conductedduring operation.

On Completion of Operation

1 Shut liquid valve 456.

2 Shut the steam supply valve when no LNG remains.

3 Open steam side vent and then open the drain whenall steam has been vented.

4 Keep vapour side valve open to system until vaporiserreaches ambient temperature.

ControlProcess control is on outlet temperature from vaporiserwith high and low temperature alarms. This is controlledon the TCV (temperature control valve).

The steam condensate from the vaporiser is returned tothe drains system through the condensate drains coolerand observation tank on deck on the aft bulkhead of themotor room.

The LNG inlet (valve FCV01) to vaporiser is controlled bysignals from the primary space pressure and gas headerpressure controllers or manually. The control loop forFCV01 is arranged with a selector switch for selection ofthe control parameter.

The following alarms and trips are available:

1 AF 557.01 - Low condensate temperature alarmSet point: + 80°C

2 AF 517.01 - High tank pressure alarmAF 517.02 Set point: 180 mbarAF 517.03AF 517.04

3 AF 582.01 - High condensate level alarmcontact switch

4 AF 580.01 - High gas outlet temperature alarmSet point: + 20°C

5 AF 519.01 - High primary space pressure alarmAF 519.02 Set point: 10 mbarAF 519.03AF 519.04

6 582.01 - High high condensate level trip and alarm

7 AF 557.01 - Low low condensate temperature trip and alarmSet point: < +70°C

8 AF 518.01 - High high tank pressure trip and AF 518.02 alarmAF 518.03 Set point: 190 mbarAF 518.04

9 AF 519.01 - High high primary space pressure AF 519.02 trip and alarmAF 519.03 Set point: -50 mbarAF 519.04

Points 6, 7, 8, 9 activate closing of valve FCV01, TCV andsteam supply, thus tripping main vaporiser.

2.6 Vaporisers - Page 1Issue: 1


2.6.3a Forcing Vaporiser and DemisterIssue: 1


PT

HS

TI PI

PI TI

LA

Vent

To No.4Vapour Dome

Forcing VaporiserYA / 5252

455

TCV

Key

LNG Liquid

LNG Vapour

Steam

Condensate

Electrical

Instrumentation

TI

KBD

OpenClose

ForcingVapouriserControlFeed-back

ForcingVapouriserControlFeed-back

Trip

Trip

Trip

Stripping/SprayHeader

1LA

H

TA

L

TI

High VapourHeader Pressure

Set

Drain

H

BoilersCombustionDemand

TT

TIC

To No.4Vapour Dome

H

DemisterYA / 5153

xxxx

Vapour HeaderCompressorsSuction

LDCompressor Trip

Steam Supply(See 2.14.1a) Re-evaporation

PI

TA

xxxx

xxxx

xxxx xxxx

xxxx

Illustration 2.6.3a Forcing Vaporiser and Demister

KBDSet

FT

HIC PIC

FI

LS

HCTrip

HC

FCV063

LineStrainer



LA H

TT

CondensateTo Gas ExchangersDrain Cooler

LS

HC

LC

LG

2.6.3 Forcing Vaporiser and DemisterThe forcing vaporiser (YA/5152) it is used for vaporisingLNG liquid to provide gas for burning in the boilers tosupplement the natural boil off.

Both the main and forcing vaporisers are situated in thecompressor room.

Forcing Vaporiser(See Illustration 2.6.3a)

The forcing vaporiser is used to supplement boil-off gasfor fuel gas burning up to 105% MCR.

The LNG is supplied by a stripping/spray pump.

LNG flow is controlled by an automatic inlet feed valvewhich receives its signal from the Boilers CombustionControl system and an independent spill/return line with adischarge valve to the cargo tank.

Specification


Model 15-UT-25/21 - 4.2.

Shell and U tube design

Heating medium Saturated steam.



Inlet LNG temperature (°C) -163

Outlet gas temp (°C) -40.

• Alarms are provided on the outlet gas temperature,high level and low temperature of the condensatewater.

Each vaporiser is equipped with a temperature controlsystem to obtain a constant and stable dischargetemperature for various ranges of operation. Thetemperature of the gas produced is adjusted by injecting acertain amount of by-passed liquid into the outlet side ofthe vaporiser through a temperature control valve andliquid injection nozzles.

A re-evaporator is also used to ensure that accumulationof non-vaporised liquid at the vaporiser discharge isavoided and that the output is at a stable temperature.

This is made possible by:

a) Two knitted mesh filters inserted in the gas flow pathto fractionate the droplets and create the necessaryturbulence to transform the small droplets injected intoa fine fog of liquid gas and also to moisten the meshwires acting as vaporising surface;

b) Two conical baffles installed in the tube to alloweventually accumulated liquid to be directed into thegas stream on the pipe bottom.

DemisterA demister is used downstream of the forcing vaporiser toserve as a moisture separator and prevent any carry overof liquid to the LD compressors.

Both vaporiser tubes are fitted with spiral wires to promoteturbulence ensuring efficient heat transfer and productionof superheated LNG vapour at the exit of the tube nests.

A level controller is fitted on the steam condensate side ofboth the vaporisers. The controller ensures that a correctlevel of condensate is maintained at all times during itsoperation by regulating the drain valve.


Model VMS-1 0/1 2-700Shell with in / outnozzles and drain.

Gas flow (kg/h) = 3500

Service temperature (°C) -40

• An alarm is provided on the level of the drained LNG.

To prepare Forcing Vaporiser for use

1 Open shell side vent valve.

2 Crack open shell side drain valve.

3 Crack open steam supply manual valve.

4 When all air has been expelled from shell, close thevent valve.

5 When the correct level in condensate outlet isobtained, the drain valve is put on automatic.

After about 30 minutes when pressures and temperatureshave stabilised on the vaporiser.

6 Slowly open fully the steam inlet manual valve.

7 Open the instrument air supply to the vaporisercontrols.

8 In the Cargo Control Room, set the controls for theforcing vaporiser on the Bailey IMS Mimic.

9 Start the spray pump.

10 Fill up the vaporiser with liquid manually.

Check all flanges and joints for any signs of leakage.

11 When vapour is produced, switch the control for liquidvalves TCV and FCV to remote.

! WARNINGThorough checks around the forcing vaporiser andthe associated flange connections must beconducted during operation.

On Completion of Operation

1 Shut liquid valve 455 which automatically shuts downthe vaporiser.

2 Shut the steam supply valve when no LNG remains.

3 Open steam side vent and then open the drain whenall steam has been vented.

4 Keep vapour side valve open to system until vaporiserreaches ambient temperature.

Controls and SettingsThe forcing vaporiser is basically started and stopped bythe opening or closing of liquid valve 455.

The vapour outlet temperature is controlled by valve TCV3713 on the vaporiser by-pass. This valve closes withoutair.

The LNG inlet flow is controlled by control valve 063 whichreceives the signals from the Boilers Combustion ControlSystem.

The following alarms and trips are available:

1 AF 582.01 - High condensate level alarmSet point: 240 mm

2 AF 589.01 - Low condensate temperature alarmSet point: + 70°C

3 AF 592.01 - High gas outlet temperature alarmSet point: - 40°C

4 AF 582.01 - High high condensate level trip and alarmSet point: 292 mm

5 AF 589.01 - Low low condensate temperature trip and alarmSet point: < +50°C

6 AF 518.01 - High high tank pressure trip and AF 518.02 alarmAF 518.03 Set point: + 190 mbarAF 518.04

7 High level alarm for demister trips the low dutycompressor.

Points 4,5 and 6 activate automatic closing of valve FCV,TCV and steam supply, thus tripping the forcing vaporiser.

2.6 Vaporisers - Page 2Issue: 1


2.7.1a HD Gas CompressorsIssue: 1


Instrument Air

ThermostaticControl Valve

Steam

Condensate

ElectricMotor

GearBox

ZT

ZI

HIC

HY

TT

PT2

PT1

YT

TT

PdS

TT

L

ZS

HHY

HHX

H

H

L

HH

HH

HH

H TT

H

YT

Main Oil Pump(Drive from Gear Box)

Lubrication OilSump Tank

Vapour In

Surge Line

Vapour Out

StandbyOil Pump(ElectricDrive)

TI

PI

PI

LS

TI

TIPS PI

TI

TT

LG

Sea WaterCooling

InletGuideVanesActuator

Gas Tight Bulkhead

Oil Cooler

TI

TT

FT

FIC

PdI

NitrogenSeal Gas

Electric Motors Room Cargo Compressor Room

Key

Lub Oil

LNG Vapour

Gaseous Nitrogen

SW Cooling

Instrument Air

Steam Supply

Condensate

Electric

Instrumentation

Illustration 2.7.1a HD Gas Compressors

SurgeController

Control Panel

TTAHH

FIC

Self Regulating Valve set at 7 bar

TT

Trip

Trip

L


LL

LStart Lock Outfor Low Pressure

TT

PS

PS

Trip

Trip

TAH

T3

T3

T3

XA

E.S.D.S Activated

Alarmsin CCR

CommonTrip Alarms

CommonAlarms

Single inECR

Cargo TanksPressure

Low Differential Pressure Between

Gas Main and Primary Insulation

Pressure

- Lube Oil Level- Bearings- Gearbox Oil- Blkd Penetration- Vibrations- Diff. Seal Gas

Emergency Stop from LCP - SupplyCabinet in EngineRoom CCR

T3

T3

Trip

L.O.E/P StartLock for L Level

Start Lock for L Pressure

LL Pressure

HH TemperatureTrip

Trip

Trip

T3

XAXA

Lock To Start ForLower Level.No Trip

2.7 Gas Compressors2.7.1 HD Compressors

Gas Compressors ( YA/5121 A I B - YA/5122 A I B)Two high duty (HD) compressors, installed in thecompressor room on deck, are provided for handlinggaseous fluids: LNG vapour and various mixtures of LNGvapour, inert gas or air during the cooling down, cargooperation and tank treatments.

Two low duty (LD) compressors, installed in thecompressor room on deck, are provided for handling theLNG vapour for the boiler produced by the natural boil offand forced vaporisation, which is used as fuel.

The HD and LD compressors are driven by electricmotors, installed in an electric motor room segregatedfrom the compressor room by a gas tight bulkhead; theshaft penetrates the bulkhead with a gas tight shaft seal.

HD Compressors


Model CM 400/55

Type Centrifugal. Single stage.Fixed speed withadjustable guide vanes.

Volume flow (m3/h) 15000

Inlet pressure (mbar) 1060

Outlet pressure (mbar) 1800

Minimum inlettemperature (°C) -140

Shaft speed (rpm) 10000

Motor speed (rpm) 3580

Rated motor power (kW) 400

• The compressors are operated locally or from theCCR.

• The following conditions trip the compressors:

• Safeties in ESDS

• Tank No.1, 2, 3 or 4 - differential pressure: tank /primary space = 5 mbar

• Tank No.1, 2, 3 or 4 - differential pressure: tank /secondary space = 0 mbar

• Differential pressure: vapour header / atmosphericpressure = 3 mbar

• Differential pressure: vapour header / primarypressure header = 0 mbar

• Tank No.1, 2, 3 or 4 - very high liquid level

• Safeties on local control system (oil temperature, oilpressure, discharge gas temperature, seal gaspressure)

• Electric power failure

• Ventilation flow failure in the electric motor room

Compressor Systems

Seal Gas SystemThe seal gas system is provided to prevent lub-oil mistfrom entering the process stream (compressed LNGvapour) and to avoid cold gas flow into the gearbox andinto the lub-oil system. Seal gas is nitrogen produced bythe nitrogen generators onboard.

The seal gas is injected into the labyrinth type sealsbetween the gearbox shaft bearing and the compressorwheel.

The system is maintained by a pressure control valvewhere seal gas pressure is always higher than the suctionpressure (usually adjusted at 0.3 bar)

Seal gas entering the gearbox from the shaft seals isreturned to the lub-oil sump, separated from the oil andvented to atmosphere.

After a period of more than 8 days of non-operation, theunit must be purged with dry and warm nitrogen.

Lub-oil SystemLub-oil in the system is stored in a vented 400 litres lub-oil sump. An integrated steam immersion heater withthermostatic switch is fitted in the sump to maintain aconstant positive temperature and avoid condensationwhen the compressors are stopped.

Lub-oil is supplied from the sump through separatesuction strainer screens and one of the 2 lub-oil pumps.The discharge from the pumps is through check valves toa common lub-oil supply line feeding the gearbox,bearings and bulkhead seal. The main operational pumpis driven by the high speed shaft gear. Upon failure of thedriven pump, the stand-by electric motor driven auxiliarypump is energised immediately and a remotealarm is initiated to indicate abnormal conditions. Thestand-by electric motor driven auxiliary pump is also usedto start the compressors.

The lub-oil passes through a sea water cooled oil coolerand a thermal bypass temperature control valve, tomaintain the lub-oil inlet temperature at approximately35°C. The oil supply to the bearings is fed via a 25 micronduplex filter with an automatic continuous flow switchchange over valve.

A pressure control valve regulates the oil flow to thebearings. Excess oil is bypassed and discharged to thesump. Pump relief valves act as back up and are set at7 bar.

The lub-oil system feeds the following:

- Journal bearing on both sides of the high speed shaft;

- Journal bearing on the driven end of the low speedshaft;

- Integral thrust and journal bearing on the non drivenend of low speed shaft;

- Sprayers for the gear wheels;

- Gas compressors’ bulkhead seals

Surge Control SystemAn automatic surge control system is provided to ensurethat the compressor flow rate does not fall below thedesigned minimum. Below this rate, the gas flow will notbe stable and the compressor will be liable to surge,causing shaft vibration which may result in damage to thecompressor.

All the gas compressors are equipped with an automaticsurge control system which consists of:

- A flow transmitter;

- Suction and delivery pressure transmitter;

- A ratio station;

- An anti-surge controller;

- A bypass valve on the gas stream.

On the basis of a preset ratio between the gas flow andcompressor differential pressure signals, the anti-surgecontroller produces a signal which modulates acompressor bypass valve.

Inlet Guide VanesTo achieve the required gas flow, the compressors haveinlet guide vanes fitted at the suction end.

The vanes are operated by pneumatic actuators whichreceive control signals from the flow controller.

Rotation of the vanes is possible through its full range oftravel of -30° to +80°. The position is indicated both locallyand at the Centralised Control Room. (Range 0 to 100%)

Bulkhead Shaft SealsEach compressor shaft is equipped with a forcedlubricated bulkhead shaft seal preventing any combustiblegas from entering the electric motors room.

The seals are of flexibox supply. They are fixed on thebulkhead and float on the shafts, supported by two ballbearings.

The lub-oil seal ensures tightness between the twobearings. The lubrication comes from the main lub-oilcircuit.

Operating Procedures

To prepare for running of HD CompressorsCheck the lub-oil level in the sump tank.

1 Start lub-oil heater about 30 minutes (depending onambient temperature) prior to expected compressorstart up.

2 Open compressor suction and discharge valves.

3 Open seal gas supply manual valve.

4 Run auxiliary lub-oil pump to warm up gearbox andbearings.

Check the lub-oil system for leaks.

5 Open cooling water inlet and outlet for the lub-oilcooler.

6 Open instrument air supply to control panel.

7 Switch ON power to the control cabinet.

8 At least two alternators should be coupled to the mainswitchboard to have sufficient power available at thecargo switchboards.

9. When stopping compressor, leave auxiliary lub-oil andseal gas until compressor is warm (approx. 1 hour)

2.7 Gas Compressors - Page 1Issue: 1


9 Set up the cargo piping system for the right operationto be carried out.

In the Cargo Control Room

10 Select the appropriate mimic on HD compressor forthe correct operation.

11 IGV (inlet guide vanes) must be shut and surge valveopen before starting.



2.7.1b HD Alarm and Trip Settings

No.:

1

SetPoint

0.95 bara

Signal

contact

Item

Suction Gas Press PT 1

Tag Nr.

PSL 1 1.06 bar a

NormalOperationCondition

Inst r. Range/adjustment

-25÷200mbarg

Alarm TripInterlock

A

2 - 4-20mADischarge Gas Press. PT 2 1.80 bar a 0 ÷ 1100mbarg

-

3 +80°C contactDischarge Gas Temp.TE 2A

TSHH 2A -112°C -150... + 100°C

T

4 +70°C contactDischarge Gas Temp.TE 2B

TSH 2B -112°C -150... + 100°C

A

5 -5mm contactOil Tank Level LSL 5 ±4 mm ±6 mm A; I1

6 40µm

50µm

contact

contact

Vibration YE 9 YSH 9

YSHH 9

15...20µm 0...100µm A

T7 55°C contact

PT100Temp. Oil SystemTE 8B

TSH 8B ~42°C 0...100°C A

8 60°C contactPT100

Temp. Oil SystemTE 8A

TSHH 8A ~42°C 0...100°C T


Temp. Oil BulkheadSeal TE 9B

TSH 9B ~60°C 0...100°C A

10 15°C contactBearing Temp. TE 9A TSL 9A ~65°C 0...100°C A; I2

11 1.0 bar contactLube Oil Press. PSL 8 ~2 bar 0.1...10.3bar

A; I2

12 0.8 bar contactLube Oil Press. PSLL 8 ~2 bar 0.1...10.3bar

T

13 0.2 bar contactSeal Gas Press. PDSL 11 0.3 bar 4...bar A; I1; I2

14 0.15 bar contactSeal Gas Press. PDSLL 11 0.3 bar 4...bar T

15 - 4-20 mAFlow Transmitter FT 1 different 0...74.6/0...45 mbar

-

16

L

H;HHL;LL

-

HH

H

L

H

HHH

HH

H

L

L

LL

L

LL

-

Action

T: TripA: AlarmI1: Start-up Interlock L.O. PumpI2: Start-up Interlock Machine

2.7.2a LD Gas CompressorsIssue: 1


Instrument Air


Steam

Condensate

ElectricMotor

GearBox

ZT

ZI

HIC

HY

TT

PT2

PT1

YT

TT

PdS

TT

L

ZS

HHY

HHX

H

H

H

L

HH

HH

HH

H TT

H

YT

Main Oil Pump(Drive from Gear Box)

Lubrication OilSump Tank

Vapour In

Surge Line

Vapour Out

StandbyOil Pump(ElectricDrive)

TI

PI

PI

LS

TI

TIPS PI

TI

TT

LG

Sea WaterCooling

InletGuideVanesActuator

Gas Tight Bulkhead

Oil Cooler

TI

TT

FT

FIC

PdI

NitrogenSeal Gas

Electric Motors Room Cargo Compressor Room

Key

Lub Oil

LNG Vapour

Gaseous Nitrogen

SW Cooling

Instrument Air

Steam Supply

Condensate

Electric

Instrumentation

Illustration 2.7.2a LD Gas Compressors

RatioController

Control Panel in Switchboard Room

TTAHH

FIC

Self Regulating Valve set at 7 bar

TT

Trip

Trip

L


LL

LStart Lock Outfor Low Pressure

TA

PS

PS

Trip

Trip

TT

Lock To Start ForLower Level.No Trip

T3

T3

T3

XA

E.S.D.S Activated

Alarmsin CCR

CommonTrip Alarms

CommonAlarms

Single inECR

Cargo TanksPressure

Low Differential Pressure Between

Gas Main and Primary Insulation

Pressure

- Lube Oil Level- Bearings- Gearbox Oil- Blkd Penetration- Vibrations- Diff. Seal Gas

Emergency Stop from LCP - SupplyCabinet in Engine RoomCCR

T3

T3

Trip

L.O.E/P StartLock for L Level

Start Lock for L Pressure

LL Pressure

HH TemperatureTrip

Trip

Trip

T3

XAXA

2.7.2 LD Compressors


Model CM 300/45

Type Centrifugal. Singlestage. Variable speedwith adjustable guidevanes.

Volume flow (m3/h) 4000

Inlet pressure (mbar) 1060

Outlet pressure (mbar) 1800

Minimum inlet temperature (°C) -140

Maximum shaft speed (rpm) 24000

Motor speed (rpm) 1775 to 3550

Rated motor power (kW) 150

• The compressors are operated locally or from theCargo Control Room.

• The following conditions trip the compressors:

• Safeties in ESDS

• Tank No. 1, 2, 3 or 4 - differential pressure: tank/primary space = 5 mbar

• Tank No. 1, 2, 3 or 4 - differential pressure: tank/secondary space = 0 mbar

• Differential pressure: vapour header/atmosphericpressure = 3 mbar

• Differential pressure: vapour header/primary pressureheader = 0 mbar

• Safeties in combustion control system.

• Safeties on local control system (oil temperature, oilpressure, discharge gas temperature, seal gaspressure)

• Electric power failure

Compressor Sub-systems

Seal Gas SystemThe seal gas system is provided to prevent lub-oil mistfrom entering the process stream (compressed LNGvapour) and to avoid cold gas flow into the gearbox andinto the lub-oil system. Seal gas is nitrogen produced bythe nitrogen generators onboard.

The seal gas is injected into the labyrinth type sealsbetween the gearbox shaft bearing and the compressorwheel.

The system is maintained by a pressure control valvewhere seal gas pressure is always higher than the suctionpressure (usually adjusted at 0.3 bar)

Seal gas entering the gearbox from the shaft seals isreturned to the lub-oil sump, separated from the oil andvented to atmosphere.

Lub-oil SystemLub-oil in the system is stored in a vented 400 litres lub-oil sump. An integrated steam immersion heater withthermostatic switch is fitted in the sump to maintain aconstant positive temperature and avoid condensationwhen the compressors are stopped.

Lub-oil is supplied from the sump through separatesuction strainer screens and one of the 2 lub-oil pumps.The discharge from the pumps is through check valves toa common lub-oil supply line feeding the gearbox,bearings and bulkhead seal. The main operational pumpis driven by the high speed shaft gear. Upon failure of thedriven pump, the stand-by electric motor driven auxiliarypump is energised immediately and a remote alarm isinitiated to indicate abnormal conditions. The stand-byelectric motor driven auxiliary pump is also used to startthe compressors.

The lub-oil passes through a sea water cooled oil coolerand a thermal bypass temperature control valve, tomaintain the lub-oil inlet temperature at approximately35°C. The oil supply to the bearings is fed via a 25 micronduplex filter with an automatic continuous flow switch overvalve.

A pressure control valve regulates the oil flow to thebearings. Excess oil is bypassed and discharged to thesump. Pump relief valves act as back up and are set at7 bar.

The lub-oil system feeds the following:

- Journal bearing on both sides of the high speed shaft;

- Journal bearing on the driven end of the low speedshaft;

- Integral thrust and journal bearing on the non-driven end of low speed shaft;

- Sprayers for the gear wheels;

- Gas compressors’ bulkhead seals

Surge Control SystemAn automatic surge control system is provided to ensurethat the compressor flow rate does not fall below thedesigned minimum. Below this rate, the gas flow will notbe stable and the compressor will be liable to surge,causing shaft vibration which may result in damage to thecompressor.

All the gas compressors are equipped with an automaticsurge control system which consists of:

- A flow transmitter;

- A compressor differential pressure transmitter;

- A ratio station;

- An anti-surge controller;

- A bypass valve on the gas stream.

On the basis of a preset ratio between the gas flow andcompressor differential pressure signals, the anti-surgecontroller produces a signal which modulates acompressor bypass valve.

Inlet Guide VanesTo achieve the required gas flow, the compressors haveinlet guide vanes fitted at the suction end.

The vanes are operated by pneumatic actuators whichreceive control signals from the flow controller.

Rotation of the vanes is possible through an angle of 100°.The position is indicated both locally and at theCentralised Control Room on the DCS.

Bulkhead Shaft SealsEach compressor shaft is equipped with a forcedlubricated bulkhead shaft seal preventing any combustiblegas from entering the electric motors room.

The seals are of flexibox supply. They are fixed on thebulkhead and float on the shafts, supported by two ballbearings.

The lub-oil seal ensures tightness between the twobearings. The lubrication comes from the main lub-oilcircuit.


To prepare for running of LD CompressorsCheck the lub-oil level in the sump tank.

1 Start lub-oil heater about 30 minutes (depending onambient temperature) prior to expected compressorstart up.

2 Open compressor suction and discharge valves.

3 Open seal gas supply manual valve.

4 Run auxiliary lub-oil pump to warm up gearbox andbearings.

Check the lub-oil system for leaks.

5 Open cooling water inlet and outlet lub-oil cooler(usually left open).

6 Open instrument air supply to control panel.

7 Switch ON power to the control cabinet.

8 Switch ON power to the variable speed controller.(Each LD compressor is supplied from a separatecargo switchboard ie Port and Stbd).

In the Centralised Control Room.

9 Set up the cargo piping system for the correctoperation to be carried out.

10 Select the appropriate mimic on LD compressor forthe correct operation.

11 IGV (inlet guide vanes) must be shut and motor speedadjusted to 50% before compressor can start.

12 Message “Ready to start” appears on the mimicdisplay below the compressors when the safeties areclear.

13 Start the compressor motor.

14 Switch compressor control to automatic mode.





2.7.2b LD Alarm and Trip Settings

No.:

1

SetPoint

0.95 bara

Signal

contact

Item

Suction Gas Press. PT 1

Tag Nr.

PSL 1 1.06 bar a

NormalOperationCondition

Instr. Range /adjustment

-25÷200mbarg

Alarm TripInterlock

A

2 - 4-20mADischarge Gas Press. PT 2 1.80 bar a 0+ 1100mbarg

-

3 +80°C contactDischarge Gas Temp.TE 2A

TSHH 2A -9°C -150... + 100°C

T

4 +70°C contactDischarge Gas Temp.TE 2B

TSH 2B -9°C -150... + 100°C

A

5 -5mm contactOil Tank Level LSL 5 ±4 mm ±6 mm A;I1

6 40µm

50µm

contact

contact

Vibration YE 9 YSH 9

YSHH 9

15...20µm 0...100µm A

T7 55°C contact

PT100Temp. Oil SystemTE 8B

TSH 8B ~42°C 0...100°C A


Temp. Oil SystemTE 8A

TSHH 8A ~42°C 0...100°C T


Temp. Oil BulkheadSeal TE 9B

TSH 9B ~60°C 0...100°C A

10 15°C contactBearing Temp. TE 9A TSL 9A ~65°C 0...100°C A;I2

11 1.0 bar contactLube Oil Press. PSL 8 ~2 bar 0.1...10.3bar

A;I2

12 0.8 bar contactLube Oil Press. PSLL 8 ~2 bar 0.1...10.3bar

T

13 0.2 bar contactSeal Gas Press. PDSL 11 0.3 bar 0...4 bar A;I1;I2

14 0.15 bar contactSeal Gas Press. PDSLL 11 0.3 bar 0...4 bar T

15 - 4-20 mAFlow Transmitter FT 1 different 0...74.6/0...25 mbar

-

16

L

H;HHL;LL

-

HH

H

L

H

HHH

HH

H

L

L

LL

L

LL

-

Action

T: TripA: AlarmI1: Start-up Interlock L.O. PumpI2: Start-up Interlock Machine

2.8.1a Vacuum PumpsIssue: 1


VSPI

TI

TS

FS

FS

Vacuum Pump(Outboard)

Vacuum Pump(Inboard)

Motor VacuumPumpYA/5201A

Motor VacuumPumpYA/5201B

No 3. Mast Riser

Cooling Water Inlet

Secondary Insulation Spaces Main

Primary Insulation Spaces Main

Cooling Water Outlet

Cargo Compressor RoomElectricMotors Room

TI

TSTA

100¡CH

VA

568569

571

AW826VX

AW827VX

Lub Oil

AW072VX

Trip

Trip

Trip

Key

SW Cooling

Secondary Space Nitrogen

Primary Space Nitrogen

Lub Oil

Electrical

Instrumentation

TA

L

-60¡C

Illustration 2.8.1a Vacuum Pumps

FA

L

LA

L

LS

VSPI

TI

TS

FS

FS

TI

TSTA

100¡CH

VA

572

Lub Oil

AW072VX

Trip

Trip

FA

L

TA

L

-60¡C

FA

L

LA

L

LS

FA

L

FS

Trip

2.8 Vacuum Pumps2.8.1 Vacuum pumps(See Illustration 2.8.1a)Two vacuum pumps located in the cargo compressorroom are used to evacuate the primary and secondaryspaces atmosphere in the following cases:

1 To replace air with nitrogen for inerting;

2 To replace methane with nitrogen for gas freeingbefore dry docking after there has been leakage ofcargo;

3 To test tightness of the membranes at regular intervalsor after membrane repairs.

4 When the associated tank is opened up.

The pumps are driven by electric motors situated in theelectric motors room through a gas tight bulkhead seal.The two pumps are used in parallel to evacuate theprimary and secondary spaces in order to reduce the timetaken to achieve the vacuum of 200 mbar a.

The pumps are sea water cooled from the deck coolingsea water system (refer to 2.12). The pumps are startedand stopped from the starter panel in the CCR. Auto fromthe CCR and local from the ECR.

! CAUTIONIf there is a failure or stoppage and the vacuum pumpis hot and the cooling water has stopped, await forroom temperature before restarting in order to avoidshock due to cold wate r.

! CAUTIONIf there is a computer control failure, the vacuumpumps can only be stopped from the ECR and notfrom the compressor room or CCR.

! CAUTIONIf the primary space pressure were to be reducedbelow the secondary space pressure there is a dangerof distorting the secondary barrier by lifting it off itssupporting insulation. A maximum pressuredifference of 30 mbar is allowed.

Discharge from the pumps is led to No. 3 mast riser.

Control and Alarm SettingsEach vacuum pump will stop if the lubrication oil tanklevel, or flow is low, the discharge temperature is high orthe suction temperature is low.

AF 621.01 Low suction temperature alarmAF 621.02 Set point: -60°C Trip the pumps

AF 622.01 High discharge temperature alarmAF 622.02 Set point: +170°C Trip the pumps

AF 619.01 High vacuum alarmAF 619.02 Set point: 200 mbar a Trip the pumps

AF 624.01 Low lubrication oil flow alarmAF 624.02 6/10 drops per 10 seconds Trip the pumps

AF 624.03 Low lubrication oil level alarmAF 624.04 Set point: 5 cm Trip the pumps

AF 623.01 Low cooling water flow alarmAF 623.02 Normal flow rate 1500l/h

Specification

Vacuum pumps:Two horizontal rotary dry vacuum pumps, single stagedtype P8O manufactured by MPR industries, capable ofcreating a vacuum of 200 mbar a in the primary andsecondary insulation spaces and driven at 875 rpm by 27kW increased safety electric motors through a gas tightbulkhead seal (817 m3/h). Suction temperature -50°C to+45°C


1 Open the sea water cooling water inlet and outlet atthe vacuum pump. Check through the pump drainvalve that there is no water in the pump. A sampleintake is fitted on the drain valve in order to permitsampling during operation. Then vent the pumpcooling water lines. When evacuating the insulationspaces, the secondary barrier space is evacuated to950 mbar a before the primary barrier space suctionisolating valve is opened. Both spaces are taken downto 200 mbar a. This process ensures that it is notpossible to lower the pressure in the primary barrierinsulation space without having the same pressure inthe secondary barrier insulation. Check pump lub-oiltank level.

2 Ensure free rotation of pump. Operate manual lub-oilpump and ensure oil drips are evident at each sightglass.

If the pump has been stopped for more than 24 hoursit is essential to turn the rotor by hand 2 or 3 turnsbefore starting the pump to ensure that the blades arenot stuck on the cylinder.

3 The vacuum pumps can now be started.

2.8 Vacuum Pumps - Page 1Issue: 1


2.9.1a Inert Gas and Dry Air SystemsIssue: 1


2.9.1a Inert Gas and Dry Air System

Combustion Air Fans

Ignitor

CombustionChamber

Fuel Inlet

SteamAtomizing

Burner Unit andCombustion Chamber

FromBallast Pump

Scrubber

EffluentSeal

Vent toFunnel

Chiller Unit Pump

Intermediate Dryer UnitDemister

Vent to Funnel

Inert Gasto DeckFinal Dryer Unit

Electric80 kWHeater

Fan

FilterandDrain

Cooler

ChillerUnit

SprayerBar

Light Ship Draught

CI001VF

206

Effluent PipeNot Lined

Combustion Air

Steam

Diesel Fuel Oil

Chilled Water

Sea Water

Inert Gas

Sea Water Fiber Glass Lined Effluent Pipe

Key

O2 Analyser

RefrigerationCompressor

and Evaporator

ReactivationDryer System

Demister

DesiccantVessel

UnitNo.1

DesiccantVessel

UnitNo.2

Effluent Discharge Overboard

Min.2m

B1 B2

2.9 Inert Gas and Dry Air Systems2.9.1 Inert Gas and Dry Air Plant (XAI5321 and

XD/5321 A through F)The dry air / inert gas plant, installed in the engine room,produces dry air or inert gas which is used for the tank andpiping treatments prior and after a dry docking or aninspection period.

The operating principle is based on the combustion of alow sulphur content fuel and the cleaning and drying of theexhaust gases.

The inert gas plant includes an inert gas generator, ascrubbing tower unit, two centrifugal fans, an effluentwater seal, a fuel injection unit, an intermediate dryer unit(refrigeration type), a final dryer unit (adsorption type) andan instrumentation / control system.

Manufacturer Navalimpianti.

Inert gas delivery rate (Normal m3/h) 6500

Dry air delivery rate (Normal m3/h) 6500

Delivery pressure (bars) 0.3

Inert gas/dry air dew point (°C) -45

Inert gas composition (% vol) Oxygen 1

Carbon dioxide < 15

Carbon monoxide < 100 ppm

Hydrogen < 100 ppm

Sulphur oxide < 2 ppm

Nitrogen oxide < 65 ppm

Nitrogen balance to 100%

Soot complete absence.

• The dry air/inert gas plant is locally operated.

The connection to the cargo piping system (refer to2.2.1a) is made through two non-return valves and a spoolpiece which is in the normally closed position and theconnection to the gas header is made through aremovable bend (not normally connected).

Working PrincipleInert gas is produced by combustion of Gas Oil suppliedby the Gas Oil Pump with air provided by blowers, in thecombustion chamber of the Inert Gas Generator.

A good combustion is essential for the production of agood quality, soot free, low oxygen inert gas.

The products of the combustion are mainly carbondioxide, water and small quantities of oxygen, carbonmonoxide, sulphur oxides and hydrogen. The nitrogencontent is generally unchanged during the combustionprocess and the inert gas produced consists mainly of85% nitrogen and 15% carbon dioxide.

Initially, the hot combustion gases produced are cooledindirectly in the combustion chamber by a sea waterjacket. Thereafter cooling of the gases mainly occurs inthe scrubber section of the generator where the sulphur oxides are washed out. The sea water for the Inert GasGenerator is supplied by one of the ballast pumps viaballast main isolating valve 206.

Before delivery out of the generator, water droplets andtrapped moisture are separated from the inert gases by ademister. Further removal of water occurs in theintermediate dryer stage, where the refrigeration unitcools the gas to a temperature of about 5°C. The bulk ofthe water in the gas condenses and is drained away withthe gas leaving this stage via a demister. In the final stage,the water is removed by absorption process in a dualvessel desiccant dryer. The desiccant dryer units work onan automatic change over cycle, where the out of linedesiccant unit is first reactivated with warm dry air whichhas gone through the reactivation dryer system.

A Pressure Control valve located at the outlet of the DryerUnit maintains a constant pressure throughout thesystem, thus ensuring a stable flame at the generator.

Dewpoint and oxygen content of the Inert Gas producedare permanently monitored. The oxygen level controls theratio of the air/fuel mixture supplied to the burner. Theoxygen content must be below 1% by volume and thedewpoint up to a maximum of - 65°C with a minimum of-55°C. Both parameters are displayed locally andremotely through the Bailey IMS.

For delivery of Inert Gas to the cargo system, twocombined remote air-operated control valves operatedthrough solenoid valves are fitted on the distributionsystem, ie the Purge valv e and the Delivery valve .

Dry-Air ProductionThe Inert Gas Generator can produce Dry-Air instead ofInert Gas with the same capacity.

However, for the production of Dry-Air:

a There is no combustion in generator;

b There is no measure of oxygen content.

The oxygen signal is overridden when the mode selectoris on Dry-Air production.

After the processes of cooling and drying, and if thedewpoint is correct, the dry air is supplied to the cargosystem through the delivery valve (with the purge valveclosed).

Burner DescriptionThe combustion air is supplied to the main burner by two‘roots’ type blowers of 50% capacity each. The quantity ofcombustion air to the burner can be manually adjusted bya regulating valve in the excess air discharge line.

Fuel (Gas oil) is supplied at a constant pressure by theGas oil electric pump which has a built-in pressureoverflow valve.

Before ignition or start up of the unit, and with the pumprunning, all the fuel is pumped back via this fuel oiloverflow valve which also serves to regulate the deliverypressure of the pump.

The fuel oil flows to the nozzle of the main burner via twosolenoid valves and two fuel oil regulating valves.

A programme switch in the local control panel regulatesone of the solenoid valves which also operates the pilotburner and initial firing.

The main burner is ignited by a pilot burner. The fuel oil isatomised in 2 steps. Firstly, the fuel oil is dispersed by aspray nozzle. Then it is subjected to a tangential impulseflow of steam which when it comes into contact with theaxially orientated impulse flow of fuel, causes the ultrafinedispersion of the fuel oil.

Atomising steam for the ultramiser burner is fed via aspecial steam superheater. A pressure reducer stabilisesthe incoming steam pressure and the correct atomisingpressure for the main burner can be adjusted.

The pneumatic valve in the steam line is opened a fewseconds after ignition of the pilot burner. The steamsuperheater is fitted in the combustion chamber. Thesteam is further heated in the steam superheater, locatedin the combustion chamber to produce dry steam forefficient atomisation of fuel in the burner.

• For alarms and operating indications, refer to themanufacturer’s P & I diagrams.

2.9 Inert Gas and Dry Air Systems - Page 1Issue: 1


2.10.1a Nitrogen Production SystemIssue: 1


TS15

PI35

PCV35

PI40

R12.COOLER

UNIT

PS20

PS

L

BufferTank7.5m3

8 bar

PT

DPS5

DPS

PI PI PI

PI35

PT

PT35

Key

Gaseous Nitrogen

Oxygen Enriched Air

Air

Chilled Water

Electrical

Illustration 2.10.1a Nitrogen Producton System

Drain

Drain

Drain

R12.Cooler

Unit

AO225

H>5%

H

H L

HDPA1-2

DPA O225

DPA H.T. Dew Point

PT35

H.P. Delivery

DPS5

Filter Blocked

O2 >5%

TS15

H.T. AirPT35

L.P. Delivery

DPA H.T. Dew Point

AO225

PS20

L.P. Accumulator

Key

Drain

DrainDrain

130m3/h Screw Compressor

130m3/h Screw Compressor

N2 57.5m3/h Membrane

To Funnel

Freon Dryer Unit

N2 57.5m3/h Membrane

M

M

2.10 Nitrogen Production System2.10.1 Nitrogen Production Plant (XA/5221)Two nitrogen generators, installed in the engine room,produce gaseous nitrogen which is used for thepressurisation of the barrier insulation spaces, as seal gasfor the HD and LD compressors, fire extinguishing in thevent mast risers and for purging of various parts of thecargo piping.

The two high capacity units (45m3/h each), will operate inparallel when high nitrogen demand is detected and willstart automatically, i.e. during initial cooling down. Whenloading only one unit will need to be run - the other unitbeing kept on standby.

The operating principle is based on the hollow fibremembranes through which compressed air flows and isseparated into oxygen and nitrogen. The oxygen is ventedto the atmosphere via the engine funnel and the nitrogenstored in a 7.5m3 buffer tank ready for use.

The high capacity unit consists of two AS 36 - 12 barscrew compressors, two air dryers, 3+3 stage filtersarranged in series, before passing into the membraneunits. An oxygen analyser, after the membrane, monitorsthe oxygen content, and if out of range, above 3% O2.

The nitrogen is stored in a 7.5m3 buffer tank, where highand low service pressure set points actuate the start andstopping of the generators. It is filled at a pressure of 7-8 bar abs and delivery pressure og 3 bar abs.

High Capacity UnitManufacturer TecnocoNominal flow rate (N m3/h) 57.5 + 57.5Nitrogen purity 97%Dew point (°C) -55 at 8 bar (g)Outlet gas composition (%vol) Oxygen < 3

Carbon dioxide < 30 ppmNitrogen balance to 100%

Screw compressor:Kaeser type AS 36 160 Nm3/hCompressed air atmembrane inlet 12 barMaximum back pressureO2 enriched air 0.5 barNominal power 23kWNitrogen temperature 5 ÷ 45°CFeed temperature 5 ÷ 45°C

Nitrogen dryers: Zander - 99% at 1 micron oil retentiondown to 0.5 mg/m3 at 7 bar and 20°CDew point (with dryingcapability of membranes,final dew point will be < -55°C) -26°C

A three way pneumatic operated valve is installed on themembrane outlet. This valve is controlled by the O2concentration analyser, redirecting the flow to the funnel ifO2 above 5%.

• The gaseous nitrogen generators are operatedautomatically, locally or from the CCR.

Control Systems and InstrumentationThe control panel permits fully automated unmannedoperation of the units. The following alarms and controlsare mounted on the control panels.

Push Buttons for Start/Stop Operation Selection for N2 delivery valve close/open/autoPush button for audible alarm acknowledgementContinuous N2 delivery pressureContinuous O2 content reading

Oxygen AnalyserA fixed O2 content analyser is installed on the packageunits, which is connected before the remotely operatedthree way valve.

The analyser has the following characteristics, O2 range 0to 25%, with an output signal of 4 to 20 mA for the remoteindicator, alarm panel and three way valve actuation.

Remote Control PanelThe following instruments, signals and controls areinstalled on the panel: Oxygen content indicator 0 to 25% O2N2 delivery pressure indicator 0 to 4 barStart/stop push buttonsAlarm acknowledgement push button

Audible and visual alarms for the following:N2 Pressure to users: < 2.9 bar (g) locally & CCR remote panelN2 Pressure to users: > 3.1 bar (g) locally & CCR remote panelN2 Pressure in buffer tank: > 9 bar (g) locally & CCR remote panelN2 Pressure in buffer tank: < 4 bar locally & CCR remote panelO2 Percentage: > 5% after 5 minutesDew point: > 65% after 5 minutesFilter dirty: > 1 barFeed air temperature: < 55°C locally & CCR remote panelCompressor failure: locally & CCR remote panelProcess shut-down: locally & CCR remote panel

Shut down applies in the following situations:O2 percentage: > 5% after 5 minutesDew point: > 65% after 5 minutesFeed air temperature: < 55°CN2 Buffer tank N2 pressure: > 9 bar (g)

2.10 Nitrogen Production System - Page 1Issue: 1


2.11.1a Ballast SystemIssue: 1


PIxxxx

PT

PI

PIxxxx

PT

PI

PIxxxx

PT

PI

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LT

D

Cro

ss O

ver

Cro

ss O

ver

301

240

265

260203

280

255355

330

340

350

207

270

204

290 295 275285 291

305

232332

320

331

242342

341 241

231

322 222

321

221

312

310

311

211

210 200220

212

205

206 202 250

201 230

Key

Sea Water Ballast

Sea Water Ballast Stripping

Port SeaChest

OverboardDischarge

Ballast TankNo. 4 Port




Ballast TankNo. 4 Stbd




Main Direct Bilge Suction

To ER CentralWater Cooling

To Cargo SystemWater Cooling

Illustration 2.11.1a Ballast System

FOREPEAK

AFTPEAK VOID

SPACE

Starboard Sea Chest

High Sea Chest

Pipe TunnelBilge Suction

To InertGas Scrubber

PORTBALLAST PUMP NO. 1

STARBOARDBALLAST PUMP NO. 2

StrippingEductor

D Draught Level Sensor

D

D

D

CofferdamNo.3

CofferdamNo.3

In E.R UnderShaft

H

L

LIxxxx

LT

LIxxxx

Stb'd SideAbove ForeDry Double Bottom

LIxxxx

LT

H

L

2.11 Ballast System2.11.1 Ballast System Description(See Illustration 2.11.1a)The ballast spaces beneath and around the out board sideof the cargo tanks are utilised as ballast tanks to optimisedraft, trim and heel during the various load conditions ofthe vessel.

Ballast will be carried during the return passage to theloading port, when only sufficient gas is carried to maintainthe tanks and their insulation at cryogenic temperatures.

The ballast spaces are divided into 8 tanks, that is portand starboard under each of the 4 cargo tanks. Inaddition, the fore and aft peak tanks are also used to carryballast when required. This gives a total ballast capacity of26081m3, approximately 26733 tonnes when filled withsea water.

Two, 1200m3/h, vertical centrifugal pumps are fitted, whichenable the total ballast capacity to be discharged orloaded in approximately 24 hours using 1 pump, or 12hours using both pumps. The pumps are driven by electricmotors and are located on the engine room floor,starboard side forward.

The 600 mm fore and aft ballast main runs through theduct keel with tank valves mounted on tank bulkheads.This main reduces to 500mm at tank No. 3 and to 300 attank No. 1. The 200mm stripping main also runs thoughthe duct keel on the port side, this is connected to thestripping eductor.

Both ballast pumps fill and empty the tanks via the portside 600mm main.

Stripping and final educting is done using 1 pump as thedriving water for the eductor on the 200mm stripping main.

The fore peak ballast space can also be filled and emptiedusing the ballast mains. The cross over between the 2mains being at No. 1 ballast tank.

All ballast pipes are of GRP. with galvanised steelbulkhead pieces.

All valves are AMRI butterfly valves hydraulicallyoperated, fail safe type, except cross-over and masters.

2 Ballast pumps, electric motor driven XA/404A & BMake: - Kvaerner SingaporeType: - Double suction, single stage axially split centrifugal

Rated output: 1200m3/h at 30m head, are mounted at theforward end bottom platform of the E.R. These pumpstake their suction from the sea/sea cross over or from thehigh sea chest, the latter being the normal operation whenloading ballast and from tanks via port side header whendischarging. Ballast Eductor 180m3/h at 30m head.

The ballast pumps are used to supply sea water to theinert gas system.

System ControlThe ballast system is controlled entirely from the controlroom using the keyboard in conjunction with mimicELSAG BAILEY Ballast.

The ballast pumps are started and stopped using themimic board, provided that the switches on the localcontrol panel are set to remote. When on local control, thepumps can be started and stopped from the local controlpanel, and can be stopped from this panel regardless ofthe position of the local/remote switch. The local controlpanels always take priority and can wrest control from thecontrol room at any time.

All hydraulically operated valves in the system are alsooperated using the keyboard in conjunction with mimicELSAG BAILEY Ballast. Two basic types of valve arefitted, those which can be positioned at the fully closedposition or fully open, and those which can be positionedat any point between fully open and fully closed. Theposition of all valves is shown on the mimic. Provision ismade for a portable hand pump to be used to operateeach valve in the event of hydraulic accumulator failure.The pump discharge valves and the overboard dischargetank valves are multi-positional. All other valves are eitheropen or closed. In addition to being operable from thecontrol room, the valves can also be operated from thehydraulic power station, using the push buttons on theindividual solenoids.

Mimic ELSAG BAILEY Ballast also shows when thepumps are switched to remote, the pumps suction anddischarge pressure, the position of the manually operatedvalves and the level in each tank, in terms of inage.

System Capacities and RatingsBallast pumps: Kvaerner Singapore Model: CAD 350-12V48AAN, each rated at 1200m3/hagainst a head of 30 mlc at 1188rpm.

Control and Alarm Settings

Point No. Setting DescriptionAF 452.01 16m Fore peak tank level highAF 452.02 20m No.1 port ballast tank level highAF 452.03 20m No.1 stbd ballast tank level highAF 452.04 20m No.2 port ballast tank level highAF 452.05 20m No.2 stbd ballast tank level highAF 452.06 20m No.3 port ballast tank level highAF 452.07 20m No.3 stbd ballast tank level highAF 452.08 20m No.4 port ballast tank level highAF 452.09 20m No.4 stbd ballast tank level high

Operating ProceduresIt is assumed that the main sea water cross-over pipe isalready in use, supplying other sea water systems, eg.main circulating system, sea water service system, andthat the cargo and ballast valve hydraulic system is alsoin use.

A) To ballast the ship

! CAUTIONMaloperation of the ballast system will cause damageto the GRP pipework. Damage is generally caused bypressure surge due to sudden changes in the flowand the presence of air pockets. During the ballastingoperation great care must be taken to ensure that flowrates are adjusted smoothly and progressivel y. Inparticula r, the pumping rate should be reduced to onepump when filling only one tank and use made of thedischarge to sea to further reduce the rate beforeshutting of the final tank valve.

It is necessary to eliminate air pockets that may bepresent in the piping before proceeding with normalballasting operations. This is achieved by runningballast by gravity into either the fore peak or No. 1tank.

It is important not to compress any air in the system.To achieve this, the valve admitting water to thesystem should be opened last.

i) Fill by gravityAll operations are carried out from the control room usingthe keyboard in conjunction with the mimic board ELSAGBAILEY Ballast.

1 Open the valve 200 to the fore peak tank.

2 Open ballast main valves 210, 220, 205 this willenable initial line filling to expel air trapped in the lines.

3 Open the gravity filling valve from sea 265. When aflow has been established the fore peak valve 200 andforward isolation 210 can be shut.

4 Open the valve(s) on the tank(s) to be filled asrequired by the ballast plan.

No.1 Port 211

No.1 Stb’d 212

No.2 Port 221

No.2 Stb’d 222

No.3 Port 231

No.3 Stb’d 232

No.4 Port 241

No.4 Stb’d 242

5 As the level in each tank reaches that required, openthe valve of the next tank before closing the valve ofthe full tank.

6 When all the tanks are at their correct level shut thetank valves, ballast main valves 220, 205 and gravityfilling valve 265

Note The speed when filling by gravity will sharplydecrease as the level of the water line isapproached. The tanks will require to be filled totheir capacity with the ballast pump.

2.11 Ballast System - Page 1Issue: 1


2.11.1a Ballast SystemIssue: 1


PIxxxx

PT

PI

PIxxxx

PT

PI

PIxxxx

PT

PI

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LIxxxx

LT

H

L

LT

D

Cro

ss O

ver

Cro

ss O

ver

301

240

265

260203

280

255355

330

340

350

207

270

204

290 295 275285 291

305

232332

320

331

242342

341 241

231

322 222

321

221

312

310

311

211

210 200220

212

205

206 202 250

201 230

Key

Sea Water Ballast

Sea Water Ballast Stripping

Port SeaChest

OverboardDischarge









Main Direct Bilge Suction

To ER CentralWater Cooling

To Cargo SystemWater Cooling

Illustration 2.11.1a Ballast System

FOREPEAK

AFTPEAK VOID

SPACE

Starboard Sea Chest

High Sea Chest

Pipe TunnelBilge Suction

To InertGas Scrubber

PORTBALLAST PUMP NO. 1

STARBOARDBALLAST PUMP NO. 2

StrippingEductor

D Draught Level Sensor

D

D

D

CofferdamNo.3

CofferdamNo.3

In E.R UnderShaft

H

L

LIxxxx

LT

LIxxxx

Stb'd SideAbove ForeDry Double Bottom

LIxxxx

LT

H

L

ii) To ballast the ship using the port ballast pump

1 Confirm the manual operated valves on the sea watersuction are open. Open the valve(s) on the tank(s) tobe filled as required by the ballast plan.

Fore peak 200

No.1 Port 211

No.1 Stb’d 212

No.2 Port 221

No.2 Stb’d 222

No.3 Port 231

No.3 Stb’d 232

No.4 Port 241

No.4 Stb’d 242

Aft peak ballast operations are performed by engineroom general service pumps

2 Open ballast isolating valves 210 (if required to fill theFore Peak) 220, 205, 280

3 Open sea water inlet valves to the pump 290, 295,240, 201

4 Start the port ballast pump

5 Open the pump discharge valve 207.

6 As the level in each tank reaches that required, openthe valve for the next tank before closing the valve tothat tank which is full.

7 When all tanks are near to the required level, reducethe flow rate progressively by discharging to sea viaoverboard discharge valve 255.

8 Close the final tank valve when it reaches the requiredlevel.

9 Close the pump discharge valve 207 and stop thepump.

10 Close all other valves

iii) To ballast the ship using the stb’d ballastpump

1 Follow operations 1 to 2 inclusive above.

2 Open the valves 290, 295, 260, 202.

3 Open valve 270 stb’d pump isolating valve to ballastmain.

4 Start the pump.

5 Open pump discharge valve 204.

6 Follow operations 6 to 8 inclusive above.

7 Close the pump discharge valve 204 and stop thepump.

8 Close all other valves.

B) To deballast the ship

! CAUTIONMaloperation of the ballast system will cause damageto the pipework. Damage is generally caused bypressure surge due to sudden changes in the flowrate. During the deballasting operation this can becaused by the opening of a full, or partly full tank intothe ring main when it is under vacuum. This is aparticular risk when eductors are in use.

Under no circumstances should a vacuum be drawnon a closed ballast main.

Before starting the deballasting operations, the main linesmust be purged of any air pockets in the following manner.

1 Open overboard discharge valve 255.

2 Open ballast main valve 280 and isolation main valves205, 220 and 210 (if the fore peak is to be deballasted)

3 Open fore peak valve 200.

A flow will now be established

4 Open the valve(s) on the tank(s) to be emptied asrequired by the deballast plan.

Fore peak 200

No.1 Port 211

No.1 Stb’d 212

No.2 Port 221

No.2 Stb’d 222

No.3 Port 231

No.3 Stb’d 232

No.4 Port 241

No.4 Stb’d 242

When it becomes necessary to start the ballast pumps,

5 Open valves 230, 201 (port pump) 250, 202, 270(stb’d pump).

6 Close valve 280.

7 Check that a ballast tank valve is open.

8 Start ballast pump.

9 Open pump discharge valve 207 (port), 204 (stb’d).

10 As the level reaches that required, open the valve onthe next tank before closing the valve on that tank.

11 When suction has been lost on all tanks that arerequired, close the pump discharge valve 207 (port),204 (stb’d) and stop the pump(s).

12 Close tank valves, isolating main valves 210, 220,205, pump inlet valves 230, 201 (port), 250, 202(stb’d), 270 and overboard discharge valve 255.

13 Strip the ballast tanks as required (see below).

C ) To strip the ballast tanks using the ballasteductor

Using the port ballast pump.

1 Open sea water valve 291.

2 Open ballast pump inlet valves 290, 295.

3 Open ballast eductor driving water supply valve 330.

4 Open ballast eductor overboard discharge valve 355.

5 Open main ballast pump overboard discharge valve255. (to regulate driving water throughput to eductor).

6 Open ballast stripping main isolating valves 310 (ifstripping the fore peak), 320, 305.


8 Open ballast pump discharge valve 207.

9 Open valve on first ballast tank to be stripped

Fore peak 200

No.1 Port 311

No.1 Stb’d 312

No.2 Port 321

No.2 Stb’d 322

No.3 Port 331

No.3 Stb’d 332

No.4 Port 341

No.4 Stb’d 342

10 Open ballast eductor suction valve 340 (automatic).

11 When one tank has been stripped, open the next tankvalve before closing the previous tank.

12 When all tanks have been stripped close eductorsuction valve 340.

13 Close ballast pump discharge valve 207 and stoppump.

14 Close all other valves opened in operations 1 to 6.

D ) To supply sea water to the inert gas scrubbersystem via the ballast pump.

Using the stb’d ballast pump.

1 Open sea water valve 291.

2 Open pump suction valves 290, 295.

3 Ensure inert gas system is ready to receive ballastpump supply. Open inlet valve to inert gas scrubbersystem 206.


5 Open ballast pump discharge valve 204.



2.11.2a Cargo Valves Hydraulic SystemIssue: 1


Trip Trip

MMM

Illustration 2.11.2a Cargo Valves Hydraulic System

Key

Control Air

Hydraulic Oil System

Deck Sea Water Cooling

Instrumentation

Distribution Control Rack No. 2High Pressure Low Flow

Control Blocks forLiquid Dome Valves

Valve Numbers010, 011, 012, 013, 110020, 021, 022, 023, 120,030, 031, 032, 033, 130,040, 041, 042, 043, 140

Control Blocks forESDS Manifold Control Blocks

Valve Numbers001002003004005006007008401408

Valve Numbers114124134144431441501502

Valve Numbers400403404406410411420421430440451452

5 LitreAccumulator

for eachESDS Valve

Pneumatic PilotControl Valves

To Individual ESDSManifold Valves

(see Illustration 2.11.2c)

Drain

700 LitreHydraulicOil Tank

Deck SeaWater Cooling

To ESDS PortAccumulators

To ESDS StarboardAccumulators

To Other ESDSControl Blocks

Drain

115 bar

Distribution Control Rack No. 2Low Pressure High Flow

To Starboard ESDSControl Block

Hydraulic CoolingCirculating Pump

Control Blocks

P4

P5

CoolerPdA PdA PdA PdA

TT

HTA

TT

HHTA

LS LS

L

LA

LL

LA

PT

LL

PA

PT

LL

PA

115 bar

115 bar

10 bar

2.11.2 Cargo and Ballast Valves Hydraulic System

General DescriptionAll valves necessary for the normal operation of the cargoand ballast system are hydraulically operated by twoseparate hydraulic power packs situated on Upper Deckcross alleyway. Control of the power pack units and thevalve operation is via the IMS Elsag Bailey mimic and keyboard in the cargo control room.

All remotely operated valves are piston operated exceptfor the liquid dome valves which have vain type actuators.The supply of oil is controlled by solenoid valves arrangedin two racks in the hydraulic room on Upper Deck. RackNo.1 which is on the starboard side as you enter thehydraulic room, controls the ballast, bilge and bunkeringvalves. Rack No.2, situated on the port side controls thecargo valve operation.

The following valves:- the ballast pump discharge valves,ballast pump overboard discharge to sea, main, auxiliaryand stripping/spray pump discharge valves can bethrottled in and stopped at any intermediate positionbetween fully open and fully shut. All other valves remotelyoperated are arranged to be either fully open or fully shut.

The ESDS cargo manifold valves each have their ownhydraulic accumulators to ensure there is always sufficientpressure for their operation.

Cargo Operations, System Capacity and Rating.(illustration 2.11.2a)

There are three electric motor driven hydraulic pumpunits with this power pack, a small 0.75kw motor is usedto drive an oil circulating cooling pump and two mainmotors (26 kW), each driving a hydraulic tandem pumprated at 80 l/min and 5 l/min, with a normal workingpressure 110/115 bar.

Pressure filter: type 10/20 micron, with a pressuredifferential alarm, visual indicator for blockages and amanual change over to a standby filter.

Return filter: 125 micron, with a pressure differential alarmand visual indication for blockage.

Hydraulic oil tank: 700 litres

Cooling pump; flow rate 20 l/h at 5 bar

ESDS hydraulic accumulators, fitted in proximity to theESDS manifold valves with a capacity of 5 litres peraccumulator.

Hydraulic Power Pack No. 2 (Cargo)The hydraulic power pack consists of a 700 litre oil tankwith two sets of hydraulic tandem pumps situated underthe tank. This is best described as a high pressure lowflow and a low pressure high flow system, the valvesconcerned as indicated.

Suction for each of the pumps is through 125 micronfilters, before passing into the main pressure rail throughindividual non return valves. The normal operatingpressure is up to 110 bar, with pressure relief valves set to115 bar. The flow now passes through pressure line filters10/20 micron, fitted with a differential pressure alarmswitch with a manual change over to the standby filter.

The return oil passes through a 125 micron filter beforereturning to the storage tank.

A control panel with alarm indication is fitted to the frontof the power pack tank, which has the selection control forthe pumps in lead / lag configuration. Pressure switchescontrol the pump cut in/out, with low low pressure alarmand pump failure alarm transmitted to the IMS ElsagBailey. The oil level in the tank is monitored with a lowlevel alarm switch and a low low alarm which will trip thepumps. The temperature of the oil is also monitored, witha high temperature trip switch protecting the system.

A small oil circulation pump draws from the service tankvia a 125 micron suction filter, the discharge from thepump passes via a 10/20 micron filter fitted with andifferential pressure alarm and manual by-pass, to a tubecooler which is cooled from the deck sea water system(see section 2.12)

There is no accumulator fitted directly to this system, apartfrom the individual accumulators fitted to the manifoldESDS valves.The accumulators are pressurised byhydraulic lines P4 & P5 up to a working pressure of 110bar, where it will be maintained by the inlet check valveand by the pneumatic pilot valve which controls the outletto the manifold ESDS valves. In the event of the ESDSbeing activated, the pilot air line is vented, enabling theaccumulator control block to change over, allowing thehigh pressure hydraulic oil to be directed onto the closingside of the manifold valve actuating piston. Theemergency hand pump opening and closing connectionsfor these valves are over ridden by the flow from theaccumulator system.

Emergency Hand Pump OperationAll the hydraulic valves apart from the liquid dome valveshave an emergency hand pump connection. There aretwo portable emergency hand pump units, one availableon deck and one in the duct keel space for use on theballast valves. The isolating valves on the distributionblock are first shut off and the flexible hoses from theemergency hand pump fitted to the snap on connectors,the control of direction is via a hand operated change overcontrol block.



2.11.2b Ballast Valve Hydraulic SystemIssue: 1


Control Blocks forBallast Valves

Illustration 2.11.2b Ballast Valve Hydraulic System

Key

Hydraulic Oil System

Accumulator

Drain

To BunkerSystem Valves

To BilgeSystem Valves

Pump Cut Out

Pump Cut In

LL

LA

115 bar

TAHH

Trip

PS

PSTrip

LSTT

Distribution Control Rack No. 1

400 Litre Hydraulic Oil Tank

LLPA

PdA PdA PdA

32Litre

115 bar

MR001VR CE001VR SE158VRMR002VR CE002VR SE160VR CE003VR SE168VR CE004VR SE175VR

200, 201, 202, 204, 207,220, 230, 240, 250, 255,260, 270, 280, 290, 291,320

PT

M M

Ballast Operations, System Capacity and Rating(illustration 2.11.2b)

There are two electrically driven hydraulic pumps in thepower pack, which are used for the control of the ballast,bilge and bunkering valves. Each pump is rated at 80l/minwith a normal working pressure of 110 bar.

Pressure filter: 10/20 micron, with a pressure differentialalarm, visual indicator for blockages and a manual changeover to a standby filter.

Return filter: type 125 with a pressure differential alarmand visual indication for blockage

Hydraulic oil tank: 400 litres

System accumulator: 32 litres

Hydraulic Power Pack No.1 (Ballast)The hydraulic power pack consists of a 400 litre oil tank inwhich two hydraulic pumps are submerged. Suction foreach pump is through a 125 micron filter, the dischargefrom each pump passing into the main high pressure railthrough individual non return valves. The normaloperation pressure is up to 110 bar, with pressure reliefvalves set at 115 bar. A 32 litre accumulator acts as abuffer for the storage of pressurised oil for the period thatthe pumps are not running, the accumulator is itself prepressurised with nitrogen in a bladder located in the top ofthe accumulator which acts to dampen out pressurepulsations. The discharge is led into a common line beforepassing through a 10/20 micron filter, which is fitted with adifferential pressure alarm switch with a manual changeover to the standby filter.

The return oil passes through a 125 micron filter beforereturning to the service tank.

A control panel with alarms indication is fitted to the frontof the power pack tank, which has the selection control forthe pumps in lead / lag configuration. Pressure switchescontrol the pump cut in/out, with low low pressure alarmand pump failure alarm transmitted to the IMS ElsagBailey alarm mimic. The oil level in the tank is monitoredwith a low level alarm switch and a low low alarm whichwill trip the pumps. The temperature of the oil is alsomonitored, with a high temperature trip switch protectingthe system.

The high pressure discharge from the pumps is led via theaccumulator and pressure filter to the distribution solenoidrack which contain the 26 valves that are required to

operate the ballast system. The rack also contains 28further valves for the operation of the bilge and bunkeringsystems.

Emergency Hand Pump OperationAll the hydraulic valves apart from the liquid dome valveshave an emergency hand pump connection. There aretwo portable emergency hand pump units, one availableon deck and one in the duct keel space for use on theballast valves. The isolating valves on the distributionblock are first shut off and the flexible hoses from theemergency hand pump fitted to the snap on connectors.



2.11.2c Cargo and Ballast Valve ControlIssue: 1


LowPressure

HighFlow

Key

Hydraulic Oil

Control Air

EmergencyHand PumpConnection

BallastValveGroup


Illustration 2.11.2c Cargo and Ballast Valve Control

P4 To Port ESDS Accumulators

P4 To Starboard ESDS Accumulators

Pneumatic PilotControl Valves

Typical for eachESDS Valve

ReturnDirect toService Tank

ValveGroup C

ValveGroup B

Liquid DomeValve Group

ESDS Valve Group A

To other ESDSControl Blocks





2.12 Deck Salt Water Cooling SystemIssue: 1


Engine Room Cargo Compressor Room

Cargo Compressor Room

Illustration 2.12 Deck Salt Water Cooling System

Key

Sea Water

H

To BallastPumps

Low Suction Chest

Suction fromBallast Tanks

FromGeneralService Pumps

VacuumPumps

Cargo HeatersObservation Tank /Drains Cooler

HD Compressors

LD Compressors

AntiSiphonLoop

O.6m AboveLoad Water Line

CondensateCooler Outlet

Hydraulic Room

291

H

265

To Engine RoomSW Cooling System

275

285

Cargo HydraulicSystem Cooler

To Engine Room

2.12 Deck Salt Water Cooling SystemThe cargo compressor room is supplied with sea water forcooling the HD and LD gas compressors lub oil system,and for the vacuum pump jackets. A supply is also led tothe cargo heaters condensate drains cooler, which ismounted on the aft bulkhead of the motor room.

The deck salt water cooling system is supplied from 2engine room mounted sea water pumps XA/1496A & B.Normally the pumps will take their suction from either thehigh or low sea water chests. In the situation where theship is in dry dock, the pumps can draw from the ballasttank system via hydraulic valve 265.

The compressor room and cargo heater drains cooler seawater discharge line is led via an anti-syphon loopoverboard through No. 4 starboard ballast tank, thedischarge being 600mm above the loaded water line. Theanti-syphon loop has its vent situated above thecompressor room deck. The deck sea water system alsosupplies the cargo hydraulic system oil cooler which issituated in the hydraulic room on the upper deck.

2.12 Deck Salt Water Cooling System - Page 1Issue: 1


2.13.1a Deck Instrument and General Service Air SystemsIssue: 1


HydraulicRoom

Key

General Service Air

Instrument Air

HydraulicStation

SprayingNozzles

SprayingNozzles

SprayingNozzles

VentMastNo.2

SprayingNozzles

For

cing

ing

Vap

oris

er

Mai

n V

apor

iser

H.D

. Com

pres

sor

Gas

Hea

ters

L.D

. Com

pres

sor

Gly

col H

eate

rs

Stbd. BunkerCrane

Port BunkerCrane

Main DeckLadderHoist

Main DeckLadderHoist

To Suez CanalSearch Light

To Forecastle

Deck

Weed Blow forEmergencyFire PumpSea Water Box

De-watering Pump No.3Secondary Barrier




SupplyfromEngineRoom

BarrierConnection

Water Trapand Drain

Manifold

Manifold

Illustration 2.13.1a Deck Instrument and General Service Air Systems

2.13 Air Systems2.13.1 General Service and Control Air SystemThe general service air is supplied by a single 240m3/h at8.5bar compressor XA/226 mounted in the engine roomwith a 3m3 receiver X/A237 in line.

The control instrumentation air is supplied by 2 x 290m3/hat 8.5bar compressors XA/224A & B mounted in theengine room. The compressors discharge into a 5m3

receiver, before passing into the distribution line via anautomatic refrigeration and absorption dryer unit.Instrumentation compressors are arranged for one to bein the duty run mode and the other to be in a standbycondition. For emergency use there is a cross overconnection between the general service andinstrumentation before and after the air receivers. Theoperation and control of both the general service andinstrumentation air compressors and the dryer unit is fromthe engine room.

The general service air supplies the following deckequipment: bunker crane port and starboard,accommodation ladder hoists port and starboard andsecondary space dewatering pumps mounted in secondarybarrier well. A number of outlets are arranged around thedeck of the ship to facilitate the use of pneumatic powertools etc. At the forecastle there is a facility for connectionof the Suez canal searchlight, there is also a line leadingdown to the emergency fire pump sea chest for weedblowing. At the starboard aft corner of the accommodationthere is a water trap to enable all water to be drained fromthe system.

The control and instrumentation air supplies the followingequipment on deck: stripping excess flow regulating valvenozzles at each cargo tank, the supply of air into thecompressor room for the control of the HD and LDcompressors, vaporisers and heater systems, for theglycol heaters in the motor room and all glycol systemregulating valves for the cofferdam heating. The systemalso operates the No. 2 vent mast riser fire smotheringsystem with the release of nitrogen.

2.13 Air Systems - Page 1Issue: 1


2.14.1a Deck Steam SystemIssue: 1


HC

LC

PIC

HC

LC

PIC

T

T

OdA

Key

Steam

Condensate

Control Air

Sea Water

Instrument

YA/5142

Drip Tray Heatingfor Manifold

From EngineRoom SteamSupply

Return toObservationDrain Tankvia DrainsCooler inEngineRoom

Vent GasHeater

CofferdamHeater

MainVaporiser

YA/ 5500B

VA/ 060VR

VA/ 040VD SP/ 015SC SP/ 016VD

VA/ 041VD

VA/ 040VD

VA/ 041VDSP/ 001VD

YA/ 5500A

VA/ 060VR

VA/ 061VR

VA/ 042VD SP/ 015SC SP/ 017VD

VA/ 043VD

VA/ 042VD

VA/ 043VDSP/ 001VD

YA/5152

YA/5122A

YA/ 5122B

YA/ 5121A

YA/ 5121B

Compressor RoomElectric Motors Room

Illustration 2.14.1a Deck Steam System

YA/5151

SP/ 013SC SP/ 011VD

SP/ 012VD

VA/ 031VD

SP/ 001VD

SP/ 014SCVA/ 032VD

SP/ 001VD

VA/ 033VD

SP/ 001VD

SP/ 021SCVA/ 034VD

SP 001VD

SP/ 021SC SP/ 002VD

SP/ 021SC SP/ 002VD

SP/ 002VD

VA/ 035VD

SP/ 001VD

SP/ 021SC SP/ 002VD

SP/021SCSP/002VD

VA/ 052VD

VA/ 036VD

SP/ 001VD

L.D.Compressor

Oil Sump

L.D.Compressor

Oil Sump

H.D.Compressor

Oil Sump

VAO24

VAO25

VAG52

VA/ 061VR

Boil OffHeater

ForcingVaporiser

H.D.Compressor

Oil Sump

Drip Tray Heatingfor Manifold

Deck SeaWater Cooling

ICARE GasSample Analyser

CondensateDrains Cooler

Observation Tank

DrainDrainTo Engine RoomAtmosphericDrains Tank

2.14 Deck Steam System2.14.1 Deck Steam Description

(See Illustration 2.14.1a)Deck steam is distributed to the cargo compressor room,electric motor room and main deck.

The cargo steam is used for heating of the following heatexchangers.

a) Main vaporiserb) Forcing vaporiserc) Gas compressor sump heatingd) Vent Gas heatere) Glycoled water heaters

The steam to inert gas plant is for the inert gas generatorburner gas oil atomiser system.

Heating steam at 8 bar, 175°C is supplied from the LPheating steam range via water separators.

The heating drains from the cargo heat exchangers areled to a condensate drains cooler (located outside thecompressor and motor room on the aft bulkhead), which iscooled from the deck sea water cooling system (seesection 2.12). The drains having passed through thecondensate cooler flow into an observation tank, whereany oil contamination will be spotted, before returning viathe atmospheric drains tank to the engine room. Theobservation tank on deck is fitted with a gas analyser forthe indication of a possible tube failure in any of the cargoheat exchangers.

The degassing tank has its vent led on deck to a safeposition above the cargo compressor room.

The heating drains from the inert gas plant are led to thecontaminated drains cooler in the engine room, beforepassing on to the observation tank and atmosphericdrains tank.

Steam to Cargo Compressor RoomThe steam supply to the cargo compressor room is viaisolating manual valves VA025 and VA024 located in theengine room.

Glycoled Water Heaters The use of these 2 heaters is to ensure heating of thecofferdams and liquid dome of each tank, boil off heatingand tank warm up.

The heating system maintains a permanent ambienttemperature above +5°C.

The heat exchangers are of shell and tube design with theglycol water passing through the tubes in 2 passes.

Steam is fed to the heaters by means of two control valvesie high flow steam controller and low flow steam controller.

The high flow and low flow steam controllers operate at5 bar and 3 bar steam pressure respectively depending onthe load conditions (refer to 2.5.x for more information onglycoled heaters).

VaporisersTwo steam heated vaporisers are located in the cargocompressor room. They are both of shell and tube typedesign.

One is the main vaporiser and the other is designed as theforcing vaporiser.

The steam supply to these vaporisers is by means of apneumatic control valve on each unit.

Inert Gas Generator Atomising SteamThe atomising steam is dried in a superheater fitted in thecombustion chamber envelope, before being fed to themain burner. Prior to starting the unit, water in the steamsupply can be drained through the manual bypass valveon the drain trap. In service, the drains discharged fromthe main burner can be adjusted through a pressurereducer.

An ON-OFF pneumatic operated valve in the steam lineopens a few seconds after ignition of the pilot burner andcloses if the pilot and main burners are out of operation.

Operating procedures

Supplying Steam to Cargo Auxiliaries Room andElectric Motors Room

1 Open drain valves on water separators on the decksteam line.

2 Crack open manual valve VA025 and VA024 to supplysteam on deck.

3 Warm through lines until steam is seen blowing outfrom the water separator drain lines.

4 Open fully manual valves VA025 and VA024.

5 Set up the gas heat exchangers’ drains cooler for useand opening sea water inlet and outlet cooling watervalves.

6 The fuel gas heater, main heater, forcing vaporiserand main vaporiser are then set up and operated asdescribed under operating procedures for gas heatersand vaporisers 2.5 and 2.6.

7 For the glycol cofferdam steam heater, the drains areled to the observation tank in the engine room via amanual valve which has to be opened.

8 The glycol boil off steam heater, main and forcingvaporiser, vent gas, HD and LD compressor sumpheater drains are led to the condensate drains coolerand observation tank on deck, before passing to theatmospheric drains tank in the engine room.

Supplying Steam to Inert Gas Generator

1 Open isolating valves on dryer unit steam drains trap.

2 Open isolating valves on inert gas generator steamdrains trap.

3 Open heating drains return valve to drains cooler inengine room.

4 Crack open manual valve in engine room for steamsupply to inert gas generator.

5 Drain water from steam lines for inert gas generator byopening the bypass on the drains trap for inert gasgenerator unit.

6 Open up manual valve fully when lines are fullywarmed through.

Number 2 Riser Gas HeaterThis unit is also supplied with steam from the deck steamsystem, raising the temperature of vented gas from -140to 0°C. A high temperature alarm is provided on the gasoutlet from the heater and alarm inlet temperature low (-116°). The condensate outlet has a low temperaturealarm with trip, a high level alarm with trip and a levelswitch fitted.

2.14 Deck Steam System - Page 1Issue: 1


CRYOSTAR

Part 3Controls and Instrumentation

3.1.1a IMS System OverviewIssue: 1


Cargo(with redundancy)

Cargo Plants Ballast & Fuel Oil Valves

Gate-Way

Gate-Way

CTS

Cargo Redundant INFINET

Ballast(with redundancy)

Illustration 3.1.1a IMS System Overview

OperatorInterfaceStation


WheelhouseAlarm

Back-up


EGP(with redundancy)

T/G1

MSWB

ER SensorsT/G2 T/G3

Gate-Way

Boiler 1Control

Engine Room Redundant INFINET

ER + Auxiliary(with redundancy)

Boiler 2Control

TorqueMeter

System

MCC

Gate-Way

OfficerÕs Cabins, Mess Cargo Alarm

OfficerÕs Cabins, Mess Engine Room Alarms

Cargo System Alarm

Machinery System Alarm and Engineer Calling

AlarmBack-up

AlarmBack-up



LAN


Ship AdministrativeLAN

INFINET to INFINETBridge

Engine Control Room

ACCOMMODATIONWHEELHOUSE

SHIPS OFFICE

Cargo Control Room

Key

RS 422 Cable

PART 3: CONTROLS ANDINSTRUMENTATION

3.1 Integrated Monitoring SystemSystem Overview Maker: Elsag Bailey Type: INFI-90

Control and monitoring facilities for the cargo systems areprovided by the Integrated Monitoring System (IMS) INFI90. The IMS functions can be classified as follows:

alarms and alarm management;

process control;

trending;

saving and retrieving files;

alarm / log printer.

The Mulitifunctional Processor Module (MFP) is the heartof the INFI 90 system, which accepts both digital andanalogue input/output signals. The MFP modules operateon a local area network called the Control Way, whichallows complete process data to be shared to the operatorconsoles called Operator Interface Stations (OIS).Operator interface stations are located in the cargo controlroom and engine control room. The bridge and theC.E.O's cabin OIS, offer only an overview of alarm, controland monitoring information.

Operator StationThe CCR is the main location of the IMS, with the CPUcabinets which are fed via an UPS system located on theafter bulkhead of the CCR. The main console in the cargocontrol room contains two operator stations, which canperform the cargo operation supervision, control,configuration, alarm acceptance and log printoutfunctions. Each monitor is linked to a trackball which sitson the console desk top and a command keyboard, whichis located in a draw to the side.

Access is gained to the cargo operating system by placingthe trackball on the SNAM Master Menu grey key on theoperator screen marked Ballast and Cargo Systems andleft clicking. A pop up menu will appear called CargoOperation Monitoring, which is used to gain access to therelevant process, again with the positioning of thetrackball and left clicking.

The keyboards are used for entering alphanumerical dataand issuing commands, having first selected the processtarget with the trackball.

Apart from the information log print out, it is also possible fora screen shot (dump) being sent for hard copy to a printer.

AlarmsAn alarm condition is indicated on the operator screen andalso sent to the designated alarm printer with the time anddate.The alarms are divided into 6 groups according to theirpriority status;Group S; forms the diagnostic (internal) systemGroup 1; forms the alarms designated criticalGroup 2; forms the alarms designated non-criticalGroup 3; forms the alarms of the fire detection systemGroup 10; forms the alarms for the boiler port sideGroup 11; forms the alarms for the boiler starboard side

Command ControlCommand of the electric pumps is via the MSDD (Multi-State Device Driver) pop up display, which is initiated fromthe trackball selection of a pump. The visual image on thescreen allows the operation of the pumps via thecommand keyboard, with the selection option of eitherautomatic or manual operation. The display shows the laststate selection, indication state, feed back, auto/manualselection and keyboard command state. When selected tothe run state, the image of the pump (triangle in a circle)will change from blue (Stopped) to green (Run). A yellowindicator will appear in the bottom left hand corner of thedialog box if it is in an alarm condition.

Command function of the valves that are either Open orClosed is from the RCM (Remote Control Memory) pop updisplay, which is initiated from the trackball selection of avalve. The visual image shows the current position andstate of the valve. The keyboard is used to give thecommand order. When selected and the command toopen is given, the visual image of the valve will changefrom red (Closed) to green (Open). A yellow indicator willappear in the bottom left hand corner of the dialog box if itis in an alarm condition.

LoggingData is collected by the log over a period of time. Thecollection period depends on the type of log: either on aregular schedule or only under certain conditions. Whenthe log ends, the data can be printed automatically to aprinter. The log data is retained on the hard disk, so that itis possible to reprint the log. Only a limited number ofretained historical log data files can be kept on thecomputer's hard disk; as new logs are collected, the oldestare deleted. To keep log data files as permanent records,it maybe copied to floppy disks. Reprints of log files canbe done directly from floppy disk if required.

Six types of logs are available: periodic, trigger, systemevents/operator action, trend, trip, and SOE logs.Periodic logs collect and print data at regular intervals oras the events occur. Periodic logs are suited for logsrequired on a regular schedule, such as an end-of-shiftlog. The system can configure up to 64 periodic logs.

Trigger logs collect and print data according to triggerconditions. Using trigger tags, it is possible to define fourtypes of trigger conditions: collect, print, hold, andresume. Data collection begins when a collect triggercondition is detected. Data collection stops and the logprinted when a print trigger condition is detected. Triggerlogs are suited for batch logging where a batch can startand end at any time. The system can be configured for upto 64 trigger logs.

System Event/Operator Action logs record all tag alarmsand are printed at regular intervals. The system caninclude in the log returned-to-normal alarms and digitalchanges of state. The system can also create a log ofoperator actions, such as control actions, logins, andalarm acknowledgments. The printed logs list events lineby line, in which specific information can be shown oneach line. There are only the two system event logs: alarmlog and operator action log.

Trend logs print out collected trend data.. Trend logs areconfigured to print at regular intervals. The printed formatof a trend log is fixed; with the specific the trend tagsincluded in each log. The system can configure up to 64trend logs.

Trip logs collect data before and after a trip. A trip occurswhen values or states of tags that are specified meetconditions that have been set (e.g.. when an analoguetag's value exceeds 100).The specific tags are arrangedto collect data for the amount of data collected before andafter the trip. When a trip condition occurs, a trip logcontaining the pre-trip and post-trip data is printed. Theprinted format of a trip log is fixed; with only the specifictags to include and the amount of pre-trip and post-tripdata. Trip log data can also be plotted onto a graphicdisplay. The system can configure up to 20 trip logs.

SOE (Sequence of Events) logs collect data for selectedcritical digital points where the given situation requiresthat the sequence of changes of state for these points orgroup of points be known in the most exacting wayspossible. SOE logs meet this requirement by listing alldigital state transitions in time order and in one-millisecond resolution.

TrendingTrend displays may be obtained for the display elementsin which a variable has been configured to be logged,such as a level or a temperature. Trend displays areprovided in either one of two forms ie,

either current trend displays

or historical trend displays

Trend logs present trend data in columns. The source forthe trend log data is the actual trend data file. Theresolution is independent of the actual trend sample.Trend graphic displays and trend logs show the same databecause both sample the trend data file in the samemanner.

Up to 64 trend logs can be configured, and each can haveone of four periods: hour, shift, day, and week.

Up to 20 trend tag names can be configured on a singlelog, and up to 240 values can be reported for each trendindex. Trend logs can be configured to print automaticallyor manually (on demand).

A more detailed account is given in the Lan 90 OperationInstruction Manual.

Illustrations 3.1.1b and 3.1.1c give an over view of thescreen displays

3.1 Integrated Monitoring System - Page 1Issue: 1


Typical System Screen Shots - Page 1Issue: 1


H

255

207

H

280

355

330

H

270

- 0 Bar

0.8 A

- 0. Bar

201

H

H

230 H

BALL . P1

REMOTE

H

240

2048.3 %

202

H

H

H

250H

BALL . P2

REMOTE

260

0.1 Bar

0.6 A

0.2 Bar

INERT GASSCRUBBER

350

DIRECTBILGE SUCTION

H

290

H

291

H

BALL. TANKS

H

CONTROLS SEL. ECR ******CROSS OVER

13%

4.7%

TUNNELSUCTION

0.0 Bar0.0 Bar

EDUCTOR

- 0.1 Bar

305

205

0.0 %

TRIM 0 . 25 m LIST 0 . 59 DEG WIND SPEED ***** kn WIND DIRECTION *** DEG

BALLAST-PUMPS

HYDRAULICOIL PRESSURE 118.4 Bar

OUT BOARD

OUT BOARD

CCONTROLACQUIST.

265

SEA CHEST

ESD SIGNALSTO SHORE (ELECT)

STOP MAINCARGO PUMPS

STOP SPRAYPUMPS

STOP EMERG.PUMP

STOP H. D.COMPRESSORS

CLOSING MANIF.VALVES

STOP L.D.COPMRESSORS

CLOSING MASTERFUEL GAS VALVE

S

R

S

R

RESET

1

1

TANK PRESSURE

HEADER PRESSURE

COMPR. ROOM VENTIL. OFF

HYDR. POWER PACK L.P.

HIGH PRESS MANIFOLD

&

A DISAB.

B DISAB.ESD A STATUS

ESD B STATUS

NORMAL

NORMAL

MAIN SWB POWER FAILURE

FUSE PLUGS

321

MANIF.STBD

321

MANIF.PORT

432

CARGO TKGAS DOME1432

CARGO TKLIQ. DOME121

COMP.ROOM

432PORT

1

1 1

1

4321STARBOARD

OVERR. AT SEA

VERY HIGH LEV (>99%)1

2

3

4TANKS

1

1

2

3

4TANKS

1

1

MANUAL RELEASE

SDPT

AFTDECK FORE

DECKCOMPRROOM SDPT

MANIFOLD

1

CCR WH

ESD SYSTEM A

ESD SYSTEM B

TEST

TEST

OFF

OFF

&SHIP/SHORE PNEUM

INHIBIT

SHIP/SHORE ELECTR

1

C

PORT STBDLP

AIR

TRIM 0 . 00 m LIST 0 . 00 DEG WIND SPEED 0 . 00 kn

CARGO ESD STATUS

ESD SYSTEM A

ESD SYSTEM B

WIND DIRECTION 0 . 0 DEG

SECONDARY SPACE

DOUBLE HULL

WATER PRESENCE INSIDE SECONDARY INSULATIONTANK 4 TANK 3 TANK 2 TANK 1

ALARM VERY HIGH

ALARM HIGH

TANK 1-117.12-131.69-162.65-162.70-162.59

TANK 2-117.72-117.63-117.64-117.56

TANK 3-115.01-127.00-162.75-162.77-162.71

TANK 4-113.19-125.20-162.73-162.71-162.68

CARGO TEMPERATURE ( C)

TOP75%50%25%BOT

SECONDARY BARRIER TEMPERATURE ( C o) TANK 4

-28-35-83-42-32-48-94-79-42

TANK 3-33-36-63-55-31-43

-101-60-48

TANK 2-30-50-41-58-40-47

-103-57-53

TANK 1-32-39-81-50-20-42

-106-72-42

-44 -52 -50 -37

1 TANK TOP-CENTER2 AFT BLKD-CENTER 3 BOTTOM-AFT STBD4 BOTTOM-AFT PORT5 WALL-AFT STBD (UP)6 WALL-AFT PORT (DW)7 BOTTOM-AFT CENTER8 BOTTOM-CENTER9 FORE BLKD-UP

10 FORE BLKD-DOWN

15 . 512 . 215 . 414 . 815 . 916 . 1

14 . 813 . 414 . 615 . 014 . 710 . 7

14 . 413 . 714 . 715 . 014 . 514 . 9

15 . 714 . 815 . 716 . 416 . 014 . 0

1 TANK TOP-CENTER2 AFT BLKD-CENTER7 BOTTOM-AFT CENTER8 BOTTOM-CENTER

11 TANK TOP-FORE12 WALL-CENTRE STBD

DOUBLE HULL TEMPERATURE ( C o)

1

11

9210

8

7

12

5

3

PORT STBD

TRIM 0 . 00 m LIST 0 . 00 DEG WIND SPEED

WATER BARRIER DETECTOR TEST

0 . 00 kn WIND DIRECTION 0 . 0 DEG

TEMPERATURE SENSORS

6

4

TRIM 0 . 10 m LIST 0 . 00 DEG WIND SPEED 0 . 00 kn WIND DIRECTION 0 . 0 DEG

BALLAST-TANKS

HYDRAULICOIL PRESSURE 117.9 Bar

TK 4 PORT2.004 m

874.8 m3

H

H

H

241

341

H PORT 6.846 m

320

TK 4 STBD1.938 m

844.7 Cm3

H

H

242

342

H STBD 6.918 m

TK 3 PORT19.868 m2835 m3

H

H

231

331

TK 3 STBD19.967 m2849 m3

H

H

232

332

TK 2 PORT4.063 m1525 m3

H

H

221

321

TK 2 STBD4.118 m1531 m3

H

H

222

322

TK 1 PORT20.175 m2401 m3

H

H

211

311

TK 1 STBD19.634 m2303 m3

H

H

212

312

H

310

H

220

H

210

H

200

H FWD

6.590 m3

FOREPEAK

13.496 m976.3 m3

H AFT

7.410 m

AFTPEAK

2.161 m271.4 m3

H STBD 6.918 m

BALL. PMPS.

DENS 1.025 kg/Cm 3

>

>

>>

>

> >

>

>

1>

1>

1>

1>

1>

1>

T

275 295285

340

22.3

21.1

AMBIENT AIR TEMPERATURE ( C)

SEA TEMPERATURE ( C)

3.1.1b Typical System Screen Shots

Typical System Screen Shots - Page 2Issue: 1


TRIM 0 . 25 m LIST 0 . 45 DEG WIND SPEED 0 . 00 kn WIND DIRECTION 0 . 1 DEG

HYDRAULIC 0.7 BarOIL PRESSURE 5.8 BarGLYC. SYS.

17.1 0C 411 mbar

16.8 0C 62.4 mbar

MANUAL TRIP

GLYC. OUTL.

451

H

FCV

TVC

FVC

TVC

WU/BO HEATER 1

WU/BO HEATERS

GLYC.IN.

GLYC.INL.

453

450

MANUAL TRIP

GLYC. OUTL.

WU/BO HEATER 2

GLYC.IN.GLYC.INL.

452

H

T

T

454

405

V. MAIN

063

L. MAIN

BOILERS

19.5

72

28

105

-5

460

AUTO

CO 105

REMOTE

REMOTE

REMOTE

MANUAL

CO 72

REMOTE

0C

%

%

%

%

H

HDC 1

MAN

REMOTE

AUX LO P

REMOTE

HDC1 ALARMSTRIPEMERG. STOPCOMMON ALARMHIGH VIBR.

HDC1 STATUS

430

PALPALLTAHTAHH

PDALPDALL

TAHHTAH

TAH0.00 ASURGEVALVE

1.10 mBar 24.4 C

PAL 1.44 mBar

108 DEG

IGV

H

410

OIL SUPPLY

H

HDC 2

MAN

LOCAL

AUX LO P

REMOTE

HDC2 ALARMSTRIPEMERG. STOPCOMMON ALARMHIGH VIBR.

HDC2 STATUS

440

PALPALLTAHTAHH

PDALPDALL

TAHHTAH

TAH0.00 ASURGEVALVE

444 mBar 25 . 1 C

PAL 212 mBar

80 DEG

IGV Y VIBRATION -0.5 mmE-3

H

420

OIL SUPPLY

TRIPRST

TRIM 0 . 00 LIST 0 . 00 DEG WIND SPEED 0 . 00 kn WIND DIRECTION 0 . 0 DEG

HYDRAULIC 107 BarOIL PRESSURE 121 BarLOADING

HIGH DUTY COMPRESSORS

26 C

27 C

X VIBRATION 0.4 mmE-3

SEAL GAS

MANUAL

CO 0.0

REMOTE

SEAL GAS

MANUAL

CO 0.0

REMOTE

TAL

TAL

LAL

LO SUMPTANK

LAL

LO SUMPTANK

H

LDC 1

MAN

REMOTE

AUX LO P

REMOTE

LDC1 ALARMSTRIPEMERG. STOPCOMMON ALARMHIGH VIBR.

LDC1 STATUSREADY TO START

431

PALPALLTAHTAHH

PDALPDALL

TAHHTAH

TAH0.000 RPMSURGEVALVE

461 mBar 16.4 C

PAL

SET TIME

12.0

SET TIME

24.0

98 . 7 mBar H

411

OIL SUPPLY

H

LDC 2

MAN

REMOTE

AUX LO P

REMOTE

LDC2 ALARMSTRIPEMERG. STOPCOMMON ALARMHIGH VIBR.

LDC2 STATUS

441

PALPALLTAHTAHH

PDALPDALL

TAHHTAH

TAH0.000 RPMSURGEVALVE

1 . 10 mBar 25 . 5 C

PAL 0 . 61 mBar

107 DEG

IGV

X VIBRATION - 0 . 2 mmE-3

H

421

OIL SUPPLY

TRIM 0 . 00 LIST 0 . 00 DEG WIND SPEED 0 . 00 kn WIND DIRECTION 0 . 0 DEG

HYDRAULIC 107 BarOIL PRESSURE 121 BarLOADING

LOW DUTY COMPRESSORS

0.0 C

-25.0 C

X VIBRATION 16 . 2 mmE-3

SEAL GAS

108 DEG

IGV

MANUAL

CO 0.0

REMOTE

GAS ONLY

MANUAL

CO 58

SEAL GAS

MANUAL

CO 0.0

LOCAL

TAL

TAL

LAL

LO SUMPTANK

LAL

LO SUMPTANK

********

NITROGEN SYSTEM DP PR/MAIN HEADER:ATM.PF 1017 mBar

SECONDARY HEADERPRIMARY HEADER

IN PR.

P P

AUTO

CO 6.9

IN SEC

AUTO

CO -4

SPARE

MANUAL

CO 0.0

VAC. P1

REMOTE

NotAv1

VAC. P2

REMOTE

NotAv1

OUT PR.

AUTO

CO -5

SPARE

MANUAL

CO 0.0

IN SEC

AUTO

CO -5

501

502

FAIL 1FAIL 2COMM.ALARM 1-2

N2 PROD. PLANTS STOR.TANK

TAH

TAL

VENTRISER TK3

VAHH

TAH

TALVAHH

TRIM 0.24 m LIST 0.32 0 WIND SPEED WIND DIRECTION 0.1 0.00 SB DEGkn

M. TRIP

PORT

STBD

TRIP

L.O.FALL.O.FALC.W.FAL

L.O.FALL.O.FALC.W.FAL

112 mBar

6.08 mBar

10.5 mBar

3.16 mBar

4.38 Bar0.87 BarHYDRAULIC

OIL PRESSURE

mBar 3.21

mBar 5.79

1018 mBar17 0C

6.02 mBar

3.44 mBar

PDALL

113 mBar

5.78 mBar3.65 mBar

PDALL

113 mBar

6.14 mBar3.42 mBar

PDALL

5.89 mBar2.67 mBar

PDALL

3.04 mBar

6.00 mBar

P

PP

P

H

H

MAIN VAP.

TRIPRST TRIPRST

TK4

TEMP.NON. MAIN VAP..

TK3 TK2 TK1

112 mBar

3.1.1c Typical System Screen Shots

3.2.1 Control Room LayoutIssue: 1


U.P.S

Elsag Bailey I.O.sFans Shut Down

LD No 1Surge Control

LD No 2 Surge Control

HD No 1 Surge Control

HD No 2 Surge Control

Fire Push Button

Electric Motor andCompressor Room Fire Mimic

TecnocoNitrogen GeneratorControl Panel

99% and 98.5%Cargo Tank Level Alarm

Inert Gas Indicator Winch MonitoringSystem

CCR AirConditioning

ForwardIllustration 3.2.1a Control Room Layout

Mooring ControlPrinter

Load MasterPrinter

Elsag Bailey Screen Shot Printer

LogPrinters

Foxboro CTSPrinter

ICARE Primary and Secondary Insulation Space Gas Detection System

ESDS Panel

Foxboro CTSMonitor

Foxboro CTSBackup Computer

Ship NetComputer

Elsag BaileyIMS Monitors

AutomaticWinch Control

Overhead SchematicCargo/Ballast Status Board

Cargo Control Console

Load MasterMonitor

CCTVElsag BaileyIMS Monitors

Foxboro CustodyTransfer System

3.2 Cargo Control Room, Cargo Consoleand Panels

(See Illustration 3.2.1a)Supervision of all cargo handling operations is carried outfrom the Cargo Control Room (CCR): located on deck Bof the accommodation block with a forward looking view.

The CCR houses the Cargo Console and the controlcabinets for the ELSAG Bailey (IMS) (see 3.1) a printerdesk, control cabinets for the Emergency Shut DownSystem (ESDS), and the analyser cabinet for the ICAREGas Detection system.

The Cargo Console is situated on the starboard forwardside of the CCR and contains the following:

1 Two IMS operator stations;

2 One operator station for the Custody Transfer System(CTS) (see 3.3);

3 A CCTV monitor showing the port and stbd manifoldareas and trunk deck area.

4 Master fuel gas and nitrogen injection valve control.

5 Automatic winch control.

6 CETENA Loadmaster station

7 ESDS panel

8 Manual trip button

9 Analogue gauges for the main cargo pumps,stripping/spray pumps and auxiliary cargo pump, awind speed and direction indicator, and analoguecargo tank level indicators.

Printing facilities for 1 and 2 are located on a desk on thestarboard bulkhead.

3.2 Cargo Control Room, Cargo Console and Panels - Page 1Issue: 1


Custody Transfer SystemDistributed Control SystemTelephone

Ship to Shore Communication(Hot Line)

CCTVAlarm Indication PanelDistributed Control System

ESDS PanelTrack ball Track ball

Load MasterAnalogue GaugesFor Cargo Pumps

AutomaticWinch Control Master Fuel Gas

and Nitrogen InjectionValve Controls

Keyboard

Selection SwitchFor Emergency Cargo Pump

Manual Trip Buttons

3.3 Custody Transfer SystemIntroduction(See Illustration 3.3.2a)LNG is bought and sold on its calorific content, normallyexpressed in Btu’s rather than on a volume or weightbasis. However, at the present time there are no practicalinstruments available to determine the net calorific contenttransferred during loading and discharge so that for themoment this value is determined partly by measurementand partly by analysis of cargo calculation by means of thefollowing formula:

Total energy transferred Q = Vd HL - VTsPvHv

TvPs

where :

V = the apparent volume of cargo loaded or dischargedat an average temperature Tl (m3)

d = density of cargo at temperature Tl (kg/m3)

HL = the gross calorific value of the cargo calculated fromthe component analysis of the cargo (Btu/kg) frommean value of loading and discharge sample (MLNGuses MJ/kg)

Ts = standard temperature (°K)

Tv = average temperature of gas in the cargo tanks eitherbefore loading or after discharge (°K)

TL = average temperature of liquid in cargo tanks eitherbefore loading or after discharge

Pv = the absolute pressure of the gas in the cargo tanks,that is, gauge pressure of gas + barometric pressure(mbar)

Pv = standard atmospheric pressure (1013mbar)

Hv = the gross heating value of gas vapour at 15.6°C and1013mbar (Btu/m3). This value is assumed to be aconstant 36,000 Btu/m3 based on pure methane(MLNG uses Btu/scf)

In establishing the value of the cargo transferred to andfrom the ship, the vessels responsibility is limited tomeasurement/calculation of the following values: V, Tv,Pv. These measurements/calculations are made by shipand shore representatives and are normally verified by anindependent surveyor. The values HL and d aredetermined ashore at the loading and discharge ports andthe calculations are completed by the buyers and sellers.

The quantity of cargo delivery is expressed in MMBtu ortonnes.

3.3.1 Custody Transfer MeasurementsThe Foxboro Custody Transfer CT-IV System providesthe high accuracy measurements and data logging oflevels, temperatures and pressures required for thecalculation of total LNG Cargo loaded or discharged.

All Custody Transfer Measurements can be displayed ona video monitor and in addition liquid level measurementsof each tank can be individually displayed on the remote4-Digit. LED-Type digital indicators.

The system automatically scans and prints the values of theselected measurement. In addition, the data is converted tovolumetric and mass measure, corrected for the ship’s listand trim based on manual and automatic inputs from asoftware configured to handle various functions.

The software configuration includes :

1 manually input density data representative of the totalcargo from a cargo composition library stored inmemory (up to 10 composition and density values isavailable).

2 2 analog inputs for list and trim.

3 volume expression in cubic metres

4 mass expression in tonnes.

Custody transfer measurement takes place before andafter loading and discharging. During gauging, all cargosystems on the ship should be closed and the shoreconnections isolated or disconnected. No ballastoperations should take place during measurement and thevessel should, if possible, be on even keel and upright.However, the operation can be conducted with a slighttrim if the corrections included in the tank calibrationtables are applied.

Custody Transfer Documents are produced detailing thevolumes of cargo and vapour transferred during bothloading and discharge operations.

Level measurementThe level measurement system consists of a long coaxialsensor installed in the tank and extends over the full depthin which the level is to be measured.

The liquid level is determined by measuring the electricalcapacitance of the sensor segment intersecting the liquidlevel. The capacitance of this segment is compared withthe capacitance of a reference segment located below theliquid surface. The ratio of these two measurementsresults in the accurate determination of liquid level that is

independent of liquid properties such as dielectricconstant, temperature and density.

This ratiometric method of cargo level measurementincludes an innovative calibration assurance featureincorporated to maintain the accuracy of the levelmeasuring sub system; this system is called the ON-LINEValidation System.

The level measurement accomplished provides an accuracyof ± 7.5mm over the entire gauging height. The displayresolution is 1mm at the system workstation and printer.

In the event of failure of the level sensing devices, theHSH 806 float gauges may be used for levelmeasurement providing that approval is given by theshore representatives.

The accuracy of the float gauge is the same as thecapacitance gauge.

! CAUTIONTo avoid failure the float of the float gauge must bemaintained blocked at the top position except whenduring the actual measurement.

The total gross number of cubic metres of cargo in thetanks before and after loading or discharging is calculatedusing the average level reading determined. This volumeis corrected for heel, trim, volume, vapour pressure andcargo and vapour temperatures.

The difference in these volumes at the start and end of theoperation will be taken as the apparent volume (m3) ofcargo delivered.

Temperature MeasurementTemperature measurement is accomplished by means ofPlatinum Resistance transducers (500ohms) providing anaccuracy of ± 0.2°C from -165°C to 145°C, ± 0.3°C up to- 120°C and ± 1 - 5°C up to + 80°C.

Data is displayed at the system workstation and printerwith a resolution of 0.01°C.

There are five active and five spare temperature sensorsin each tank and each reading is recorded.

The determination of whether the temperature point is invapour or liquid will be made from the liquid levelindication. It is safe to assume that any point that indicatesa temperature of more than 3° above the LNGtemperature must be in the vapour space.

Although the temperature variation over the depth of liquidshould be no more than a fraction of a degree, thevariation of vapour temperature, particularly at the end ofdischarge, will be more pronounced.

Pressure measurementAbsolute pressure measurement in each of the cargo tankis determined by intelligent pressure transmitters. Theaccuracy of the measurement is ± 0.1% of span to aresolution of 1mb at system workstation and printer.

Range of measurement is 800 to 1400mb. Ambienttemperature effect on the transmitter is ± 0.2% per 55°Cchange between limits of -30°C and +60°C.

3.3.2 Independent Very High Level Alarm SystemTwo very high level alarms per tank are provided byindependent point sensing elements. Fixed sensors insidethe cargo tanks detect the cargo at predetermined levelsand system accuracy is ± 6mm.

The very high alarm adjusted at 98.6% of the tank height,when activated will close the corresponding tank fillingvalve.

The very very high alarm adjusted at 98.5% of the tankheight, when activated will initiate an Emergency ShutDown Alarm (ESD) (refer to Section 5.2). This involves theshutting of manifold and tank loading valve of the tank inquestion. DCS has facilities to inhibit at 98.5 and 99 toallow opening of tank valve during the level alarm testing.

In addition, a blocking function is provided to allow allcargo tank level alarms to be overridden when at sea.

3.3 Custody Transfer System - Page 1Issue: 1


3.3.2a CTS MeasurementIssue: 1


Liquid Dome

High SensingRange 99%

98.5%

100%

75%

50%

25%

0%

Mid SensingRange

Low SensingRangeTank

Bottom

Feed Through

Coaxial Cables toControl Unit via Zener Barriers

HSH 806 Level Indicator

Illustration 3.3.2a CTS Measurement

High Segment

Middle Segment4 Per Tank

Local Level Indicator

Level Gauge

Weather Deck

6" Full Bore Ball Valve

Tank Ceiling

Primary Barrier

Insulated SupportBrackets

Low Segment

Column Support

3.3.2b Cargo Tank Temperature MeasurementIssue: 1


Illustration 3.3.2b Cargo Tank Temperature Measurement

1

StarboardPort

11

9

2

10

8

74 3

5

12

6

Key

Secondary Space

Double Hull

Secondary Barrier Temperature C 1 Tank Top Centre 2 Aft. Bulkhead Centre 3 Bottom Aft. Stboard 4 Bottom Aft.Port 5 Wall Aft. Starboard (Up) 6 Wall Aft. Starboard (Down) 7 Bottom Aft. Centre 8 Bottom Centre 9 Forward Bulkhead Up10 Forward Bulkhead Down

Double Hull Temperature C 1 Tank Top Centre 2 Aft. Bulkhead Centre 7 Bottom Aft. Centre 8 Bottom Centre 9 Forward Bulkhead Up11 Tank Top Forward12 Wall Centre Stboard

°

°

Cargo Record Sheet - Page 1Issue: 1


3.3.3a Cargo Record Sheet

TRANSPORTI MARITTIMI

PORT ................................................ DATE .................................................N˚ .....................

LNG/C ...................................................

CARGO RECORD

CARGO VOLUMES WHEN VESSEL IS LOADED

VESSEL LIST ...... VESSEL TRIM ................

Cist. N˚

Tank N˚

LIQUID LEVEL IN METRES LIQUID VOLUME IN CUBIC METRES

Gauge Reading a Trim Correction b List Correction c Tape Correction d Correct Level e Volume At -160˚C Multi Temperature Correct Volume f

Liquid Average Temperature -˚C

Liquid Average Temperature -˚C

1-S

1-D

2-S

2-D

3-S

3-D

4-S

4-D

VAPOUR SPACE

Temperature ˚C Pressure mm H2O Tank Capacity m3 Vapour Volume m3

CARGO VOLUMES WHEN VESSEL IS EMPTY

VESSEL LIST ...... VESSEL TRIM ................ DATE ...................................

TOTAL .................................

FACT .......................... CORRECTED TOTAL .......................

AVG ............... AVG ............... TOTAL ..........................

TOTAL .................................

FACT .......................... CORRECTED TOTAL .......................

AVG ............... AVG ............... TOTAL ..........................

Cist. N˚

Tank N˚

LIQUID LEVEL IN METRES LIQUID VOLUME IN CUBIC METRES

Gauge Reading a Trim Correction b List Correction c Tape Correction d Correct Level e Volume At -160˚C Multi Temperature Correct Volume f

1-D

1-S

2-D

2-S

3-D

3-S

4-D

4-S

1-D

1-S

2-D

2-S

3-D

3-S

4-D

4-S

Avg.

VAPOUR SPACE

Pressure mm H2O Tank Capacity m3 Vapour Volume m3

SPECIFIC GRAVITY

Tank N˚ Reading g

CUBIC METRES

THERMIES

BTU

METRIC TONS

h

i

j

k

NET LIQUID CARGO VOLUME

(Difference between loaded vessel and empty vessel corrected liquid volumes)

CUBIC METRES

VAPOUR DISPLACEMENT

(Difference between empty vessel and loaded vessel corrected vapour volumes)

Average Vapour

Temperature ˚CAverage Vapour

3.3.3 Failure of CTS ComputerIf the computer should fail during custody transfer, it isusually still possible to read and record the individuallevel, temperature and signal readings from the localdigital read-out panels otherwise the levels have to bemeasured using the HSH 806 float gauges. The volumecalculations and corrections have to be made by handusing the hard copy of the tank gauge tables.

The Cargo Record report sheet is used in conjunction withthe gauging tables, which contain the correction figuresfor Trim, List, Bottom Fine Gauging and Thermal (levelgauge) of each individual tank, to give the accurate valuesof the cargo C.V, Btu, m3 and metric tons.

The ships trim, list, local tank gauge readings, averagetank temperature, vapour space temperature, cargospecific gravity figures are required. With these figuresproceed as follows.

Under trim correction table (for relevant tank):The gauge reading is read from the right hand side(interpolate gauge figure), the actual gauge figure is filledin column [a]. Move across the page until below the trimvalue of the ship (interpolate trim figure). The correctionvalue in mm will also require interpolation (a +ve value isby the head and a -ve value is by the stern). Insertcorrection value in column [b].

Under list correction table (for relevant tank):The gauge reading is read from the right hand side(interpolate gauge figure). Move across the page untilbelow the actual list value of the ship (interpolate listfigure). The correction value in mm will also requireinterpolation (a +ve or -ve value correction value is given).Insert this value in column [c].

Under thermal correction table (for relevant tank):The gauge reading is read from the right hand side(interpolate gauge figure). Move across the page untilbelow the vapour temperature (interpolate temperaturefigure), the actual vapour temperature figure is given incolumn [v]. The mm correction figure is +ve and filled incolumn [d].

The correct tank level value to be inserted into column [e]can now be calculated as follows:-

e = a+b+c+d

From this gauge corrected figure [e], using the BottomFine Gauging Table, an accurate volume (m3º) of eachtank is established, which is inserted in column [f].

The sum total of column [f] will give the total contents ofthe tanks.

The net liquid cargo volume, value [h], is the subtractionof the remaining volume after discharge, from the loadedvolume.

[f] net = [f] loaded -[f] discharged

The loading terminal will give the ship the specific gravityvalve of the LNG cargo, filled in column [g] and the PCSvalue.

Ship ’s Figures

The Thermie of the cargo is calculated as follows:-

Specific gravity [g] x PCS x net liquid cargo volume [h] = The Btu of the cargo is calculated as follows:-

Thermie ÷ 0.252 =Btu

This figure inserted in [J].

The metric tons of the cargo is calculated as follows:-

m3 [h] x specific gravity [g] = metric tons

This figure is inserted in [k].

When the computer is back on line it can be used in themanual mode to perform the level calculations.

3.3 Custody Transfer System - Page 2Issue: 1


Thermies

Part 4Cargo Operations

4.1 Overview Operating Procedures - Page 1Issue: 1


Ballast

DRYDOCK

Heating Cargo Tanks 4.3.6a

Gas Freeing Cargo Tanks 4.3.7a

Aerating Cargo Tanks 4.3.8a

Evacuating

Insulation Spaces4.3.1

Drying

Cargo Tanks 4.3.3a

Inerting Cargo

Tanks4.3.3b

Purging Cargo

Tanks with Cargo

Vapour4.3.4a

Cooling Down

Cargo Tanks4.3.5a

Discharging without GasReturn from Shore

Discharging with GasReturn from Shore

4.2.3a

Return Voyage in Ballastwith Gas Burning

4.2.4

Loading with/without

Ship Compressors4.2.1b

4.2.1c

Loaded Voyage with

Gas Burning4.2.2a

4.2.2b

PART 4: CARGO OPERATIONS4.1 Overview Operating ProceduresIntroductionIn normal service, each operating procedure will befollowed by a subsequent procedure (See Illustration 4.1Basic Cargo Operations Sequence Chart) necessitatingthat some valves will be left open. For ease ofexplanation, it is assumed that, although unlikely, allvalves are closed at the beginning of each operatingprocedure, unless otherwise stated.

Note: Before commencing any operation it is importantto check that reversible bends are in the correctpositions so that all tanks are in communicationwith the appropriate vapour and liquid headers.

! CAUTIONBefore removing any reversible bend it is imperativeto ensure that the pipeline and bend is inerted toprevent the pipeline being opened in a gaseouscondition. After changing the bend it is againnecessary to inert the section of pipeline in order toprevent the possibility of an air/gas mixture and icebeing formed.

All valves involved in an operation are annotated withvalve designation in the colour of the process flow.

In the following procedures, the principal cargo lines,headers, pumps, heat exchangers and compressors areshown in a simplified perspective view with coloursdesignated to represent specific flows. The valvesinvolved in the operation are coloured in accordance withthe process flow and it should be recognised that whileliquid, vapour and other fluids may be present in otherparts of the lines, only the main flows associated with anoperation are shown.

Note: This is if the trade route is through the Suez Canal,were charges would be made if gas were held inthe tanks.

Illustration 4.1 Basic Cargo Operations Sequence Chart

seeNote!

Deballast

Loaded Voyage WithoutGas Burning

4.4.16a

4.4.1a

4.2.1a Cargo Lines CooldownIssue: 1


Key


Illustration 4.2.1a Cargo Lines Cooldown

040

160

134

138

137

144

180

148

147

128

124

127

170

114

010

118

117

152

151

153

154

402156

155

008006

058056

158

157

LNG

LNG Vapour

052

054

004

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

002

101

161

162

116

115119

112

013

011

110062

492

126

125

485

482

483487

484

486129

120

122

022021

481 491

111

012

113

403

171051

001003

053

173164

163

103

401

489

501

105

005 165

166

175055057

177168

167

107007

172

102

104

004002

052174

488

502

106

176

178

108

023020

121

123

131

133

141

136

135139

132

033

031

030130

493

032

146

145149

142041

140

494

042

000061

143

410

430FCV

FCV

FCV

FCV

451

453 460

452

FCV

FCV

FCV

FCV

TCV

TCV

TCV

TCV

470

190

090

574

404

405

063

454

450

420

455

456

440 411

431

AW/912

480421

441

400

406

043

4.2 Normal In-Service Operations4.2.1 LoadingIt is assumed that all preparatory tests and trials havebeen carried out as per section 4.2.10 on the ballastvoyage prior to arrival at the loading terminal

• All operations for the loading of cargo are controlledand monitored from the ship’s Cargo Control Room.The loading of LNG cargo and simultaneousdeballasting are carried out in a sequence to satisfythe following:

• The Cargo tanks are filled at a uniform rate.

• List and trim are controlled by the ballast tanks.

• The cargo tanks are to be topped off at the fillheights given by the loading tables.

• During topping off, the ship should have a trimlimited 1m by the stern, but if possible kept on aneven keel.

• During the loading, the ship may be trimmedaccording with terminal maximum draught, in orderto assist in emptying the ballast tanks.

• The structural loading and stability, as determinedby the loading computer, must remain within safelimits.

• An officer responsible for the operation must bepresent in the Cargo Control Room when cargo isbeing transferred. A deck watch is required for routinechecking and/or any emergency procedures that mustbe carried out on deck during the operation.

• During the loading operations, communications mustbe maintained between the ship’s Cargo ControlRoom and the terminal: telephone and signals for theautomatic actuation of the Emergency Shutdown fromor to the ship.

• At all times when the ship is in service with LNG andmainly during loading, the following are required:

• The pressurisation system of the interbarrierspaces must be in operation with its automaticpressure controls.

• The secondary Level Indicating system should bemaintained ready for operation .

• The temperature recording system and alarms forthe cargo tank barriers and double hull structureshould be in continuous operation.

• The gas detection system and alarms must be incontinuous operation.

• Normally when loading cargo, vapour is returned tothe terminal by means of the HD compressors orshore compressor. The pressure in the ship’s vapour

header is maintained by adjusting the compressorflow.

• The cargo tanks must be maintained incommunication with the vapour header on deck, withthe vapour valve on each tank dome open.

• The vent mast No. 2 is maintained ready during theloading operation, for automatic venting, as a back up,with the vent heater in service.

• If the tanks have not been previously cooled down,LNG spraying is carried out.

Alongside Terminal

• Connect and bolt up the shore ground cable.

• Connect and test the shore communication cable.

• Test the telephone for normal communication withthe terminal.

• Test the back up communication arrangements withthe terminal.

• Change over the blocking switch for the shutdownsignal from the terminal, from the blocked to theterminal position.

• Connect the terminal loading arms to the four LNGcrossovers and one vapour crossover. This operationis done by the terminal personnel.

• Check that the coupling bolts are lubricated andcorrectly torqued.

• In the cargo control room (Cargo Control Room),switch on the cargo tank level alarms and levelshutdowns which are blocked at sea:

• Switch the Very High Level alarm from blocked tonormal on each tank.

• Switch the High and Low Level alarms from blockedto normal on each tank.

• Verify that alarms for Level Shutdowns blocked arecleared.

• Connect the nitrogen purge hoses to the crossoverconnections 108, 106, 104, 102 (or 107, 105, 103,101) and 488 (or 489), then purge the air from eachloading arm.

• Pressurise each loading arm with full nitrogenpressure through the purge valve, and soap testeach coupling for tightness.

• Bring the ship to a condition of no list and trim, andrecord the arrival conditions for custody transferdocumentation. Official representatives of buyer andseller are present when the printouts are run.

Cargo lines cool down :

• Assuming the ship is starboard side alongside.

• Open valves, 180,170,160.

• On each vapour dome open the following valves toallow the supply of LNG to the spray rings:-114,117, 118, 124, 127, 128, 134, 137, 138, 144, 147and 148.

• Open the vapour manifold valve 402.

• Open manifold valves, 157, 158, 155, 156, 153,154, 151 and 152, which will allow liquid into thestripping/spray main via cross over valve 160.

• Assuming that the aft loading arm is the first to becooled down

• Open liquid manifold valve 058.

• Crack open the liquid filling valves 010 and 040 fortanks No.1 and 4.

• Inform the terminal that the ship is ready to receiveLNG.

• Open the LNG quick closing valve 008 on the liquidmanifold.

• The terminal should be instructed to begin pumping ata slow rate for approximately 15 minutes, in order togradually cool down the terminal piping and the shipsheaders.

• Open valve 052

• Slowly increase the terminal pumping rate until theliquid main and spray headers have cooled down(approximately 15/20 minutes).

Note: In order to avoid the possibility of pipe sectionshogging, the liquid header and crossovers must becooled down and filled as quickly as possible.

• Open the filling valves to the tanks 040, 030, 020and 010 fully.

• On completion of the loading arms cooldown

• Open liquid manifold valves 056, 054, 052 and theLNG manifold quick closing valves 006, 004 and 002.

• Inform the terminal to increase the loading rate to theships maximum capacity.

• Close valves 152, 154, 156 and 158.

• On each tank keep open the stripping/spray valves tothe spray rings in order to avoid over pressure due toline warm up.

• Start one HD compressor and adjust the flow rate tomaintain the tank vapour pressure at 20/25 mbar g.

4.2 Normal In-Service Operations - Page 1Issue: 1


+ 40

+ 30

+ 10

+ 20

- 10

0

- 20

- 30

- 40

- 50

- 60

- 70

- 80

- 90

- 100

- 110

- 120

- 130

- 140

0 1 2 3 4 5 6 7 8 9 10 11 12

Main Assumptions :

Cooling-Down performed in 10 hours and requiring about 500 - 800 m of LNG Primary membrane temperature = average temperature given by sensors on tripod mast (uppermost + lowest)/2

TYPICAL COOLING-D OWN CURVES(INVAR MEMBRANE NO-96 SYSTEM)

Legend :

Hours

C

Previous cooling-down curves observed on'Methania' and MISC 'Tiga' series ships

Cooling-down curve observed on'Hanjin Pyeong Taek' (gas trials, tank No. 3)

Selected cooling-down curve for new130,000 - 138,000 m class LNG carriers

o

3

3

4.2.1b Loading With Vapour Return To Shore Via Ship HD CompressorIssue: 1


Key

Degassing Line IntoMain Cargo PumpCable Penetration

LNG

LNG Vapour

Illustration 4.2.1b Loading With Vapour Return To Shore Via Ship HD Compressor

040

494

420

440

404

410

430FCV

406

403

030

493

006

056

008

058

402

102

104

488

106

108

157

155

153002

151

004

052

054

161

051

001003

164401

005 165

055057167

007

020

492

010

491

502

FCV

152

154

156

158

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Anti-SurgeControl

To Load Cargo with Vapour Return to Shore Via HDCompressorIt is assumed for clarity of the description that all valvesare closed prior to use and that the ship is stb’d sidealongside.

1 Checks to be made before cargo operation:

Test remote operation of all tank valves and manifoldcrossover valves.

Test remote operation of ballast valves. Test HDCompressors, ballast pumps, safety systems andbulkhead heating systems.

2 Safety precautions:

Ensure hull water curtain is in operation on stb’d side.

Prepare fire fighting equipment, water hoses andprotective clothing for use. In particular the manifolddry powder monitors should be correctly aligned readyfor remote operation. Ensure the water spray systemon deck is ready for operation, filters installed and offshore blanks removed.

3 Prepare both HD Compressors YA/5121 A&B for usewith seal gas and lub oil system in operation. (See2.7)

4 Nitrogen system: Ensure that nitrogen storage tank isat maximum pressure and that the two nitrogenproduction plants are ready for use.

• Arrange nitrogen piping to preferentially feed theprimary insulation spaces.

• Open the additional supply valves 561, 564.

• Adjust set point of the nitrogen supply regulatingvalves 530, 510 at 6mbar.g and 520 at 3mbar.g.

• Adjust set point of the nitrogen regulating reliefvalves, primary insulation space, 540 at 8mbar.gand secondary insulation space, 560 at5mbar.g.(see illustration 4.2.1b)

5 Switch on unblocking level alarms in the CustodyTransfer System and run custody transfer print-out forofficial tank gauging.

6 Open gas outlet valves on tank gas domes (normallythese valves are left open).

Tank No. 1: 491

Tank No. 2: 492

Tank No. 3: 493

Tank No. 4: 494

7 Open vapour crossover valve 403.

8 On high duty gas compressors open valves 410, 420,430, 440.

9 Check - connection of liquid and vapour arms.

- communications with shore.

- ship/shore electrical and pneumatic connection andsafety devices ESDS.

- carry out safety inspections.

Complete the relevant ship/shore safety checklist.

10 Open filling valve of tank No.4 and tank No. 1 fully,040 and 010.

Open filling valves of tank No. 2: 020, and tank No. 3:030: (see cargo line cooldown)

11 Increase loading rate.

12 Start deballasting programme. Keep draught, trim andhull stresses within permissible limits by controllingdeballasting.

Refer to trim and stability data provided.

13 Start bulkhead heating in cofferdams. This shouldalready be running in automatic.

14 Monitor tank pressures in order to achieve a pressureof about 80mbar.g. Open valve 404 vapour header tocompressors and valve 406 on the compressorsdischarge side. Start one or both HD compressors asnecessary. Close valve 403 vapour header tocrossover.

15 Adjust opening of tank filling valves to maintain evendistribution.

16 Ease in the filling valve of each tank as the tankapproaches full capacity. Arrange to terminate tanksat 15 minutes intervals.

17 Level alarms. When any tank approaches 95%capacity inform shore.

Standby valve before level approaches about 97%.

Close valve at correct filling limit capacity (see fillingdiagram). High level alarm will sound at 98.5%capacity and filling valve concerned will automaticallyclose.

Very high level alarm will operate at 99% capacity andwill initiate the Emergency Shut Down System.

! WARNINGThe high and very high level alarms and shut downsare emergency devices only and should on noaccount be used as part of the normal topping-offoperation18 Before topping-off the first tank, request shore to

reduce loading rate and continue reducing whentopping off each following tank. When a tank is at itsrequired level, close the corresponding loading valve

tank No. 1: 010, tank No. 2: 020, tank No. 3: 030. It isconvenient to finish loading by tank No. 4 for ease ofline draining, leave a capacity of 50m3.

19 Stop loading when the final tank reaches a capacityaccording to the filling chart, minus an allowance forline draining and leave the tank loading valve open(040).

20 Liquid lines including the horizontal part of themanifolds will automatically drain to tank No. 4. Theinclined parts of the manifold are purged inboard withnitrogen.

21 On completion of draining loading arms, close theliquid manifold ESDS valves.

The shore lines are now pressurised at 2 to 3 bar withnitrogen.

Open the manifold ESDS by pass valve 151, 153,155, 157 to allow the nitrogen to flush the liquid intoNo. 4 tank.

Close the by pass valves when the nitrogen pressurehas fallen to 0 bar.

Repeat the operation 3 times, or until no liquidremains in the manifold lines.

The purging of the liquid lines should be carried outone at a time.

When gas readings obtained from an explosimeter areless than 50% LEL at the vent cocks, all valves areclosed and the loading arms are ready to bedisconnected.

Leave loading valve of tank No. 4 (040) open until thepiping has returned to ambient temperature.

In Cargo Control Room:

22 Tank level alarms.

Inhibit independent level alarms prior to proceed tosea.

23 Complete deballasting operation to obtain an evenkeel situation for final measurement. Whenmeasurement is completed adjust ballast tank levelsfor sailing condition.

24 Stop the HD compressors just prior to sailing, beforeclosing vapour manifold ESDS valve 402 for nitrogenpurging and disconnection of loading arms, Ifdeparture is delayed, the vapour return to shoreshould be continued.

25 Disconnect vapour arms.

26 Prepare cargo system for gas burning at sea.

27 Open valves necessary to allow warming up. Theseare normally the loading valves, pump dischargevalves and spray valves on the tank domes.



4.2.1c Loading With Vapour Return To Shore Via Shore CompressorIssue: 1


040

494

493

006

056

008

058

403

402

030

492

491

010

020

Illustration 4.2.1c Loading With Vapour Return To Shore Via Shore Compressor

Key


LNG

LNG Vapour

404

051

001003

053

501005

055057

007

502

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Loading with Vapour Return To Shore Via ShoreCompressorThe loading with vapour return via shore compressor isthe same as normal loading except that the ships H.D.compressors are not used. Instead the vapour headercross over valve 403 is opened and vapour supply to theships H.D. compressors isolating valve 404, is closed.

The vapour now returns directly from the vapour header tothe manifold line. The pressure in the tanks is maintainedat a safe level by shore control of the terminal compressor,which draws the vapour directly from the ship.



4.2.1d Nitrogen Setting up During LoadingIssue: 1


Tank 1

Tank 2

Tank 3

Tank 4

To No 3 TankSecondary Space



Supply from NitrogenStorage Tank

Main Vaporiser

No 5 Cofferdam


No 4 Cofferdam


No 3 Cofferdam

PrimarySpace

SecondarySpace


No 2 Cofferdam

No 1 Cofferdam

Insulation SpacesExhaustControl

542

541

563

532

531

521

522

512511

572

571

574

AW/826VX

AW/827VX

568569

501

502

530

510

520 567

566

562

565564

561

Liquid NitrogenShore Supply

555

556

560

557554

550

553

540

552

551

Illustration 4.2.1d Nitrogen Setting Up During Loading

Key

Nitrogen ToSecondary InsulationSpaces

Nitrogen ToPrimary InsulationSpaces

Excess Nitrogen Is VentedTo Mast 1

Nitrogen Setting Up During Loading

The operating procedure for the normal inerting is asfollows (see illustration 4.2.1d).

1 Start one nitrogen generator to pressurise the buffertank. The pressure drop in the buffer tank actuates thestarting of the generator. In the case of a largenitrogen demand, the stand-by generator willautomatically start.

2 Adjust the set point of the nitrogen supply regulatingvalves 520 to the secondary header at 2 mbar and510 to the primary header at 4mbar.

3 At the forward part of the trunk deck, ensure that thevalves 551, 552, 556, and 557 are open.

4 Adjust the set point of the nitrogen exhaust regulatingvalves 540 (primary) at 6mbar and 540 (secondary) at4mbar.

If either the supply or exhaust regulating valves fail, thethe stand-by regulating valve can be brought intooperation, 530 (supply) and 550 (exhaust). Under normaloperations these valves are left isolated.

In cases where other consumers reduce the availability ofnitrogen for the insulation spaces, the pressure maytemporarily fall below the atmospheric pressure.

This condition is NOT CRITICAL insofar as the differentialpressure (Ps - Pp) between the secondary spacespressure (Ps) and the primary space pressure (Pp) doesnot exceed 30mbar:

(Ps - Pp) < 30mbar

! WARNINGWhen the depression in the primary insulation spacesrelative to the secondary insulation spaces reaches30mbar, the two insulation spaces shall beimmediately inter-connected - which will involve amanual operation.

When put in communication and therefore subjected tothe same nitrogen pressure, the primary and secondaryinsulation spaces can withstand a large depressurisationwithout any damage.

It should be noted that, even with the tanks fully loaded, apressure lower than atmospheric pressure in the primaryinsulation spaces is not harmful to the primary membrane.

In this respect, it should be recalled that this membrane is subjected to a -800mbar gauge vacuum pressure - both during global testing at the construction stage and also forthe insulation spaces cycles purging.

4.2 Nitrogen Setting Up During Loading - page 4Issue: 1


4.2.2a Cargo Tank Stripping With Other Tanks In ServiceIssue: 1


Key


Illustration 4.2.2a Cargo Tank Stripping With Other Tanks In Service

LNG

LNG Vapour

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

101

161

162 114

116

115119

112

013

011

010110062

492

128126

125

124

127

485

482

483487

484

486129

170

120

122

022021

481 491

118

111

012

113117

403

160

171051

001003

053

173164

163

103

401

489

501

105

005 165

166

175055057

177168

167

107007

172152

151

102

052

002004

054

153

104

174

154

402

488

502156

106006

056

176

155

008

058178

158

157

108

023020

121

123

131

133

141

134

136

135139

132

033

031

030130

493

138

032

137

144

146

145149

142

043

041

040140

494

180

148042

000061

143

147

410

430FCV

FCV

FCV

FCV

451

453 460

452

FCV

FCV

FCV

FCV

TCV

TCV

TCV

TCV

470

190

090

480

404

405

063

454

450

420

455

456

440 411

431

AW/912

480421

441

400

406

4.2.2 Gas Freeing With Other Tanks In ServiceCargo Tank Stripping With Other Tanks In Service(see illustration 4.2.2a)

It may become necessary to displace LNG vapour withinert gas in a cargo tank with other tanks still in service inorder to prepare a tank for inspection. There are twopossibilities when this can be carried out i.e

During the first laden voyage.

During the ballast voyage.

These two possibilities use the same procedures. TankNo.1 will be demonstrated for this example. This vessel isassumed to in gas burning mode. (Only the valvesconcerned with the gas burning operation are open, allother valves are closed.)

1 Strip all possible LNG from tank No.1. During theladen or ballast voyage, remove the maximum LNGwith the stripping pump and transfer to the other tanksvia the stripping/spray main, liquid header and thefilling pipes.

2 Open valves 170, 090 and 190.

3 Open the filling valves on the other tanks, 020, 030and 040.

4 Ensure the filling valve on tank No.1 is shut.

5 Start the stripping pump in tank No.1 and open thedischarge valve 110.

! CautionChanges in temperature or barometric pressure canproduce differentials far in excess of 30mbar in theinsulation spaces which are shut in. With the cargosystem out of service and during inerting, alwaysmaintain the primary insulation space pressure at orbelow tank pressure and always maintain thesecondary insulation space pressure at or below theprimary insulation space pressure. Severe damage tothe membranes will result if the differentials exceed30mbar. In case of emergency, put in communicationthe primary and secondary membranes.

4.2 Cargo Tank Stripping With Other Tanks In ServiceIssue: 1


4.2.3a Cargo Tank Warm Up With Other Tanks In ServiceIssue: 1


Illustration 4.2.3a Cargo Tank Warm Up With Other Tanks In Service

Key


LNG Warm Vapour

LNG Vapour

CL045FO

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

101

161

162 114

116

115119

112

013

011

010110062

492

128126

125

124

127

485

482

483487

484

486129

170

120

122

022021

481 491

118

111

012

113117

403

160

171051

001003

053

173164

163

103

401

489

501

105

005 165

166

175055057

177168

167

107007

172152

151

102

052

002004

054

153

104

174

154

402

488

502156

106006

056

176

155

008

058178

158

157

108

023020

121

123

131

133

141

134

136

135139

132

033

031

030130

493

138

032

137

144

146

145149

142

043

041

040140

494

180

148042

000061

143

147

410

430FCV

FCV

FCV

FCV

451

453 460

452

FCV

FCV

FCV

FCV

TCV

TCV

TCV

TCV

470

190

090

480

404

405

063

454

450

420

455

456

440 411

431

AW/912

480421

441

400

406

Gas Freeing With Other Tanks In ServiceCargo Tank Warming Up With Other Tanks In Service(see illustration 4.2.3a)

Warming up tank No.1

During the laden or ballast voyage, tank No.1 is warmedby re-circulating heated LNG vapour. This warm vapour isre-circulated by one L.D. compressor and heated via thecargo heaters to 50°C. The hot vapour is introducedthrough the filling pipe at the bottom of the tank toevaporate any remaining LNG liquid that was unable to beremoved via the stripping out process.

Excess vapour generated during the warming-upoperation of the tank is burned in the main boilers orvented to atmosphere.

The warm-up procedure is as follows;

1 Stop the L.D. compressor in use for gas burning andclose gas heater valve outlet 453.

2 Install spool piece CL.045FO and open valve 063 todischarge heated vapour to the LNG header.

3 Prepare gas heaters YA/5141B for use. Thetemperature set point is adjusted to 50°C(corresponding to gas burning case).

4 Start the L.D. compressor YA/5122B.

5 At the vent mast No.2 open valves 481, 483, 484 and486. The set point of regulating valve 487 is adjustedto 1080mbar a. Vent heater YA/5142 is now preparedfor use.

6 Open the compressor suction valve 404 from thevapour header.

7 Open the inlet and outlet valves from the compressor411 and 431.

8 Open the heater inlet and outlet valves 451 and 453.

9 Open the vapour valves on each tank 491, 492, 493and 494.

10 Open the filling valve 010 on tank No.1.

11 Monitor the pressure in tank No.1 and adjust thecompressor flow in order to maintain the pressure inthe tank at 1060 mbar a.

12 At the end of the operation, when the coldesttemperature of the secondary barrier is at least +5°Cstop and shut down the gas burning system, stop theL.D. compressor and shut the tank filling valve 010.

13 Close the tank vapour.valve 491.

! CautionChanges in temperature or barometric pressure canproduce differentials far in excess of 30mbar in theinsulation spaces which are shut in. With the cargosystem out of service and during inerting, alwaysmaintain the primary insulation space pressure at orbelow tank pressure and always maintain thesecondary insulation space pressur e at or below theprimary insulation space pressure. Severe damage tothe membranes will result if the differentials exceed30mbar. In case of emergenc y, put in communicationthe primary and secondary membranes.

4.2 Cargo Tank Warm Up With Other Tanks In Servic eIssue: 1


4.2.4a Cargo Tank Gas Freeing With Other Tanks In ServiceIssue: 1

Illustration 4.2.4a Cargo Tank Gas Freeing With Other Tanks In Service

Key


Inert Gas

LNG Vapour

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

101

161

162 114

116

115119

112

013

011

010110062

492

128126

125

124

127

485

482

483487

484

486129

170

120

122

022021

481 491

118

111

012

113117

403

160

171051

001003

053

173164

163

103

401

489

501

105

005 165

166

175055057

177168

167

107007

172152

151

102

052

002004

054

153

104

174

154

402

488

502156

106006

056

176

155

008

058178

158

157

108

023020

121

123

131

133

141

134

136

135139

132

033

031

030130

493

138

032

137

144

146

145149

142

043

041

040140

494

180

148042

000061

143

147

410

430FCV

FCV

FCV

FCV

451

453 460

452

FCV

FCV

FCV

FCV

TCV

TCV

TCV

TCV

470

190

090

480

404

405

063

454

450

420

455

456

440 411

431

AW/912

480421

441

400

406


Gas Freeing With Other Tanks In ServiceCargo Tank Gas Freeing ( Version 1)(see illustration 4.2.4a)

This following procedure is not undertaken whist thevessel is in gas burning mode on either laden or ballastvoyage.

After the cargo tank has been warmed up (see CargoTank Warming Up With Other Tanks In Service), the LNGvapour is displaced with inert gas. The inert gas from theinert gas generating plant is introduced into the bottom ofthe cargo tank via the LNG filling pipe. The gas from thetank is vented from the top of the tank through the gasdome safety valves to the vent mast.

The gas freeing procedure is as follows;

1 Prepare the inert gas generating plant for use in inertgas mode.

2 Open the vapour valves on the tanks that are notbeing gas freed 492, 493, 494.

Ensure the vapour valve on tank No.1 remains shut.

3 At vent mast No.2 open valves 481, 483, 484 and 486.Adjust the set point of regulating valve 487 to 150mbargauge.

4 Prepare vent heater YA/5142 for use.

5 Install spool piece CL.045FO and open valves 460and 063 to supply the inert gas to the LNG header.


7 Remove the plug on the gas dome safety valves ontank No.1. This is in order to evacuate the inert gas intank No.1 to the vent mast.

8 Start the inert gas plant delivering to No.1 tank.Monitor the methane content inside the tank until ithas reached the acceptable level.

9 Open valve XH/5321G upstream of the two non returnvalves on the dry air /inert gas discharge line.

10 Monitor tank No.1 pressure and check that tank No.1pressure is always higher than the insulation spacepressure, taking into account the pipe losses betweenthe gas dome safety valves and vent mast.

11 When the hydrocarbon content from tank No.1 hasfallen below 2.5%, isolate and shut off the tank. Stopthe inert gas supply and shut down the plant.


4.2 Gas Freeing With Other Tanks In Service - Version 1Issue: 1


4.2.4b Cargo Tank Gas Freeing With Other Tanks In ServiceIssue: 1

Illustration 4.2.4b Cargo Gas Tank Freeing With Other Tanks In Service

Key


Inert Gas

LNG Vapour

(Second Version)

1

2

1

2

To EngineRoom

To InsulationSpaces


Flexible Hose


Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

101

161

162 114

116

115119

112

013

011

010110062

492

128126

125

124

127

485

482

483487

484

486129

170

120

122

022021

481 491

118

111

012

113117

403

160

171051

001003

053

173164

163

103

401

489

501

105

005 165

166

175055057

177168

167

107007

172152

151

102

052

002004

054

153

104

174

154

402

488

502156

106006

056

176

155

008

058178

158

157

108

023020

121

123

131

133

141

134

136

135139

132

033

031

030130

493

138

032

137

144

146

145149

142

043

041

040140

494

180

148042

000061

143

147

410

430FCV

FCV

FCV

FCV

451

453 460

452

FCV

FCV

FCV

FCV

TCV

TCV

TCV

TCV

470

190

090

480

404

405

063

454

450

420

455

456

440 411

431

AW/912

480421

441

400

406


Gas Freeing With Other Tanks In ServiceCargo Tank Gas Freeing ( Version 2)(see illustration 4.2.4b)

It is not possible to use gas burning and the gas freeingprocedure at the same time. Due to the fact that the gasfreeing operation of a cargo tank will take approximately20 hours, a significant amount of LNG vapour from boil-off, will have to be vented to atmosphere. In order to avoidthis the following procedure can be adopted.

The following procedure calls for the separation of the fuelgas line from the inert gas line by installing additional pipeelements.

The gas freeing procedure is as follows;The vessel is in gas burning mode.

1 Prepare the inert gas generating plant for use in inertgas mode.

2 Open the vapour valves on the tanks that are notbeing gas freed 492, 493, 494.

Ensure the vapour valve on tank No.1 remains shut.

3 At vent mast No.2 open valves 481, 483, 484 and 486.Adjust the set point of regulating valve 487 to 150mbargauge.

4 Prepare vent heater YA/5142 for use.

5 Connect the flexible hose between the inert gas lineand liquid line.

6 Ensure the jettison discharge valve 000 is shut.

7 Open the inert gas supply valve 061 to the LNGheader.


8 Remove the plug on the gas dome safety valves ontank No.1. This is in order to evacuate the inert gas intank No.1 to the vent mast.

8 Start the inert gas plant delivering to No.1 tank.Monitor the methane content inside the tank until ithas reached the acceptable level.

9 Open valve XH/5321G upstream of the two non returnvalves on the dry air /inert gas discharge line.

10 Monitor tank No.1 pressure and check that tank No.1pressure is always higher than the insulation spacepressure, taking into account the pipe losses betweenthe gas dome safety valves and vent mast.

11 When the hydrocarbon content from tank No.1 hasfallen below 2.5%, isolate and shut off the tank. Stopthe inert gas supply and shut down the plant.


4.2 Gas Freeing With Other tanks In Service - Version 2 - page 2Issue: 1


4.2.4c Initial Insulation Space InertingIssue: 1


Tank 1

Tank 2

Tank 3

Tank 4

From No 3 TankSecondary Space




Main Vaporiser

No 5 Cofferdam


No 4 Cofferdam


No 3 Cofferdam

PrimarySpace

SecondarySpace


No 2 Cofferdam

No 1 CofferdamInsulation SpacesExhaustControl

542

541

532

531

521

522

512 511

572

571

480

AW/826VX

AW/827VX

568569

Illustration 4.2.4c Initial Insulation Space Inerting

Evacuation Of Insulation Spaces (First Step)

Key

Nitrogen FromSecondary InsulationSpaces

Nitrogen FromPrimary InsulationSpaces

Initial Insulation Space Inerting

First Step: Evacuation of Insulation Space

! CAUTIONTo avoid major damage to the secondary barrie r,never evacuate a primary insulation space whilstleaving the associated secondary space underpressure, and never fill a secondary space whilst theprimary space is under a vacuum.

Prior to putting a cargo tank into service initially, or afterdry docking, it is necessary to replace the ambient humidair in the insulation space with dry nitrogen.

This is done by evacuating the insulation spaces with thevacuum pumps and refilling them with nitrogen. Theprocedure is repeated until the oxygen content is reducedto less than 3%.

Evacuation of all the insulation spaces takes approximately8 hours. Refilling nitrogen takes approximately 4 hoursusing the main vaporiser. Three cycles are usuallynecessary to reduce the oxygen to less than three per centby volume.

! CAUTIONChanges in temperature or barometric pressure canproduce differentials far in excess of 30mbar ininsulation spaces which are shut in. With the cargosystem out of service and during inerting, alwaysmaintain the secondary insulation space pressure ator below the primary insulation space pressure.Severe damage to the membranes will result if thedifferentials exceed 30mba r. In case of emergenc y,put in communication the primary and secondarymembranes.

Before refilling with nitrogen, the insulation spaces areevacuated to 200mbar absolute pressure. The evacuationof the insulation spaces is also used in order to check theintegrity of the barriers during periodical test.

To avoid possible damage to the secondary membrane,the secondary insulation spaces must be evacuatedbefore the primary insulation spaces. The pipe work at thevacuum pumps suction has been designed to ensure thatthe evacuation of the primary spaces cannot take placewithout having first evacuated the secondary spaces, orensuring that they will be both evacuated simultaneously.

Two electrically driven vacuum pumps, cooled by sea water,are installed in the cargo compressor room. They draw fromthe pressurisation headers and discharge to the vent riserNo. 3.

The operating procedure is as follows: (All valves areassumed SHUT) (See Illustration 4.2.4c).

• Isolate any pressure gauge, transducer or instrumentwhich should be damaged by the vacuum and installtemporary manometers to allow pressures in theinsulation spaces to be monitored.

• On each tank, open the valve 542, 532, 522, 512connecting the pressurisation header with thedewatering columns of the secondary insulationspaces.

• In the compressor room, open the valve 569 and thevalves 571, 572 to the suction of the vacuum pumps.

• Prepare the vacuum pumps for use.

• Start both vacuum pumps.

• Monitor the secondary insulation spaces pressure;when it has been reduced to 200mbar abs in all thespaces, stop the pumps.

• Close the valves 542, 532, 522, 512 on trunk deck.

• Then, on each tank, open valves 541, 531, 521, 511connected the pressurisation header with the afttransverse of the primary insulation spaces.

• Open valve 568, the vacuum pumps suction from theprimary pressurisation header.

• Start both vacuum pumps.

• Monitor the primary insulation spaces pressure; whenit has been reduced to 200mbar abs in all the spaces,stop the pumps.

• Close the valves 541, 531, 521, 511 on trunk deck.

• Close the valves 568, 569 and the valves 571, 572 atthe pumps’ suction.

• Stop the vacuum pumps.

During the evacuation of the insulation spaces thetightness of the primary and secondary insulation spacesrelief valves has to be confirmed and if suspected ofleaking, blanked until operation completed. Blanks mustbe clearly marked and notices posted.

General notes on the vacuum pumps

Ensure cooling water is available and on.

Ensure lub oil tank is full and power supply to the pumpsis available.

Ensure that bulkhead seal system is full.

Ensure that pump is free to rotate

Ensure that lub oil is feeding

Close pump drains.

Adjust cooling water flow to obtain 30/40° at cooling wateroutlet from vacuum pipes.

After shut down clean suction filter.

• Total volume of the primary and secondary space isabout 5700m3.

4.2 Initial Insulation Space Inerting - Page 1Issue: 1


4.2.4d Filling from Liquid Nitrogen (Second Step)Issue: 1


Tank 1

Tank 2

Tank 3

Tank 4


Liquid NitrogenShore Supply




Main Vaporiser

No 5 Cofferdam


No 4 Cofferdam

CLO36FO

CLO43FO


No 3 Cofferdam

PrimarySpace

SecondarySpace


No 2 Cofferdam

No 1 Cofferdam


542

541

532

531

521

522

512

557554

550

560

556

511

555553

551

540

552

568

573

FCV

TCV

456

480

502

501

Illustration 4.2.4d Filling From Liquid Nitrogen (Second Step)

Key

Nitrogen Supply ToSecondary InsulationSpaces

Nitrogen Supply ToPrimary InsulationSpaces

Liquid Nitrogen

Second Step: Initial Filling From Liquid Nitrogen(see figure 4.2.4d)After evacuation, the next step consists in filling theinsulation spaces with nitrogen. The cycle is repeated untilthe oxygen content in the spaces is less than 3%.

The nitrogen is supplied from shore as liquid nitrogen. It isvapourised in the main vaporiser, then feeds the insulationspaces.

The operating procedure is as follows:

• Install the spool piece CL.036FO and open the valve480 to supply liquid nitrogen to the vaporiser.

• Ensure that the pressure intake from which thevaporiser might be tripped on high pressure, is inservice on the primary header.

• Prepare the main vaporiser for use and set thetemperature control of the delivery gas at 20°C.

• Open control valves 456 at vaporiser inlet.

• Install the spool piece CL.043FO and open the valves573, 568 to supply nitrogen to the pressurisationheaders.

• Open the isolation valves 551, 552, 556, 557 for theinsulation exhaust control system.

• Crack open the primary space supply valves 541, 531,521, 511 on each tank.

• When shore is ready, open the manifold valve 502 or501.

• Gaseous nitrogen is produced by the vaporiser inmanual mode until the conditions are stabilised, thenthe vaporiser is put in automatic mode.

• Adjust the opening of the primary space supply valvesfor balancing the pressure rise in all the spaces.During filling, always maintain the pressure in theprimary space 100mbar above the secondary space.

• When the pressure in the primary spaces reaches300mbar a (100mbar above the pressure in thesecondary spaces), crack open the secondary spacesupply valves 542, 532, 522, 512 on each tank. Then,adjust the opening of these valves for balancing thepressure rise in all the spaces.

• Adjust the set point of the exhaust valve 540 to createa leak in order to balance the vaporiser productionwith a 300mbar per hour pressure rise in the insulationspaces.

• When the pressure in the insulation spaces is950mbar a, stop the liquid nitrogen supply to thevaporiser. Close manifold valves 502 or 501. Allvalves at the inlet and outlet of the vaporiser will bekept open until warming up of the lines.

• Close 573, and set the opening of the control valves540, 560 at 4mbar.

Three cycles are usually necessary.

Operating Procedure for the Completion of theNitrogen Filling

• The final filling of the insulation spaces, betweenabout -50mbar and the atmospheric pressure+ 2mbar is carried out at reduced flow rate from the onboard nitrogen production plant.

• The same operating procedure as for the normalservice is used (see figure 4.3.5a).

• After the final filling, check the oxygen content in allthe spaces. If it is higher than 3%, repeat inertingoperation.There is also the possibility to check the o2

content at the vacuum pump discharge.

! CAUTIONChanges in temperature or barometric pressure canproduce differentials far in excess of 30mbar in theinsulation spaces which are shut in. With the cargosystem out of service and during inerting, alwaysmaintain the primary insulation space pressure at orbelow tank pressure and always maintain thesecondary insulation space pressure at or below theprimary insulation space pressure. Severe damage tothe membranes will result if the differentials exceed30mbar. In case of emergenc y, put in communicationthe primary and secondary membranes.

4.2 Initial Insulation Space Inerting -Page 2Issue: 1


4.2.5a Insulation Space Inerting During Normal Service Issue: 1


Tank 1

Tank 2

Tank 3

Tank 4





No 5 Cofferdam


No 4 Cofferdam


No 3 Cofferdam

PrimarySpace

SecondarySpace


No 2 Cofferdam

No 1 Cofferdam

542

541

563

562

566

532

531

521

522

512511

530

510

520

InsulationSpacesDistributionControl530

564

561510

520

567

Illustration 4.2.5a Insulation Space Inerting During Normal Service

Key

Nitrogen Supply ToSecondary InsulationSpaces

Nitrogen Supply ToPrimary InsulationSpaces


540

556

560

557

554

550 552

Insulation Space Inerting During Normal ServiceThe primary and secondary insulation spaces are filledwith dry nitrogen gas which is automatically maintained byalternate relief and make up as the atmospheric pressureor the temperature rises and falls, under a pressure ofbetween 2 and 6mbar above atmospheric.

The nitrogen provides a dry and inert medium for thefollowing purposes:

• To prevent formation of a flammable mixture in theevent of an LNG leak.

• To permit easy detection of an LNG leak through abarrier.

• To prevent corrosion.

Nitrogen, produced by generators and stored inpressurised buffer tank, is supplied to the pressurisationheaders through make-up regulating valves located on thecompressor room. From the headers, branches are led tothe primary and secondary insulation spaces of each tank.Excess nitrogen from the insulation spaces is vented tothe mast No. 1 through regulating relief valves.

Both primary and secondary insulation spaces of eachtank are provided with a pair of pressure relief valveswhich open at a pressure, sensed in each space, of10mbar above atmospheric. A manual by pass with a cutout valve and a ball valve is provided from the primaryspace to the pressure relief valves mast for local ventingand sweeping of a space if required.

The two high capacity units (57.5m3/h each), will operatein parallel when high nitrogen demand is detected and willstart automatically, i.e. during initial cooling down. Whenloading only one unit will need to be run - the other unitbeing kept on standby. (see section 2.10).

The operating procedure for the normal inerting is asfollows: (see figure 4.2.5a)

• Adjust the set point of the nitrogen supply regulatingvalve 520 to the secondary header at 2mbar andregulating valve 510 to the primary header at 4mbar

• At the forward part of the trunk deck, ensure that thevalves 552, 554, 556, 557 are open.

• Adjust the set point of the nitrogen exhaust regulatingvalve 540 (primary) at 6mbar and regulating valve 560(secondary) at 4 mbar.

There is a standby exhaust regulating valve 550, whichcan be connected to either the primary or secondarysystem in the event of failure of one of the masterregulating valves.

The nitrogen supply to the insulation spaces has astandby regulating valve 530, which can be connected toeither the primary or secondary system in the event offailure of one of the master regulating valves.

In the event of cargo gas leakage into insulation spaces,this can be swept with a continuous feed of nitrogen byopening the exhaust from the space, allowing a controlledpurge. Close monitoring of the gas analyser on this spacewill be necessary during purging.

In cases where other consumers reduce the availability ofnitrogen for the insulation spaces, the pressure maytemporarily fall below the atmospheric pressure.

This condition is NOT CRITICAL insofar as the differentialpressure (Ps - Pp) between the secondary spacespressure (Ps) and the primary space pressure (Pp) doesnot exceed 30mbar:

(Ps - Pp) < 30mbar

! WARNINGWhen the depression in the primary insulation spacesrelative to the secondary insulation spaces reaches30mbar, the two insulation spaces shall beimmediately inter-connected - which will involve amanual operation.

When put in communication and therefore subjected tothe same nitrogen pressure, the primary and secondaryinsulation spaces can withstand a large depressurisationwithout any damage.

It should be noted that, even with the tanks fully loaded, apressure lower than atmospheric pressure in the primaryinsulation spaces is not harmful to the primary membrane.In this respect, it should be recalled that this membrane issubjected to a -800mbar gauge vacuum pressure - bothduring global testing at the construction stage and also forthe insulation spaces cycles purging.

In Service Tests

Classification society regulations require that the barriersof a membrane tank should be capable of being checkedperiodically for their effectiveness.

The following covers the practice, recommendations andthe precautions which should be taken during the in-service periodical examination of the primary andsecondary membranes.

! CAUTIONMeasurement devises which may otherwise bedamaged should be isolated prior to thecommencement of the test. The barrier spaces mustat all times be protected against over pressure, whichmight otherwise result in membrane failure.

Method For Checking The Effectiveness Of The Barriers1 Primary Membrane

Since each primary insulated space is provided with apermanently installed gas detection system capable ofmeasuring gas concentration at intervals not exceedingthirty minutes, any gas concentration in excess with regardto the steady rates would be the indication of primarymembrane damage. It results that each primary membraneis in terms of tightness, continuously monitored and aspecial test would not be required to check its effectiveness.However that maybe, each primary membrane can betested according to the method described below for thesecondary membrane.

2 Secondary Membrane In order to check its effectiveness, the secondary (orprimary) membrane is submitted to a global tightness test,which is the reiteration of the equivalent test carried outduring the cargo containment building.Procedure

2.1 Reduce the insulated space pressure at the back ofthe membrane to be tested to 200mbar a.

2.2 After a stabilising period of about 8 hours, record bymeans of an accurate measuring device, the vacuumdecay over the next 24 hour period.

2.3 From the results obtained, the selection of the 10hours continuous period during which the temperaturevariations of the compartments surrounding the testedmembrane are minimum.

2.4 The allowable limit for vacuum decay of the space isgiven by the equation:

where e = the thickness in meters of the insulated spaceat the back of the membrane.

In Service Global Tightness TestThe global test is carried out either during a maintenanceperiod, or when the cargo tanks have been warmed upand gas freed.

To overcome any doubtful results arising from possibleleaks through equipment connected with the insulatedspaces ie valves, pressure relief valves, electric cableglands etc, their effectiveness must be carefully checked,and eventually replaced with blank joints, insofar as thespaces remain protected against any over pressure.

Test Of Secondary Membrane3.1 The pressure of the secondary space is reduced to

200mbar a, while the primary space is maintained at aslight vacuum (i.e. -100mbar)

Under these conditions, the secondary membrane is

submitted by one side to the atmospheric pressureexisting inside the primary space, by the other to thereduced pressure existing inside the secondary space.

3.2 The vacuum decay is carried out on this space only bythe method described in 2.2/2.4.

In spite of the precautions taken for providing againstleaks of the equipment, it is important to check whetherthe vacuum decay of the secondary barrier space (∆∆Ps)corresponds with a pressure reduction of the primaryspace (∆∆Pp). If this is not the case there may be anexternal leak which must be located and rectified beforeanother test is conducted.

When comparing (∆∆Pp) and (∆∆Ps) it is necessary to takeinto account the primary and secondary space volumes asshown in the equation below:

where (es) and (ep) represents the thickness of thesecondary and primary spaces.

Primary Membrane Test Procedure4.1 The pressure of the primary and secondary barrier

spaces is reduced to 200mbar a simultaneously, incommunication, in order to prevent the potentialcollapse of the secondary barrier due to a higherpressure than that of the primary space.

4.2 The primary and secondary spaces are isolated andthe vacuum decay procedure is followed on theprimary space only. Method as described in 2.2/2.4.

Under these conditions, the primary membrane issubmitted by one side to the atmospheric pressureexisting inside the tank, and by the other to the reducedpressure existing inside the primary space.

Since both faces of the secondary membrane are in anequal pressure system, no flow can be generated throughany eventual leak of this membrane. Therefore themeasured vacuum decay is the correct figure of thetightness of only the primary membrane.

! CAUTIONChanges in temperature or barometric pressure canproduce differentials far in excess of 30mbar in theinsulation spaces which are shut in. With the cargosystem out of service and during inerting, alwaysmaintain the primary insulation space pressure at orbelow tank pressure and always maintain thesecondary insulation space pressure at or below theprimary insulation space pressure. Severe damage tothe membranes will result if the differentials exceed30mbar. In case of emergency, put in communicationthe primary and secondary membranes.

4.2 Insulation Space Inerting - Page 1Issue: 1


∆∆Pp = ∆∆Ps es

ep

∆∆P≤≤ 0.8e

4.2.6a Loaded Voyage With Normal Boil-Off Gas BurningIssue: 1


Key


LNG Vapour

ME001VR

450

451

FCV

460453

421

FCV

441

404

494

493

492

491

FCV

452

FCV

TCV

TCV454

431

411

Illustration 4.2.6a Loaded Voyage With Normal Boil-Off Gas Burning

FCV

FCV

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Anti-SurgeControl

4.2.6 Loaded Voyage with Normal Boil-Off GasBurning

IntroductionDuring a sea passage when the cargo tanks contain LNGthe boil-off from the tanks is burned in the ship’s boilers.The operation is started on deck and controlled by theship’s engineers in the Engine Control Room. If for anyreason the boil-off cannot be used for gas burning, or if thevolume is too great for the boilers to handle, any excessvapour is heated and vented to atmosphere (Section2.2.3) via main mast riser.

OperationThe cargo tank boil-off gas enters the vapour header viathe cargo tank gas domes. It is then directed to one of theLD compressor which pump the gas to the boil-off gasheater. The heated gas is delivered to the boilers at amaximum temperature of +25°C via control valveME001VR. The compressor/s speed and inlet guide vaneposition is governed by cargo tanks pressure. The systemis designed to burn all boil-off gas normally produced by afull cargo and to maintain the cargo tank pressure (i.e.temperatures) at a predetermined level.

If the propulsion plant steam consumption is not sufficientto burn the required amount of boil off, the tank pressurewill increase and eventually the steam dump will opendumping steam directly to the main condenser. The maindump is designed to dump sufficient steam to allow theboiler to use all the boil off produced even when the shipis stopped.

The flow of gas through the LD compressors is controlledby adjusting the compressors speed and inlet guide vaneposition. This is directed by the boiler combustion controlwhen gas burning is initiated. The normal boil off in theboiler combustion control have to be selected as well asthe maximum and minimum allowed tank pressures andthe tank pressure at which the main dump operates.

For normal operation the normal boil off valve is selectedat 60% (boil-off provides 60% of the fuel required toproduce 90% of the boiler full steam capacity) and theminimum and maximum tank pressures are selected at1050 and 1090mbar a.

If the normal boil off valve has been correctly adjusted, thetank pressures will remain within the selected values.Should the selected normal boil off value be too large, thetank pressure will slowly be reduced until it reaches theminimum value selected. If the tank pressure valuereduces to below the minimum value selected, the normalboil off value will be reduced until the tank pressure hasincreased again above the selected value.

If the selected normal boil off value is too small, the tankpressure will slowly increase until it reaches the maximumvalue selected. If the tank pressure value increases abovethe maximum selected value, the normal boil off value willbe increased until the tank pressure reduces again belowthe selected value.

If the tank pressure continues to increase because thesteam consumption is not sufficient to burn all the requiredboil off, the steam dump will open.

The steam dump is designed to open when the normalboil off valve is 5% above the original selected value andwhen the tank pressure has reached the preselecteddump operating pressure.

With the present setting, an increase of 5% of the normalboil off corresponds approximately to an increase of tankpressure by 40mbar above the maximum tank pressureselected.

The cargo and gas burning piping system is arranged sothat excess boil-off can be vented should there be anyinadvertent stopping of gas burning in the ship’s boilers.The automatic control valve 487 at the main mast riser isset at 1150mbar absolute to vent the excess vapour toatmosphere.

If the gas header pressure falls to less than 40mbar abovethe primary insulation spaces pressure an alarm willsound.

In the event of automatic or manual shut down of the gasburning system (or if the tank pressure falls to 10mbarabove the insulation spaces pressure), valve ME001VRwill close and the gas burning supply line to the engineroom will be purged with nitrogen via valve XH5321G.

Operating Procedures(See Illustration 4.2.6a)It is assumed that all valves are closed prior to use:

1 Prepare LD compressors YA5122 A or B, the boil-offheaters and the engine room gas burning plant foruse.

2 Open 487 forward mast isolating valve on gas burningheader.

3 Tank gas domes

Open and lock in position valve 491 (Tank No. 1)




The valves should already be locked in the openposition.

4 Open valve 404 and 421 vapour supply tocompressors and gas heaters.

5 Boil-off gas heater

Open 451 and 453 heater inlet and outlet

Open glycoled water supply to heater

In Cargo Control Room

6 Forward mast

Position mast selector to gas burning header

Adjust set point PIC 487 to 1150mbar a.

7 Gas compressors

Adjust normal boil off valve (IGV) to 60% for loadedcondition, tank pressures minimum and maximum at1060mbar a and 1090mbar a and steam dumpopening pressure at 1130mbar a.

When the Engine Room is ready to start gas burning,ensure that there is sufficient nitrogen to purge the lines tothe boiler i.e. >5.0 bar in storage tank.

8 Ensure that the gas outlet temperature of the heater isapproximately 25°C

Open valve ME001VR

Start LD compressor/s

This operation will then be controlled and monitored fromthe Engine Control room.

Note: If the volume of boil-off exceeds demand in theboilers the steam dump should be put intooperation.

Should the system shut down for any reason valveME001VR will close automatically.

10 Stop the compressor.

When stopping gas burning for any reason

11 Stop LD compressor/s

Close valve ME001VR gas supply to engine room

Adjust set point of vent mast control PIC 487 to1100mbar a.

4.2 Loaded Voyage with Normal Boil-Off Gas Burnin g - Page 1Issue: 1


4.2.6b Loaded Voyage With Forced Boil-Off Gas BurningIssue: 1


Key


LNG

LNG Vapour421

441

FCV

Illustration 4.2.6b Loaded Voyage With Forced Boil-Off Gas Burning

480

455

FCV

TCV

190 130

134

136193

135 138

493

494

460453

451

FCV

ME001VR

492

491

118

114

191

115

116

110

126

125

192

170

452

FCV

TCV

454TCV

128

120

041

144

146

145

194

180

148

124

404

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Loaded Voyage with Forced Boil-Off Gas Burning

IntroductionConsideration must be given to economics of gas versusfuel oil burning before undertaking forced boil off.

If during a loaded passage, additional fuel gas from thecargo tanks is required to be burned in the ship’s boilers,it can be made available by forced vaporisation using theequipment on board.

The above operation, called Forced Boil-Off will be usedto complement gas burning up to 100% of the boilers fuelrequirement.

OperationThe normal gas burning arrangement is maintained andthe forcing vaporiser is brought into operation.

A single stripping / spray pump is used to pump LNG tothe forcing vaporiser. The excess flow from the pump isreturned to the tank through the spray ring control valves(144, 134, 124, 114).

The following tank valves are adjusted to maintain asuitable pressure at the vaporiser.

Tank No. 1: 191

Tank No. 2: 192

Tank No. 3: 193

Tank No. 4: 194

Note: In normal operation the controlled return isdirected back to the same tank where the liquidis being drawn from.

After vaporisation the LNG vapour produced passesthrough a demister where the possibility of liquid LNGcarry-over is eliminated. The vapour then combines withthe natural boil-off gas from the vapour header beforebeing drawn into the suction of the LD compressors.

One or two LD compressors are used depending on theamount of fuel gas required by the boilers.

The flow of gas through the compressors is controlled viathe boiler combustion control unit by adjusting the openingof the guide vanes.

The boiler combustion control has to be switched toForced Boil-Off (FBO) mode.

The amount of forced boil-off to be produced is controlledby the throttling of the FCV to the forcing vaporiseroperated by the Boiler Combustion control.

When changing over to 100% gas burning, the fuel oil(FO) flow through the FO rails is adjusted to minimum.The FO supply to the burners will then be cut out and theFO system put on recirculation. The FO combustioncontrol loops are maintained energised to enablerelighting of FO burners in an emergency.

In the event of automatic or manual shut down of the gasburning system (or if the tank pressure falls to 5mbarabove the insulation spaces pressure), valve ME001VRwill close and the gas burning supply line to the engineroom will be purged with nitrogen via valve XH5321G. FObooster devices are incorporated in the control loop toallow a quick change-over should the gas burning betripped.

Operating Procedures(See Illustration 4.2.6b)For illustration purposes No. 3 tank stripping/spray pumpand return operation is shown.

The cargo piping system is arranged for normal gasburning during loaded voyage as detailed in 4.2.6a.

It is assumed, that all valves are closed prior to use.

1 Prepare the forcing vaporiser for use.

2 Open the stripping/spray isolating valve on the tank/sto be used.

Tank No. 1: 114, 115, 116, 118

Tank No. 2: 124, 125, 126, 128

Tank No. 3: 134, 135, 136, 138

Tank No. 4: 144, 145, 146, 148

If cargo tanks No. 1 or No. 2 is used, open stripping/spray header isolating valve 170. If tank No. 4 is usedopen stripping/spray header isolating valve 180.

3 Open valve 190 stripping/spray header supply to theforcing vaporiser.

4 Open stripping pump discharge valve, 110, 120, 130,140. Start stripping/spray pump and adjust return flowto tank through spray control valves 191, 192, 193,194.

8 Run up forcing vaporiser (See 2.6.3).

9 Set boiler combustion control on FBO mode.

10 Start second LD compressor depending on gasdemand.

11 Set control of liquid supply to vaporiser and LDcompressors control to auto mode.

4.2 Loaded Voyage with Forced Boil-Off Gas Burnin g - Page 1Issue: 1


4.2.7a(i) Discharging With Gas Return From ShoreIssue: 1


Key


LNG

LNG Vapour

041

042

031032

494

493

005

055057

007

401

051

001003

053

403 021022

011012

492

491

Illustration 4.2.7a(i) Discharging With Gas Return From Shore

052

002004

054

402

006

056

008

058

170

160

134

130

138

137

040

180

190

090

173

175

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.2.7 Discharging with Gas Return from Shore

IntroductionDuring a normal discharge only the main cargo pumps willbe used and a quantity of cargo will be retained on boardfor cold maintenance of the cargo tanks.

The quantity to be retained is according to voyageduration of ballast passage.

If the ship has to warm-up tanks for technical reasons thestripping/spray pumps will be used to discharge theremaining cargo on completion of bulk discharge with themain cargo pumps.

During cargo discharge, LNG vapour is supplied fromshore to maintain pressure in the cargo tanks.

OperationThe main cargo pumps discharge LNG to the main liquidheader and then to shore via the midship liquid cross-overmanifold connections.

After an initial rise in pressure, the pressure in the tanksdecreases and it becomes necessary to supply LNGvapour from shore via the manifold and cross-over to thevapour header into the cargo tank gas domes in order tomaintain a pressure of 1090mbar a.

Should the vapour return supply from shore be insufficientto maintain tank pressures, other means of supplyingvapour to the tanks either by using the tank sprayers orthe main vaporiser have to be used. See ‘Dischargingwithout Gas Return from Shore Section 4.4.1a for moreinformation.

The boil-off gas heater should be prepared and lined upfor use in order to avoid venting cold LNG vapour throughthe main mast riser.

Ballasting is undertaken concurrently with discharging.The ballasting operation is programmed to keep thevessel within the required limit of draught, trim, hull stressand stability following indications obtained from theloading calculator.

During the discharge period, the ship is kept on an evenkeel. If it is required to empty a cargo tank, the ship istrimmed according to terminal maximum draught by thestern to assist in stripping of the tank.

Each tank is normally discharged to the following levels:-

Tank No. 1 0.47m (216m3),

Tank No. 2 0.30m (242m3),

Tank No. 3 0.30m (242m3),

Tank No. 4 0.30m (200m3).

This is the required capacity to maintain normal boil off ofthe tanks in a cooled condition on the ships normal traderoute. If the length of the ballast voyage is extended, thenrequired capacity would be altered accordingly in order tomaintain the normal boil off for tank cooling and boilerconsumption.

If the vessel is to warm-up one or more tanks for technicalreasons, the ship shall be trimmed according to terminalmaximum draught. The cargo remaining in the tanks to bewarmed up will be discharged to shore or to other tanksusing the stripping/spray pumps on completion of bulkdischarge.

Stripping pump is run together with the remaining mainpump until the main pump stops on low dischargepressure cut-out.

On completion of discharge, the loading arms andpipelines are purged and drained to No. 4 cargo tank andthe arms are then gas freed and disconnected.

Due to the manifold configuration it is necessary to purgethe cargo lines using nitrogen at a pressure of at least 3.0bar; this being done several times to ensure successfuldraining at the manifold connections.

The vapour arm remains connected until just beforesailing if a delay is expected.

Operating Procedures(See Illustration 4.2.7a(i))It is assumed that all valves are closed prior to start.

Preliminary preparation:

1 Checks to be made prior to starting cargo operations

Test remote operation of all tank discharge valves andmanifold ESD valves.

Test remote operation of ballast valves.

Test operation of Emergency Shut Down Systems(ESDS).

2 Safety precautions:

Ensure sprays for hull water curtain at midships are inoperation.

Prepare fire fighting equipment, water hoses andprotective clothing for use.

3 Prepare vent gas heater for use (See 2.5.1).

4 Cargo tanks level alarms

Switch on high level alarms.

5 Tank vapour domes - confirm that:





These valves must be locked open at all times whenthe ship has cargo on board, unless a tank is isolatedand vented for any reasons.

6 Vapour cross-over

Open valve 403

7 Cargo pumps

Check that power supply to cargo pumps..

8 Check connections of liquid and vapour arms

Check communications with shore.

Check ship/shore link.

When shore is ready to purge manifold connections withnitrogen:

9 Liquid manifold connections (assuming port-sidedischarge with 2 liquid hard-arms)

Purge connections then close valves.

10 Vapour manifold connection

Purge connection then close valve.

If shore agree:

11 Vapour manifold

Open manifold ESD valve 401.

12 Liquid connections

Open manifold ESD valves 003, 005, 001, 007.

13 Test Emergency Shut Down System (ESDS) fromshore and from ship as required. Re-open liquid andvapour ESD valves.

When it is agreed with shore that cool-down maycommence:

14 To cool down the cargo and discharge lines proceedas follows (assuming using stripping/spray pump No.3 and centre manifold lines).

14.1 Open discharge valve 130 from No. 3 stripping/spray pump to 20%.

14.2 Open the following valves 160, 173, 053, 175,055, 134, 137, 138. Crack open 190 and 090.

14.3 Start stripping/spray pump

14.4 When hard-arms and shore side lines havecooled down to -100 °C, open valves 190 and090 fully and valves 010 and 040 to 20%. Thiswill now cool down the ships liquid line.

The cooling down is complete when the manifold andships liquid line is approximately -130°C.

14.5 Stop the stripping/spray pump.

Shut valves 090, 130 173, 175.

14.6 When spray line has warmed up, close valves 190, 160, 134, 137, 138.

On completion of cool down and when shore is ready fordischarge, proceed as follows as shown on the followingpage.

4.2 Discharging with Gas Return from Shor e - Page 1Issue: 1


4.2.7a(ii) Stripping Cargo Tanks With Gas Return From ShoreIssue: 1


Key


LNG

LNG Vapour

161

163

165

167

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

052

054

110

492

170

120

491

493

130

144

140

494

148

147

160

053

164

166

055

180

403

401

003

005

Illustration 4.2.7a(ii) Stripping Cargo Tanks With Gas Return From Shore

15 Open No. 3 tank main cargo pump discharge valve031 or 032 to 20%.

Inform the Engine Control Room that a main cargo pumpis about to be started.

Start pump.

16 Check lines for leakage.

Open discharge valve fully on the running pump.

17 When shore is ready to receive further cargo, proceedas for 15 and 16.

The preferred sequence in chronological order of cargopump starting, to obtain a stable discharge operation is asfollows:

Tank No. 3, Tank No. 2, Tank No. 4, Tank No. 1,

18 Monitor tanks pressure.

19 Request vapour return from shore and continue tomonitor pressure to confirm that it stabilises.

20 As the discharge pressure and flow rate increase,continue to monitor the pipework and hard arms forleakage.

21 Adjust pump discharge valves to obtain optimumperformance as indicated by current, dischargepressure and pump graph.

22 It is important to maintain the tanks at a pressure of atleast 1090mbar a in order to avoid cavitation and tohave good suction at the pumps. If the tanks pressurefalls to 1040mbar a request shore to increase gasreturn.

If shore can no longer supply gas return, the mainvaporiser will have to be started up to restore thetanks pressure.

23 Start ballasting operations

Keep draught, trim and hull stresses withinpermissible limits by controlling the various ballasttank levels.

Refer to trim and stability data provided.

24 Continue to monitor tanks pressure and cargo pumpscurrent and discharge pressures.

25 Throttle each pump discharge valve as required toprevent tripping on low current as level in each tankdrops.

Stop main cargo pumps in each tank at approximately0.47m in tank No.1 and 0.3m in tanks No. 2,3 and 4.

Throttle in main cargo pump discharge valve to 40%before stopping the pump. If 2 main cargo pumps arein use in a tank, when the level reaches 0.65m, throttlein the discharge valve on one pump to 40% and stopthat pump. This is in order to reduce turbulencearound the pump suction.

On completion of final tank and after all cargo pumps havebeen stopped:

26 Drain liquid line

27 Stop gas return from shore.

If stripping of tanks ashore is required: (See Illustration4.2.7a(ii))

28 At manifold crossover

Open valves 164, 166 etc.

Close valves 053, 055 etc.

29 Stripping/spray header

Open 180, 170 and check that 003 and 005 are stillopen

Open 160 stripping/spray header to liquid manifoldcross-over

30 At required tanks

Open stripping/spray discharge valves from individualtanks to give the required performance, 110, 120, 130,140.

Start stripping/spray pump.

On completion:

31 Stop final pump

Close valves 164, 166.

Open valves 144, 147, 148 to drain down the headerline to tank No. 4. When completed:

Leave open valves 144, 147, 148, 160, 170, 180, inorder to warm up line. When the line has warmed upclose these valves.

Purging and draining of loading arms.

Purging is carried out one line at a time.

When shore terminal is ready to inject nitrogen and thepressure at the manifold is 2.5 bar, open manifold bypassvalves 164, 166.

32 Close bypass valve when pressure on manifold dropsto 0 bar. Repeat operation a further twice. On the lastoperation shut bypass valve at approximately 1 bar inorder to eliminate the risk of liquid back flow fromship’s liquid line.

Open the test drain valve on the loading arm to ensurethat there is no liquid present. When the required amountof methane (usually less than 1%) is showing at the drainvalve, close the shore terminal ESDS valves.

33 When purging is completed proceed with thedisconnection of the liquid arms.

34 Complete ballasting operations for final measurementand for sailing condition.

Shortly before departure:

35 Vapour line connection

Purge the vapour line with nitrogen from the shoreterminal at a pressure of 2 bar.

Close valve 401 and 403.

Confirm that the gas content is less than 1% byvolume at drain valve 489.

After confirming that gas content is less than 1%volume:

36 Disconnect the vapour arm.

37 Prepare cargo system for gas burning at sea.

4.2 Discharging with Gas Return from Shore - Page 2Issue: 1


4.2.8a Ballast Voyage With Normal Boil-Off Gas BurningIssue: 1


Key


LNG Vapour

ME001VR

450

451

FCV

460453

421

FCV

441

404

494

493

492

491

FCV

452

FCV

TCV

TCV454

431

411

Illustration 4.2.8a Ballast Voyage With Normal Boil-Off Gas Burning

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.2.8 Ballast VoyageA characteristic of the cargo tanks of the Gas Transportmembrane type is that as long as some quantity of LNGremains at the bottom of the tanks, the temperature at thetop will remain below -50°C.

However, if the ballast voyage is too long, the lighterfractions of the liquid will evaporate. Eventually most ofthe methane disappears and the liquid remaining in thetanks at the end of the voyage is almost all LPG with ahigh temperature and a very high specific gravity whichprecludes pumping.

Due to the properties of the materials and to the design ofthe membrane cargo containment, cooling down prior toloading is, theoretically, not required for the tanks.However, to reduce the vapour generation and to preventany thermal shock on the heavy structures, eg the pumptower, loading takes place when the tanks are in a “coldstate”.

Cold Maintenance During Ballast VoyageDifferent methods are used to maintain the cargo tankscold during ballast voyages.

1 For short voyages a sufficient amount of LNG isretained in each tank at the end of discharge. Thelevel must never be above 10% of the length of thetank and the quantities can be calculated byconsidering a boil-off of approximately 0.18% per dayand the need to arrive at the loading port with aminimum layer of 10cm of liquid spread over the wholesurface of the tank bottom (with the ship even keel).

These actual quantities will have to be confirmed aftera few voyages.

With this method of cold maintenance, the tank bottomtemperature should be below -150°C and the topbelow -50°C which allows loading without furthercooling down.

2 During longer ballast voyages, the lighter parts of theliquid layer remaining in the tank, will evaporate, thusmaking the liquid almost LPG and at temperatures ofhigher than –100°C. The upper parts of the tanks willreach almost positive temperatures and under theseconditions it will be necessary to cool down the tanksbefore loading.

Three methods of cooling down are possible, and the oneselected will depend on the operating conditions of theship.

2.1 Cool down the tanks with LNG supplied from shore

2.2 Cool down the tanks just before arrival at the loadingterminal. At the previous cargo discharge, a LNG heelis retained in one of the tanks, provided that the heeldoes not exceed 10% of the tank length. On top of thequantity to be sprayed, the amount of the LNG heel tobe retained will be calculated by assuming a boil offequivalent of 50% of the boil off under ladenconditions.

2.3 Maintain the cargo tanks at cold during the ballastvoyage by periodically spraying the LNG so that theaverage temperature inside the tanks does notexceed -120°C/-130°C. As before, a LNG heel is keptin one of the tanks, provided that the level does notexceed 10% of the tank length. On top of the quantityto be sprayed, the amount of the LNG heel to beretained will be calculated by assuming a boil offequivalent of 50% of the boil off under ladenconditions.

Cooling down is carried out by spraying LNG inside thetanks for whichever method is used. Each tank is providedwith two spray rings, one capable of a large flow rate(equivalent to 55m3/h for all the tanks) and another ofsmall flow rate (equivalent to 35m3/h for all the tanks).

Note: It is obvious that this system will generate moreboil-off than the first proposed system. Thequantity of LNG to be retained on board will haveto be calculated with enough margin to avoid thesituation at mid-voyage where the residual is tooheavy for the pump to operate.

Conservation of bunkers is important, consequently theco-operation of all members of the management team isessential to ensure as much boil-off gas as possible isused to supply boiler fuel demand, thus keeping fuel oilconsumption to a minimum.

The LD. gas compressor is used for gas burning on theballast voyage in the same way as on loaded, with controlof compressor from vapour header pressures. (seesection 4.2.8a gas burning operation)

If a long delay at the loading port is experienced, theremaining heel will slowly boil off and the gas available forburning will reduce, care must be taken to stop gasburning as the tank system pressures continue to drop asthe temperature rises. The degree of natural warm-up willdepend on the time factor, voyage and weatherconditions.

After refit the first ballast voyage will have to be madeusing fuel oil only.

Due to the different calorific values of fuel oil and gas,engine power will require controlling to preventoverloading the boilers.

4.2 Ballast Voyag e - Page 1Issue: 1


4.3.1a Drying Cargo TanksIssue: 1


Key


Dry Air

Wet Air

040

460

405

453

470

454

450

090

480

063 030

020

010

483487

481

485

491

492

493

494

Illustration 4.3.1a Drying Cargo Tanks

482

CL045FO

1

2

1

2

To EngineRoom

To InsulationSpaces

Dry Air From Engine Room


Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3 Out of Service Operations4.3.1 Drying and Inerting Tanks

During a dry docking or inspection, cargo tanks whichhave been opened and contain wet air must be dried toavoid primarily the formation of ice when they are cooleddown and secondly the formation of corrosive agents if thehumidity combines with the sulphur and nitrogen oxideswhich might be contained in excess in the inert gas. Thetanks are inerted in order to prevent the possibility of anyflammable air/LNG mixture. Normal humid air is displacedby dry air. Dry air is displaced by inert gas produced fromthe dry air/inert gas plant.

The inert gas is primarily nitrogen and carbon dioxide,containing less than 1% oxygen with a dew point of -45°Cor below.

! WARNINGInert gas from this generator and pure nitrogen willnot sustain life. Great care must be exercised toensure the safety of all personnel involved with anyoperation using inert gas of any description to avoidasphyxiation due to oxygen depletion.

Dry air and inert gas are introduced at the bottom of thetanks through the filling piping. The air is displaced fromthe top of each tank through the dome and the vapourheader, and is discharged from the vent mast No. 2.

The operation, carried out at shore or at sea, and will takeapproximately 40 hours to reduce the oxygen content toless than 2% and the final dew point to -40°C.

During the time that the inert gas plant is in operation fordrying and inerting the tanks, the inert gas is also used todry (below -40°C ) and to inert all other LNG and vapourpipework. Before introduction of LNG or vapour, pipeworknot purged with inert gas must be purged with nitrogen.

Operating Procedure for Drying Tanks(see figure 4.3.1a)Dry air, with a dew point of -45 °C, is produced by the dryair/inert gas plant at a 6500 m3/h about flow rate.

• Prepare the dry air/inert gas plant for use in the dry airmode.

• Install the spool piece CL.045FO to connect the outletof the heaters with the LNG header.

• Ensure that the valves 450, 453, 454, 470, 405, 090are shut.

• Open the valves 460 and 063 to supply dry air to theLNG header.

• Open tank filling valves 040, 030, 020, 010.

• Open tank vapour valves 494, 493, 492, 491.

• Open 481, 482, 483, 485 to vent through the mast No.2. Eventually, tank pressure is controlled via theregulating valve 487. In this case, close 482.

• Start the dry air production. When dew point is-45°C, open the valve XH/5321G upstream the twonon return valves on the dry air/inert gas dischargeline.

• Monitor the dew point of each tank by taking a sampleat the vapour domes. When the dew point is -40 °C orless, close the filling and vapour valves of the tank.

• Wet air which may be contained in the discharge linesfrom the cargo pumps, float level piping and anyassociated pipe work in the cargo compressor roommust be purged with dry air.

• When all the tanks are dried, stop the plant. Close thesupply valve 063 to the LNG header and close valve481 to the venting system at the mast riser No. 2.

Note: It is necessary to lower the tanks dew point by dryair to at least -25°C, before feeding tanks with inertgas in order to avoid formation of corrosive agents.

4.3 Out of Service Operations - Page 1Issue: 1


4.3.1b Inerting Tanks Prior to Gas FillingIssue: 1


Key


Dry Air

Inert Gas

Illustration 4.3.1b Inerting Tanks Prior To Gas Filling

040

460

450

030

090

480

063

405

020

010

494

493

492485

483487

481 491

453

470

454

CL045FO

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Operating Procedure for Inerting Tanks(see figure 4.3.1b)Inert gas, with an oxygen content less than 1% and a dewpoint of -45 °C, is produced by the dry air/inert gas plantwith a flow rate of 6500m3/h.

• Emergency pump wells have to be inerted withnitrogen before inerting the cargo tanks.

• Prepare the dry air/inert gas plant for use in the inertgas mode.

• Install the spool piece CL.045FO, to connect the outletof the heaters with the LNG header.

• Ensure that the valves 450, 453, 454, 470, 405 and090 are shut.

• Open the valves 460 and 063 to supply inert gas to theLNG header.

• Open tank filling valves 040, 030, 020, 010.

• Open tank vapour valves 494, 493, 492, 491.

• Open 481, 482, 485 to vent through the mast No. 2.Eventually, tank pressure is controlled via the blow offvalve (on/off) 487. In this case, close 482, open 483.

• Start the inert gas production. When oxygen content isless than 1% and dew point is -45 °C, open the valveXH/5321G upstream of the two non return valves onthe dry air/inert gas discharge line.

• By sampling at the vapour dome, check theatmosphere of each tank by means of the portableoxygen analyser. O2 content is to be less than 2% andthe dew point less than -40 °C.

• During tank inerting, purge for about 5 minutes the aircontained in the lines and equipment by using valvesand purge sample points.

• When the inerting of the tanks, lines and equipment iscompleted, set the regulating valve 487 to 1060mbar ain order to pressurise all the tanks to this pressure.

• When the operation is completed, stop the supply ofinert gas and close the valves XH/5321G and 063 andremove the spool piece CL.045FO.



4.3.1c Drying And Inerting Cargo Tanks Using Nitrogen From ShoreIssue: 1


Illustration 4.3.1c Drying And Inerting Cargo Tanks Using Nitrogen From Shore

Key


Liquid Nitrogen

Gaseous Nitrogen

Wet Air

470

453 460

454

FCV

TCV

456

480

502

063

405

040

030

494

493

020

492

010

491481

483487

485

482113

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Note: Until the ship is ready to load LNG, the tanks maybe maintained under inert gas as long asnecessary. If required, pressurise the tanks20mbar above atmospheric pressure and, toreduce leakage, isolate all the valves at theforward venting system.

Drying and Inerting Tanks with Nitrogen (see figure 4.3.1c)Drying and inerting of the cargo tanks can be carried outin one operation by using nitrogen instead of dry air andinert gas.

Considering the large quantity of nitrogen required for thisoperation (about 160m3), liquid nitrogen is supplied fromshore; it is then vapourised in the main vaporiser (see2.6.2) and supplied to the tanks according to the sameprocedure as described above for dry air and inert gas.

Note: Keep tanks in an inert gas condition as short as possible, due to the possibility of corrosionbeing formed.



4.3.2a Displacing Inert Gas (Gassing Up) With LNG VapourIssue: 1


Key


LNG

LNG Vapour

LNG Vapour andInert Gas Mixture

Illustration 4.3.2a Displacing Inert Gas (Gassing Up) With LNG Vapour

040

063

FCV

420

440

406

404

030

410

403

160

402

152

002004

154

156

008158 006

020

062

CL/042F0483

487

485

010

492

491

405

470

453 460

454

180

494

FCV

TCV

456

190

090

493

FCV

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3.2 Displacing Inert Gas with LNG VapourAs the first step in preparing to receive cargo after thetanks and piping have been dried and inerted, the inertgas in the tanks is displaced with LNG vapour at atemperature of about +20°C. The inert gas must beremoved before the tanks are cooled down to avoid theformation of solidified CO2.

The LNG vapour is lighter than the inert gas and isintroduced at the top of the tank through the vapourpiping. The mixture of inert gas and LNG vapour isdischarged from the bottom of the tank through the normalfilling piping into the LNG deck header. The dischargedmixture is normally vented to atmosphere until themethane content reaches 5%; then, it is discharged toshore via the HD compressors. Depending on the portauthorities, the discharge mixture may be returned toshore during the entire operation.

The displacing operation is continued on each tank untilthe discharge from the bottom of the tank indicates amethane content of 90% and a CO2 concentration of lessthan 1% (or less if required by the terminal).

The inert gas in the piping used for cooling down isdisplaced with dry nitrogen to avoid the possibility ofblocking the sprayers with solidified CO2. Other pipingmay remain filled with inert gas.

The LNG vapour is produced by the main vaporiser fromLNG received from the shore terminal. The operation willtake approximately 20 hours.

Preparation

• Check that the nitrogen pressurisation system for theinsulation spaces is in fully automatic operation.

• Check that the gas detection system is in normaloperation.

• Install the following spool pieces:

• CL.045FO compressor suction from the LNGheader.

• CL.036FO LNG supply to main vaporiser from thestripping/spray header.

• CL.043FO outlet of the vaporiser to the vapourheader.

• CL.042FO LNG header to venting system at mastNo. 2.

• Fit the special conical strainer in the crossoverconnection through which LNG will be supplied.

• Prepare the main vaporiser for use.

• Prepare both HD compressors for use.

Operating Procedure (see figure 4.3.2a)

The operating procedure is as follows:

• At the vaporiser, set the outlet temperature of thevapour at +20°C and pressure control valve at theLNG inlet at 60mbar above atmospheric pressure.

• At the venting mast No. 2, open 062, 483, 485. set thepressure control valve 487 at 150mbar aboveatmospheric pressure.

• Open 160 connecting the stripping/spray header withthe manifolds.

• Close 180, 170 to limit the section of the header usedfor the supply of the main vaporiser.

• Open 190 to supply LNG to the vaporiser.

• Open 470, 405 to supply LNG vapour in the vapourheader.

• Open vapour valves 494, 493, 492, 491 on each tank.

• Open filling valves 040, 030, 020, 010 on each tank.

• Open 152 to supply LNG from the manifold.

• Ensure that water curtain under the manifolds is inoperation.

• When shore is ready to supply LNG, open ESDS valve002.

• Monitor the exhaust gas at the sample intake of eachfilling line and at the mast No. 2. When the methanecontent is 5% (or less according to the port authoritiesrequirements), prepare to discharge gas to theterminal.

• Set the compressor control to maintain a tankpressure of 60mbar above atmospheric pressure.

• Open the inlet and outlet valves of the HDcompressors 420, 440 or 410, 430.

• Open the valves 063 compressor suction from theLNG header and 406 compressor discharge to thevapour manifold.

• Open 402 (or 401) the vapour manifold valve.

• Start one or both HD compressors as necessary.

• After the vapour return to shore with the compressorshas been stabilised, reset the regulating valve 487 to100mbar above atmospheric pressure to avoidventing except for safety.

• Monitor the exhaust gas at the sample intake of eachfilling line. When the methane content is 90% or higherand the C02 content 1% or less, throttle the fillingvalves until they are only just cracked open.

• Request the terminal to stop the LNG supply.

• Stop both compressors.

• Close valve 152 at the liquid manifold.

• Do not shut down the main vaporiser until it has beenwarmed up.



4.3.3a(i) Tank Cool Down With Return Through LNG HeaderIssue: 1


Illustration 4.3.3a(i) Tank Cool Down With Return Through LNG Header

Key


LNG

LNG Vapour

063

FCV

440

420

406

402

020

040

010

116

115

114

118

128

487483

485484

486

481

126

125

170

030

136

135

134

138

148

144

146

145

160

180

152

002194

193

192

191

430FCV

410

124

004154

156

006008

158

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3.3 Tank Cool Down

IntroductionArriving at the loading terminal to load the first cargo afterrefit or when repairs requiring the vessel to be gas free thecargo tanks will be inert and at ambient temperature. Afterthe cargo system has been purge-dried and gassed up,the headers and tanks must be cooled down beforeloading can commence. The cool-down operation followsimmediately after the completion of gassing up, usingLNG supplied from the terminal.

The rate of cool-down is limited for the following reasons:

a) To avoid excessive pump tower stress.

b) Vapour generation must remain within the capabilitiesof the HD compressors to maintain the cargo tanks ata pressure of 70mbar (about 1085mbar absolute ).

c) To remain within the capacity of the nitrogen system tomaintain the interbarrier and insulation spaces at therequired pressures.

Unlike rigid cargo tank designs, vertical thermal gradientsin the tank walls are not a significant limitation on the rateof cool-down.

LNG is supplied from the terminal to the cool-down bobbinpiece and from there direct to the spray header which isopen to the cargo tanks. Once the cargo tank cool-downis nearing completion the liquid manifold cross-overs,liquid header and loading lines are cooled down.

Cool-down of the cargo tanks is considered completewhen the top and bottom temperature sensors in eachtank indicate temperatures of -130°C or lower. Whenthese temperatures have been reached, and the FoxboroCTS registers the presence of liquid, bulk loading canbegin.

Vapour generated during the cool-down of the tanks isreturned to the terminal via the HD compressors and thevapour manifold as in the normal manner for loading.

During cool-down, nitrogen flow to the primary andsecondary spaces will significantly increase. It is essentialthat the rate of cool-down is controlled so that it remainswithin the limits of the nitrogen system to maintain theprimary and secondary space pressures at 4.0mbar and3.0mbar respectively.

Once cool-down is completed and the build up to bulkloading has commenced, the tank membrane will be at ornear to liquid cargo temperature, it will take some hours toestablish fully cooled down temperature gradients throughthe insulation. Consequently boil-off from the cargo will behigher than normal.

Monitor the tank pressure and temperature cool downrate, Adjust the opening of the control valves 191, 192,193, 194 to obtain an average temperature fall of 20/25oCper hour during the first 5 hours. There after 10/15oC perhour

Preparation for Tank Cool-down

• Place in service the heating system for thecofferdams.

• Prepare the records for the tank, secondary barrierand hull temperatures.

• Check that the nitrogen pressurisation system for theinsulation spaces is in automatic operation and linedup to supply the additional nitrogen necessary tocompensate for the contraction from cooling of thetanks. Prior to the cooling down, the nitrogen pressureinside the primary insulation spaces will be raised to6mbar. Pressurise the buffer tank at maximumpressure.

• Check that the gas detection system is in normaloperation.

• Fit the special conical strainer in the crossoverconnection through which LNG will be supplied.

• Prepare all the nitrogen generators for use.

• Prepare both HD compressors for use.

• Prepare the vent steam heater YA/5142 for use.

Operating Procedure - Gas Return Through LNGHeader (See figure 4.3.3a(i)As reported by several ship operators, it seems acceptedthat the vapour return through the LNG header instead ofthe vapour header, makes the cool-down operation moreefficient and prevents liquid droplets in the vapour stream.As far as the pressurisation of the insulation spaces andthe LNG spraying lines to the tanks are concerned, theoperating procedure of 6.5.2 is applicable. The onlyalternative concerns the return of the vapour to shore viathe LNG header and the HD compressor(s).The lines are arranged as follows:

• Suction of the HD compressor(s) from the LNGheader:

• Use the spool piece CL.045FO (already in use forthe gassing up), open the valve 063 from the LNGheader and close 404 from the vapour header.

• Open the inlet and outlet valves of the compressors410, 420, 430, 440.

• Open the valve 406 compressor discharge to thevapour manifold.

• Open the filling valve 040, 030, 020, 010 on eachtank.

• All the tanks are kept connected to the vapour header.

• At the venting mast No. 2, open 481, 483, 484, 486.

• Set the pressure control valve 487 at 100 mbar toavoid venting, except for safety.

• Close the valve 403 connection between the vapourheader and the crossover.

• Monitor the tank pressure and temperature cool downrate, Adjust the opening of the control valves 191, 192,193, 194 to obtain an average temperature fall of20/25oC per hour during the first 5 hours. There after10/15oC per hour

Note: This is the preferred operational procedure whichwill normally take approximately 10/12 hours.




4.3.3a(ii) Tank Cool Down With Return Though Vapour HeaderIssue: 1


Illustration 4.3.3a(ii) Tank Cool Down With Return Through Vapour Header

Key


LNG

LNG Vapour

FCV

440

420

406

402

116

115

114

118

128126

125

170

136

135

134

138

148

144

146

145

160

180

152

002194

193

192

191

430FCV

410

124

004154

156

006008

158

FCV

FCV

493

494

492

491

483487

484

486

481

127

117

137

147

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Operating Procedure - Gas Return Through VapourHeader (see figure 4.3.3a(ii))

• Arrange nitrogen piping to preferentially feed theprimary insulation spaces. Open the additional supplyvalves 561, 564.

• Adjust set point of the nitrogen supply regulatingvalves 530, 510 at 6mbar and 520 at 3mbar.

• Adjust set point of the nitrogen regulating relief valves540 at 8mbar and 560 at 5mbar.

• Open the valve 160 connecting the stripping/sprayheader with the manifolds.

• Open the valves 180, 170 on the stripping/sprayheader.

• Open 152 to supply LNG from the liquid manifold.

• At each vapour dome Open the spray valves 144, 145,146, 148; 134, 135, 136, 138; 124, 125, 126, 128; 114,115, 116, 118, open the control valves 194, 193, 192,191 to supply LNG to the spray rings.

• Open vapour valves 494, 493, 492, 491 on each tank.

• At the venting mast No. 2, open 481, 483, 484, 486.set the pressure control valve 487 at 100mbar aboveatmospheric pressure to avoid venting, except forsafety.

• Open the inlet and outlet valves of the compressors410, 420, 430, 440.

• Open the valves 404 compressor suction from thevapour header and 406 compressor discharge to thevapour manifold.

• Open 402 (or 401) the vapour manifold valve.

• When shore is ready to supply LNG, open ESDS valve002.

• After cooling down of the lines, request the shore tosupply a pressure of 4 to 5 bars at the ship’s rail.

• Monitor the tanks pressure and the temperaturecooling down rate.

• Adjust the opening of the control valves 194, 193, 192,191 to obtain an average temperature fall of 20/25°Cper hour during the four to five first hours and then10/15°C per hour.

• Start one compressor (or both as necessary) in orderto maintain the tank pressure at about 30mbar aboveatmospheric.

• Adjust the opening of the control valves supplyingLNG to the spray rings in order to an even cool-downfor all the tanks. If necessary open the by pass valves147, 137, 127, 117.

• Check the nitrogen pressure inside the insulationspaces. If it has a tendency to fall, reduce the coolingdown rate.

• In case where other consumers reduce the availabilityof nitrogen for the insulated spaces, the pressure maytemporarily fall below the atmospheric pressure. Thiscondition is not critical insofar as the differential (Ps -Pp) between the secondary space pressure (Ps) andthe primary space pressure (Pp) does not exceed30 mbars.

(Ps - Pp < 30 mbars)

• When the average of the temperatures shown by thesensors installed on the pump towers is-130°C, request the terminal to stop LNG supply andclose the valve 152. The other valves will remain openuntil the lines warm-up.

• Stop the compressor(s) if the loading does not takeplace after cooling down.

Note: This operating procedure is very time consumingand is not the preferred method. The operationpreferred is gas return through LNG header.




4.3.4a Tank Warm UpIssue: 1


Illustration 4.3.4a Tank Warm Up

LNG Vapour

Warm LNG Vapour

Key


FCV

440

420

410

430FCV

404

494

493

492

491

484

482481

483487

485

486

040

453

454

063

451

452

FCV

FCV

030

020

010

TCV

TCV

CL045FO

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3.4 Tank Warm UpTank warm up is part of the gas freeing operations carriedout prior to a dry docking or when preparing tanks forinspection purposes.

The tanks are warmed up by recirculating heated LNGvapour. The vapour is recirculated with the two HDcompressors and heated with the cargo heaters to 80°C.In a first step, hot vapour is introduced through the fillinglines to the bottom of the tanks to facilitate the evaporationof any liquid remaining in the tanks. In a second step whenthe temperatures have a tendency to stabilise, hot vapouris introduced through the vapour piping at the top of thetanks.

Excess vapour generated during the warm up operation isvented to atmosphere when at sea, or returned to shore ifin port. (The instructions which follow apply to the normalsituation, venting to atmosphere at sea).

The warm up operation continues until the temperature atthe coldest point of the secondary barrier of each tankreaches 5°C.

The warm up operation requires a time dependent on boththe amount and the composition of liquid remaining in thetanks, and the temperature of the tanks and insulationspaces. Generally, it requires about 30 hours.

Initially, the tank temperatures will rise slowly asevaporation of the LNG proceeds, accompanied by highvapour generation and venting. A venting rate ofapproximately 8000 m3/h at 60°C can be expected. Oncompletion of evaporation, tank temperatures will riserapidly and the rate on venting will fall to between 1000and 2000 m3/h at steadily increasing temperatures.Temperatures within the tank and insulation are indicatedin the cargo control room

Rolling and pitching of the vessel will assist evaporation.Temperature sensors at the aft end of the tank give a goodindication of the progress of warm-up. Slight listing of thevessel will assist in correcting uneven warm-up in any onetank.

Gas burning should continue as long as possible,normally until all the liquid has evaporated, ventingceased and tank pressures start to fall.

Preparation

• Strip all possible LNG from all tanks as follows:

• When discharging the final cargo, remove themaximum LNG with the stripping pumps.

• If discharge of LNG to shore is not possible,vaporise it in the main vaporiser and vent thevapour to the atmosphere through the mast No. 2.

• If venting to the atmosphere is not permitted, thevapour must be burned in the boilers.

• For maximum stripping, the ship should have zerolist and should be trimmed down at least 0.8m bythe stern.

• Run the stripping pumps until suction is lost.

• Switch cargo/stripping pumps power lock ‘on’.

• Remove the emergency pump that may have beenplaced in a cargo tank.

Rolling and pitching of the vessel will assist evaporation.Temperature sensors at the aft end of the tank give a goodindication of the progress of warm-up. Slight listing of thevessel will assist in correcting uneven warm-up in any onetank.

Gas burning should continue as long as possible,normally until all the liquid has evaporated, ventingceased and tank pressures start to fall.

Operating Procedure (see figure 4.3.4a)

During the tank warm up, gas burning may be used bydirecting some vapour from the heater outlet, to theboilers and by controlling manually this operation.

• Install the spool piece CL.015FO and open the valve063 to discharge heated vapour to the LNG header.

• Prepare the gas heaters YA/5141 A and B for use.

• Prepare the glycoled water heaters

• Adjust temperature set point at 80°C.

• Prepare both HD compressors YAI5121 A and B foruse.

• At vent mast No. 2, open the valves 481, 483, 484,486.

• Adjust the set point of 487 at 190 mbars.g.

• Prepare the vent heater YA/5142 for use.

• Open the valve 404, the suction of the compressorsfrom the vapour header.

• Open the compressor inlet and outlet valves 410, 430,420, 440.

• Open the heater inlet and outlet valves 451, 452, 453,454.

• Open the vapour valves 494, 493, 492, 491 on eachtank.

• Open the filling valves 040, 030, 020, 010 on eachtank.

• Start both HD compressors manually and graduallyincrease flow by the inlet guide vane position.

• Monitor the tank pressure and adjust the compressorflow for maintaining the tank pressure to about 1180mbars a.

• Check that the pressure in the insulation spaces whichhave a tendency to increase remains inside the presetlimits.

• Monitor the temperatures in each tank and adjust theopening of the filling valve to make uniform thetemperature progression in all the tanks.

• After twenty/twenty-four hours, the temperatureprogression slows down. Eventually, the procedure ofthe second method described below, may be moreefficient.

• At the end of the operation, when the coldesttemperature of the secondary barrier is at least +5°C,or before switching to the second step, stop and shutdown gas burning system if used. Stop both HDcompressors, shut the filling valves on all tanks andrestore the normal venting from the vapour header.

Operating Procedure 2nd Method

Considering the waste of time for changing the position ofheavy spool pieces, which must be put back in theiroriginal position for the next operation (gas freeing), theship operators are not in favour of the above procedureand it may be regarded as optional.

During tank warm up, gas burning may be used bydirecting some vapour from the heater outlet to theboilers, and by manually controlling this operation.

Open the valve 405 to discharge heated vapour to thevapour header.

Prepare the gas heaters YA/5141 A and B for use. Adjustthe temperature set point to 80°C.

Prepare both HD compressors YA/5121 A and B for use.

At vent mast No. 2, install the spool piece CL 042FO andopen the valves 062, 483, 484, 486.

Adjust the set point of 487 at 190mbar g.Prepare the vent heater YA/5142 for use.

Install the spool piece CL 045FO and open the valve 063,the suction of the compressors from the LNG header.

Open the compressor inlet and outlet valves 440, 410,420, 430.

Open the heater inlet and outlet valves 454, 453, 451,452.

Open the vapour valves 491, 492, 493, 494 on each tank.

Open the filling valves 010, 020, 030, 040 on each tank.

Start both HD compressors manually and graduallyincrease flow by the inlet guide vane position.

Monitor the tank pressure and adjust the compressor flowfor maintaining the tank pressure at about 190mbar gabove atmospheric pressure.

Ensure that the pressure in the insulation spaces, whichhave a tendency to increase, remain inside the presetlimits.

Monitor the temperatures in each tank and adjust theopening of the vapour valve to make uniform thetemperature progression in all the tanks.

At the end of the operation, when the coldest temperature ofthe secondary barrier is at least +5°C, stop and shut downthe gas burning system if used, stop both HD compressorsand shut the filling valves on all the tanks and restore thenormal venting from the vapour header.



4.3.4b One Tank Warm upIssue: 1


Illustration 4.3.4b One Tank Warm Up

LNG Vapour

Warm LNG Vapour

Key


FCV

FCV

404

494

493

492

491

484483

487

485

486

040

453

454

063

451

452

FCV

FCV

030

020

010

TCV

TCV

400

406

FCV

FCV

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3.4b One Tank Warm UpWhen it is required that a single cargo tank be warmed upfor maintenance procedures to be carried out, theoperational procedures are as follows.

Gas burning will be maintained as long as possible beforethe tank warm up procedure is commenced.

It is assumed that the tank to be warmed up has beenstripped are cargo as far as practical.

Operating Procedure(see illustration 4.3.4b)Install spool piece CL 045FO

• Open bypass cross connecting valves 400 and 406.This enables the HD and LD compressors to bebypassed.

• Open valve 062, 483 and 485 at No.2 vent mast riser.Adjust the set point of valve 487 at 150mbar g

• Open liquid filling valve to tank 040

• Bring into line one of the duel purpose heaters. Open451,453.

• Control the vapour outlet temperature to 80 °C

Follow the procedure described in 4.3.6 Tank Warm, fortemperature rise control rates.



4.3.5a Gas FreeingIssue: 1


XH5321G

460

063 030

040

020

010

Key


LNG Vapour

Inert Gas

494

493

492483

487

485

491

Illustration 4.3.5a Gas Freeing

481

CL045FO

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3.5 Gas FreeingAfter the tanks have been warmed up, the LNG vapour isdisplaced with inert gas.

Inert gas from the inert gas plant is introduced at thebottom of the tanks through the LNG filling piping. Gasfrom the tanks is vented from the top of the tank throughthe vapour header to the vent mast No. 2, or to shore if inport. (The instructions which follow apply to the normalsituation, venting to the atmosphere at sea).

Inerting is necessary to prevent the possibility of havingan air/LNG vapour mixture in the flammable range. Theoperation is continued until the hydrocarbon content isreduced to less than 2.5% (50% of the LEL). Theoperation requires about 20 hours.

In addition to the cargo tanks, all pipe work and fittingsmust be gas freed. This is best done with inert gas ornitrogen, while the plant is in operation for gas freeing thetanks .

The operating procedure is as follows: (see figure 4.3.5a)

• Prepare the inert gas plant for use in the inert gasmode.


• At vent mast No. 2, open the valves 481, 483, 485 andAdjust the set point of 487 at 20 mbars.g.

• Install the spool piece CL.045FO and open the valves460, 063 for the supply of inert gas to the LNG header.


• Start the inert gas generator and run it until the oxygencontent and dew point are acceptable.

• On the dry air/inert gas discharge line, open theisolating valve XH/5321G located before the two nonreturn valves. Change the spectacle blank over intothe open position, which is located after the non returnvalves on A deck forward of the accommodation blockport side.

• Monitor tank pressures and adjust the opening of thefill valves to maintain an uniform pressure in all thetanks. Ensure that the tank pressures are alwayshigher than the insulation space pressures by at least10 mbars, but that the tank pressures do not exceed180 mbars above atmospheric pressure. In any case,during gas freeing the pressure in the tanks must bekept low, to maximise the piston effect.

• Approximately once an hour, take samples of thedischarge from the vapour dome at the top of eachtank and test for hydrocarbon content. Also verify thatthe oxygen content of the inert gas remains below 1%,by testing at a purge valve at the filling line of one ofthe tanks being inerted.

• Purge for 5 minutes all the unused sections ofpipelines, machines, equipment and instrumentationlines.

• When the hydrocarbon content sampled from a tankoutlet falls below 2.5%, isolate and shut in the tank.On completion of tank and pipeline inerting, stop theinert gas supply and shut down the inert gas plant.Reset the valve system for aerating.

• If the tanks remain inerted without aerating, shut thevalve 481, raise the pressure to 100 mbars gauge,then shut in the tanks.

! WARNINGIf any piping or components are to be opened, theinert gas or nitrogen must first be flushed out with dryair. Take precautions to avoid concentrations of inertgas or nitrogen in confined spaces which could behazardous to personnel.

4.3 Out of Service Operations - Page 1 0Issue: 1


4.3.6a AeratingIssue: 1


460

Illustration 4.3.6a Aerating

405494

493

492

491

062

CL042F0483

487

485

020

010

030

040

XH5321G

Key


Dry Air

Inert Gas

1

2

1

2

To EngineRoom

To InsulationSpaces

Dry Air fromEngine Room


Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.3.6 Aerating

IntroductionPrior to entry into the cargo tanks the inert gas must bereplaced with air.

With the Inert Gas and Dry-Air System (see 2.6) in Dry-Airproduction mode, the cargo tanks are purged with dry airuntil a reading of 20% oxygen by volume is reached.

OperationThe Inert Gas and Dry-Air System produces dry air with adew point of -55°C to -65°C.

The dry air enters the cargo tanks via the vapour header,to the individual vapour domes.

The inert gas/dry-air mixture is exhausted from the bottomof the tanks to the atmosphere at No. 2 mast riser via thetank loading pipes, the liquid header, and removable bendCL/042FO.

During aerating the pressure in the tanks must be kept lowto maximise a piston effect.

The operation is complete when all the tanks have a 20%oxygen value and a methane content of less than 0.2% byvolume (or whatever is required by the relevantauthorities) and a dew point below -40°C.

Before entry test for traces of noxious gases (carbondioxide less than 0.5% by volume, and carbon monoxideless than 50ppm) which may have been constituents ofthe inert gas. In addition take appropriate precautions asgiven in the Tanker Safety Guide and other relevantpublications.

The pressure in the tanks is adjusted to 1020 mbars a.

Aeration carried out at sea as a continuation of gas freeingwill take approximately 20 hours

! WARNINGTake precautions to avoid concentrations of inert gasor nitrogen in confined spaces which could behazardous to personnel. Before entering any suchareas, test for sufficient oxygen > 20% and for tracesof noxious gases: CO 2 < 0.5% and CO < 50 ppm.


• Prepare the inert gas plant for use in the dry air mode.

• Install the spool piece CL.042FO for venting the

mixture inert gas / dry air from the LNG header.

• At the vent mast No. 2, open the valves 062; 483, 485.Adjust the set point of 487 at 20 mbars aboveatmospheric pressure.



• On the dry air/inert gas discharge line, open theisolating valve XH/5321G located before the two nonreturn valves. Change the spectacle blank over intothe open position, which is located after the non returnvalves on A deck forward of the accommodation blockport side.

• Start the dry air generator.

• Open the valves 460, 405 to supply dry air to thevapour header.

• Observe the tank pressures and insulation spacepressures, to ensure that the tank pressures arehigher than the space pressures by 10mbar.g at alltimes.

• Approximately once an hour, take samples from thefilling pipe test connections to test the discharge fromthe bottom of the tanks for oxygen content.

• When the oxygen content reaches 20%, isolate andshut in the tank.

• When all the tanks are completed and all piping hasbeen aired out, raise the pressure to 100mbar g ineach tank and shut the filling and vapour valves oneach tank. Restore the tank pressure controls andvalves to vent from the vapour header.

• During the time that dry air from the inert gas plant issupplied to the tanks, use the dry air to flush out inertgas from vaporisers, compressors, gas heaters,crossover’s, pump risers and emergency pump wells.Piping containing significant amounts of inert gasshould be flushed out. Smaller piping may be left filledwith inert gas or nitrogen.

! CAUTIONDuring the time a tank is opened for inspection, dryair will be permanently blown through the filling lineto prevent the entry of humidity from the ambient air.



4.4 Emergency Operations and ProceduresFire in Cargo Area and Use of Dry Powder

Operate ESDS to stop cargo operations.

Sound ships fire alarm.

Start water spray pumps.

Stop vent fans and secure crew quarters zone.

If vessel is in port the fire fighting gear (pressurised firemain) will already be arranged on deck.

Fire parties should be dressed in fire suits with B.A.Using a fine water spray curtain, ensure that the source offuel (gas/liquid) to the fire is isolated.

Dry powder either through hand held hoses or fixedmonitors is the most effective fire fighting medium.

Firefighting ProceduresAlthough the flash point of LNG is -175°C, the rapidvapourisation of any exposed LNG prevents any ignitionof the liquid itself and an LNG fire is thus a cold vapourfire.

Ignition of a flammable mixture of natural gas vapourrequires a spark of similar ignition energy as would igniteother hydrocarbon vapours. The auto-ignition temperatureof methane in air (595°C) is higher than otherhydrocarbons.

Electrostatic ignition on LNG is not a hazard during normaloperations. This is because the permanent, positivepressure in LNG tanks maintained by gas boil-off preventsair entering these spaces to form flammable mixtures intanks or lines.

Burning of LNG vapours produces a similar flame size andheat radiation to other hydrocarbon fires, but little smokeis produced.

From a firefighting viewpoint LNG/cold vapour fires havethe characteristics of both liquid and gaseoushydrocarbon fires.

The procedure for fighting these fires is:

a) Isolate the source of leak, stop loading/discharging,shut all manifold valves.

b) Sound the alarm.

c) Provide protection for adjacent equipment and forfirefighters.

d) Attack fire with a maximum of application of drypowder. Do not agitate the surface of any pool of LNG.

e) Remain on guard against possible re-ignition.

The exact procedure will depend upon the nature of theincident.

FirefightingThe following firefighting media can be used

WaterWater should not be used to extinguish LNG fires.

A water spray or fog should be used to protect personneland to cool areas adjacent to the fire.

Care is necessary to avoid water running off any adjacentstructure and aggravating burning LNG, or splashing intospill trays which may contain LNG, thus causing them tooverflow onto unprotected steelwork.

FoamFoam adequately applied to a depth of between 1 and 2m,will largely suppress the radiation from the flame to theliquid below, thereby reducing the vaporisation rate andrate of burning. The difficulty arises in trying to contain thefoam mat covering, due to the lack of structures acting ascontainment areas and the effects of wind dispersing thefoam.

High expansion foam has been used successfully on LNGpool fires. If a stable foam is used, it has been found thatif is freezes at the interface, the rate of vaporisation isreduced. If, on the other hand, the foam breaks down intothe liquid beneath, the vaporisation rate may increase. Ingeneral, unless the foam can be contained, foam fixedinstallations are not fitted to LNG ships for liquified gasfirefighting.

Smothering SystemsCO2 and nitrogen smothering systems are only effectivewhen injected into enclosed spaces, or spaces that can beisolated by the closing of doors, flaps and hatch covers.The process by which these gases fight fires, is bydisplacing oxygen to a level which will not supportcombustion. It is therefore not considered practical forfighting fires on the open cargo deck.

Dry Chemical PowderThe extinguishing power of dry chemical powder dependson the chemical reaction of the small particles whenexposed to flame. They are flame inhibiting agents andhave been widely proved in LNG fire tests.

Various types of powder are marketed, potassium basedpowders are more effective than sodium based or multi-purpose powders, but not all are foam compatible. Allpowders are liable to compact when subject to humidconditions or vibration, so filling and maintenanceinstructions should be carefully observed.

The maximum possible rate of application of dry powder isdesirable. As many high velocity jets as possible shouldbe brought to bear at once, preferably in a down winddirection. Jets should be aimed with the objective ofreducing boil-off rate by sweeping over whole fire areaand on no account must the surface of LNG pool beagitated. Possible re-ignition must be guarded against.

Fire in the Cargo Compressor Motor RoomThe cargo compressor and motor rooms are protected bya fixed CO2 smothering system consisting of 18 cylinders,each with a capacity of 60 litres. They are arranged in 2banks that are housed in the CO2 bottle store, which islocated aft of the motor room. The compressor roomrequires all 18 of the CO2 cylinders, while the motor roomrequires 9 of the 18 CO2 cylinders.

Injection of CO2 is carried out from designated compressorand motor room control box stations, located in the CO2

bottles store. Operating instructions are contained insidethe control box stations. Opening the control box station door trips the ventilation fans.

Ventilation of Hazardous SpacesNo tank, cofferdam or other enclosed space may beentered until it has been thoroughly ventilated. Theatmosphere must be tested for hydrocarbons and oxygenand a safe entry certificate issued by a responsible officer.The compressor house and motor room fans must berunning at all times.

Ballast tanks and cofferdams must be ventilated andatmospheres tested, and safe entry permits issued byresponsible officer prior to entry.

Safety trolley to be standing by point of entry.

Personnel entering must be kitted out with cap lamp andbattery, cyalume light stick, VHF transceiver and personaloxygen analyser.

Rollover

• The rollover phenomenon is characterised by asudden rapid generation of vapour. This problemarises because LNG is a multi-component mixturewhose boiling point increases as its density increases.It mainly occurs in the land storage tanks when anheavier, warmer liquid is added to the bottom of a tankcontaining a lighter liquid. The energy transmitted intothe tanks contents though the walls is partially used tovapourise the lighter layer and to warm-up the heavierlayer. When its density approaches that of the lighterlayer, it suddenly rises and, without the confiningeffect of the colder layer, rapid boiling and mixingoccur. If exhaust devices and vents have insufficientcapacity to handle the vapour so generated, tankfailure may result.

• Rollover is not expected to occur on ship since themotions in open sea serve to mix the cargo.

4.4 Emergency Operations and Procedure s - Page 1Issue: 1


4.4.1a Cargo Discharging Without Gas Return From ShoreIssue: 1


Illustration 4.4.1a Cargo Discharging Without Gas Return From Shore

405

470

494

493

041

042

031032

005

055

003

053 051

001

492

011012

022021

FCV

TCV

456

090

057

007

491

Key


LNG

LNG Vapour

FCV

TCV

455

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




CC/036FO

Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.4.1 Cargo Discharging without Gas Return fromShore

IntroductionIf the shore is unable to supply LNG Vapour to maintaintank’s pressure, the spray system and, if necessary, theMain Vaporiser is used to generate vapour in order tomaintain the required pressure. The discharging is in allother aspects the same as when being supplied with gasreturn from shore.

OperationDischarging is carried out in exactly the same manner asline cool-down and detailed in Section 4.2.3 except thatthe manifold vapour connection is not used. The mainVaporiser is set to maintain the tank’s pressure at1100mbar a. and it will operate during the entire dischargeperiod.

• If the LNG header pressure should be lost, in anemergency or other special situations, supply LNGthrough the stripping/spray header from one of thestripping pumps.

• If the vaporiser is to be used as the normal supply forvapour while discharging cargo, the LNG is taken fromthe LNG header, with an alternative supply availablefrom the stripping/spray header in an emergency.

• Prepare main vaporiser for use.

• Open main vaporiser outlet valve 470 and valve tovapour header 405.

• Open valve 090 to supply LNG from the LNG headeror 190 to supply LNG from the stripping/spray header

• Open LNG inlet valve to the vaporiser 456 andposition bend CL/036FO.

• Start up manually the vaporiser. When the vaporiserhas stabilised transfer control to the Cargo ControlRoom.

• During cargo discharge, monitor tanks pressure.

• When cargo discharge is completed, stop the mainvaporiser by closing the valve 470 or 405, leave othervalves open until the warming up of the lines iscomplete.

4.4 Emergency Operations and Procedures - Page 2Issue: 1


4.4.3a Emergency Cargo Pump Fitting SequenceIssue: 1


! WARNINGBefore commencement of operation, lower tank pressure to just above atmosphere.

Tank Top

Blind Flange

Tank LNG Liquid Level

Cable Guide

Column Flange Gasket

Support PlateAssy

LNG Discharge PipeLifting Cable

Auxiliary Cargo Pump

Lifting Assembly

Head Plate

In-Tank Power Cable

Lifting Cable

Nitrogen gas pressure displaces LNG from column

Inert column withnitrogen gasAfter inerting, stopnitrogen gas, thenbleed off nitrogen gas pressure in column

Remove blind flangeInstall column flangegasketPrepare to install thepump using liftingcable

Lower pumpLift pump and head plateLifting assembly in'closed' position

Pressurise with nitrogen gasto open suction valvewith lifting assemblyin 'closed' positionAfter opening maintain nitrogen gas pressure in column

Lower pump completelyby adjusting liftingassembly to 'open' positionCool down pumpBleed off pressure in columnto slowly introduce LNGinto the column

Operate PumpInstall head plate withlifting assy in 'closed'positionInstall electrical assemblyand support bracketInstall deck powercable assemblyStart cool down for pump bysuspending above suction valve

N2 Gas

Suction Valve

Column

N2 Gas

In-Tank Power CableSupport Blockand SpreaderBar Assembly

Cable Guide

Deck Power Cable

1 2 3 4 5 6 7 8

Nitrogen Gas Nitrogen Gas Nitrogen GasNitrogen GasNitrogen GasNitrogen GasNitrogen Gas

Illustration 4.4.3a Emergency Cargo Pump Fitting Sequence

4.4.3 Use of Emergency Cargo PumpThe emergency cargo pump is used in the event that bothmain cargo pumps have failed in a cargo tank.

The pump is suppled with a set of lifting pipes, threephase cargo power cables, cable terminal box, mountingplate and spring loaded roller guides. The cables areattached to the lifting pipe at regular intervals of 457mm.The roller guides are set out at intervals of 2438mm apart.

The pump is suspended over the column into which it isbeing lowered by a portable set of sheer legs.

Also fitted to the column is a nitrogen purge point and anoutlet purge point on the cable outlet bend.

The pump discharges into the column and out onto theliquid line via a discharge connection and valve at the topof the column.

Installation in the Tank(See Illustration 4.4.3a)When all equipment, pump, cables, electrical connectionbox and accessories are in position near the tank in whichthe pump is to be installed, prepare the sheer leg to lift the pump and start the pump installation.

- The cargo tank will inevitably contain LNG, thereforethe column into which the emergency pump is beinglowered will require the liquid to be evacuated. This isachieved by injecting nitrogen into the column. In thecase of a full cargo tank, a pressure of between 2 and3bar is required. The nitrogen forces the liquid outthrough the foot valve located at the bottom of thecolumn. On completion of the expulsion of the liquid, acheck must be made at the purge cock to ensurecomplete inerting has taken place. The tank pressuremust be reduced to just above atmospheric, beforeremoving the column top blank flange. Install a newcolumn flange gasket, then begin to install the pumpusing the lifting gear.

! CAUTIONWhen working near the open pump column all toolsand equipment used have to be attached to avoidanything falling in the column. All personal itemshave to be removed from pockets and columnopening should be temporarily covered at all timewhilst blind flange is removed.

Install the power cables on the pump. Ensure powercables are carefully laid down on deck and suitablyprotected to avoid any damage. The power cable ends aremarked “A”, “B” and “C” and should coincide with thesame markings on the pump to ensure correct phaserotation. Lower the pump in the column. Attach the headplate and lift pump and head plate with lifting assembly inthe closed position.

- When the pump is lowered into position above thesuction valve, install head plate with lifting assembly inclosed position, being very careful with the gasket.Install electrical assembly and support brackets.Install deck power cable assembly making sure that“A”, “B” and “C” markings are matched at allconnecting points.

Pump Cool-down and OperationStart cool-down for pump. Pump should be left suspendedin the empty column for 10 to 12 hours for a correct cool-down.

After 10 to 12 hours introduce nitrogen pressure in thecolumn to open suction valve with lifting assembly in theclosed position.

Decrease the nitrogen pressure slowly to let the liquid risein the column at a speed of approximately 75 to 125 mm /minute until it covers the pump completely. (Approximately2 meters).

When the liquid level is above the pump, maintain thenitrogen gas pressure and lower the pump completely byadjusting the lifting assembly to the open position.

Stop the nitrogen supply when the liquid is at the samelevel in tank and column and bleed the nitrogen from thetop of the column. The pump will have to stay for one hourimmersed in the liquid before being started.

Before starting the pump, the discharge valve has to beopened to ensure that there is no pressure built up at thetop of the column when starting the pump. If necessaryexcess pressure can be bled off via the purge cock.

When ready to start the pump, open the discharge valve20 per cent and start the pump normally.

Check operation very carefully to ensure that there is noleakage at top of column or discharge piping. Fire hosesmust be under pressure and ready in the vicinity beforestarting.

Adjust opening of the discharge valve to have requireddischarge flow and pressure within the pump capacity.If the first start is not successful refer to Section 4 for theallowable number of starts.



4.4.5a Jettisoning Of CargoIssue: 1


LNG

Illustration 4.4.5a Jettisoning Of Cargo

000061

Key


021

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Jettison

4.4.4 In Service Repairs to Tanks It maybe necessary for in-tank repairs to be carried outwith the vessel in service in which one tank can bewarmed up, inerted, aerated, entered and workundertaken on tank internals i.e. change cargo pumpinvestigate and cure problems with tank gauging systemetc. It is not envisaged that tank barrier repairs will becarried out with one tank only warmed up.

The warm-up, inert, aerating can be carried out with theremaining cold tanks providing gas for gas burning.

Aeration should be continued throughout the repairperiod, to prevent ingress of humid air to the cargo tank.

Tank venting will be via its own riser, inerting time can bereduced by floating the tank relief valves.

4.4.5 Jettisoning of Cargo

! WARNINGThe jettisoning of cargo is an emergency operation. Itshould only be carried out to avoid serious damage tothe cargo tank and/or inner hull steel structure.

A membrane or insulation failure in one or more cargotanks may necessitate the jettisoning of cargo from thatparticular cargo tank to the sea. This is carried out usinga single main cargo pump, discharging LNG through aportable nozzle fitted at ships stern via spool piece.

As jettisoning of LNG will create hazardous conditions:

a) All the circumstances of the failure must be carefullyevaluated before the decision to jettison cargo istaken.

b) All relevant fire fighting equipment must be manned, ina state of readiness and maintained so during theentire operation.

c) All accommodation and other openings and all ventfans must be secured.

d) The NO SMOKING rule must be rigidly enforced.

Weather conditions, and the heading of the vessel relativeto the wind, must be considered so that the jettisonedliquid and resultant vapour cloud will be carried away fromthe vessel. In addition, if possible, avoid blanketing thevapour with exhaust gases from the funnel.

The discharge rate must be limited to the capacity of onecargo pump only and, if necessary, reduce to allowacceptable dispersal within the limits of the prevailingweather conditions.

It is preferable for the vessel to be moving slowl y awayfrom the vapour cloud as jettisoning takes place.

Jettisoning

Under extreme circumstances it may be necessary, as alast resort, to consider jettisoning of cargo to the sea.

Dispersion models based on extensive experimental dataexist to predict the downwind concentrations for definedweather conditions, wind velocity and surface roughness.These allow prediction of downwind flammable hazardzones arising from spills of refrigerated LNG and LPG.

Wind tunnel tests have been undertaken on the release ofliquefied gases from a small sea-going tanker so as toprovide recommendations for the safe venting of gas andjettisoning of liquid. This section considers thecharacteristics of some of the principle cargoes andfactors additional to the characteristics of the cargo itselfincluding:

• The effect of the ship’s hull

• The wind speed and direction relative to the ship

• The position of discharge from the ship i.e. bow,stern or midships

• Use of cargo hose or fixed discharge nozzle anddegree of vaporisation

The salient features relating to jettisoning derived fromthese tests are summarised below. In addition, from thepresent limited knowledge of the vaporisation anddispersion characteristics of other liquefied gas cargoese.g. ammonia, an attempt is made to indicate the likelydifferences in their jettison behaviour relative to LNG/LPG.

Cargo Characteristics Relevant to Jettisoning

All spills of liquefied gases initially generate a cold denseheavier-than-air vapour cloud and show the same generaltrends in downwind dispersion.

Such liquefied gases will include not only all refrigeratedcargoes including LNG, LPG and ammonia but also allpressurised cargoes that become auto-refrigerated onrelease to the atmosphere. These vapour clouds will forma low spreading plume on the sea surface, initially

slumping upwind and extending downwind from thesource, growing in height and gradually becoming dilutedby mixture with air.

The distance at which the average concentration hasbeen diluted to the Lower Flammable Limit or toxic limit,i.e. the hazard distance, will depend not only on thequantity and rate of spill but also on the flammability/toxiclimits of the cargo itself, wind speed and atmosphericstability, with distances tending to be greatest in a stableatmosphere and low wind speeds of 5-6 knots.Information indicating the maximum downwind hazarddistances for the jettisoning of LNG and LPG onto the seais available. The Incident Controller and concernedAuthority may decide to seek guidance specific to the siteconditions.

The ambient humidity will also be a major factor on thevisible limits of the plume, since cooling of the entrainedair to below its dewpoint will result in a white visible cloud.For humidities in the range ot 60-90%, propane plumescease to be visible at dispersion distances well short ofthe LFL (2%) but beyond the UFL (10%). LNG plumes,however, remain visible beyond the LFL point (5%) for allhumidities greater than about 50%.

While little direct experimental dispersion data is availablefor the sea spills of ammonia. it may be expected that, forsimilar spill conditions, the behaviour of an ammoniaplume will be broadly similar to LNG/LPG spill plumes withthe exception that:

• Due to the toxic limit of about 500 ppm (0.05%)considerably greater dispersion distances may berequired

• A release of liquefied ammonia under pressure maybehave as a heavier-than-air gas until completelydispersed

• The higher LFL concentration (15%) should ensurethat for normal atmospheric humidities, theflammable zone will be generally well within thevisible cloud.

• Due to the considerable heat of reaction ofammonia/water mixtures and the low relativedensity of ammonia vapour, there will be a morerapid upward dispersion of the ammonia plumeabove a spill of liquid ammonia into the water.

Ecological considerations may make it very undesirable tojettison a substantial quantity of liquid ammonia intoshallow seas. In these circumstances, slow atmosphericdispersion may be preferable so as to minimise localconcentrations in the sea.

The Effect of the Ship ’s Hull

Unhindered dispersion models which can reliably predictthe vapour dispersion characteristics of unhindered landand sea cargo spills are not appropriate when the spilloccurs in the direct vicinity of an obstacle of comparablesize with the dimensions of the vapour source.

This is normally the case during jettisoning where theturbulence of the wind field generated by the ship’s hull inthe prevailing wind direction can significantly modify notonly the distribution of the vapour concentrations in theimmediate vicinity of the ship itself but also the extent ofthe downwind hazard zone.

Eddy currents on the down wind (lee) side of the ship candrag vapour concentrations onto the deck and also backonto the sea surface adjacent to the ship’s side from aliquid pool adjacent to the ship.

Under some conditions the concentrations can exceed theLFL (or toxic limit). The turbulence generated by the ship’shull can considerably reduce the downwind distance toLFL (or toxic limit) for midships jettisoning with a crosswind.

The Windspeed and Direction Relative to the Ship andthe Position of Discharge from the Ship

Experimental data on jettisoning has been derived fromboth full-scale tests and model simulation in a wind tunnel

Full scale tests at sea with an astern cargo jettisonconnection have demonstrated that LNG cargo dischargerates up to 1,200 m3/hr from the stern are practicable withthe ship steaming ahead or stationary under the followingconditions:

• The ship can manoeuvre to maintain the winddirection ideally between 300 and 600 off the bow toensure that eddy effects do not drag flammablevapour concentrations back onto the ship.

• The relative wind speed is not less than 5 knots.

• The nozzle exit velocity is 40-50 m/s.

Under these conditions it was found that:

• A large proportion of the LNG vaporised beforereaching the sea and liquid pools on the sea

surface were limited to small isolated patches thatpresented no risk to the ship’s hull.

4.4 Emergency Operations and Procedure s - Page4Issue: 1


• At an average wind speed of 5 knots, the flammableregion of the vapour cloud produced extended nofurther than 700 m downwind although the visible cloud extended appreciably further due to the condensation of atmospheric moisture. Higher windspeeds would have reduced this distance evenfurther. Despite the low wind speed, the vapourcloud dispersed without trace within 20 minutes ofstopping the discharge.

The results of wind tunnel model simulation tests of LNGjettisoning from a 75,000 m3 carrier are available. Theseillustrate the limiting safe heading of the ship relative tothe wind direction for jettisoning either from the bow orfrom the midships manifold for discharge rates of about2,000 m3/hr and wind speeds in the range of 20-40 knots.

Eddy currents caused by the hull structure can dragflammable vapour concentrations back onto the deck forall wind directions beyond about 150 either side of thelongitudinal centre line of the ship. Vertical elevation of thenozzle to 450 can reduce these concentrations for winddirections across the ship in the direction of the LNG jet byprojecting the liquid above and beyond these eddycurrents. Bow (and to a similar extent, stern) discharge ispossible for virtually all relative wind directions exceptwithin 300 of the direction of the nozzle discharge. In thesecases the nozzle elevation has little effect.

Wind tunnel tests simulating the jettisoning of pressurisedpropane amidships at a rate of 80m3/hrfrom a small sea-going tanker have also confirmed thatthe relative wind direction should be near to 00 or 1800 andthat hazardous gas concentrations can occur at deck levelat other wind directions.

Hose or Nozzle Discharge and Degree of Vaporisation

These references have confirmed that the use of a fixednozzle so as to achieve a liquid velocity of 40-50 m/s is tobe preferred over the use of a simple pipe extension orflexible hose led down to the water line, which result ingas concentrations close to the hull. Use of a correctlysized nozzle to achieve the recommended liquid velocity,or sonic two-phase flow for pressurised liquefied gas,results in gas cloud formation separated from the ship’sside.

All Iiquefied gases should always be jettisoned clear of thesteel huII structure to prevent risk of brittle fracture.

Experiments have shown that water spray jets can entrainlarge quantities of the air or vapour surrounding the liquid

jet (around 6,000 m3 air/vapour per m3 of water). Underjettisoning conditions, the cargo jet may be expected toentrain similar large quantities of atmospheric air andmoisture. Thus, in addition to any two-phase flow at the jetoutlet due to flashing of the cargo, sensible and latent heatexchange will occur between the cargo and the entrainedair/moisture. This will result in further cargo vaporisationalong the trajectory prior to striking the sea surface. Thisphenomena has been noted in the full-scale LNG jettisontests. Refrigerated ammonia, although similar in pressureand temperature to propane, will generally show lessvaporisation due to its appreciably greater latent heat.

Although the vaporisation of the jet trajectory does notaffect the total amount of vapour generated for a givencargo and discharge rate, it does cause more vapour tobe generated at or near deck level and consequentlyincrease the probability of hazardous vapourconcentrations under unfavourable wind conditions.

Ammonia is readily absorbed in water and there may beoccasions when it is thought preferable to discharge liquidammonia through a hose down to the water surface withthe ship going astern to ensure that the ammonia liquordoes not enter the ship’s cooling water systems. Small-scale experiments indicate that up to 60% of the ammoniamay go into solution in the sea water and thereforesubstantially reduce the dispersion distance for the toxichazard. It is important that water is not drawn up throughthe hose and back into the cargo tank. The powerfulabsorption of ammonia into water can result in vacuumdamage to the tank. Ecological considerations maysuggest that atmospheric dispersion is preferable asdescribed earlier.

! WARNINGToo rapid a flow of LNG will result in R. P.T when liquidhits the sea wate r.

4.4.6 Cargo Spillage on Deck and Piping Leakage

IntroductionCargo spillage should not occur under normalcircumstances but may occur due to failure of valves orpipelines by inherent or external means. Spillages arenormally of a minor nature when they first occur andvigilance is required during cargo operations so that anyfaults may be quickly identified and dealt with to preventthe situation escalating. The potential sources of spillageare from:

i) The midships manifold;

ii Cargo piping joints and valves.

There is also a possibility of spillage of liquid nitrogenif it is loaded to the main vaporiser for inerting thecargo tanks with nitrogen, during insulation space firstinerting.

i) The Midships Manifold

Any spillage occurring at the manifold will fall onto themanifold spillways which direct the spillage overboard.The ships hull in the vicinity of the manifolds isprotected by a water spray curtain supplied by thedeck fire main; this curtain should be in use at all timesduring cargo handling operations. The manifold areaon each side is also protected by spray nozzles whichcan be supplied by the deck spray system in the eventof major spillage. The ship/shore emergency manifoldvalve shut down system (ESDS) is intended to reduceany such spillage to a minimum.

ii) Cargo Piping Joints and Valves

The possibility of leakage due to piping joints has beenreduced to a minimum by the use of extensive weldingas opposed to flanging. Regular maintenance of valveglands will reduce the possibility of leakage fromvalves. Leakage from these sources will normally be ofa minor nature, but each valve is also protected with aspray nozzle supplied by the deck spray system.

Dealing with SpillagesDuring any cargo handling operations the followingprecautions should be observed :

1 Deck fire main to be pressurised;

2 Manifold Hull water spray curtain to be in operation;

3 Fire fighting equipment to be laid out ready for use;

4 Constant patrol of cargo area to be maintained;

5 Protective clothing and tools to be available at hand;

6 Deck spray pump system ready for use.

Minor SpillageMinor spillages will normally be due to leakage fromflanges or glands and can be dealt with by a fire hosewater spray whilst the leak is being stopped by tighteningdown and/or the use of wet rags. If such a leakage cannotbe stopped and it requires attention, cargo operationsshould be suspended whilst the fault is being rectified.

Protective clothing and, if necessary, breathing apparatusshould always be used when dealing with ANY form ofcargo leakage. A second person should stand-by in orderto alert the Cargo Control Room if the leakage developsinto one of a major nature.

Major SpillageA major spillage will normally necessitate the use of thewater spray system backed up by portable fire hose watersprays. The spray system not only protects the deck areaand deck housings from brittle facture but also helpsdispense and evaporate the LNG and acts as a fire curtainto protect the accommodation. In the event of a majorspillage the following action is to be taken :

STOP cargo operations.

START deck water spray system.

SHUT ship and shore manifold valves.

SOUND the general alarm.

SHUT all accommodation doors and

STOP all ventilation fans.

STOP all smoking and the use of naked lights.

USE all necessary fire fighting equipment, breathing apparatus and protective clothing.

USE hand spray to disperse liquid overboardand to warm the deck and if necessaryto deflect the gas cloud.

After a major spillage all affected areas should bethoroughly inspected for any signs of cold shock fractures.



4.4.7a Overfilling Of Cargo TanksIssue: 1


Key


LNG

LNG Vapour

Illustration 4.4.7a Overfilling Of Cargo Tanks

494

493

030

021

492

491

403

401

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.4.7 Overfilling of Cargo TanksIn the unlikely event of a cargo tank being overfilled, thehigh level trips will shut tank filling valves and initiate anESDS situation and stopping cargo loading. Gas burningand compressors must be shut down. There will possiblybe LNG in the vapour header, this will require draining intoa slack tank. Vapour pressure will rise rapidly. Use of amain cargo pump will enable the cargo to be transferredfrom the overfull tank into slack tanks, Request shore totake vapour as soon as possible.

Recovery from Off Limit Level Shutdown

• Shut the fill valves on any tanks which are near the fulllevel.

• Turn the control of any valves affected by theshutdown to shut.

• Request the terminal to restore the vapour shorereturn system. Then, proceed as follows:

• Block the tank very high level alarm.

• Reset the shut down.

• Reopen the vapour crossover manifold valve.

• Verify pressure at the crossover.

• Transfer LNG from the overfilled tank into anothercargo tank, to restore the tank level to normal:

• Open the fill valve of the tank to which the transferwill be made.

• Start one cargo pump in the overfilled tank.

• Transfer LNG until the tank level reaches normal.

• As soon as the shutdown condition is corrected,restore the very high level blocking switch to normaland resume the loading conditions.

4.4 Emergency Operations and Procedures - Page 6Issue: 1


4.4.8a Secondary Barrier Space De-WateringIssue: 1


SecondaryInsulation Space

Nitrogen Supply Columnto Secondary Barrier

Air DrivenWater Pump

Illustration 4.4.8a Secondary Barrier Space De-Watering

4.4.8 Structural Failure of Inner Hull

Introduction(See Illustration 4.4.8a)Ballast water leakage from the ballast tanks to theinsolation spaces may occur due to fracture of the innerhull plating. If the leakage remains undetected andaccumulates in these spaces:

a) Ice formation could cause deformation and possiblerupture of the insulation with subsequent cold spotoccurring due to cold convection paths being openedthrough the insulation.

b) Destruction of the insulation due to sloshing of thewater.

! CAUTIONIt is important to note that the design pressurelimitations is 0.3 meters water head.

To reduce the risk of damage from these causes, a systemof leakage detection and removal has been installed in thevessel for secondary insulation spaces.

Leak Detection and RemovalEach secondary insulation space is fitted with waterdetectors which initiate alarms in the CCR identifying theaffected space.

A group cargo alarm is also initiated in the wheelhouse viathe IMS, to indicate that water has been detected in asecondary insulation space, which may mean an innerhull failure.

! CAUTIONIt is essential that the correct functioning of thealarms of these detectors is checked frequently andthat any alarm condition is investigated immediatel y.

For water leakage removal, a permanently installed airdriven pump is located in a well at the foot of thesecondary barrier space nitrogen filling column. The pumpis permanently connected to an air supply and waterdischarge hose. Should a water indication alarm beactivated in a space, the air supply should be opened onthat pump and the water discharged overboard.

Operating ProcedureIf the moisture detector alarm is initiated or if there is anyother reason to suspect ballast leakage into a secondaryinsulation space, the following action should be takenIMMEDIATELY :

1 If ballast is being carried adjacent to the suspect leak,pump out immediately, having due regard to stressand stability.

2 Close the nitrogen supply as appropriate to isolate theaffected space.

3 Start pump and run continuously if necessary.

On completion of leakage removal.

4 Inspect inner hull thoroughly in way of the affectedtank to establish the cause of failure and repair thefracture.

Even after discharging the bulk of the water, appreciablemoisture will remain in the insulation and over the bottomarea of the tank. In order to assist drying out of theinsulation.

5 Open nitrogen supply to the affected secondaryspace.

Increase flow rate of secondary space nitrogen until thedew point measure at the exhaust is back to -40°C orbelow.

! CAUTIONNo cargo should be carried in the affected cargo tankuntil satisfactory repairs have been carried out anduntil the moisture content in the secondary space hasbeen reduced to an acceptable level.



4.4.9 Ship Shore Operations in Event of Fire orEmergency

IntroductionIn order to minimise the possibility of an emergencysituation occurring, it is essential for close liaison betweenship and shore during cargo operations and during theentire stay alongside a terminal.

Detailed plans and procedures to be followed for bothnormal conditions and abnormal/emergency conditionshave been established and are given in the CargoHandling Regulations of the LNG terminals which arecarried on board.

These manuals detail the procedures to be followed byboth ship and shore for all normal cargo operationstogether with the procedures to be followed for allforeseeable emergencies which may occur.

4.4.10 Personnel Contact with LNGIn contact with LNG or vapour, the main risks for thepersonnel are: asphyxia, low temperature andflammability.

In casualties involving asphyxia:

• Remove from exposure.

• Apply Artificial Respiration if required.

• Apply external Cardiac massage.

• Loosen clothing.

• Give oxygen if laboured breathing.

• Give non alcoholic drinks if desired.

• Keep as rest.

• Unless symptoms are minor, seek medical advice.

Cold liquefied gas spilled onto the skin removes sensibleheat on contact and latent heat on evaporation. Theseeffects can cause extensive burns to exposed skin.

In case of cold burns, the affected part should be warmedwith the hand or woollen material in the first instance. Ifthe finger or hand has been burned, the casualty shouldhold his hand under his armpit. The affected part shouldthen be placed in warm water at about 42°C. If this is notpracticable, then the casualty should be wrapped inblankets and the circulation should be allowed tore-establish itself naturally. If possible, the casualty shouldbe encouraged to exercise the affected part while it isbeing warmed. Blisters should never be cut or opened,nor clothing removed if it is adhering firmly. The entire

affected area should be covered with sterile dressing.Otherwise, the treatment should be as for hot burns.

Safety training, such as ‘Gas Carrier Safety Courses’should have been attended by all personnel involved withthe cargo operations handling LNG.

Protective clothing, boiler suit, helmet, gloves, gogglesand safety shoes are to be used at all times when workingwith LNG systems. Under special conditions lowtemperature protection suites should be available. LNGwill dilute oxygen in an atmosphere and precautions mustbe taken against oxygen deficiency in any space wheremethane can build up. SCBA must be available.

LNG cold burns should be treated in the same way as hotburns, with immersion in tepid water or wrap in a blanketto restore circulation to the burnt area, then covered witha sterile dressing, blisters must not be opened.

Oxygen from a resuscitator should be used in the case ofrespiratory failure.

4.4.11 Fire Control Procedure for Main Vent Mast(Nitrogen Injection)

Vent RisersUnder certain circumstances, excess boil-off gas must bevented to atmosphere via the cargo tank vent risers. Apartfrom the purging operations before and after docking orrepair, venting will be via the vent riser No. 2, i.e. wellaway from machinery and accommodation spaces. Undernormal venting circumstances, however, LNG vapourdiffuses rapidly and due to its low density, flammableconcentrations will not occur below the level on the ventoutlet.

Should the vapour be ignited at the vent outlet by lightningor atmospheric discharge, each riser is provided with asnuffing valve and nitrogen injection points at the bottomto extinguish the fire. Vent mast riser No. 2 is fitted with anitrogen smothering injection system which can beoperated remotely from the wheel house and cargocontrol room. Vent mast risers No. 1 and 3 are fitted withnitrogen smothering, but the injection has to be operatedlocally at the individual mast riser.

The most important action is to remove the source of fireby operating the snuffer valves. Then the fire fightingmedium. The fire will re-ignite if the steelwork of the riseris hot enough after the nitrogen is shut off.

4.4.12 Cargo Piping Valve Freeze-up ProcedureThis will result from allowing moist air into the cargosystem and not replacing it with dry air. The humidity in theair will condense and form moisture, which with theintroduction of LNG will freeze, causing pipeline blockageand cargo valve seizure.

Methanol cannot be used as a de-icer on LNG as it has afreezing point of -97°C.

4.4.13 Cargo and Ballast Valve Failure ProcedureThe cargo and ballast system valves are hydraulicallyoperated. Failure of the hydraulic supply system will resultin these valves becoming inoperable remotely.

Each valve is fitted with a remote distribution blockfurnished with in/out pipes from the remote control station.Shut off valve emergency operating connections are of thepush on instantaneous type.

An emergency hand pump with hoses can be connectedand the valve operated using the hand pump. In the eventof a deck valve failure, the hydraulic actuator will beconnected up to the emergency hand pump and the valveoperated.

Failure of ballast tank actuators will mean personnel entryinto the cofferdam and duct keel.

4.4.14 Primary Membrane Failure

IntroductionAll test carried out on the primary membrane have shownthat a fatigue fracture in the membrane will not extend.

Fatigue fractures in the primary membrane are generallysmall and will pass either vapour only, or a sufficientlysmall amount of liquid which will vapourise as it passesthrough the fracture.

It is possible, however, that a larger failure of themembrane could occur, allowing liquid to pass throughand eventually gather at the bottom of the inter barrierspace.

Leakage Detection

Vapour LeakageA small leakage of vapour through the membrane may notbe readily obvious, however, indications are likely to be:

A sudden rise in the percentage of methane vapourin one primary insulation spaceSome porosity in the primary barrier weld will allow thepresence of methane vapour in the primary insulationspace. The amount of this vapour should be kept to aminimum by the nitrogen purging. If a fracture occurs inthe primary barrier below the level of the liquid in the tank,the vapour concentration will increase slowly and steadily.If the fracture is above the liquid level, the concentrationwill exhibit a fluctuating increase. The vapourconcentration in each primary insulation space is recordeddaily, to detect any small and steady change.

An increase in pressure in one primary insulationA fracture above the liquid level in a cargo tank will allowa direct flow of vapour into the primary insulation space.This flow will vary according to the pressure in the tank.

A fracture below the liquid level in a cargo tank, resultingin a small amount of liquid vapourising as it passesthrough the fracture, will cause a small increase inpressure. (Any small quantity of liquid which enters theprimary space, then vapourises, will have the sameeffect). This increase is dependant upon the height ofliquid above the fracture and the pressure in the tank.

As the pressure relief system is common to all the primaryinsulation spaces, any increases in pressure caused byvapour leakage will be difficult to determine.

Temperature variationNo temperature change will be obvious, unless thefracture is in the immediate vicinity of the sensors belowthe cargo tank.

Leakage of methane vapour into the primary insulationspace presents no immediate danger to the tank orvessel. As much information as possible concerning thefracture and leak should be obtained and recorded.Determine whether the leak is increasing as follows:

1 After the leak is detected (and without changing theflow of nitrogen to the primary insulation space),record the gas concentration and primary spacetemperatures every hour for eight hours.

2 Then, if necessary, adjust the flow of nitrogen tomaintain the gas concentration below 30% LEL andrecord the gas concentration and primary insulationspace temperatures every four hours.

3 In conjunction with the above, record all pressurechanges occurring in the cargo tank and primaryinsulation space.



4.4.15a Barrier PunchIssue: 1


Drain ValveFlexible Hose

Reducing Valve

Nitrogen BottleNitrogen Connection

Tank Bottom/ Primary Barrier

Base of Cargo TankTrellis Structure

Support for Equipmenton Trellis Structure

Bellows Support Arm

Expansion Tube

Stripping PumpCable Conduit

Primary Insulation Space

Secondary Insulation Space

Duct Keel

Nitrogen Piping

Diaphragm

LNG Liquid

Bellows

Perforations

SITUATION NORMAL BARRIER PUNCH SYSTEMIN OPERATION

Illustration 4.4.15a Barrier Punch

Liquid LeakageA major failure in the primary membrane, allowing liquidinto the primary insulation space, will be indicated asfollows:

1 A rapid increase in the methane content of theaffected space.

2 A rise in pressure in the primary insulation spacenitrogen header, accompanied by continuousincreased venting to atmosphere.

3 Low temperatures alarms at all temperature sensorsin the insulation below the damaged cargo tank.

4 A general lowering of inner hull steel temperatures.

Although this will be limited to a few degrees only and maytake some hours to establish, it should, nevertheless, benoticeable and an added confirmation of major membranefailure.

There should be no immediate danger to the tank orvessel as the secondary barrier is of identical constructionto the primary barrier.

If a major failure is indicated by the above symptoms,carry out the following to avoid contamination of the intactprimary insulation spaces:

4.4.15 Punching DeviceA punch diaphragm, fitted below the pump tower in eachcargo tank, permits the punching of an opening in theprimary membrane. This operation will be necessary inthe event that damage to the membrane has permittedLNG to accumulate as a liquid in the primary insulationspace.

If the cargo tanks were pumped out with a head of liquidremaining the the primary space, severe damage to themembrane would result. For this reason, it is necessary tointentionally puncture the primary membrane when thedamaged tank is pumped out, and to pump the tank slowlyenough to enable the level of the liquid imprisoned in theinsulation space to fall at the same rate as the tank,without over pressurising the membrane.

The device punches a 50mm opening at the bottom of thetank. Liquid from the side walls will drain out through theopening. Liquid in the bottom portion of the insulationspace must be removed by evaporation during warmup.Use of the punching device is an extreme measure. Itfloods the insulation space with LNG, and requires thatthe tank be gas freed and entered in order to replace thepunched diaphragm.

The operation procedure for using the punching device isas follows: (see figure 4.4.15)

• The use of the punching device depends on thefollowing indications of liquid in the primary space:

• If liquid is indicated by all the temperature sensorsup to the level of the sensor 5 A/B, the membraneshould be punched at the start of the pumpingoperation.

• If liquid is indicated by all the temperature sensorsin the bottom and by either the sensor 9 A/B or 8A/B or 7 A/B or 6 A/B, the membrane should bepunched when the LNG level in the tank is 4 metersabove the level of either the sensor 9 A/B or 8 A/Bor 7 A/B or 6 A/B.

• If liquid is indicated by all the temperature sensorsin the bottom and not by the sensor 6 A/B, themembrane should be punched when the LNG levelin the tank is at the level of the sensor 6 A/B.

• If liquid is indicated only by some of thetemperature sensors in the bottom, it is evidencethat a head of liquid is not present in the side walls,and the membrane needs not be punched.

• After punching, use only one pump at a reducedpumping rate, corresponding to a liquid level fall of 0.4m/h.

• The punching device is operated as follows: (seefigure 4.4.15a)

• Connect the portable nitrogen flask with theattached pressure reducer to the punch connectionat the liquid dome of the damaged tank;

• Close the equalising valves between the punchpiping and the well of the back up level.

• Open the valves at the hose connection and on thenitrogen flask, and apply full pressure from thereducing valve (12 bars)

• After about one minute close the valves, disconnectthe nitrogen flask, and reopen the equalising valvesto the well of the back up level.

• After the tank has been gas freed and repaired, thepunching diaphragm will be replaced by welding in anew one. After re installation of the punch device,purge all lines with nitrogen at a low pressure(150mbar) to avoid actuation of the system.

• Before cooling down of the tank, open the equalisingvalves to the well of the back up level. These valvesshould remain blocked open at all times when the tankis in service to avoid the inadvertent actuation of thepunching device.

Note: If a primary membrane has been punched ordamaged to such an extent that the primaryinsulation space is in free communication with thetank, it is not possible to pull a vacuum on thespace without pulling a vacuum on the tank. At10mbar below atmospheric pressure, the tanksafety valves will open and admit air to the tank.

• With damage of this type, the cargo tank shouldbe gas freed and inerted, but not filled with air untilthe insulation space is gas freed.

• The insulation space should be gas freed bysweeping with nitrogen from the pressurisationsystem, or by combination of the two.

• The vacuum pumps may be used in this situationto assist the sweeping with nitrogen or inert gas,to reduce the pressure created in the insulationspace by evaporation of the imprisoned LNG or tomaintain the space pressure lower than the tankpressure when the tank is opened.

Primary Barrier Temporary Protection During TanksMaintenanceThe primary consideration during cargo tank entry andmaintenance is to protect the primary barrier frommechanical damage. Therefore the floor of the tank mustbe lined with plywood over the whole area where damagemay occur from personnel entering the tank, equipmentand tools etc. lighting should be hung from the cargopump/pipe tower.

The pressure in the tank will be at atmospheric so that theprimary insulation space should be maintained at a fewmbars below this to ensure that the primary barrier is heldtight against the insulation boxes at all times.

! CAUTIONEnsure that the differential pressure between the 2insulation spaces remains between 0 and -30 mba r.Severe damage will occur to membranes ifdifferentials exceed 30mba r.



4.4.16a Loaded Voyage Without Gas BurningIssue: 1


Key


494

493

492

LNG Vapour Warm

LNG Vapour

486

483487

484

481 491

Illustration 4.4.16a Loaded Voyage Without Gas Burning

1

2

1

2

To EngineRoom

To InsulationSpaces



Dual PurposeHeaters

MainVaporiser

Demister

ForcingVaporiser




Vent GasHeater

12

12

Jettison

Tank 1

Tank 4

Tank 2

Tank 3

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

Liquid Dome

Vapour Dome

4.4.16 Loaded Voyage without Gas BurningIt is possible for short periods to supply boilers on free flowwith all compressors isolated. Open 400 and 406, thisbypasses the compressors and supplies gas at headerpressure direct to C.R. This system can only be used forshort periods due to rise in pressure/ temperature of thecargo. It prevents total change over to fuel oil burning.

In the event that free flow is not an option, the followingprocedure is to be followed, venting via forward mast riserNo. 2 and heater.

IntroductionIf, for any reason, the gas burning plant cannot be usedduring sea passage, the boil-off will have to be heated andvented to atmosphere via vent mast riser No. 2. Thiscourse of action should only be taken as a last resort,since this will be a costly exercise which would alsocontribute to global warming due to the destruction of theozone layer by methane.

OperationThe cargo tank boil-off gas enters the vapour header viathe cargo tank gas domes. It is then heated in the boil-offheater, before being fed to the mast riser. This is toincrease gas speed and then to permit the gas to escapequickly from the ships deck.

Venting to atmosphere will not normally take place untilthe vessel is clear of port limits. Many port authoritiesforbid the discharge of gas to atmosphere.

As far as is possible it is preferable to burn the boil-off inthe boiler and use the steam dump system, rather than tovent gas to atmosphere.


(See Illustration 4.4.16a)

It is assumed that all valves are closed prior to use:

1 Tank gas domes





The valves should already be locked in the openposition.

2 Open valve 481, 483, 484 and 486 at the vent mastheater.

3 Set control valve 487 to 1200mbar a.

When clear of port limits

4 Start up the boil-off heater (Refer to Section 2.9).

5 Adjust set point of PIC to 1150mbar abs.

When arriving at port limits

6 Adjust set point of PIC to 1200mbar abs.

7 Prepare cargo systems for discharge (Section 4.2.4).



Part 5Safety Systems

5.1.1a Deck Water Spray SystemIssue: 1

Cargo ManifoldsPlatform

Compressor House

Sea Chest Accomidation SprayManifold

IR001VF

IR004VF

IR007VF

IR006VF

IR014VFIR009VD

IR005VF

Liquid Dome

Gas Dome

SprinklerMain Drain

Sea Chest

Emergency CargoJettison Area

From PumpsXA/405A/B

Liquid Dome

Gas Dome

Liquid Dome

Gas Dome

Liquid Dome

Gas Dome

SpinklerMain Drain

Cargo ManifoldsPlatform

FromEngine Room

Illustration 5.1.1a Deck Water Spray System

IR015VFIR018VF

IR019VD

IR016VF

Life Boat FreefallSpray


PART 5: SAFETY SYSTEMS5.1 Deck Salt Water Systems5.1.1 Spray SystemThe accommodation block front, compressor house,cargo tank domes, and manifold areas are protected bywater spray from the effects of fire, gas leakage, or liquidspill. There is a 800m3/h spray pump (XA/491), mountedon the bottom platform in the engine room, delivering to 4spray rails across the accommodation block front,compressor house sides and deck domes/manifolds. Thenozzle arrangement is as shown below: For plain verticalsurfaces, nozzles are set 800mm apart and at 45° to thevertical. Headers are 250mm from bulkheads and nozzlesare flat cone design.

Flat surfaces are protected by full cone nozzles.These are: 4 pump towers (liquid domes)

4 gas vent domesJettison valve areaLifeboat boarding area2 manifold spill trays

Nozzle numbers and capacity

i) 4 x pump towers - 4 x 4 nozzles at 46.56m3/h

ii) 4 x gas domes - 4 x 4 nozzles at 46.56m3/h

iii) 2 x manifolds - 2 x 16 nozzles at 149.76m3/h

iv) Jettison valve area - 1 x 1 nozzle at 11.64m3/h

v) Lifeboat boarding area - 1 x 1 nozzle at 15.00m3/h

vi) Accommodation front - 123 nozzles at 136.53m3/h

vii) Compressor house walls - 67 nozzles at 88.44m3/h

Nozzle types:- 1, 2, 4 AAW 3194 Each 194 ltr/min.

3 AAW 2780 Each 78 ltr/min.

5 AAW 3310 Each 250 ltr/min.

7 GAW 2246 Each 21.5 ltr/min.

6 GAW 2246 Each 17.3 ltr/min.

Pressure at Nozzles 1, 2, 3, 4 3 bar

5 2 bar

6 1.5 bar

7 2.3 bar

The spray pump has control stop/start locally in the engineroom and from push buttons on the main deck close to theaccommodation exits.

There is a drain connection provided at main deck leveland one at the forward end of the main.

5.1 Deck Salt Water Systems - Page 1Issue: 1


250mm

800mm

45 0

5.1.2a Deck Fire Main SystemIssue: 1

Fire Main Drain

XA/405A

XA/405BAI/023VF

AI/022VD

AI/025VF AI/019VFTo FireMain Drain Hawespipe

Cleaning

HawespipeCleaning

BosunStore

AI/059VF

AI/058VF

AI/056VF

AI/053VF

AI/054VF

Cofferdam Bilge Eductor

Illustration 5.1.2a Deck Fire Main System

Emergency Cargo and Machinery Cooling Water Supply

To CofferdamEductor

To CofferdamEductor

To CofferdamEductor

To CofferdamEductor

From Emergency Fire Pump

AI/015VF

AI/014VF

AI/052VF

Spill TrayFilling Line

Spill TrayFilling Line


5.1.2 Firemain SystemThe firemain system is supplied from the engine room, bytwo, two speed centrifugal pumps XA/405 A and B160m3/h at 2.3 bars or 90m3/h at 12.8bar.

The emergency fire pump YA/480 is mounted forward inthe emergency fire pump room.

Isolating valves mounted on the cargo deck, allowisolation of the forward or poop decks. 3 further isolatingvalves are situated at regular intervals along up the deck,to allow any part of the system to be supplied from eitherend of the ship.

The cofferdam eductors are driven from this system, as isthe manifold water curtain for ship side wetting duringloading and discharge.

There are 12 fire hydrants situated along the cargo deck,each with its fire hose mounted adjacent. The firemainalso supplies anchor washing water.

The emergency fire pump can be started locally, from thebridge or the fire station.

Under normal operating conditions the firemain will beunder pressure during port time, supplying the manifoldsprays and with hoses run out as a fire precaution.

5.1.3 Air locksThe motor room is fitted with a double door air lock, toensure that any hydrocarbon vapour which may bepresent on deck cannot enter the room. The doors arefitted with micro switches connected to an alarm which willsound if both doors are open together.

The motor room and air lock are maintained aboveatmospheric pressure by a supply fan. The motor room isvented by a natural exhaust trunk.

5.1.4 Dry Powder SystemThe system is supplied by Silvani Antimcendi S.P.A andconsists of: (A) 2 x 1550kg units mounted forward of theaccommodation block on ‘A’ deck. (B) a 1000kg unitmounted in the cross alleyway between theaccommodation and engine casing.

Each unit consists of:-

A powder container holding 1550kg ‘winnex’ powder.

5 x 50 ltr at 200 bar nitrogen cylinders to expel the powder.

Pneumatic/manual actuator 5pc

Pressure reducing valve 200-15bar

Pressurisation valve for container

Safety valve set at 12bar

Pressure reducer 15 to 10bar

Tank depressurisation valve

Lever safety valve set at 16bar

0 - 25bar pressure gauge

2 distribution valves

Pneumatic control powder on/off valves

Pneumatic control station contains 1 x 4 ltr 200bar pilotnitrogen cylinder, for opening of associated distributionvalve.

Each of these 1550kg units supply 2 x 10kg/s monitorsmounted forward and aft above each manifold. Eachmonitor has a 10m throw. The 1550kg units also supply 8hose stations. Each hose has a 3.5kg/s nozzle and is 30metres long.

The manifold monitors have a control station port andstarboard outboard and aft on No. 3 cargo tank liquiddome. Each dry powder hose unit has a remotelyoperated powder valve.(B) 1000kg unit mounted in the X-alleyway betweenaccommodation and engine casing. This unit supplies a10kg/s monitor with a 10 metre throw mounted above thepoop deck and positioned to protect the jettison line andnozzle.

A portable hose unit is mounted on the poop deck with 20metre hose and 3.5 kg/s nozzle.

The pneumatic actuator for this unit is mounted aft end,port side of ‘A’ deck. All equipment is similar to the 1550kgunits except that there are only 4 x nitrogen cylinders.

5.1.5 Ship Side Water Curtain SprayThis system is used when loading and discharging and isfitted to both manifolds to protect the deck, deck edge,shearstrake and vertical ship’s side from the effects ofcold embrittlement in the event on liquid leakage at themanifold. The nozzles are spaced 600mm apart and at500mm from the vertical shipside inboard.

The water for these sprays is taken from the firemain/wash down system pipeline. There are 30 GAW2761nozzles at each manifold delivering 136.8m3/h. at 3 bar.

5.1.6 CO2 Protection in Cargo and MotorCompressor Rooms

The compressor room and motor room are protected by aself contained CO2 system housed in its own CO2 room onthe starboard aft corner of the motor room.

The system consists of 2 packs of 60 Ltr cylinders. Pack1 of 14 cylinders. Pack 2 of 4 cylinders. The system is soarranged that all 18 cylinders are available for dischargeto the compressor room and 9 to the motor room.

The volume of the spaces protected are:

Compressor room 870m3 and motor room 401m3

Each space has a pneumatic control station which can beoperated manually locally or electrically via an intrinsicallysafe circuit and barriers from the fire station on the upperdeck.

Each release control station has a 4ltr nitrogen cylinderwhich releases into the actuator pipework for the cylindersselected.

Both protected spaces are fitted with a pre-release alarmsiren, to warn personnel of impending CO2 release.

The action of opening the pneumatic control stationoperates the pre-release alarm, the main discharge isdelayed by a mechanical device, actuated by hand for upto 30 seconds before release.

The ball valve to the required space is also operatedremotely and CO2 flooding takes place through nozzlesmounted below the deckheads in both or either space.

The system is fitted with a pre-alarm test connection anda flushing connection to be used to flush out anyremaining CO2 after a release.

In the case of inadvertent release, the system is fitted witha relief valve which discharges to atmosphere.

5.1.7 Vent Mast ExtinguishingNo. 2 vent mast riser is fitted with a fixed nitrogensmothering system. Activation is carried out from the mainconsole in the wheel house, or from the main console inthe cargo control room. The gas heater regulating valveand snuffer valves in the vent mast are shut, beforeinjection of nitrogen takes place.

5.1 Deck Salt Water Systems - Page 2Issue: 1


5.2.1a Emergency Shutdown SystemIssue: 1

Pvh < Patm + 3mbar

EMERGENCY SHUT DOWN SYSTEM

MANUAL RELEASE

- Cargo control room.- Wheel House.- Manifolds - port and starboard sides- Compressor room- Fore main deck- After deck - port and starboard sides

FUSIBLE PLUGS

- Each tank liquid dome (4 units)- Port and starboard manifold platforms (3 units).Cargo compressor room (2 units).

SHORE LINKS

FROM SHORE TO SHORE

HEADERS PRESSURE

Pvh : vapour header pressurePph : primary space header pressurePatm : atmospheric pressure

Pvh = Pph

OR

TANKS PRESSURE(on each tank)

Ptk < Pps + 5mbar

Ptk : tank pressurePps : primary space pressure

Ptk = Pps

OR

TANKS LEVEL(2 independent sensors per tank)

VERY HIGH LEVEL 99%

OVERRIDING AT SEA

AND

OR OR

STOP MAIN CARGO PUMPS AND EMERGENCY PUMP

STOP STRIPPING PUMPS

STOP HIGH DUTY COMPRESSORS

CLOSING MANIFOLD VALVES

STOP LOW DUTY COMPRESSORS

CLOSING MANIFOLD VALVES

Illustration 5.2.1a Emergency Shutdown System

CLOSING OF FILLING VALVEONLY ON TANK IN ALARM CONDITION

HIGH LEVEL 98.5%

- Each tank gas dome (4 units)


5.2 Emergency Shutdown System5.2.1 ESD SystemIn the event of fire or other emergency condition, theentire cargo system, gas compressors and gas isolatingvalve to the engine room may be shut down by a singlecontrol.

Shut down of the cargo system is actuated eithermanually or automatically by fire or certain off limitconditions.

Description (see illustration 5.2.1a)

• The manual emergency controls are located asfollows:

• Cargo control room.

• Cargo console on bridge.

• Each tank liquid dome (4 units).

• Port and starboard manifold platforms (2 units).

• Automatic shutdown for fire is controlled by eight fuseplugs located as follows:

• Each tank liquid dome (4 units).

• Port and starboard manifold platforms (2 units).

• Cargo compressor room (2 units).

• In port, an electrical link will inform the shore of anyship’s ESDS actuation and will stop the loading ordischarge pumps, and close the shore liquid valves.

• Automatic shutdown occurs when any of the followingconditions occurs:

• Vapour header pressure falls to within 3mbar ofatmospheric pressure.

• Vapour header pressure falls to primary insulationspace header pressure.

• Each tank pressure falls to within 5mbar of theprimary insulation space pressure.

• Each tank pressure falls to the primary insulationspace pressure.

• Very high liquid level (99%) in any tank.

• Automatic shutdown for fire.

• Shutdown signal from the terminal.

! CAUTION- Before using the blocking switch, determine exactly

what has caused the shutdown.- Before using the blocking switch, turn the controls

for all crossover valves to the shut position.- Use the blocking switch when absolutely necessary

to recover from an emergency condition.- When the emergency condition is corrected,

immediately restore the shutdown system to normal.

5.2 Emergency Shutdown System - Page 1Issue: 1


5.3.1a Gas Detection SystemsIssue: 1

AnalyserCabinet (CCR)

0-5% 0-100% 0-60%

Analyser Purging

N2

AT

AI

AT

AI

AT

AI

Tan

k 1

Tan

k 2

Tan

k 3

Tan

k 4

AnalyserExhaust

Manual Stop Valve(Outside CCR)

Primary BarrierSafety Valve Piping

Secondary BarrierSafety Valve Piping

Tan

k 4

Tan

k 3

Tan

k 2

Tan

k 1

Cargo Tank

Gas Detection in NitrogenIllustration 5.3.1a Gas Detection Systems

Gas Analyser Indication Panel (Bridge)

00 COMPRESSOR ROOM

01 ELECTRIC MOTOR ROOM

02 ELECTRIC MOTOR ROOM AIRLOCK

03 TOWER PUMP COFFERDAM NO.1




07 GLYCOLE WATER AIR VENT

08 EMERGENCY FIRE PUMP ROOM

09 CARGO CONTROL ROOM

10 TOP OF ENGINE ROOM (ABOVE BOILER NO. 1)

11 TOP OF ENGINE ROOM (ABOVE BOILER NO. 2)

12 ENGINE ROOM FAN AIR INTAKE (AFT PORT)

13 ENGINE ROOM FAN AIR INTAKE (AFT STB.)

14 ENGINE ROOM FAN AIR INTAKE (FORE STB.)

15 AIR CONDITIONING STATION AIR INTAKE

16 GLYCOLED WATER EXPANSION TANK NO. 1

17 GLYCOLED WATER EXPANSION TANK NO. 2

18 STEAM CONDENSATE OBSERVATION TANK W.D.

19 STEAM CONDENSATE OBSERVATION TANK E.R.

20 MANIFOLD CRANE AIRLOCK

VENTED DUCTS SURROUNDINGTHE GAS PIPE TO THE BOILERS (OUTLET)

ENGINE ROOM FAN AIR INTAKE(FORE PORT)

ALARM 1 ALARM 2

DESIGNATIONCHANNELS

MDXi No.1

Tank 4Engine Room

ABCD

Tank 3 Tank 2 Tank 1

MDXi No.2

ALARM 1 ALARM 2

AL 1 AL 2 FAULTDESIGNATIONCHANNELS AL 1 AL 2 FAULT

PRIMARY INSULATION SPACE INFRARED ANALYSER NO. 1 AND NO. 3

PRIMARY INSULATION SPACE INFRARED ANALYSER NO. 2 AND NO. 3

TANK NO. 1

TANK NO. 2

TANK NO. 3

TANK NO. 4

FIRST PROGRAMMER COMBUREX IR

SECOND PROGRAMMER COMBUREX IR

FAULT

RESET BUZZER LAMP TEST

00

01


5.3 Gas Detection System

The System is supplied by ‘ICARE’ France SocieteNouvelle and consists of

- 1 Infrared analyser system switchable from primary tosecondary insulation spaces,

- 1 Infrared analyser system in Primary InsulationSpace,

- 1 Infrared analyser system in Secondary InsulationSpace,

- Catalytic combustion type detectors for gas detectionin air for various spaces,

- Catalytic combustion type detectors for continuousmeasurement in boiler exhaust gas main,

- Catalytic combustion type detector for steamcondensate,

- Control panel to be located in the CCR,

- Repeater panels,

- Portable detectors & calibration equipment.

5.3.1 Infrared Gas Analyser SystemThis gas detection equipment consists of

A Cabinet Housing 4 Independent Gas DetectionSystems Based on 2 Different Principles ofDetection

Systems Based on the Principle of InfraredAbsorption for the Detection of Insulation Spaces

- An independent system consisting of an IR Comburexprogrammer and an IREX infrared detector (scale 0-5% CH4 by volume) for detecting the primaryinsulation spaces in the 4 tanks.

This system has an associated sampling systemdriven by two pumps PA1 and PA2 and a gas circuit.

Each sampling line includes a BP 143 flame arrestorfor the analysis channels and a BP 101 samplingnozzle for the “pure air” channel.

- An independent system consisting of an IR Comburexprogrammer and an IREX infrared detector (scale 0-40% CH4 by volume) for detecting the secondaryinsulation spaces in the 4 tanks.

This system has an associated sampling systemdriven by two pumps PA3 and PA4 and a gas circuit.

Each sampling line includes a BP 143 flame arrestorfor the analysis channels and a BP 101 samplingnozzle for the “pure air” channel.

- An IREX detector (scale 0-100% CH4 by volume),common to the two IR Comburex programmers andswitchable to one of the insulation spaces by a keyswitch, located on the cabinets front panel andmarked “IREX 100% Vol. CH4”.

Operation of their Comburex and IREX SystemsEach of the 2 IR Comburex programmers can thus displayand manage the gas concentration output by the twoIREX systems.

The IREX analyser that has been validated is identified onthe IR Comburex programmer LCD by a symbol at theright of the LCD as follows:

- A1 indicates that the non-redundant IREX system isselected (IREX scale 0-5% by volume for the primaryinsulation space programmer and IREX scale 0-40%by volume for the secondary insulation spaceprogrammer).

- A2 indicates that the redundant IREX system isselected (IREX scale 0-100% by volume for one of theprogrammers).

The symbols A1 and A2 are also used to distinguish eachanalyser when the user menu parameters (Alarm 1 & 2thresholds, value of standard gas, etc.) are programmedand the alarm messages or faults are displayed.

To standardise the operation of the two programmers, thetwo push buttons on each IR Comburex have beeneliminated and the functions they performed (i.e. stophorn and select channel) have therefore been reorganisedas follows:

- The “stop horn” function for the two units is performedby the cabinet front panel push button marked“RESET BUZZER”.

- The “select channel” function is available on the menuand can be accessed via the keyboard of eachprogrammer by following the procedure below:

Press the “FUNCT” key:

- message “ACCESS CODE Val. or ”

Press the “ ” key:

- message “CALL CHAN. Val. or ”

Press the “VALID” key:

- message Channel: X? or Val.”

Press one of the number keys, e.g. “1”:

- message “Call channel 1”

or press “VALID”:

- message “Call P A “

Repeat this procedure for each channel called up.

For details of the operation of these units, refer to theirrespective technical manuals (IR Comburex and IREX).

Operation of the PrinterThe 40-column printer in this cabinet prints out theconcentrations in the primary insulation space when theIREX 0-100% volume scale is switched in.

5.3.2 Catalytic Gas Analyser

Systems Based on the Principle of Catalyticcombustion

- An independent system consisting of an MDXi unitand two SX202 explosimeter detectors for detection ofthe ventilated ducts surrounding the gas pipe to theboilers.

These detectors incorporate hardware for caseassembling and are designated DTX 279

An independent system consisting of a MDXi unit andnineteen (19) SXY202 and SX202.H detectors forenvironment detection in various room and at specificspots.

These 19 detectors will be located as follows:

* 12 SX202 environment detectors in various rooms -designated DTX 285

* 4 SX202 detectors with hardware for flangeassembling (AS 233 flange) for detection on the pipecasings.

* 3 SX202.H detectors fitted with a tracer ribbon, plustheir accessories and mounting hardware, andclassified as EEx d. These detectors are installed onthe 2 glicolate water expansion tanks and on thesteam condensate observation tank.

Operation of MDXi UnitsThe operations of these units is detailed in the MDXitechnical manual.

Operation of the Cabinets Alarm BuzzerA “synthesis” function groups together the alarms andfaults of the systems described in § A and B above, andrings a buzzer and also illuminates a specific LED for eachunit.

Isolating Valves Panel

A panel groups together the valves isolating eachsampling line of the two insulation spaces

Connecting the Portable Detectors on the LinesSampling the Insulation Spaces

Three-way valves are used to connect the portabledetectors on each sampling line. It should be noted that,when one of these valves is switched for connecting aportable detector, the sampling flow to the cabinet is cutoff. A flow fault will possibly be triggered if the channel inquestion is scanned at the same time by the cabinet.

These valves are designed for padlocking in the normalposition, i.e. sampling to the cabinet.

Repeater Panel

Three alarm/fault repeater panels providing audible andvisual warnings are located in:

- the engine room,

- the wheel house,

- the ECR.

The audible warning is generated by a buzzer which, afterthe occurrence of an event, must mandatorily beacknowledged locally, even if the alarm or fault has beenacknowledged on the unit (cabinet).

5.3 Gas Detection System - Page 1Issue: 1


5.3.3 Hand Held Gas Analyser (O 2, CO2, CO, Dewpoint, CH 4)

Portable Detectors

The ICARE portable detectors can analyse the followinggases:

- Methane in air or in nitrogen, scale 0-100% LEL, i.e.0-5% CH4 by volume.

This portable unit operates with dual dilution. It isequipped with a small flowmeter chassis for checkingand adjusting the analysis sampling flows and thedilution flow from the air cylinder.

The injected airflow must be adjusted using theflowmeter cock to be the same as the analysis flow.

It is mandatory for these two flows to be equal (ball atthe same height).

- Oxygen, scale 0-25% O2 by volume.

- Carbon Monoxide, scale 0-1000 ppm CO.

- Carbon Dioxide, scale 0-20% CO2 by volume.

The operation of these units is detailed in the ICAREtechnical manual.

5.3 Gas Detection System - Page 2Issue: 1


5.4.1a De-Watering Pump ArrangementIssue: 1


SecondaryInsulation Space

Nitrogen Supply Columnto Secondary Barrier

Air DrivenWater Pump

Illustration 5.4.1a De-Watering Pump Arrangement

5.4 Inner Hull Failure5.4.1 Leakage Detection

Water Leakage to Secondary Insulation Space In the event of a crack in one of the boundary bulkheadsbetween the cargo tanks and the ballast tanks, thesecondary insulation space may be flooded with seawater. Corrective action must be taken immediately on thesounding of a water detection alarm, to stop the leakageand to remove water from the insulation space.

A water leak is very serious, and prevents furtheroperation until the leak is repaired. The damage to themembrane and to the secondary insulation will be muchless if the corrective action described below is taken veryquickly. If the water level rises higher than 0.3m in theinsulation space, the pressure increases higher than thedesign pressure limitation and can permanently damagethe secondary membrane. For these reasons, it is mostimportant that the water detection system be keptpermanently in operation and in good conditions.

As soon as an alarm is sounded, the operation procedureis as follows: (see figure 5.4.1a)

• As corrective action, immediately empty all of theballast tanks having a common boundary with theaffected secondary space. adjust the level in the othertanks as necessary to maintain acceptable hull stressloadings. do not exceed the hull stress limits for shearor bending moment at the loadmaster.

• Isolate the leaking secondary space from thepressurisation system by closing the valve AW/901,915, 927 or 932VX.

• Connect up hoses for water discharge and forcompressed air supply and exhaust to the couplingsfitted on the cover of the well, then start the pump. Thedewatering pump is permanently installed in a sump,at the lower part of a well.

• Run the pump continuously if necessary until all tracesof water are removed.

• Inspect carefully the inner hull surrounding theaffected tank to establish the cause of failure andrepair the fracture.

• To dry the moisture remained in the secondary spaceafter pumping out the sea water, proceed withevacuation and nitrogen refilling cycles until themoisture content is at an acceptable level.

• After any period of use, the dewatering pump shouldbe lifted out of the well, disassembled, cleaned andre-lubricated to maintain it in a condition ready forimmediate use.

! WARNINGDepending on the water level in the sump or due topriming problems with the pump, it may happen thatno water be discharged when the pump is running.Before concluding that, in spite of the water detectoralarms, no water leakage exists, a sounding throughthe well, by means of a water reagent, will be carriedout. Corrective actions will be taken accordingl y.

Water leakage from the secondary insulation space drainsinto a well built into the double bottom of the adjacentcofferdam. A gas tight well built through the cofferdamcontains the air driven pump and moisture detectors.

The moisture detectors sounding and alarm in the CCR.Every loaded voyage the water detectors must be testedand proved to operate.

! WARNINGIt is important to note that the design pressurelimitation is 0.3 metres water head.

! WARNINGIt is essential that the correct functioning of thealarms of the water detectors are checked frequentlyand that any alarm condition is investigatedimmediatel y.

! CAUTIONNo cargo should be carried in the the affected cargotank until satisfactory repairs have been carried outand until the moisture content in the secondary spacehas been reduced to an acceptable level.

! WARNINGAlways be aware that a crack in the inner hull willallow nitrogen into the ballast tank. All entry must beaccompanied by recognised entry procedures.

5.4 Inner Hull Failure - Page 1Issue: 1


5.5.1a Fire Detection SystemIssue: 1

1

2

2

1

Illustration 5.5.1a Fire Detection System

0311 0310

03070306 0308

03020301IJ/001QI

0305 0304

0303

0407 0406

0404 0405

04020401

K/IJ4C

K/IJ3

WheelhouseMainAlarmand

ControlPanel

K/IJ3A

K/IJ4

K/IJ4A

IJ/002QI K/IJ4B

0403

0301

0309

0313 0312

I.S. cable way(Automation pipe cable way)

Electric Motor Room

Cargo Machinery Rooms

Compressor House

Gastight push button

IS alarm push button

Smoke detector IS typeoptical addressable

Smoke detector gastight

Smoke detector with short circuit protection

Barrier for IS circuit 2 circuits

Barrier for IS circuit 1 circuit

Forward Rooms

Paint Store

Entrance

Hydraulic Station

Bosun Store

Bowthruster Room

Emergency Fire Pump Motor Room


5.5 Fire Detection System5.5.1 Fire Detection SystemThe vessel is fitted with a full cover fire detection systemdivided into 5 loops as follows.

Accommodation zone Loop 00

Bridge deck

A, B, C, D Decks

Upper deck

Accommodation stairways

Engine room Loop 01

E.R. main floor

1st, 2nd, 3rd flat

Engine casing

Aft zone rooms Loop 02

Steering gear room

Aft stores (upper deck)

Fwd zone rooms Loop 03

Bow thruster room

Emergency fire motor p/p room

Various fwd rooms

Cargo machinery rooms Loop 04

Electric motor room

Compressor room

The system is controlled from the master control unit onthe bridge. Power for this unit is supplied from 220Vemergency switch board or 18 hour battery unit via arectifier

There is an all fire spaces mimic alarm panel mounted onthe bridge port side and a cargo fire space, compressorand motor room mimic alarm panel in the cargo controlroom. The engine room space mimic alarm panel ismounted in the engine control room.

A cumulative alarm repeater panel type is mounted in thefire station located on upper deck.

System TestsA weekly function test must be carried out, to test thecontrol unit with a number of smoke detector heads testedin rotation with proprietary smoke test kit. The operationshould be entered into the bridge log.

In addition, power to the unit should be switched off toprove the back up battery system.

Cargo Rooms Loop 004The supply/return cables to this loop are blue, and circuitsintrinsically save and supplied via zener barriers

The motor room loop consists of:-

1 x 1.5 Alarm push button

2 x 1.5 Smoke detectors (optical addressable intrinsicallysafe type)

The compressor room loop consists of:-

1 x 1.5 Alarm push button

3 x 1.5 Smoke detectors (optical addressable intrinsicallysafe type)

The Fwd room loop- 03 is supplied via a zener barrier typeIJ/001Q1 and consists of the following

Paint store

1 x smoke detector (optical addressable intrinsically safetype)

The entrance to forward spaces

1 x gas tight alarm push button

1 x smoke detector (optical addressable gas tight type)

Hydraulic station

2 x smoke detectors (optical addressable type gas tight)

Bosun store

1 x gas tight alarm push button


Bow thruster room


1 x smoke detector (optical addressable gas tight type)with short circuit protection unit mounted on detectorsocket

Emergency fire pump room


1 x smoke detector (optical addressable gas tight type)with short circuit protection unit mounted on detectorsocket.

5.5 Fire Detection System - Page 1Issue: 1


LAMP TEST

E.R. CASING

BOW THRUSTERROOM

EM. FIREMOTOR

PUMP ROOM

ACKN.

47

50

46

48

E.R. MAIN FLOOR

TURBO/GEN.ZONE

43

42

44

4945

PURIFIERSROOM

1st E.R. FLAT

36

34

28

2629

272524

20

22

1917

23

2118

32

30

35 33

E.C.R.

3rd E.R. FLAT

UPPER DECK

39

38

4041 37

MAIN SWITCHBOARD ROOM

STEERING GEAR ROOM

2nd E.R. FLAT

31

PAINTSTORE

ENTRANCE

BOSUNSTOREHYDRAULIC

CENTER

ELECTRICMOTORROOM

COMPRESSORROOM

AFTSTORE

RUBBISHSTORE

D.A.

14

13

9

10

12 6

7

8 3 2

1

4

5

16

15

11

"A" DECK "B" DECK "C" DECK "D" DECK BRIDGEDECK

Illustration 5.5.1b Fire Sensor Control Panel

5.6.1a Gas Dangerous ZonesIssue: 1

Illustration 5.6.1a Gas Dangerous Zones


5.6 Gas Dangerous Spaces and Zones(See Fig 5.6.1a)Under the IMO Code for the Construction and Equipmentof Ships Carrying Liquefied Gases in Bulk:

Gas-dangerous spaces or zones, are zones on the opendeck within 3.0 metres of any cargo tank outlet, gas orvapour outlet, cargo pipe flange, cargo valve, andentrances and ventilation openings to the cargocompressor house.

The entire cargo piping system and cargo tanks are alsoconsidered gas-dangerous.

The port trunkway is also considered a gas-dangerouszone.

In addition to the above zones, the Code defines othergas-dangerous spaces.The area around the air-swept trunking, in which the gasfuel line to the engine room is situated, is not considereda gas-dangerous zone under the above Code.

All electrical equipment used in these zones, whether afixed installation or portable, is certified ‘safe typeequipment’. This includes intrinsically safe electricalequipment, flame-proof type equipment and pressurisedenclosure type equipment. Exceptions to this requirementapply when the zones have been certified gas free, e.g.during refit.

5.6 Gas Dangerous Spaces and Zones - Page 1Issue: 1


5.7.1a Glycol Heating SystemIssue: 1

452

454

451

453

TSTT

TI

PITI TI

TAH90°C

TAHH100°C

TT

TI

KBDVDU

TSTT

TI

PITI TI

TAH90°C

TAHH100°C

TT

TI

KBDVDU

LS LSTrip Trip

LA

L

LA

L

TIC

HC

TIC

HC

YA/5141B

YA/5141A

Stand-by Main Supply

To GasDetector Unit

Main Supply

Stand-by Main Return

Main Return

YA/5501B

YA/5501C

YA/5501A

Electric MotorsRoom

Cargo CompressorRoom

Illustration 5.7.1a Glycol Heating System

YA/5500B

Steam

Condensate

HighFlow

LowFlow

YA/5500A

To IcareGas Detector

GlycolPump

GlycolPump

Condensate

HighFlow

LowFlow

GASSEPARATOR

BULKHEAD

GLYCOLEXPANSIONTANK

GLYCOLEXPANSIONTANK

GLYCOLRESERVETANK

WATER / GLYCOLSTORAGE TANK

Steam

Key

LNG Vapour

Glycol Heating toBoil-off Heaters

Glycol Heating to Cofferdamsand Liquid Domes

Steam Heating

Condensate

Control Air


5.7 Glycol Heating System5.7.1 Descriptio n (see illustration 5.7.1a)

The glycol heating system is located in the cargo motorroom and is comprised of two distinct heating circuits. Onecircuit is used for maintaining the temperature inside thecofferdam spaces and the casing around the cargo pumptower penetration, while the second circuit is used forheating LNG vapour in the dual purpose vapour heatersYA/5141A/B. The separation must be maintained due tothe potential risk of a tube failure on the dual purposeheaters and possible leakage of LNG vapour into thesystem. It is possible, when warming up the cargo tanks,to utilise the cofferdam glycol circulating pump after firstchanging over the isolating spectacle blanks. For thisreason there is an Icare Gas Detection monitoring systemconnected on the glycol outlet side from both the dualpurpose heaters and on both system expansion tanks.

The system is comprised of:-

Three glycol circulating pumps, YA/5501 A, B and C,each rated at 40m3/h

Two 800kW steam heaters, YA/5500A/B, each withhigh and low steam demand regulating valves.

An expansion tank of capacity 0.8m3, on both thecofferdam and dual purpose heating circuits, eachwith gas detection sample lines.

A 4m3 glycol storage tank.

A 3m3 glycol / water storage tank.

5.7.2 Glycol Heating for LNG Dual Purpose HeatersGlycol is circulated via pump YA/5501C, through thesteam heat exchanger YA/5500A, which raises thetemperature of the glycol to 80°C. It is then flows into thedual purpose LNG vapour heaters YA/5141A/B located inthe cargo compressor room. The glycol will raise the LNGvapour temperature to a range between 0 and 50°C,depending upon the temperature control setting. PumpYA/5501B is maintained in a stand-by mode to ensurecontinued circulation of the dual purpose heaters in theevent of failure of the main circulating pump. Thespectacle blanks and isolating valves are maintained openonto this system, while the isolating valves and spectacleblanks onto the cofferdam system remain closed

If it is required that pump YA/5501B takes over the dutiesof the cofferdam circulating system, the isolating valvesand spectacle blanks onto the dual purpose heatingsystem must first be closed and isolated.

It is possible, if required, to operate the cofferdamcirculating pump on the dual purpose LNG heater system.This is achieved by changing over a series of spectacleblanks and then running the three pumps and steamheaters YA/5500A/B in parallel. This operation might onlybe considered necessary when warming up the cargotanks prior to refit due to the high demand on the system.

5.7 Glycol Heating System - Page 1Issue: 1


5.7.2a Cofferdam Heating SystemIssue: 1

NO 5 COFFERDAM

Liquid Dome No. 4

NO 4 COFFERDAM NO 3 COFFERDAM NO 2 COFFERDAM NO 1 COFFERDAM

Key

Stand-by Glycol Water

Main Glycol Water

FL005VR FL005VR

Illustration 5.7.2a Cofferdam Heating System

Liquid Dome No. 3 Liquid Dome No. 2 Liquid Dome No. 1

FL005VR

FL006VR

FL005VR

FL005VR

FL005VR

FL005VR

FL005VR

FL006VR

FL006VR

FL006VR

FL006VR

FL006VR

FL006VR

FL006VR

FL006VR

FL006VR


Cofferdam Heating SystemThe purpose of this system is to ensure that the cofferdamand casing around the cargo pump tower penetration arekept at all times at 5°C, when the cargo tanks are in a coldcondition. Each cofferdam is heated by two independentsystems, one is in service, while the other is on stand-by.

The maximum heating condition is determined by thefollowing extreme operating conditions:-

External air temperature :- -18°CSea water temperature:- 0°C

The requirements for the individual cofferdams are asfollows:-

No 1 Cofferdam 44kW with a heating coil length of382m

No 2, 3 and 4 Cofferdams each require 53kW, eachhaving a coil length of 462m

No 5 Cofferdam 10kW with a heating coil length of90m.

The cargo pump tower penetrations ie liquid domes, eachrequire 3kW under the same extreme operatingconditions, with a coil length of 26m.

Pump YA/5501A and glycol heater YA/5500B areassigned to heating the cofferdam system. It is normallyisolated from the dual purpose LNG glycol heating systemby spectacle blanks and valves, but in the event of abreakdown of pump YA/5501A, pump YA/5501B can beused as a stand-by, having first changed over the isolatingvalves and blanks.

Any failure of the cofferdam heating system with cargo onboard must be treated as serious and repairs must beeffected immediately. In the case of suspected leaks,regular soundings of the cofferdams will indicate intowhich space glycol water is leaking. Each cofferdam isfitted with two temperature sensors which will also give anearly indication of a heating tube failure.

In the event of pump YA/5501A being required for duty oncargo tank warming up with its subsequent connectionwith the dual purpose LNG vapour heaters, a gas sampleline is led off from the glycol expansion tank due to thepossible risk of LNG vapour entering the system.

5.7 Glycol Heating System - Page 2Issue: 1


5.8.1a Nitrogen Sweeping With Gas Concentration Below Alarm PointIssue: 1


Tank 1

Tank 2

Tank 3

Tank 4




Main Vaporiser

No 5 Cofferdam

No 4 Cofferdam

No 3 Cofferdam

PrimarySpace

SecondarySpace

No 2 Cofferdam

No 1 Cofferdam


542

541

563562

566

532

543 531

521

522

533

512

540

560550

511

530

510

520

InsulationSpacesDistributionControl530

510

544

520

534

524

514

567

523

513

575

561

574 AW/918VD

AW/926VD

AW/931VD

AW/943VD

Illustration 5.8.1a Nitrogen Sweeping With Gas Concentration Below Alarm Point

Key

Nitrogen ToPrimary InsulationSpaces

Nitrogen/MethaneMixture From Sweeping Action

5.8 Insulation and Barrier Systems5.8.1 Leakage Detection

LNG Vapour Leakage to the Primary Insulation Space If the gas detection system indicates an excessiveconcentration of LNG vapour in one or more primaryinsulation spaces and if the temperature sensors installedon the bottom of the secondary membrane do not indicatea drop in temperatures, the leakage is a vapour leakage.

The following steps are taken, as soon as possible, to:

• reduce the excessive concentration of LNG vapourand,

• prevent the spread of LNG vapour to other spaces.

Gas Concentration Below the Alarm Point (see figure 5.8.1a)A level of gas concentration of 15% in volume or slightlymore, is controlled by increasing the normal flow ofnitrogen to produce a sweeping action through theinsulation space.

The sweeping is made by opening the small bypass valvebetween the primary space connection and the vent mastof the tank.

• Open the isolating valve AW/918, 926, 931 or 943VDon the bypass of the tank affected.

• Open valve 544, 534, 524 or 514 on the tank affected.

• Sweep in this manner by venting through the bypassvalve for a number of hours. Then, return all valves totheir normal positions, and shut the valves on thebypass used for sweeping.

• Observe the level of gas concentration in theinsulation space after the valves are repositioned fornormal operation, and repeat the sweepingprocedure, if necessary. If the gas concentrationrequires, the sweeping operation is maintained andthe ball valve adjusted to reduce the gasconcentration below of the alarm point.

Gas Concentration Above the Alarm Point If the primary space is contaminated with a concentrationof gas which cannot be controlled by sweeping throughwith the small manual bypass valve, then the large borebypass valves 543, 533, 523, or 513 must be used. Thiswill place a high demand on the nitrogen productionsystem.

5.8 Insulation and Barrier Systems - Page 1Issue: 1


5.8.2a Evacuation Of Damaged Insulation SpacesIssue: 1


Tank 1

Tank 2

Tank 3

Tank 4





Main Vaporiser

No 5 Cofferdam


No 4 Cofferdam


No 3 Cofferdam

PrimarySpace

SecondarySpace


No 2 Cofferdam

No 1 Cofferdam


542

541

532

543 531

521

522

533

512511

560550

540

544

534

524

514

523

513

569

572

571

568

AW/918VD

AW/826VX

AW/827VX

AW/926VD

AW/931VD

AW/943VD

Illustration 5.8.2a Evacuation Of Damaged Insulation Spaces

Key

Nitrogen FromSecondary InsulationSpaces

Nitrogen From DamagedPrimary InsulationSpaces

5.8.2 Damage to Primary Insulation Space -Gas inInterbarrier Space

When a membrane leak is stopped or the tank itself hasbeen gas freed, it is necessary to gas free the insulationspace affected.

The gas freeing is carried out in an identical manner to theinitial inerting described in 4.3.2, by evacuating andrefilling with nitrogen. Care must be exercised with thevapour evacuated from the insulation space to avoidforming a combustible mixture with air. The evacuationprocedure may have to be repeated two or more times to

reduce the gas concentration to an acceptable level (0.2%).


• If the insulation spaces of the non affected tanks areunder their normal operating conditions, increase theirpressure up to 8mbar g.

• Isolate the primary and secondary insulation spacesof the non affected tanks from the primary andsecondary pressurisation headers by closing thevalves 541, 531, 928 or 511 and 542, 532, 522 or 512.

• Connect the insulation spaces of the affected tankwith the pressurisation headers by opening thecorresponding valves.

• Evacuate both the primary and secondary spaces ofthe affected tank as described in 4.3.1. It is assumedthat the membrane damage, if large, is temporarilymade tight.

• Refill with nitrogen, either produced from the ship’sgenerators or supplied from shore, both spaces asdescribed in 4.3.2.

• If the hydrocarbon content is not reduced sufficiently,repeat the cycle; of evacuation and nitrogen filling.

• The hydrocarbon content of the primary space ischecked after each nitrogen sweep. It is measuredwith a portable gas detector, or with the inboard gasdetection equipment or from samples taken at thesample connections provided on deck and analysedwith shore equipment.

• During the gas freeing of a contaminated insulationspace, and particularly when welding work formembrane repairs are necessary, the following pointsmust to be carefully met:

• Once the insulation space is gas freed and beforeany hot work, the gas mixture flowing through theleak is checked by means of a portable gasdetector. When three samples, carried out every 15

minutes, show an hydrocarbon content of less than0.2%, cutting and welding can proceed.

• The nitrogen in the insulation spaces must bereplaced by air if large areas of membrane are to beworked upon. The hydrocarbon content of the barrierspaces must be checked daily, with the vacuum pumpdischarge analysed.

• As the safety depends on the analysis of the gaseousmixture contained in the insulation space, it isessential that the portable gas detectors to beselected according to the nature of the mixture and theaccuracy required for the final hydrocarbon content.

• For measuring the residual content of hydrocarbonin air, a gas detector with a range 0-100% of thelower flammability limit (LFL), or preferably with arange 0-10% LFL, is acceptable.

• Due to the low residual hydrocarbon content, thegas analyser should be one which is normally usedto measure non combustible mixtures.

• If the above portable detector is not accurateenough to measure low hydrocarbon contents, asample is taken from the vicinity of the leak andanalysed with the ship’s gas detection equipmentpreviously re-calibrated.

5.8.3 Damage to Primary Insulation Space -Emergency Discharge of LNG

In the event of an accidental break in the primarymembrane of a tank, the primary insulation space will befilled with LNG in a time proportional to the size of thebreak.A break in the membrane will be signalled by:

• the gas detection alarm, not immediately after thebreak, but few minutes later when the insulationspace is sampled by the gas detection system;

• a drop in temperatures of the secondary barrier;

• a rise in pressure in the tank and in the primaryinsulation space with the possibility of lifting theinsulation space safety valves.

In this event, it is necessary to immediately segregate thedamaged insulation space from the others and to vent it toatmosphere.

Leakage of LNG into the primary insulation space alsolowers the temperature of the hull surrounding the tank,and requires additional heating in the cofferdams.

Segregating and Venting the Damaged PrimaryInsulation Space

• The damaged primary insulation space is isolatedfrom the others and vented to atmosphere via valves543, 533, 523 or 513.

• Shut the gas detection sampling valve at the damagedspace.

• Check the pressure in the damaged space and adjustthe bypass valve to reduce the pressure below safetyvalves lifting point, 10mbar g.

• Check the heating in both cofferdams aft and forwardthe tank.

• At the first opportunity, the damaged tank should beemptied and gas freed and the primary space gasfreed.

• If the tank is to remain out of service for one ormore voyages before repairs, the tank should befilled with inert gas and shut in at a slightoverpressure (about 100mbar g).

• Depending on the size of the break in themembrane, the primary insulation space (after gasfreeing) may either be left in communication withthe tank and isolated from the other spaces, or beconnected with the pressurisation system as fornormal service.



5.8.4 Primary Insulation Space Drainage - Barrier Punch SystemIssue: 1

Drain ValveFlexible Hose

Reducing Valve

Nitrogen BottleNitrogen Connection

Tank Bottom/ Primary Barrier

Base of Cargo TankTrellis Structure

Support for Equipmenton Trellis Structure

Bellows Support Arm

Expansion Tube

Stripping PumpCable Conduit

Primary Insulation Space

Secondary Insulation Space

Duct Keel

Nitrogen Piping

Diaphragm

LNG Liquid

Bellows

Perforations

SITUATION NORMAL BARRIER PUNCH SYSTEMIN OPERATION

Illustration 5.8.4 Primary Insulation Space Drainage - Barrier Punch Systems


5.8.4 Primary Insulation Space Drainage - BarrierPunch Systems

Punching Device for the MembraneA punch diaphragm, fitted below the pump tower in eachcargo tank, permits the punching of an opening in theprimary membrane. This operation will be necessary inthe event that damage to the membrane has permittedLNG to accumulate as a liquid in the primary insulationspace.

If the cargo tanks were pumped out with a head of liquidremaining in the primary space, severe damage to themembrane would result. For this reason, it is necessary tointentionally puncture the primary membrane when thedamaged tank is pumped out, and to pump the tank slowlyenough to enable the level of the liquid imprisoned in theinsulation space to fall at the same rate as the tank withoutoverpressurising the membrane.

The device punches a 50mm dia opening at the bottom ofthe tank. Liquid from the side walls will drain out throughthe opening. Liquid in the bottom portion of the insulationspace must be removed by evaporation during warmup.

Use of the punching device is an extreme measure. Itfloods the insulation space with LNG, and requires thatthe tank be gas freed and entered in order to replace thepunched diaphragm.

The operation procedure for using the punching device isas follows: (see figure 5.8.4)

• The USE of the punching device depends on thefollowing indications of liquid in the primary space.

• If liquid is indicated by all the temperature sensorsup to the level of the sensor 5 A/B, the membraneshould be punched at the start of the pumpingoperation.

• If liquid is indicated by all the temperature sensorsin the bottom and by either the sensor 9 A/B or 8A/B or 7 A/B or 6 A/B, the membrane should bepunched when the LNG level in the tank is 4 metresabove the level of either the sensor 9 A/B or 8 A/Bor 7 A/B or 6 A/B.

• If liquid is indicated by all the temperature sensorsin the bottom and not by the sensor 6 A/B, themembrane should be punched when the LNG levelin the tank is at the level of the sensor 6 A/B.

• If liquid is indicated only by some of thetemperature sensors in the bottom, it is evidencethat a head of liquid is not present in the side walls,and the membrane need not be punched.

• After punching, use only one pump at a reducedpumping rate corresponding to a liquid level fall of0.4m/h.

• The punching device is operated as follows: (seefigure 5.8.4)

• Connect the portable nitrogen flask with theattached pressure reducer to the punch connectionat the liquid dome of the damaged tank;

• Close the equalising valves between the punchpiping and the well of the emergency level.

• Open the valves at the hose connection and on thenitrogen flask, and apply full pressure from thereducing valve (12 bars).

• After about one minute close the valves, disconnectthe nitrogen flask, and reopen the equalising valvesto the well of the emergency level.

• After the tank has been gas freed and repaired, thepunching diaphragm will be replaced by welding anew one. After re installation of the punch device,PURGE all lines and the internal bellow with nitrogenat low pressure (150mbar) to avoid actuation of thesystem.

• Before cooling down of the tank, open the equalisingvalves to the well of the emergency level. Thesevalves should remain blocked open at all times whenthe tank is in service to avoid the inadvertent actuationof the punching device.

Notes : - If a primary membrane has been punched ordamaged to such an extent that the primaryinsulation space is in free communication withthe tank, it is not possible to pull a vacuum on thespace without pulling a vacuum on the tank. At10mbar below atmospheric pressure, the tanksafety valves will open and admit air to the tank.

- With damage of this type, the cargo tank shouldbe gas freed and inerted, but not filled with airuntil the insulation space is gas freed.

- The insulation space should be gas freed bysweeping the inert gas from the tank through thedamaged barrier, or by sweeping with nitrogenfrom the pressurisation system, or bycombination of the two.

- The vacuum pumps may be used in thissituation to assist the sweeping with nitrogen orinert gas, to reduce the pressure created in theinsulation space by evaporation of theimprisoned LNG or to maintain the spacepressure lower than the tank pressure when thetank is opened.



5.9.1a Ventilating the Ballast TanksIssue: 1

RemovableWatertight Manhole Cover

FWD

(View Outboard)

Illustration 5.9.1a Ventilating the Ballast Tanks


From Cofferdam / DuctKeel Supply Fan




5.9 Ventilation of Ballast and Trunk Void 5.9.1 Ventilating a Double Hull Ballast TankVentilation of ballast tanks is necessary to ensure that theatmosphere inside the tank is safe before entry can takeplace. The oxygen content in the tank may be low, forexample, due to the effects of corrosion.

The SNAM regulations for tank entry must be compliedwith. A permit to work must be completed prior to entryand adhered to.

The double hull ballast tanks can be ventilated via the ductkeel and cofferdam forced ventilation system. The ballasttank to be inspected must first be deballasted via the mainand stripping line. Warning notices must then be posted inthe CCR and ECR that the ballast pumps are isolated andshould not be started. Once empty, there are two manhole covers on deck that are removed (two per tank),warning notices and guard rails are arranged around theopenings. Entry can now take place, tank entryprocedures being followed for this action. In the duct keelthere are two man hole covers for each double hull ballasttank, one in a forward and one in an aft position. Removalof these covers will now allow the forced ventilation for theduct keel and cofferdam to flow through the ballast tankand ventilate (see illustration 5.9.1a ).

See Section 6 Inner Hull Inspection Routes.

! WARNINGThe spaces to be inspected must be thoroughlyventilated before entry as there is the possibility ofvery low oxygen content due to corrosion of thesteelwork.

5.9 Ventilation of Ballast and Trunk Void - Page 1Issue: 1


5.9.2a Ventilating the Trunk Void SpacesIssue: 1

FWD

Illustration 5.9.2a Ventilating the Trunk Void Spaces


Cofferdam / Duct KeelSupply Fan(On No. 1 and No. 5 Cofferdams)

Flexible HoseConnection

Flexible HoseConnection

Above TankVoid Space

Duct Keel


5.9.2 Ventilating the Trunk Deck Void SpaceThe trunk deck void spaces have five man hole covers pertank, two on the port side slope forward and aft, two on thestarboard side slope forward and aft and one on the toparea of the cargo tank. The cofferdam space has a manhole cover, one port and one starboard. Removal of twoman hole covers on the trunk deck void and one man holecover on the cofferdam, will allow a flexible hose with thecorrect size flanges to be connected between the twotanks. The forced ventilation system for the duct keel andcofferdam is now led into the trunk deck void so ventilatingthe space. Tank entry regulations must be followed beforeentry. (see illustration 5.9.2a )

See Section 6 Inner Hull Inspection

5.9.3 IMO Code for Existing Ships CarryingLiquefied Gases in Bulk

Ships complying with the IMO code are, after an initialstructural survey, issued with a Certificate of Fitness.

Periodical structural surveys of renewal of the certificateare held at intervals not exceeding 5 years andintermediate surveys of safety equipment, pumping andpiping systems at intervals not exceeding 30 months.

A Certificate of Fitness may be extended for a period ofgrace of up to one month from the expiry date.

The Code requires that ships be equipped with fivefiremen’s outfits and three sets of safety equipment forpersonnel protection, each having an approved SCBA.

The safety equipment sets as supplied to LNG shipsshould be similar to the firemen’s outfits except that inplace of the fire resistant suit, suitable clothing is providedto protect personnel from LNG when worn with eitherSCBA or a protective face mask, it should be either asolvent proof material or PVC and consist of trouserscapable of being worn over sea-boots and a jacketcomplete with hood. Additionally the axe is excluded fromthe safety equipment set.

Where possible the respective sets of equipment shouldbe stowed in pairs and clearly identified as either afireman’s outfit or safety equipment. All compressed airequipment should be inspected monthly, and should beinspected and tested by an expert: at least once a year.Inspections should be recorded in the Record of SafetyAppliances and Inventory of Equipment.

5.9 Ventilation of Ballast and Trunk Void - Page 2Issue: 1


Part 6Inner Hull

PART 6: INNER HULL6.1 IntroductionGeneralAn Inner Hull Inspection (also known as a cold spot/paintcoating inspection) is an integral part of vesselmaintenance procedure. It takes place during the loadedvoyage and essentially serves two purposes :

1 Indication of possible breakdown of the cargo tanksinsulation;

2 Detection of damage to structural coatings.

A breakdown of the cargo tank insulation membranes mayallow LNG ( -160°C ) to enter the insulation spaces. Thiswill effectively reduce structural steel temperatures and, ifsevere and prolonged, will be recognisable through theformation of frost (cold spots) on the internal structures ofthe ballast tanks, void spaces, or the cofferdams.(Continued contact with such low temperatures couldcause fracturing of the structural steel, leading to possibleingress of water from ballast tanks, subsequent extensivedamage, and expensive repair costs).

Whilst checking for possible breakdown of the cargo tanksinsulation the condition of internal structural paint coatingsmay also be monitored. Early detection of damage,together with prompt repair, will prevent furtherdeterioration and subsequent corrosion development.

Hence, each ballast tank, void space, and cofferdaminspection comprises all structural surfaces adjacent tothe cargo tank plus all remaining surfaces.

The inspections of the Fore and Aft Peaks are purely forPaint Coating inspection.

If the damaged area is accessible, it may be possible tocarry out minor repairs during the inspection, otherwiseidentified damage should be recorded and reported forfurther attention.

Every ballast tank is inspected every xxxx? months. Eachvoid space and cofferdam, compartments are inspectedevery xxxx? months.

On departure from the loading port it is necessary to delayinspection for approximately xxxx? hours. This allowsample time for cargo tank insulation temperatures tostabilise and for any faults to become apparent.

The inspection is a rigorous and time consuming procedure.It is therefore important that inspection personnel arephysically fit and maintain concentration throughout toensure a thorough examination is accomplished.

ContentsThis part of the manual contains pages of illustrations in adouble sided format, each page showing a perspectiveillustration of the tank in question.

Each illustration provides information to enable routineinspections of the wing and double bottom ballast tanks(port and stbd), the fore and aft peaks, the above tank voidspaces, and the cofferdams.

The pages are laminated, allowing Snam personnel to usethem as a photocopy master document or to carry anindividual page into the relevant ballast tank, void space,or cofferdam without worry of damage, and to allow anyproblem areas identified to be marked on the illustrationwith a coloured pen or chinagraph pencil.

Each illustration shows the inspection route to befollowed, the individual compartment labelling, and thepoint of access. This ensures that :

1 Every compartment within the relevant ballast tank,void space, and cofferdam is entered;

2 Location of personnel in an emergency situation iswithout unnecessary delay.

Inspection

! CAUTIONWhen undertaking any ballast tank, void space, orcofferdam inspection the relevant sections of the ICSTanker Safety Guide (Liquefied Gas) and SMSprocedures should be consulted and therecommendations adhered to.

The Chief Officer is personally responsible for inner hullinspections.

The inspection team should consist of at least two menwho will carry out the inspection and a third man,positioned just inside the ballast tank, void space, orcofferdam being inspected, who will be in constantcommunication with the inspection team via portable VHFequipment. A further two men are to be in position nearthe ballast tank, void space, or cofferdam entrance withbreathing apparatus, resuscitation equipment and, tomonitor progress of the inspection team, a copy of therelevant page from this section.

Protective clothing must be worn and all equipmentcarried must be thoroughly checked before proceedingwith the inspection. Personal oxygen analysers must be

carried as the areas being inspected may have a lowoxygen content in parts, even after ventilation.

On sighting a cold spot it is important to:

1 Ascertain the centre of the cold spot. Use a portablethermistor type temperature meter to periodicallyrecord the temperature distribution in and around thecold spot - this will assist in discovering the locationand extent of the fault in the cargo tank insulation;

2 Observe any change in recorded temperatures. If thesituation deteriorates be prepared to take contingencymeasures.

The entry precautions listed below must be observed.

Entry PrecautionsApart from oxygen deficiency, which can be expected inballast tanks, void spaces, or cofferdams which have beenclosed for some time, there is a danger of natural gas ornitrogen leakage from an insulation space.

Natural gas is non-toxic but can suffocate rather thanpoison. Any leakage of natural gas or nitrogen into anenclosed ballast tank, void space, or cofferdam will tend tolower the oxygen content by displacing air. Furthermore,natural gas is odourless and therefore gives no warning ofits presence by smell. It is also lighter than air at ambienttemperatures and so will tend to concentrate in theunderdeck stiffening structures. It is important that testingof these areas is carried out to ensure ventilation haseffectively dispersed any gas.

! WARNINGTo avoid danger of oxygen starvation it is necessarybefore entering any enclosed ballast tank, void space,or cofferdam to :

- Ventilate thoroughly;- Test the oxygen content with the portable

oxygen analyser;- Confirm absence of all hydrocarbon vapours

with an explosimeter. It should be rememberedthat explosimeter readings are unreliablewhere the oxygen content is low;

- Position the safety equipment at or near thepoint of entry of personnel. The safetyequipment should be checked weekly.

! WARNINGBefore entry to any ballast tank, void space, orcofferdam personnel carrying out an inspectionshould ensure that :

- the ballast tank, void space, or cofferdam hasbeen opened up in good time and remainsopen;

- a valid permit to work has been issued by theappropriate authority;

- all personnel concerned are informed that theinspection is taking place.

AccessThe entry point to the wing and double bottom ballasttanks (port and stbd) is through watertight hatches fromthe main deck, or through the manhole access points inthe duct keel.

The entry point to the above tank void spaces is fromeither the port or stbd passageways or through watertighthatches on the trunk deck.

The entry to the cofferdam spaces separating the cargotank, is via the individual watertight hatches located on thestarboard side of the main deck.

To access the WB Deep Tank enter the focsle space,descend through two compartments and use one of twowatertight manholes.

Compartment NumberingEvery internal compartment within a ballast tank, voidspace, or cofferdam has a unique matrix typealphanumeric label :

1 Ballast tanks make use of frame numbers (precededby Fr) cross referenced with a level number orathwartship identifier, eg P and S

2 Void spaces also use frame numbers (preceded by Fr)but cross referenced with an individual compartmentidentification A

3 Cofferdams’ internal compartments have an individualnumber cross referenced with the particular cofferdamnumber and a level letter.

6.1 IntroductionIssue: 1


6.1a No. 1 Cofferdam Perspective ViewIssue: 1

Frame 243

Frame 246

FWD

STARBOARD

PORT

No. 1 Cofferdam Perspective View

Watertight Manhole

A1

A2

A3

A4

A5

F9

C1

C2

C3

C4

C5

C6

Inspection Route

Key


Illustration 6.1a No. 1 Cofferdam Perspective View

6.1b No. 1 Port Ballast Tank Perspective ViewIssue: 1

Fr 211

Fr 215

Fr 219

Fr 223

Fr 227

Fr 231

Fr 235

Fr 239

Frame 246

Fr 243

FWD

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

(View Outboard)

o. 1 Port Ballast Tank Perspective View

Watertight Manhole

Inspection Route

Key

Frame 207

P10

P11

P12

P13

P14

P15

P16

P17


Illustration 6.1b No. 1 Port Ballast Tank Perspective View

6.1c No. 1 Starboard Ballast Tank Perspective ViewIssue: 1

Frame 207

Fr 211

Fr 215

Fr 219

Fr 223

Fr 227

Fr 231

Fr 235

Fr 239

Frame 246

Fr 243

FWD

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

(View Outboard)

No. 1 Starboard Ballast Tank Perspective View

Watertight Manhole

Inspection Route

Key

S10

S11

S12

S13

S14

S15

S16

S17


Illustration 6.1c No. 1 Starboard Ballast Tank Perspective View

6.1d No. 1 Above Tank Void Space Perspective ViewIssue: 1

Access Hatch toCofferdam No. 1

FWD

PORT

STARBOARD

Position ofVapour Dome

Position ofLiquid Dome

Frame 207

Fr 211

Fr 215

Fr 219

Fr 223

Fr 227

Fr 231

Fr 235

Fr 239

Fr 243

Frame 246

Inspection Route

Key

A9

A8

A7

A6

A5

A4

A3A2

A1


Illustration 6.1d No. 1 Above Tank Void Space Perspective View

6.1e No. 2 Cofferdam Perspective ViewIssue: 1

Frame 59

Frame 62

FWD

STARBOARD

PORT


Watertight Manhole

B1B2

B3

B4

B5

B6

B7

B8

B9

C1

C2

C3

C4

C5

C6

Inspection Route

Key


Illustration 6.1e No. 2 Cofferdam Perspective View

6.1f No. 2 Port Ballast Tank Perspective ViewIssue: 1

P10

P11

P12

P13

P14

P15

P16

P17

Inspection Route

Key

Frame 156

Fr 160

Fr 164

Fr 168

Fr 172

Fr 176

Fr 180

Fr 184

Fr 188

Fr 192

Fr 196

Fr 200

Frame 207

Fr 204

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

FWD

(View Outboard)

No. 2 Port Ballast Tank Perspective ViewWatertight Manhole


Illustration 6.1f No. 2 Port Ballast Tank Perspective View

6.1g No. 2 Starboard Ballast Tank Perspective ViewIssue: 1

S10

S11

S12

S13

S14

S15

S16

S17

Inspection Route

Key

Frame 156

Fr 160

Fr 164

Fr 168

Fr 172

Fr 176

Fr 180

Fr 184

Fr 188

Fr 192

Fr 196

Fr 200

Frame 207

Fr 204

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

FWD

(View Outboard)

No. 2 Starboard Ballast Tank Perspective ViewWatertight Manhole


Illustration 6.1g No. 2 Starboard Ballast Tank Perspective View

6.1h No. 2 Above Tank Void Space Perspective ViewIssue: 1

Frame 156

Fr 160

Fr 164

Fr 168

Fr 172

Fr 176

Fr 180

Fr 184

Fr 188

Fr 192

Fr 196

Fr 200

Frame 207

Fr 204


FWD

PORT

STARBOARD

No. 2 Above Tank Void Space Perspective View



A9

A8

A7

A6

A5

A4

A3A2

A1

Inspection Route

Key


Illustration 6.1h No. 2 Above Tank Void Space Perspective View

6.1i No. 3 Cofferdam Perspective ViewIssue: 1

Frame 153

Frame 156

FWD

STARBOARD

PORT


Watertight Manhole

D1D2

D3

D4

D5

D6

D7

D8

D9

C1

C2

C3

C4

C5

C6

Inspection Route

Key


Illustration 6.1i No. 3 Cofferdam Perspective View

6.1j No. 3 Port Ballast Tank Perspective ViewIssue: 1

P10

P11

P12

P13

P14

P15

P16

P17

Inspection Route

Key

Frame 156

Fr 160

Fr 164

Fr 168

Fr 172

Fr 176

Fr 180

Fr 184

Fr 188

Fr 192

Fr 196

Fr 200

Frame 207

Fr 204

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

FWD

(View Outboard)

No. 2 Port Ballast Tank Perspective ViewWatertight Manhole


Illustration 6.1j No. 3 Port Ballast Tank Perspective View

6.1k No. 3 Starboard Ballast Tank Perspective ViewIssue: 1

S10

S11

S12

S13

S14

S15

S16

S17

Inspection Route

Key

Frame 105

Fr 109

Fr 113

Fr 117

Fr 121

Fr 125

Fr 129

Fr 133

Fr 137

Fr 141

Fr 145

Fr 149

Frame 156

Fr 153

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

FWD

(View Outboard)

No. 3 Starboard Ballast Tank Perspective ViewWatertight Manhole


Illustration 6.1k No. 3 Starboard Ballast Tank Perspective View

6.1l No. 3 Above Tank Void Space Perspective ViewIssue: 1

Frame 105

Fr 109

Fr 113

Fr 117

Fr 121

Fr 125

Fr 129

Fr 133

Fr 137

Fr 141

Fr 145

Fr 149

Frame156

Fr 153


FWD

PORT

STARBOARD



A9

A8

A7

A6

A5

A4

A3A2

A1

Inspection Route

Key



Illustration 6.1l No. 3 Above Tank Void Space Perspective View

6.1m No. 4 Cofferdam Perspective ViewIssue: 1

Frame 102

Frame 105

FWD

STARBOARD

PORT


Watertight Manhole

E1E2

E3

E4

E5

E6

E7

E8

E9

C1

C2

C3

C4

C5

C6

Inspection Route

Key


Illustration 6.1m No. 4 Cofferdam Perspective View

6.1n No. 4 Port Ballast Tank Perspective ViewIssue: 1

Frame 59

Fr 62

Fr 66

Fr 70

Fr 74

Fr 78

Fr 82

Fr 86

Fr 90

Fr 94

Fr 98

Fr 102

Frame105

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

FWD

(View Outboard)

No. 4 Port Ballast Tank Perspective View

Watertight Manhole

P10

P11

P12

P13

P14

P15

P16

P17

Inspection Route

Key


Illustration 6.1n No. 4 Port Ballast Tank Perspective View

6.1o No. 4 Starboard Ballast Tank Perspective ViewIssue: 1

Frame 59

Fr 62

Fr 66

Fr 70

Fr 74

Fr 78

Fr 82

Fr 86

Fr 90

Fr 94

Fr 98

Fr 102

Frame 105

Watertight Manhole

Turn of Bilge

Double Bottom

Upper Deck

Wing Tank

FWD

(View Outboard)

No. 4 Starboard Ballast Tank Perspective View

Watertight Manhole

S10

S11

S12

S13

S14

S15

S16

S17

Inspection Route

Key


Illustration 6.1o No. 4 Starboard Ballast Tank Perspective View

6.1p No. 4 Above Tank Void Space Perspective ViewIssue: 1

Frame 59

Fr 62

Fr 66

Fr 70

Fr 74

Fr 78

Fr 82

Fr 86

Fr 90

Fr 94

Fr 98

Fr 102

Frame 105



FWD

PORT

STARBOARD




A9

A8

A7

A6

A5

A4

A3A2

A1

Inspection Route

Key


Illustration 6.1p No. 4 Above Tank Void Space Perspective View

6.1q No. 5 Cofferdam Perspective ViewIssue: 1

Frame 59

Frame 62

FWD

STARBOARD

PORT


Watertight Manhole

Inspection Route

Key

F1F2

F3

F4

F5

F6

F7

F8

F9

C1

C2

C3

C4

C5

C6


Illustration 6.1q No. 5 Cofferdam Perspective View

6.1r Fore Peak Ballast Tank (Port Side Perspective View)Issue: 1

Frame 258

Fr 262

Fr 266

Fr 270

Fr 274

Fr 278

Fr 281

ChainLocker

Fore Peak Ballast Tank (Port Side Perspective View)

Enterance to BowThrust Room


Illustration 6.1r Fore Peak Ballast Tank (Port Side Perspective View)

6.1s Fore Peak Ballast Tank (Starboard Side Perspective View)Issue: 1

Frame 258

Fr 262

Fr 266

Fr 270

Fr 274

Fr 278

Fr 281

ChainLocker

Fore Peak Ballast Tank (Starboard Side Perspective View)


Illustration 6.1s Fore Peak Ballast Tank (Starboard Side Perspective View)

Part 7Stress and Damage Stability

PART 7 : STRESS AND DAMAGE STABILITY7.1 IntroductionProceduresThe Stability Information supplied on board iscomprehensive and requires careful study to appreciatethe amount of information available.

Volumes 1 and 2 cover Damage Stability. 26 cases ofdamage are studied in various conditions of loading.

Two volumes cover bending moments and shear forces atvarious load conditions.

One volume covers stability and draft for set loadingconditions.

One volume covers the instructions for the Master.

One complete set must be retained in an approved placeand be stamped for approval by the Classification Society.These must be produced upon renewal of StatutoryCertification.

! WARNINGThere is a limit on partially filled cargo tanks, between10% of the tank length and 80% of the tank height.

7.1.1 Loading Stability ComputerThe Loading Stability Computer is an R.I.N.A. approvedPC running Windows 3.1 environment. The LoadingStability software is produced by CETENA and is provided with compartment volumes, ship characteristics, Bonjeancurves and hydrostatics. This data allows the program tocalculate any loading condition for an intact condition or adamaged stability condition.

Operation-Main MenuIn common with other Windows applications the programopens to a main menu. The tool bar, immediately belowthe ship name, allows pop-up menus and sub-menus tobe selected. These are as follows:

Loading ConditionNew this allows the data for a new loading condition to beentered and ports, terminals, loading condition name,voyage number, type etc can be entered or selected.These are Loading Condition Name-This describes theloading condition to be entered

Voyage Number- This parameter gives the voyageidentification code in numerics or alphanumeric.

Type- The type of voyage, e.g. cargo or ballast can beselected from predefined list by clicking on the typerequired.

Loading Port- The pre-entered loading ports can beselected in a similar way

Unloading Terminal- Again these can be selected fromthe pre-defined list.

Sea Water Density- This is pre-defined as 1.025t/m3

Date- The date of the operation can be automatically setby computer time or input manually.

Note- Up to 80 characters can be entered for a user note.When the data is entered, either the OK or Cancel buttoncan be selected to close the form or return to main menu.

Open- This enables a previously stored loading conditionto be opened and all the pre-defined conditions are listedby name. The required file can be selected by pointingand clicking on the required name. When the loadingcondition has been set-up, data may be input using theadded loads function. This shows a screen form whichallow cargo tanks and all other tanks contents to beentered. For each tank either the sounding or ullageshould be entered and the specific gravity selected fromthe list of fluids. The volume filling percentage and weightwill therefore be calculated. Data entry is by selection ofthe field to enter the data by clicking a cell. When the datahas been entered and confirmed by pressing the enter keyor by selecting another cell, the data is automaticallyperformed.

Options- When each value is entered normally the entirestability calculation is performed and results shown in thelower part of the screen. Manual, automatic and periodicrecalculation can be selected from the options functions,and the timing of periodic recalculations can be selectedthrough this function. To complete the definition of theloading condition, it is also possible to introduce additionalmasses via the added loads which allow a weight to beadded at a longitudinal centre of gravity, vertical centre ofgravity and transverse centre of gravity, or by framenumber. This is useful if the vessel is carrying heavyequipment, e.g ship to ship transfer equipment. In thematrix of results, the loading condition is summarised onscreen.

Cargo- This gives the cargo value for all four tanks intonnes and metre cubed. Ballast; this gives the total valueof ballast in tonnes and cubic metres.

Deadweight- This calculates the deadweight fromdisplacement and lightship displacement.

Displacement- This gives the total of all loaded weightsincluding cargo, ballast and other tanks, plus deadweight.If this value exceeds the permitted maximum for full load draught, a warning message will be shown, displacementnot allowed. In this case the operator must cancel thewarning by clicking on OK to continue to enter loadingconditions.

EG, KG, YG- These give the co-ordinates in metres of theship’s centre of gravity.

Angle of heel- This gives the value of the heel angle indegrees.

Max SF percent- This gives the maximum value of sheerin percentage in either harbour or navigation mode and itsposition forward of the aft perpendicular.

Max BM percent- This gives the maximum value ofbending moment in percentage in harbour or navigationmode and its position forward of the aft perpendicular.

INSTANT rate- This value is automatically entered if thecomputer is in on-line mode and is not given if any of theload gauges are out of order. This calculates the rate ofship loading from the difference in measured tank levelafter a given interval.

AVG rate- This value gives the average rate of the loadingand unloading operation calculated by considering thedifference between the cargo in m3 when the on-line key is pressed and the cargo measured last time ofacquisition. This value is only available when computer isin on-line mode.

Residual- This shows the remaining time required tocomplete loading or unloading operations, assuming thatthe current rate value is constant. In order to calculate the residual time, the value of total final cargo in cubic metresis required and is only available if the computer is in on-line mode.

Fore draught- This is the computed value of forwarddraught corrected to take into account the actual positionof the draught sensor.

LBP/2 draught- This is a computed value of midshipsdraught.

Aft draught- This is a computed value of the aft draught,corrected to take into account the actual position of thedraught sensor.

Calc Trim- This is computed as the difference betweenforward and aft draught. This is shown as negative if theship is trimmed by the stern.

GM Solid- This is the computed value of the transversemetacentric height above the centre of gravity correctedfor free surface effect.The central part of the screen shows the calculationresults while keys are provided to switch to different resultpages or graphical presentations.

Bending Moment Sheer Force- These provide a table ofbending moment and sheer force from frames 15 to 258,showing the actual moment and actual sheer for allowable at sea (navigation) and allowable at port (harbour)conditions. Bending moment is shown in tonne metres(TM) and %, and sheer force is shown in tonnes andpercent. The maximum sheer force, bending moment andframes are shown at the bottom of the screen.

GZ Levers- The KN value and GZ levers in metresagainst heel angle in degrees from 0-75 degrees areshown for each condition.

Trim & Stability- A table of trim giving displacements todraughts and LCG, and stability giving KG, KMT, GM solidand GM fluid, plus correction for free surface effect isshown by this key.In each case graphs sowing the values of bendingmoment and sheer force and shown together with a GZstability diagram when these are selected.

Printing- This allows printing of the data used forcalculations and results obtained. Damaged stability; theprecalculated ship damaged conditions are shown fromcases 1-26 which show combinations of floodedcompartments. These may be selected and the hull andflooded compartments are shown graphically on thescreen. Keys 1-26 allow the flooded compartments to bechosen and the key label in red indicates the conditionchosen. A window showing the precalculated results canbe obtained by pressing the key labelled HIDE DATA.

Introduction 7.1 - Page 1Issue: 1


7.2 Cases

Twenty six cases have been studied in the DamageStability volumes for various states of loading.

The Cargo Systems and Operating Manual give pictorialrepresentations of information that can be readilyobtained from these volumes.

For reference the first page displays the location ofassumed damaged compartments.

Following on from these pages are various damageconditions when the vessel is FULLY LOADED(Condition No. 4).

Note that GZ curves have been drawn to display clearlythe righting lever about an assumed centre of gravity forvarious angles of heel.

Cases 7.2 - Page 1Issue: 1


Damage No GZ - CURVES FOR FOLLOWING ANGLE OF HEELHeel 0 2 4 6 9 12 15 20 25 30 36 43 50

1 GZ 0 0.077 0.149 0.232 0.365 0.508 0.665 0.963 1.31 1.682 2.064 2.193 1.9642 GZ -0.219 -0.15 -0.086 -0.011 0.107 0.232 0.368 0.627 0.932 1.286 1.679 1.781 1.6343 GZ -0.602 -0.549 -0.496 -0.436 -0.34 -0.236 -0.123 0.097 0.371 0.683 1.052 1.183 1.0994 GZ -0.841 -0.794 -0.746 -0.693 -0.606 -0.51 -0.406 -0.19 0.088 0.419 0.813 0.999 0 9685 GZ -0.79 -0.741 -0.69 -0.634 -0.543 -0.444 -0.335 -0.112 0.176 0.515 0.92 1.106 1.0636 GZ -0.792 -0.743 -0.692 -0.636 -0.545 -0.446 -0.337 -0.114 0.175 0.513 0.919 1.107 1.0647 GZ -0.559 -0.506 -0.455 -0.396 -0.297 -0.188 -0.066 0.179 0.49 0.855 1.27 1.427 1.3368 GZ -0.561 -0.508 -0 457 -0.397 -0.299 -0 19 -0.068 0.177 0.488 0.854 1.27 1.426 1.3359 GZ -0.251 -0.208 -0.166 -0.111 -0.019 0.087 0.208 0.447 0.747 1.091 1.433 1.579 1.49210 GZ -0.268 -0.225 -0.186 -0.135 -0.049 0.049 0.163 0.394 0.691 1.033 1.365 1.516 1.4411 GZ -0.007 0.045 0.092 0.149 0.244 0.347 0.466 0.71 1.022 1.358 1.668 1.785 1.67412 GZ -0.001 0.063 0.123 0.192 0.306 0.432 0.575 0.859 1.203 1.58 1.985 2.113 1.90613 GZ -0.001 0.063 0.123 0.192 0.306 0.432 0.575 0.859 1.203 1.58 1.986 2.113 1.90614 GZ -0.001 0.064 0.124 0.194 0.308 0.43 0.567 0.828 1.144 1.519 1.941 2.067 1.92715 GZ -0.206 -0.135 -0.068 0.008 0.132 0.264 0.409 0.684 1.01 1.374 1.767 1.894 1.73216 GZ -0.001 0.062 0.121 0.189 0.3 0.418 0.551 0.803 1.099 1.433 1.791 1.94 1.8517 GZ -0.642 -0.574 -0.51 -0.436 -0.315 -0.184 -0.04 0.239 0 57 0.951 1.369 1.568 1.51218 GZ -0.001 0.076 0.148 0.23 0.361 0.501 0.654 0.945 1.273 1.605 1.925 2.053 1.95619 GZ -0.86 -0.785 -0.714 -0.632 -0.497 -0.35 -0.186 0.131 0.511 0.945 1.416 1.642 1.61520 GZ -0.001 0.075 0.147 0.229 0.36 0.5 0.654 0.946 1.279 1.618 1.953 2.079 1.97321 GZ -0.802 -0.727 -0.655 -0.571 0.435 -0.286 -0.12 0.203 0.592 1.023 1.481 1.696 1.65122 GZ -0.008 0.086 0.159 0.243 0.376 0.519 0.677 0.978 1.329 1.717 2.138 2.259 2.123 GZ -0.414 -0.357 -0.305 -0.239 -0.126 0.001 0.141 0.418 0 75 1 108 1.496 1.696 1.65624 GZ -0.001 0.054 0.105 0.168 0.272 0.388 0.52 0.784 1.113 1.494 1.859 1.97 1.81725 GZ -0.002 0.058 0.115 0.183 0.294 0.417 0.556 0.831 1.167 1.558 1.932 2.044 1.88726 GZ 0 0.056 0.105 0.167 0.27 0.384 0.515 0.777 1.104 1.483 1.848 1.956 1.799



7.2.1Damaged compartments numbers 41 and 214.

This is damage to the forecastle space and forward dry space.

Expected heel to port 0°

Freeboard to deck opening immersion No. 13 &14 7.99m

Angle of heel to immersion of opening No. 10 33.5°

Permisable minimum GM 0m

Excess GM 2.606m

Trim -1.54m Draught Aft10.19m

MidshipsDraught

9.42m

Draught Fwd8.65m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

10

10

13

10

14

13/147.99m

214

41

214

Location of Damage

LNG Cargo



7.2.2Damaged compartments 41, 214, 213, 49, 34, 400 and 500.

This is extensive assumed damage to the forecastle space,Boatswain’s store, forward paint store and pump space, 1 portballast tank and 1 centre cargo tank. Secondary flooding occursin the duct keel and cofferdam spaces.

Expected heel to port 6.3°

Freeboard to deck opening immersion No.10 6.83m

Angle of heel to immersion of opening No.10 35.6°

Permisable minimum GM 0.261m

Excess GM 2.345m

Trim 0.28m

Location of Damage

Compartments Connected to Damage Zone

LNG Cargo

Draught Aft9.95m

MidshipsDraught10.09m

6.3°

GZ(Metres)

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Lollto Port

Draught Fwd10.23m

10

10

10

6.83m

400

214

41

213

213

214

49

34

500



7.2.3Damaged compartments 34, 35, 49, 51, 401 and 500.

This is extensive damage to 1 port and 2 port ballast tanks and1 and 2 centre cargo tanks. Secondary flooding occurs in theduct keel and cofferdam spaces.





Excess GM 1.366m

Trim -0.43m

Draught Aft9.61m

MidshipsDraught

9.40m

Draught Fwd9.19m

17.9°

GZ(Metres)

0.8

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


51

35

49

34

500

401

10

10

10

3.65m

Location of Damage


LNG Cargo



7.2.4Damaged compartments 35, 36, 51, 53, 402, 500.






Excess GM 0.838m

Trim -0.29m

Draught Aft9.17m

MidshipsDraught

9.02m

Draught Fwd8.87m

23.5°

0.8

1.0

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

GZ(Metres)

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


53

36

51

35

402

500

10

10

10

2.18m

Location of Damage


LNG Cargo



7.2.5Damaged compartments 36, 37, 53, 55, 403, 500.






Excess GM 0.759m

Trim -0.49m

Draught Aft9.41m

MidshipsDraught

9.17m

Draught Fwd8.93m

22.1°

GZ(Metres)

0.8

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


10

10

10

2.45m

53

36

500

55

37

403

Location of Damage


LNG Cargo



7.2.6Damaged compartments 36, 37, 54, 56, 403 and 500.

This is extensive damage to 3 starboard and 4 starboard ballasttanks and 3 and 4 centre cargo tanks. Secondary floodingoccurs in the duct keel and cofferdam spaces.

Expected heel to starboard -22.1°




Excess GM 0.753m

Trim -0.49m

MidshipsDraught

9.17m

-22.1°

GZ(Metres)

0.8

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Lollto Starboard

Draught Aft9.41m

Draught Fwd8.93m

10

10

10

2.44m

54

36

500

56

37

403

Location of Damage


LNG Cargo



7.2.7Damaged compartments 37, 55, 201, 404 and 500.

This is extensive damage to 4 port ballast tank, port bunker tankand 4 centre cargo tank. Secondary flooding occurs in the ductkeel and cofferdam spaces.





Excess GM 1.544m

Trim -1.54m

GZ(Metres)

0.8

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll

Draught Aft10.50m

MidshipsDraught

9.73m

Draught Fwd8.96m

16.5°

37

500

404

201 55

10

10

10

3.29m

Location of Damage


LNG Cargo



GZ(Metres)

0.8

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


Draught Aft10.50m

MidshipsDraught

9.73m

Draught Fwd8.96m

-16.5°

37

Location of Damage


LNG Cargo

202 56

500

404

10

10

10

3.28m


This is extensive damage to 4 starboard ballast tank, starboardbunker tank and 4 centre cargo tank. Secondary flooding occursin the duct keel and cofferdam spaces.





Excess GM 1.540m

Trim -1.54m



Draught Aft13.94m


Draught Fwd6.88m

9.6°

GZ(Metres)

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


10

10

10

2.26m

Location of Damage


LNG Cargo

200

200

201

207

7.2.9Damaged compartments 200, 201 and 207.

This is extensive damage to the port bunker tank and machineryspaces with secondary flooding to the machinery storestarboard aft.





Excess GM 1.088m

Trim -7.06m



Draught Aft14.08m


Draught Fwd6.74m

-10.6°

GZ(Metres)

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


202

200

200

20710

10

10

1.82m

Location of Damage


LNG Cargo


This is extensive damage to the starboard bunker tank andmachinery spaces with secondary flooding to the machinerystore starboard aft.





Excess GM 0.840m

Trim -7.34m



9

Draught Aft15.51m


Draught Fwd6.08m

0.3°

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

GZ(Metres)

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


208

200

1

200

9

9

8.74m

Location of Damage


LNG Cargo


This is extensive damage to the machinery spaces on the portside, the CO2 room and refrigeration spaces with secondaryflooding to the machinery store starboard.





Excess GM 2.466m

Trim -9.43m



Draught Aft10.70m

MidshipsDraught

9.58m

Draught Fwd8.46m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll

0°

14

9

9

9

Location of Damage

LNG Cargo

206

206

1

7.2.12Damaged compartments 206 and 1.

This is damage on the port quarter to the CO2 room,refrigeration spaces and aft peak ballast tank.





Excess GM 2.606m

Trim -2.24m



Draught Aft10.70m

MidshipsDraught

9.58m

Draught Fwd8.46m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

9

9

9

Location of Damage

LNG Cargo

208

208

1

15

2.83m

15


This is damage aft to the machinery store, refrigeration spacesand aft peak.





Excess GM 2.606m

Trim -2.24m




This is underwater damage to the forecastle space, forward dryspace and 1 port and starboard ballast tanks. Secondaryflooding occurs in the duct keel and cofferdam spaces.


Freeboard to deck opening immersion No.13,14 8.26m



Excess GM 2.606m

Trim 1.34mDraught Aft

9.78m


Draught Fwd11.12m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

Location of Damage


LNG Cargo

10

10

13

14

1013/14

8.26m

215

49

50

41




This is underwater damage to the forecastle space, forward dryspace and 1 port ballast tank.





Excess GM 2.518m

Trim -0.34mDraught Aft

9.79m

MidshipsDraught

9.62m

Draught Fwd9.45m

5.8°

0.4

0.2

0.2

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

GZ(Metres)

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


215

41

49

10

10

10

7.15m

Location of Damage

LNG Cargo




This is underwater damage to 1 port and 1 starboard ballasttanks, 2 port and 2 starboard ballast tanks and the duct keel.





Excess GM 2.606m


9.62m


Draught Fwd12.78m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

Location of Damage


LNG Cargo

49

50

51

52

500

1013/14

10

10

13

14

8.33m




This is underwater damage to 1 port and 2 port ballast tanks.





Excess GM 1.902m

Trim 1.04m Draught Aft9.16m

MidshipsDraught

9.68m

Draught Fwd10.20m

15.8°

GZ(Metres)

0.8

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


5149

10

10

10

4.74m

Location of Damage

LNG Cargo




This is underwater damage to 2 and 3 ballast tanks and the ductkeel.





Excess GM 2.606m


10.77m


Draught Fwd11.97m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

1013/14

500

53

54 52

10

10

13

14

7.28m

Location of Damage


LNG Cargo




This is underwater damage to 2 and 3 port ballast tanks.





Excess GM 1.889m

Trim -0.06.m Draught Aft9.67m

MidshipsDraught

9.64m

Draught Fwd9.61m

18.1°

0.8

1.0

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

GZ(Metres)

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


Location of Damage

LNG Cargo

5153

10

10

10

3.53m




This is underwater damage to 3 and 4 ballast tanks and the ductkeel.





Excess GM 2.606m

Trim -1.73mDraught Aft

12.03m


Draught Fwd10.30m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

53

500

Location of Damage


LNG Cargo

56 54

55

1013/14

10

10

13

14

6.16m

Draught Aft10.48m

MidshipsDraught

9.61m

Draught Fwd8.74m

17°

0.8

1.0

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

GZ(Metres)

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


5355

Location of Damage

LNG Cargo

10

10

10

3.15m




This is underwater damage to 3 and 4 port ballast tanks.





Excess GM 1.919m

Trim -1.74m

7.2.22Damaged compartments 55, 56, 12 and 500.

This is extensive underwater damage to 4 port and starboardballast tanks, the duct keel and extending through to the engineroom double bottom tank (void space). Secondary floodingoccurs in the engine room.





Excess GM 2.042m

Trim -2.10m

Draught Aft11.57m


Draught Fwd9.47m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

GZ(Metres)

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

10

10

13

14

1013/14

6.64m

Location of Damage


LNG Cargo

500

56

55



Draught Aft13.93m


Draught Fwd6.61m

12°

GZ(Metres)

0.6

0.4

0.2

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

40 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


Location of Damage


LNG Cargo

203

200

55

10

10

10

1.3m




This is extensive underwater damage to 4 port ballast tank andthe engine room double bottom tank. Secondary flooding occursin the engine room and machinery store.





Excess GM 0.813m

Trim -7.32m

Draught Aft13.46m


Draught Fwd7.26m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

204

200

10

10

11

11

11

4.86m

Location of Damage


LNG Cargo




This is extensive underwater damage to the engine room doublebottoms with secondary flooding to the engine room andmachinery store.





Excess GM 2.042m

Trim -6.20m

Draught Aft13.57m


Draught Fwd7.21m

0.1°

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve


204

203

200

10

10

11

11

11

4.75m

Location of Damage


LNG Cargo




This is extensive underwater damage in the engine roomtowards the aft end. secondary flooding occurs in the engineroom and machinery store.





Excess GM 2.447m

Trim -6.35m

Draught Aft13.40m


Draught Fwd7.28m

0.2

0.4

0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

GZ(Metres)

0.240 8 12 16 20 24 28 32 36 40 44 48 52

Heal (Degrees)

GZ Curve

Angle of Loll 0°

0°

200

10

10

11

11

11

4.93m

Location of Damage


LNG Cargo




This is extensive underwater damage near the propeller in theengine room. Secondary flooding occurs in the engine room andmachinery store.





Excess GM 1.506m

Trim -6.11m