gs ep saf 334 - foam fire extinguishing systems · 5.2 medium- and high-expansion foams ... •...

Exploration & Production

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GS_EP_SAF_334_02_EN.doc

GENERAL SPECIFICATION

SAFETY

GS EP SAF 334

Foam fire extinguishing systems

02 10/05 Addition of EP root to document identification

01 10/03 Change of Group name and logo

00 04/01 Old TotalFina SP SEC 334

Rev. Date Notes


General Specification Date: 10/05

GS EP SAF 334 Rev: 02


GS_EP_SAF_334_02_EN.doc /28

Contents

1. Scope .......................................................................................................................4 1.1 Purpose of the specification...............................................................................................4

1.2 Applicability........................................................................................................................4

2. Reference documents.............................................................................................4

3. Terminology and definitions ..................................................................................5

4. Foam extinguishing agents....................................................................................7 4.1 Expansion ..........................................................................................................................7

4.2 Foam concentrate type ......................................................................................................8

4.3 Other foam properties......................................................................................................10

4.4 Compatibility ....................................................................................................................11

5. Foam application rates .........................................................................................11 5.1 Low-expansion foams......................................................................................................11

5.2 Medium- and high-expansion foams................................................................................13

6. Foam production systems....................................................................................14 6.1 General ............................................................................................................................14

6.2 Water supply....................................................................................................................15

6.3 Concentrate tank .............................................................................................................15

6.4 Foam proportioning..........................................................................................................15

6.5 Foam makers...................................................................................................................18

6.6 Foam distribution and discharge......................................................................................19

6.7 Mobility of systems ..........................................................................................................20

6.8 Foam production systems schemes ................................................................................20

6.9 Foam station ....................................................................................................................21

7. Applicability to typical equipment .......................................................................23 7.1 Liquid hydrocarbon storage .............................................................................................23

7.2 Helidecks .........................................................................................................................26

7.3 Enclosures .......................................................................................................................26

7.4 Drilling mud systems........................................................................................................27

7.5 High value equipment ......................................................................................................27






7.6 Other storage...................................................................................................................27

7.7 Loading operation on jetty ...............................................................................................27

Appendix 1 Typical foam station.............................................................................28






1. Scope

1.1 Purpose of the specification The purpose of this general specification is to define the requirements for the design of foam fire extinguishing systems for oil and gas production, processing and storage installations.

Foam extinguishes fire in four ways:

• Smothering fire and preventing air from mixing with flammable vapours

• Control and reduction of flammable vapours release

• Separating flames from fuel surface

• Providing some cooling effect for fuel and adjacent metal surfaces.

Foam is not suitable for:

• Three-dimensional flowing liquid-fuel fires or for gas fires

• Chemicals releasing sufficient oxygen to sustain combustion

• Energised un-enclosed electrical equipment

• Water-reactive metals

• Water-reactive materials.

1.2 Applicability This specification is not retroactive. It shall apply to new installations and to major modifications of existing installations. This specification applies to onshore and offshore installations.

This specification does not cover:

• Selection of equipment to be protected by foam application (refer to GS EP SAF 311)

• Chemical foams systems (which are considered as obsolete)

• Mobile foam-generating systems.

2. Reference documents The reference documents listed below form an integral part of this General Specification. Unless otherwise stipulated, the applicable version of these documents, including relevant appendices and supplements, is the latest revision published at the EFFECTIVE DATE of the CONTRACT.

Standards

Reference Title

Not applicable






Professional Documents

Reference Title

API 14G Fire prevention and Control on open Type Offshore Production Platform

API 14J Design and Hazard Analysis for Offshore Production Facilities

Regulations

Reference Title

NFPA 11 Low-Expansion Foam

NFPA 11A Medium and High-Expansion Foam Systems

NFPA 11C Mobile Foam Apparatus

NFPA 16 Installation of Deluge Foam - Water Sprinkler and Foam - Water Spray Systems

NFPA 18 Standard on wetting agents

NFPA 30 Flammable and Combustible Liquids Code

NFPA 59 Storage and Handling of Liquefied Petroleum gases at Utility Gas Plants

Codes

Reference Title

IP Code Part 15 Area Classification Code for Petroleum Installations

Other documents

Reference Title

Safety Concept

Total General Specifications

Reference Title

GS EP SAF 311 Rules for the selection of fire-fighting systems

GS EP SAF 321 Fire pump stations and fire water mains

3. Terminology and definitions Concentration Percentage of foam concentrate contained in a liquid foam solution

(typically ranging from 3 % to 6 %) before it is expanded into foam






Expansion Ratio of final foam volume to original foam solution volume

Eductor Device using the Venturi principle to introduce a proportionate quantity of foam concentrate into a water stream. The wording "inductor" is frequently misused

Fluid category As per French regulation, hydrocarbons fluids are sorted as follows: • Fluid category A: liquefied hydrocarbons with True Vapour Pressure

(TVP) > 1 bara at 15°C - A1: Liquefied at t < 0°C - A2: Liquefied in other conditions

• Fluid category B: Liquid hydrocarbons with flash point < 55°C

• Fluid category C: Liquid hydrocarbons with: 55°C ≤ flash point < 100°C- C1: With flash point ≤ storage temperature - C2: With storage temperature < flash point

• Fluid category D: liquid hydrocarbons with: 100°C ≤ flash point: - D1: With flash point ≤ storage temperature - D2: With storage temperature < flash point As per British regulation, hydrocarbons fluids are classified as follows:

• Fluid class 0: Liquefied Petroleum Gases (LPG)

• Fluid class I: Liquid hydrocarbon with a flash point below 21°C

• Fluid class II: Liquid hydrocarbon with a flash point above 21°C but below 55°C - II(1): Stored below flash point - II(2): With storage temperature above flash point

• Fluid class III: liquid hydrocarbon with a flash point above 55°C - III(1): Flash point above 55°C but below 100°C and stored below

flash point - III(2): Same as III(1) but stored above flash point

• Unclassified: Liquid hydrocarbon with a flash point above 100°C. Unclassified petroleum liquids should be considered as class III(2) when handled at, or above, their flash point temperature

As per American regulation (NFPA), hydrocarbons fluids are classified as follows:

• Fluid class I - IA: Liquid having a flash point below 22.8°C and a boiling point

below 37.8°C - IB: Liquid having a flash point below 22.8°C and a boiling point

above 37.8°C - IC: Liquid having a flash point at or above 22.8°C and below 37.8°C

• Fluid class II: Liquid having a flash point at or above 37.8°C and below 60°C






• Fluid class III - IIIA: Liquid having a flash point at or above 60°C and below 93°C - IIIB: Liquid having a flash point at or above 93°C.

Foam A mixture of air, water and foam concentrate forming a stable aggregation of small bubbles of low density that exhibits a tenacity for covering horizontal surfaces.

Foam, concentrate

A concentrated liquid foaming agent as received from the MANUFACTURER. In this document, "foam concentrate" and "concentrate" are used interchangeably.

Foam, solution A homogeneous mixture of water and foam concentrate. In this document, "foam solution" and "solution" are used interchangeably.

Submergence Completion of the filling of an enclosure with a high-expansion foam.

Surfactant Chemical agent decreasing the surface tension and increasing the wetting capability, and additionally the penetration into porous solid materials.

4. Foam extinguishing agents

4.1 Expansion

4.1.1 General Foams are sorted out into three expansions levels:

• Low-expansion: expansion < 20 (vol./vol.)

• Medium-expansion: 20 < expansion < 200

• High-expansion: 200 < expansion.

Their adequate use is summarised here-after.

4.1.2 Low expansion Low-expansion foams are the most widely used for pool fires of liquid hydrocarbons. Their main effectiveness in fire prevention, control and fire-fighting is that some of them (AFFF, FFFP) can actually spread and wet the surface of most fuels, and form a thin layer acting as an effective vapour seal arresting the combustion and suppressing the evolution fuel vapours. They can be sprayed at large distances, they stick to equipment and they also provide a cooling coat onto the equipment.

4.1.3 Medium expansion Medium-expansion foams were developed to meet the need for foams that were more wind resistant than high-expansion foam for outdoor applications. Medium-expansion foams can be used on solid fuel and liquid fuel fires where some degree of in-depth coverage is necessary, for instance engine enclosed or semi-enclosed rooms, transformer rooms, etc.

Medium-expansion foams can also provide quick and effective coverage of flammable liquid spill fires (pool fires) or some toxic liquid spills where rapid vapour reduction is essential.






4.1.4 High expansion High-expansion foams are agents for control and extinguishing of Class A (combustible material) and Class B (flammable fluids) fires and are particularly suited as flooding agent in confined spaces. Although application onto a LNG spill will accelerate LNG vaporisation, high expansion foam can be used to provide vapour dispersion control for LNG spills, forcing the vapours upwards once they have been heated up by the foam itself. High expansion foams can also be used on LPG pools for the same purposes but the risks in doing so are increased as compared to LNG because of the higher MW of LNG vapours. If the decision to proceed is taken nevertheless, then the foam application system shall be sized in such a way that a foam blanket at least 1.5 m thick can be laid on top of the LPG pool.

High-expansion foams and, to a lesser extent, medium-expansion foams, have the following effects on fires:

• Where generated in sufficient volume, they can prevent the free movement of air, and if accumulated in depth, they provide an insulating barrier, and prevent fire from spreading.

• Where forced to the heart of the fire, part of the water in the foam is converted to steam, thus reducing the oxygen rate; additionally the conversion of water to steam absorbs heat.

• Due to their low surface tension, the solution that is not converted into steam tends to penetrate combustible materials and plug them off.

• Class A fires are controlled when the foam completely covers the burning material. If the foam is maintained long enough, the fire can be extinguished.

• Class B fires can be extinguished when the surface is cooled below the flash-point, or when a foam blanket of sufficient depth is established over the liquid surface.

As general rule, high-expansion foam shall not be used outdoor because of the effects of wind and the lack of confinement.

4.2 Foam concentrate type There are different types of foam concentrates that can be sorted out as follows:

• Proteins and Fluoro-proteins

• Synthetic: Aqueous Film Forming Foam (AFFF)

• Film-Forming Fluoro-Proteins (FFFP)

• Alcohol-resistant.

4.2.1 Protein and Fluoro-protein foams They are based on hydrolysed proteins from natural material. In addition and contain stabilising and inhibiting products to protect from freezing, prevent corrosion, resist bacterial decomposition, control viscosity, and to ensure readiness for use under emergency conditions. They are not expensive and have a good stability and fire resistance. They have a limited storage time capability and are increasingly replaced by AFFF.

Fluoro protein foams are essentially a compromise between protein and chemical foams such as AFFF (see section 4.2.2). In addition to proteins, they contain a synthetic fluorinated surfactant additive that decreases the surface tension and enhances the surface coverage effectiveness and the penetration into materials. They are cheaper and have a better fire resistance and stability than synthetic foams.






Protein and Fluoro-protein concentrates produce low expansion foam (6 to 12).

4.2.2 Synthetic foams Synthetic-foam concentrates are based on foaming agents other than hydrolysed proteins and include the following types.

Under normal storage conditions, the life duration of synthetic foam concentrates is significantly higher than protein or fluoro-protein concentrates even when mixed with water. For this reason they are more suitable for such application as twin-agent skid.

4.2.2.1 Aqueous-Film Forming Foams (AFFF) They are the most commonly used for low-expansion foams. They are based on fluorinated surfactants, plus stabilising and anti-freezing additives. They can be regarded as super detergents which, in solution, have such a low surface tension that they can actually spread and wet the surface of most fuels, and form a thin layer acting as an effective vapour seal arresting the combustion. They should preferably be applied as a spray.

Their main advantage is the very high speed of fire control they provide. They are particularly valuable for first-aid use in dealing with spill fires without any appreciable depth. They can be used with conventional water spray nozzles on fixed installations (deluge systems) and/or water monitor/hose reels.

They produce low expansion foam (6 to 12).

4.2.2.2 Medium- and high-expansion foams They are usually derived from hydrocarbon surfactants. They require specially designed foam generators, which can be air-aspirating or blower-fan type. They are mainly used to fill enclosures.

They can have expansion up to 1000.

4.2.2.3 Other synthetic foams Other synthetic foam concentrates are based on hydrocarbon surface active agents, and are listed as wetting agents, foaming agents, or both. In general, their use is limited to portable nozzle foam application for spill fires. For further details, refer to NFPA 18.

4.2.3 Film-Forming Fluoro-Proteins (FFFP) They can be considered as an adequate alternative to AFFF (see section 4.2.2). They consist of fluorinated surfactants to produce an aqueous film suitable for suppression of hydrocarbon vapours. They utilises a protein base plus stabilising and inhibiting additives to protect against freezing, corrosion, and bacteria. They can be used with conventional water spray nozzles on fixed installations (deluge systems).

4.2.4 Alcohol-resistant foams They are used for fighting fires on water-soluble materials where the above foams are not effective. They can be of the main three types:

• Natural polymers such as proteins or fluoro-proteins (see section 4.2.1), in addition with alcohol-insoluble materials that precipitate as an insoluble barrier in the bubble structure






• Synthetic concentrates (see section 4.2.2) containing a gelling agent surrounding the foam bubbles and forms a protective surface at the surface of the water-soluble spill

• Natural polymers such as fluoro-proteins (see section 4.2.1), and containing a gelling agent acting as above.

4.3 Other foam properties

4.3.1 Spread Foams shall have good spreading capabilities, which can be quantified by the following:

• Surface tension: < 25 Pa

• Kinetic viscosity: < 1.15 10-4 m2/s (1.15 Stoke) @ 0°C < 0.45 10-4 m2/s (0.45 Stoke) @ 20°C.

4.3.2 Non-corrosiveness Foams shall have a pH comprised between 6 and 7.

4.3.3 Concentration Concentration of foam concentrate in the solution is determined by the type of foam concentrate used. It generally ranges from 3 % to 6 %. This information is provided by the VENDOR. The foam production facility shall be designed for a given foam concentrate concentration and it is necessary to ensure that the right concentration shall be used throughout the life of the facility.

4.3.4 Burn back resistance Ability of a foam blanket to resist direct flame impingement such as would be experienced in a partially extinguished petroleum fire. This information is provided by the VENDOR. Burn back resistance is also linked with the drainage rate (see below).

4.3.5 Drainage rate Rate at which solution drains from a foam. A single value is used to express the drainage rate and is called "25 % drainage time" which is the time (in minutes) it takes for 25 % of the total solution contained in the foam to drain. A typical value is 4 minutes however drainage rate varies with the type of concentrate and the expansion factor: the highest the expansion factor and the lowest will be the drainage time. It ranges from a few seconds for a high expansion foam to several hours for a very low expansion foam. Free flowing foams capable of quickly forming a cohesive blanket around obstruction loose their water rapidly, conversely foams that retain their water for a long time are stiff and do not spread rapidly over the burning area.

4.3.6 Life duration Foam concentrates loose their quality over long periods of storage time. Typical life duration ranges between one and two years but can be drastically increased if elementary precautions are taken such as protecting the concentrate storage from sun (or flare) radiation.

4.3.7 Usable temperature Foam concentrate performances are drastically impacted by temperature. Usable temperature varies with the chemical type of concentrate but a typical temperature range for best






performance is 0°C to 50°C. This information is provided by the VENDOR and shall be compatible with the prevailing weather conditions.

4.4 Compatibility

4.4.1 Compatibility of foam concentrates Precautions shall be taken to avoid the risk of mixing concentrates (or solutions) of different expansions characteristics.

With the exception of synthetic foams for specific uses (see section 4.2.2) and alcohol-resistant foams (see section 4.2.4), it can be assumed, at the design stage, that the different chemical types of low-expansion foams are compatible each-other, but this shall be checked at the engineering stage.

4.4.2 Compatibility of foam with dry chemical agents Some expanded foams might not be compatible with all dry chemical agents. The MANUFACTURERS of the dry chemical and foam concentrate to be used shall confirm that their products are mutually compatible. AFFF and FFFP concentrates are generally compatible with dry chemical agents.

5. Foam application rates

5.1 Low-expansion foams

5.1.1 General The critical application rate (l/m2/min) is defined as the rate below which extinction is impossible. It shall be multiplied by a safety factor allowing for foam lost from spraying and possible yield drops of the materials.

The safety factors are depending on the release method (spreading or spraying or sprinkling in combination with fire water). The application rate shall be equal to, or greater than, the critical application rate multiplied by the safety factor.

In addition, it is emphasised there is a maximum practicable size of a pool fire that can be extinguished with foam, about 7000 m2, regardless of the foam type and application rate.






5.1.2 Application rates for spreading

Concentrate Critical rate (solution) l/m2/min

Safety factor Required rate

(solution) l/m2/min

Protein 2.5 1.2 3.0

Fluoro-protein 1.8 1.2 2.2

Synthetic - AFFF - Medium expansion - Low expansion

1.2 1.0 1.8

1.2 1.2 1.2

1.5 1.2 2.2

FFFP 1.2 1.2 1.5

Alcohol-resistant 2.5 1.2 3.0

5.1.3 Application rates for spraying

Concentrate Critical rate (solution) l/m2/min

Safety factor Required rate

(solution) l/m2/min

Protein 2.5 1.5 3.8

Fluoro-protein 1.8 1.5 2.7

Synthetic - AFFF - Medium expansion - Low expansion

1.2 1.0 1.8

1.5 1.5 1.5

1.8 1.5 2.7

FFFP 1.2 1.5 1.8

Alcohol-resistant 2.5 1.5 3.8

5.1.4 Foam-water systems It is COMPANY's policy to avoid the installation of two distinct fire water distribution network on board their ships (specifically FSO and FPSO) and as a consequence foam-water system shall be implemented on board these vessels.

As general rule, where foam solution is discharged in combination with water by sprinklers or spray systems, the design discharge rate shall be at least 6.5 l/m2/min. The foam concentrate storage shall be designed for a period of application of at least 10 minutes, based on this minimum rate and over the entire area to be protected.

For further details, refer to NFPA 16.






5.2 Medium- and high-expansion foams

5.2.1 Total flooding systems In order to provide adequate protection, sufficient medium–or high–expansion foam shall be discharged at a rate adequate to fill the enclosure to an effective depth above the hazard and before an unacceptable degree of damage occurs.

5.2.1.1 Foam depth For high-expansion foams applied to Class A fires, the minimum depth of foam shall be 110 % the highest hazard, and at least 60 cm. For medium- or high-expansion foams applied to Class B fires, the minimum depth can be considerably higher and shall be determined by tests.

5.2.1.2 Submergence time For high-expansion foams, maximum time to achieve complete submergence of the enclosure shall meet the recommendations of NFPA 11A, summarised in next table.

Light or unprotected steel construction

Heavy or protected or fire resistive construction

Sprinklered Not sprinklered Sprinklered Not

sprinklered

Combustible materials 4 to 7 min. 3 to 5 min. 6 to 8 min. 4 to 6 min.

Combustible liquids 4 min. 3 min. 5 min. 3 min.

Flammable liquids 3 min. 2 min. 5 min. 3 min.

5.2.1.3 Rate of discharge For medium-expansion foam, the rate of discharge shall be determined by tests.

For high-expansion foam, the rate of discharge shall be consistent with the here-above maximum submergence times, considering:

• The break-down effects of sprinklers discharge, if any

• The compensation for normal foam shrinkage

• The compensation for foam leakage, if any.

The rate of discharge of the foam shall be at least:

Rate = (Rs + V/T ) x Cn x Cl

where: Rate (m3/min)

V: Submergence volume (m3)

T: Submergence time (min)

Rs: Rate of foam break-down by sprinklers (m3/min)

Cn : Compensation for normal foam shrinkage

Cl: Compensation for leakage.






Cn shall be taken equal to 1.15 unless otherwise specified.

Cl shall be taken as 1.0 for a totally tight and enclosed room, and 1.2 for a building with openings normally closed. For other cases, it shall be either specified or assumed from experience.

Rs shall be specified by the SUPPLIER.

5.2.1.4 Quantity Sufficient high-expansion foam quantity shall permit continuous operation of the entire system for 25 minutes or four times the submergence time, whichever is less and in any case at least for 15 minutes.

After extinguishing and in order to avoid any risk of spontaneous re-ignition, foam shall be maintained at the nominal submergence volume for at least 60 minutes for un-sprinklered locations and 30 minutes for sprinkled locations.

For medium-expansion foam, the quantity and the maintenance time shall be determined by tests.

5.2.2 Local application systems A local application system consists of a fixed foam generating device that is such arranged as to discharge foam directly onto confined but not totally enclosed fires or spills.

On flammable or combustible fluids and solids, sufficient high-expansion foam shall be discharged at a rate to cover the hazard to a depth of at least 60 cm within 2 minutes. Sufficient high-expansion foam quantity shall permit continuous operation of the entire system for at least 12 minutes.

High-expansion foams have proven effective in reducing down-wind vapour concentration from LNG spills in confined areas up to 100 m2. The application rates and the quantity shall be determined by tests following the recommendations of NFPA 59A.

6. Foam production systems

6.1 General Foam production systems consist in the set of the following items:

• Water pump (or pressurised water collector). Refer to section 6.2

• Concentrate tank. Refer to section 6.3

• Foam proportioning. Refer to section 6.4

• Foam makers. Refer to section 6.5

• Foam distribution and discharge. Refer to section 6.6

The operation of the foam production systems is depending on their mobility: fixed, semi-fixed, mobile and portable. For further details, refer to section 6.7.






The main foam production systems schemes are:

• Low expansion, centralised (generally fixed)

• Low expansion, de-centralised (generally semi-fixed, mobile or transportable)

• High expansion (of any type of mobility).

For further details on foam production system schemes, refer to section 6.8.

6.2 Water supply The water supply to foam systems can be hard or soft, fresh, brackish or seawater, but shall be of suitable quality so that adverse effect on foam formation or stability cannot occur. In particular, the use of seawater may decrease slightly the efficiency of the foam, but is considered as acceptable, provided it has been specified to the SUPPLIER.

No corrosion inhibitor, emulsion breaking chemicals, or any other additive can be present without prior consultation with the foam concentrate SUPPLIER. Optimum foam production is obtained using water at temperatures between 4°C and 38°C.

6.3 Concentrate tank Most of concentrates are generally to be diluted into water in a proportion ranging from 3 % to 6 %. Within this range the concentration is only an economic choice. Generally, 3 % concentrates are used since they are less than twice the price of 6 % concentrates, and because they require smaller, cheaper and lighter tanks and associated piping and equipment. For information 1 % concentrate for AFFF foam is marketed by some VENDORS but in the absence of experience this product is not recommended.

The amount of concentrate shall be at least sufficient for the largest hazard to be protected, or for the group of hazards that are to be protected simultaneously. The available supply of concentrate in the system, V, shall be at least:

V = S x Rate x t x C

where: S: Surface to protect (m2)

Rate (l/m2/min)

t: Application time (min)

C: Concentration of concentrate in the solution

The concentrate shall be stored in a place where the temperature is maintained between 2°C and 38°C, unless otherwise specified by the SUPPLIER. To avoid deterioration of concentrate by atmosphere, the storage vessel shall have an expansion dome with a volume of at least 2 % of the total capacity (this dome can be combined with the manway). The storage vessel shall also be equipped with a breathing valve set typically at ± 5 mbar whose capacity shall be driven by the vessel filling/emptying rate. If installed in the open air, the storage vessel shall be suitably shielded to avoid concentrate deterioration by sun radiation. Conversely in cold climate an adequate heating system and piping heat tracing shall be provided.

6.4 Foam proportioning The most commonly used method of foam proportioning is the in-line eductor (see section 6.4.1). Others methods can be used where in-line eductor method is not achievable or not efficient enough; they can be one of the following in sections 6.4.2 to 6.4.5






6.4.1 In-line eductor A Venturi eductor is located in the water supply line to the foam maker. The eductor is connected by single or multiple lines to the concentrate tank. It is pre-calibrated, and it may be adjustable. Its main disadvantages are the pressure drop across it (about 33 %), which shall be taken in account in the design and its inability to maintain proportion when the water flow rate changes. Another limitation of use is caused by the maximum allowable difference of elevation between the eductor and the concentrate tank. In practice it shall not exceed 3 metres.

Where practicable, it is the preferred method since the simpler the safer.

6.4.2 Direct pumping proportioners A suitably designed positive displacement pump in the water supply line is coupled to a second, smaller, positive displacement concentrate pump to provide proportioning. This system allows a constant proportion rate even if the flow rate varies.

6.4.3 Metered proportioning

WATER PRE-MIX

CONTROLVALVE

CONCENTRATEDEMULSIFIER

PUMP

Control lineControl line

DRAIN

CONCENTRATEDEMULSIFIER TANK

VENTURI A separate concentrate pump is used to inject concentrate into the water stream. The control valve can be actuated either by a conventional controller (not recommended) or by direct application of the fluid pressure onto a diaphragm (as shown on sketch). In that later case the system is referred to as a balanced pressure proportioning system. This system allows a permanent proportion rate even if the water flow rate varies.






6.4.4 Pressure proportioners

WATER PRE-MIX

Pre

ssur

isat

ion

line


VENTURI

WAT

ERC

ON

CE

NTR

ATE

SOLU

TIO

N

A suitable method is provided for displacing concentrate from a closed tank by water. The proportion rate changes if the water flow rate varies.

6.4.5 Around the pump proportioners

WATER

PRE-MIX

WATERPUMP


EDUCTOR

ME

TER

ING

VA

LVE

SH

UT

OFF

VA

LVE

The differential pressure between the discharge and suction of the water pump is used to induct concentrate into water by orifices. This arrangement is especially suitable when pressure losses may constitute an inconvenience. This system allows a permanent proportion rate even if the water flow rate varies.






6.5 Foam makers

6.5.1 General Where high-expansion foams are used, it is essential that the air forced to make foam does not promote hazards. Air from outside the hazard area shall be used for foam generation unless it is established that air from inside the hazard area can be successfully employed.

Where foam is discharged into enclosed or semi-enclosed areas, vents shall be suitably provided to avoid re-circulation of combustion products into the air inlets of the foam generators.

6.5.2 Foam maker types The methods used to generate foam include the following types.

6.5.2.1 Foam hoses In practice, the nozzle reaction limits the solution flow to about 1000 l/min. However, the foam hoses cannot be considered as the primary means of protection or large areas or equipment, such as storage tanks over 9 m in diameter or 6 m in height.

6.5.2.2 Fixed foam nozzles A specially designed nozzle designed to aspirate air that is connected to a supply of foam solution.

6.5.2.3 Pressure foam makers A foam maker utilising the Venturi principle for aspirating air into a stream of concentrate solution (this device is suitable for medium expansion foams). In this configuration a specially designed section makes jet streams of foam solution to create a low pressure region which aspirate sufficient amounts of air that is then entrained to produce foam. With such a design the expansion is limited to 250.

WATER

CONCENTRATE

AIR

AIR

SOLUTION

6.5.2.4 Foam monitors A large-capacity foam stream from a nozzle that is supported in position and can be directed by one person. In practice, the range of reach of foam monitors is limited to less than 30 meters, and they cannot be considered as the primary means of protection of large areas or equipment, such as storage tanks over 18 m in diameter.






6.5.2.5 Blower type They may be fixed or portable. In this configuration the foam solution is discharged as a spray onto screens through which an air stream developed by a fan or a blower is passing. The blower may be powered by electric motors, internal combustion engines, air, gas, or hydraulic or water motors. Most commonly, a water motor is powered by the foam solution. In this design the expansion has no practical limitation (up to 1000).

WATER

CONCENTRATE

AIR

AIR

SOLUTION

6.5.2.6 Foam-water spray nozzles/sprinklers They are air-aspirating discharge devices, able to distribute foam, or water, in a special direction. They differ in design from foam-water nozzles/sprinklers.

6.5.2.7 Non-air aspirating spray nozzles They discharge foam solution as AFFF and FFFP. They have special applications as the preventive protection of the skirts of liquid hydrocarbon storage tanks. The use of conventional water spray nozzles is possible, pending VENDOR's approval.

6.6 Foam distribution and discharge

6.6.1 General The piping normally empty when not in use shall be of a metallurgy approved by a COMPANY's specialist. The piping shall slope 1 % downwards to allow draining and rinsing after use. Fittings for adequate draining and rinsing after tests or use shall be provided.

6.6.2 Distribution and discharge of foam to storage tanks The distribution and discharge of foam to storage tanks containing liquid hydrocarbons require the specific devices downstream of foam makers:

6.6.2.1 Foam discharge on the rim seal (floating roof tank) Special foam barrels shall be provided to distribute and discharge the foam downstream the foam makers, onto the whole circumference. A breakable seal shall be provided on the concentrate line, at the inlet of the foam box.

6.6.2.2 Sub-surface application Discharge of foam into a storage tank from an outlet near the tank bottom.

Note: Semi sub-surface application systems where foam is discharged at the liquid surface within a storage tank from a floating hose that rises from a piped container near the tank bottom are not recommended.






6.7 Mobility of systems

6.7.1 Fixed systems These systems are complete installations in which foam is piped from a central foam station, discharging through fixed delivery outlets to the hazard to be protected. Any required pumps shall be permanently installed. See section 6.9.

6.7.2 Semi-fixed systems The hazard area is equipped with fixed discharge outlets connected to piping that terminates at a safe distance. Foam-producing materials are transported to the scene after the fire starts and are connected to the piping.

6.7.3 Mobile systems These systems include any wheel mounted foam-producing unit. They can be self-propelled or towed by a vehicle. These units can be connected to a suitable water supply or can utilise a premixed foam solution.

6.7.4 Portable systems These systems are of the type where the foam-producing equipment and materials, hoses, etc., are transported by hand. In practice, the nozzle reaction limits the solution flow to about 1000 l/min.

6.8 Foam production systems schemes

6.8.1 Centralised foam production

WATER

WATER PUMP

CONCENTRATE TANK

FOAMMAKER

FOAMMAKER

FOAMMAKER

SOLU

TIO

N D

ISTR

IBUTION PIPING

In this configuration the eductor is close to the water pump and the solution is distributed through a combination of fixed pipes, hoses, etc., up to the foam makers, either fixed or mobile.

Main applications are large and specific installations where the risks are identified, such as a drilling mud module. This arrangement requires special care during design to ensure that the adequate concentration shall be delivered where needed.






6.8.2 Decentralised foam production

WATER

WATER PUMP

CONCENTRATE TANK

FOAMMAKER

FOAMMAKER

WAT

ER

DIS

TRIBUTION PIPING

CONCENTRATE TANK

In this configuration the concentrate is distributed by fixed pipes to ejectors close and upstream of the foam makers.

Main applications are large and specific installations, where the risks are varied and independent.

6.8.3 Line generators In this configuration the eductor and foam generators are close to the water pump and the foam is distributed by fixed pipes to a set of fixed foam barrels. This configuration is not recommended by COMPANY, considering the large pipe diameter it requires. Centralised foam production shall be given preference instead (see section 6.8.1).

6.9 Foam station

6.9.1 Purpose The foam station is required to supply foam solution to a specific area of the facilities wherever a fire is to be extinguished and/or to provide the fixed extinguishing system with foam solution until external support may intervene. The design of the foam station shall be such that foam solution can be supplied wherever needed in less than two minutes after the alarm has been given. The foam station shall be located at a safe distance of the place where the fire may occur.

6.9.2 Components A foam station consists of the following components (refer to Appendix 1 (“Typical foam station”), for further details):

6.9.2.1 Concentrate tank Refer to section 6.3, for further details on the concentrate tank. The concentrate tank shall be built of GRE or stainless steel (grade to be approved by COMPANY's specialist) or any other suitable alternative approved by COMPANY's specialist.

6.9.2.2 Concentrate pumps Two 100 % capacity pumps shall be provided. They shall discharge at a nominal pressure 2 barg above the water pressure at the eductor. As a general rule both pumps shall be electric






driven, connected to the essential power system. However one of the pump may supplied by an independent and dedicated battery set if it is not established that essential power shall be available in all fire scenarios. In case the concentrate flow rate does not exceed 15 m3/h, it is acceptable to install pumps driven by a hydraulic motor using the fire water itself as a source of power. In order to avoid plugging, the pumps shall take concentrate from 100 mm above the bottom of the storage vessel.

6.9.2.3 Proportioner The concentrate under pressure coming from the pump shall be injected into the fire water stream by means of a proportioner designed to handle flow rate from 100 % down to 10 % of the design capacity under the prevailing operating pressure conditions. For reasons of pressure drop and poor flow rate flexibility, the use of an eductor is not recommended for this specific application. A manual metering valve shall be installed upstream of the proportioner to allow for concentration adjustment (typically from 3 % to 6 %).

6.9.2.4 Control panel A control panel whose functions are described below in 6.9.3 shall be provided. It shall be supplied with power coming from the emergency power supply or a set of independent batteries designed for four hours of operation.

6.9.2.5 Automatic valves The concentrate suction line from the tank to the pumps shall be equipped with an automatic valve so that the piping downstream of the tank could be maintained full of fresh water while the system is not operating. In a similar fashion the concentrate injection line shall be fitted with an automatic valve upstream of the metering valve to avoid leakage of concentrate to the normally dry section of the fire water network, downstream of the deluge valve. A third automatic valve, normally closed, shall be provided on the recycle line and shall only open upon actuation on the switch over "foam/water" pushbutton (see section 6.9.3)

6.9.2.6 Piping Suitable flushing and testing lines and valves shall be supplied. Piping in contact with concentrate shall be stainless steel.

6.9.3 Mode of operation The foam station shall start operation only after the fire water flow has been established. The concentrate pump shall start after the suction valve has been opened and the concentrate discharge valve shall open only once it has been established that the concentrate pump is running. The opening of the concentrate discharge valve shall be automatic.

The concentrate pump discharge line shall be fitted with a pressure switch that will start the stand by pump if the first pump has failed to build up the normal operating pressure 20 seconds after the foam station has been activated.

Pushbuttons shall be provided, both in the main control room and on the local control panel to start the pumps manually, provided the deluge valve has been opened.

A pushbutton shall be provided in the main control room to switch over from "foam" mode back to "water" mode. When activated the concentrate discharge valve shall close but the pump shall continue to operate circulating the concentrate back to the storage vessel. Concentrate pump shutdown shall be from the local control panel only.






7. Applicability to typical equipment

7.1 Liquid hydrocarbon storage The combination of French regulation, considering the use of AFFF or FFFP concentrates, and NFPA 11 shall be used as a basis for the recommendations applicable to liquid hydrocarbon storage and can be summarised as follows:

7.1.1 Methods of protection The protection of liquid hydrocarbons storage tanks consists in an adequate combination of a preventive cooling effect (Q1), provided by water and of a control and/or extinguishing effect (Q2) provided by foam discharge.

The foam can be discharged by various means, including:

• Foam monitors and hand-lines

• Surface application with fixed foam discharge outlets

• Sub-surface application

• Semi-sub-surface application.

7.1.2 Foam monitors and hand-lines Foam monitors and hand-lines have practical limitations and cannot be considered as the primary means of protection for large tanks (refer to section 6.5). Nevertheless, they shall be installed as supplementary means of protection as per local regulation (if any), or otherwise by following the recommendations of NFPA 11 and NFPA 30.

7.1.3 Fixed foam discharge The weak point of storage tanks is the junction of the vertical skirt and the roof. Depending whether the roof is of a fixed-type, or of a floating-type, and in this latter case, depending on the design of the seal of the floating roof, there is a great variety of fixed foam discharge outlets. They shall comply with the recommendations of NFPA 11.

Foam shall be discharged:

• Onto a bund on fire

• And into the annulus ring of floating-roofs of the tanks on fire

• On the skirts of the tanks in a bund on fire.

7.1.4 Sub-surface application Sub-surface foam injection systems are suitable for protection of liquid hydrocarbons fixed-roof tanks in fire. For this purpose, Fluoro-proteins, AFFF and FFFP can be used with low-expansion ratios ranging from 2 to 4. Foam shall be discharged as low as possible but at least 30 cm above the highest possible tank water level.

These systems are not suitable for floating-roof tanks, and shall not be used on alcohol or any polar solvent requiring alcohol-resistant foams.

Other requirements, such as the minimum number of discharge points, the maximum foam velocity, the minimum discharge time, shall comply with the recommendations of NFPA 11.






7.1.5 Fire-water and foam flow rates

7.1.5.1 Scenario #1: Tank on fire

Fixed roof tanks

Item to be protected Cooling effect Q1 (solution flow rate)

Foam Q2 (solution flow rate)

Tank itself 15 l/min/m circumference Discharge into the tank at a rate of: - 2.5 l/min/m2 for fluids B, C1, D1 - 2 l/min/m2 for fluids C2

Tanks closer than: - 2.5 x R (note 1) or - R (note 1) + 15 m

- 10 l/min/m of circumference, 3000 l/min minimum

- or water curtains (note 2)

Floating roof tanks



Tank on fire itself 15 l/min/m circumference Discharge onto the tank rim seal at a rate of (note 3):

- 7.5 l/min/m2 for fluids B, C1, D1

- 6 l/min/m2 for fluids C2

Tanks closer than:

- 2.5 x R (note 1) or - R (note 1) + 15 m

- 10 l/min/m of circumference, 3000 l/min minimum

- or water curtains (note 2).

Note 1: R = radius of tank on fire

Note 2: Recommended rate is 25 l/min/linear m of water curtain

Note 3: Fluid classification as per French regulation.






7.1.5.2 Scenario #2: Bund on fire

Fixed roof or floating roof tanks



Tank inside the bund on fire

Application of foam solution on the tank skirt at a rate of 15 l/min/m of circumference

Bund on fire itself - Fixed foam generators (see formula in note 2)

- Add 50 % for fixed foam monitors

Tanks closer than:

- R (note 1) + 30 m of the edge of the bund on fire

15 l/min/m circumference

Note 1: R = radius of the tank to be protected

Note 2: FBA being the foam solution flow rate in l/min to be applied directly onto the bund, is given by the formula FBA = S x q - Ft with:

• S = Bund surface(m2) minus horizontal surface of the tank(s) in the bund

• q = foam solution application rate:

- 2.5 l/min/m2 for fluids B, C1 and D1

- 2 l/min/m2 for fluids C2

• Ft = Foam solution flow rate applied onto the tank skirt (l/min).

The rates mentioned above, for both fire scenarios, are minimum requirements as per applicable regulation, however they can be made larger if this results in substantial savings in engineering and material costs. In this respect COMPANY's practice shall be to take 15 l/min/m2 (instead of for 10 l/min/m2) cooling water on tank close to a tank on fire to avoid the existence of two different water application systems or the installation of a flow control system.

As per applicable regulations, the whole circumference of the tanks close to a tank on fire or a bund on fire shall be cooled down, even if not exposed to the fire radiation. It is nevertheless recommended at the project stage to verify if cooling only 50 % of the circumference is advisable (tank farm configuration permitting) and acceptable by Authorities. The decision to proceed shall be submitted to DGEP/SE approval.

7.1.6 Water supply and concentrate storage The water supply shall comply with the general rules as defined in GS EP SAF 321 (“Fire pump stations and fire water mains”).






The storage of concentrate shall be sized for:

• 20 minutes for the scenario tank on fire

• 60 minutes for the scenario bund on fire

whichever is the larger and considering the availability of an external support and unless otherwise specified by Local Regulations.

7.2 Helidecks

7.2.1 Definitions Heliports are areas arranged and equipped in such manner that they allow permanently, the landing and taking off of helicopters. They may or may not be fitted with refuelling facilities. Helicopters may shutdown on heliports.

Helidecks are areas that allow temporarily and occasionally the landing and taking-off of helicopters after a preliminary inspection has been carried out by the pilot (e.g. offshore wellhead platform). It shall be assumed that helidecks are not equipped with refuelling facilities. Helicopters do not shutdown on helidecks.

7.2.2 Heliports Heliports shall be provided with two foam monitors or hose, each having its own concentrate tank. The foam expansion shall be medium. The minimum application rate shall be 6 l/m2/min over the whole landing area. The system shall be designed to maintain this application rate for at least 5 minutes. The peripheral area does not require foam application.

In case a heliport cannot be equipped with a fixed foam generation system, then a twin agent skid shall be provided. It shall store enough pre-mix solution (3 % AFFF) to ensure an application of 2 l/m2/min during two minutes and over the whole landing area.

For heliports capable of loading two or more helicopters, or which may be used for public transportation, additional requirements shall be defined in a particular project specification.

7.2.3 Helidecks Considering that there is no personnel present on-board during the take-off and landing phases, COMPANY do not require the installation of any foam fire-fighting system, either fixed or twin-agent, on helidecks.

Helidecks made of aluminium shall be protected with a fixed low expansion foam application system specifically designed to protect the helideck itself and its supporting structure. This system shall be in accordance with applicable Local Regulations.

7.3 Enclosures For the definition of types of enclosure and protection requirement, refer to GS EP SAF 311, “Rules for the Selection of Fire-Fighting Systems”. If applicable, reference shall be made to NFPA 11A and the following guidelines shall be considered:

• High-expansion foam shall be used

• The systems can be either fixed, semi-fixed, mobile or portable; depending on the risk and the volume of foam to be discharged






• The activation shall be automatic for unmanned enclosures (upon fire or gas detection, for instance in a pump shelter) and shall be manual for permanently manned enclosures.

7.4 Drilling mud systems The drilling mud systems shall be equipped with a fixed foam system. Low-expansion foam shall be used. For further details, refer to NFPA 11.

7.5 High value equipment Foam may be supplied by overhead piped systems for protection of hazardous occupancies associated with potential flammable liquid spills in the proximity of high-value equipment, such as export or main transfer pumps, etc. This is not a standard protection system but can be applicable in specific cases upon facility OWNER's decision.

The design, construction, operation and tests of these systems requiring both foam and water spray criteria shall be as per NFPA 16.

7.6 Other storage Storage of other flammable materials such as methanol, glycol, corrosion inhibitors, pour-point depressors, de-emulsifiers and miscellaneous chemicals in barrels can be protected by suitable foam application. Specific requirements shall be carefully assessed and included into the SAFETY CONCEPT.

7.7 Loading operation on jetty The fixed fire-fighting equipment installed on jetties where loading/unloading operation with arms or hoses take place, shall include foam fire-fighting systems, and in particular:

• A below-deck foam-water discharge system, well protected from radiation, that is most suitable to secure a base of operations during a large vessel fire, where a jetty extends away from the shore or has a configuration that would render fire-fighting more difficult

• Fixed foam/water monitors located at least 15 m from the nearest loading arm or hose, and sited high enough to apply foam on the deck of an empty tanker or a minimum height of 12 metres.

The minimum application time shall be 30 minutes. AFFF with a concentration of 3 % is the most suitable foaming agent. The system shall comply with the recommendations of NFPA 11 and NFPA 16.




Appendix 1



Appendix 1 Typical foam station

PG

XARUN

PG

ZSO

PSL

SO

LUTIO

N O

UT

FIRE WAT. IN

&

FireDetection

PBCCR

&

T20"

or

&

or

PBCCR

PBCCR

or

& or

&

XARUN

&

&

or

&

LG

PBCCR

or

PBLOC

PBLOC

+/- 5 mbarNC

NO

Recycle line

Metering valve3% to 6%

Set @10 barg

FOAM"ON"

P1"RUN"

P2"RUN"

FOAM"OFF"

Closeddrain

GRE

SS Flushing connection

P1

P2

NO

NO

NO

NO

From Fire & Gas panel

Proportioner

100 mm

Exp.dome

S