20.104 construction of steelwork

8/17/2019 20.104 Construction of Steelwork

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PETRON S

TECHNIC L ST ND RDS

DESIGN AND ENGINEERING PRACTICE

TECHNICAL SPECIFICATION

CONSTRUCTION OF STRUCTUR L

STEELWORK

PTS 20 104

APRIL 1989

PETRON S


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PREF CE

PETRONAS Technical Standards (PTS) publications reflect the views, at the time of publication,

of

PETRONAS OPUs/Divisions.

They are based

on

the experience acquired during the involvement with the design, construction,

operation

and

maintenance

of

processing units and facilities. Where appropriate they are based

on, or reference

is

made to, national and intemational standards and codes

of

practice.

The objective is

to

set the recommended standard for good technical practice to be applied by

PETRONAS OPUs

in

oil and gas production facilities, refineries, gas processing plants, chemical

plants, marketing facilities or any other such facility, and thereby to achieve maximum technical

and economic benefit from standardisation.

The information set forth in these publications is provided

to

users for their consideration and

decision to implement. This is of particular importance where PTS may not cover every

requirement or diversity

of

condition at each locality. The system of PTS

is

expected to

be

sufficiently flexible to allow individual operating units to adapt the information set forth n

PTS

to

their own environment and requirements.

When Contractors or Manufacturers/Suppliers use PTS they shall be solely responsible for the

quality

of

work and the attainment

of

the required design and engineering standards.

n

particular, for those requirements not specifically covered, the Principal will expect them to follow

those design

and

engineering practices which will achieve the same level of integrity as reflected

in the PTS. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his

own responsibility, consult the Principal or Its technical advisor.

The right to use

PTS

rests with three categories

of

users :

1 PETRONAS and Its affiliates.

2) Other parties who are authorised

to

use

PTS

subject to appropriate contractual

arrangements.

3) Contractors/subcontractors and Manufacturers/Suppliers under a contract with

users referred to under 1) and 2) which requires that tenders for projects,

materials supplied or - generally - work performed

on

behalf

of

the said users

comply with the relevant standards.

Subject to any particular terms and conditions as may be set forth in specific agreements with

users, PETRONAS disclaims any liability

of

whatsoever nature for any damage (Including Injury

or

death) suffered by any company

or

person whomsoever as a result

of

or in connection with the

use, application or implementation of any PTS, combination of PTS or any part thereof. The

benefit

of

this disclaimer shall Inure

n

all respects to PETRONAS and/or any company affiliated

to PETRONAS that may Issue PTS

or

require the use

of

PTS.

Without prejudice to any specific terms n respect

of

confidentiality under relevant contractual

arrangements,

PTS

shall not, without the prior written consent

of

PETRONAS, be disclosed by

users to any company or person whomsoever and the PTS shall be used exclusively for the

purpose they have been provided to the user. They shall be returned after use, Including any

copies which shall only

be

made by users with the express prior written consent

of

PETRONAS.

The copyright of

PTS

vests

n

PETRONAS. Users shall arrange for PTS to be held

n

safe

custody and PETRONAS may

t

any time require Infonnatlon satisfactory to PETRONAS

n

order

to ascertain how users Implement this requirement.


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T BLE OF

CONTENTS

1.0 GENERAL

1 1 Scope

1.2 Performance

f

Work

1.3 Errors

And

Omissions

1.4 Referenced Documents

1.5 Documentation

1.6 Glossary

1.7 Abbreviations

2.0 MATERIALS

2 1 General

2 2

Weldable Structural Steel

And

Steel Products

3.0 WELDING

3 1 General

4.0 WELDING CONSUMABLE

4 1

Types Of Electrodes Wires

And

Fluxes

4.2 Conditions And Storage

4.3 Heating

And

Baking Requirements

5 0

QUALIFICATION OF WELDING PROCEDURE

5 1 General

5 2

Parameters

In

Welding Procedure Specification

5 3

Welding Procedure Qualification Test

5.4 Essential Variables In Qualification Of Welding Procedures

5 5

Procedure Qualification Record

5 6 ~ ~ o Permitted Welding Processes

5 7

Testing Requirements For Procedural Qualification Test

5 8

Acceptance Criteria

5 9 Retest

6.0 QUALIFICATION OF WELDERS AND WELDING OPERATORS

6 1 General

6 2

Qualification Test For SMAW with Covered Eiectrodes

7.0 PRODUCTION WELDING

7 1

General

7 2 Welding Sequence

7.3 Weld Preparations


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7.4 Weld Execution

7.5 Preheating And Interpass Temperatures

7.6 Stress Relieving - Post Weld Heat Treatment

8.0 FABRICATION

8 1

General

8.2 Material Preparation

8.3 Forming Of Tubular And Cones

8.4 Spacing of Seams And Splices

8.5 Laying-Out Alignment And Fit-up

8.6 Temporary And Non-Structural Attachments And Cut-Outs

8.7 Finishing Of Surfaces

8.8 Repair And Remedial Procedures

8.9 Ancillaries And Temporary Works

9.0 TOLERANCES

9 1

General

9.2 Local Tolerances For Structural Components And Sub-Assemblies

9.3 Global Tolerances For The Completed Structure

9.4 Miscellaneous Structural Tolerances

9.5 Launchways

10.0 INSPECTION AND TESTING

10 1

General

10.2 Personnel

10.3 Testing Of Welds

10 4 NOT Reporting Requirements

11.0 PLACING DRAWINGS

12.0 AS-BUILT DRAWINGS


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1 0 GENERAL

1 1

Scope

a This specification shall govern the material specifications, shop and field welding

fabrication and inspection requirements of all structural steel for the Works,

i.e.

i

Platform support structures

Uackets,

piles etc)

ii) The deck, whether constructed of plate girders, box girders or tubular frames,

and

all associated support structures in or

on the

deck, access

and

protection

steelwork e.g stairways, walkways

and

handrails,

and

bridges

iii) Deck to substructure connection

iv) Structural steel

in

or on

the

substructure, such as J-tubes, subsea pipeline

bridges, manifold jackets

and

supports for e.g piping, process equipment,

electrical equipment, instrumentation equipment, etc

v) Jetties

vi) Steel skirt to foundation if any)

b

The

Contractor shall supply

all

steel, materials, labour, tools, equipment and services

and

perform or arrange

all

tests specified or necessary unless speCifically directed

otherwise

in

the contract)

to

ensure that the requirements of this SpeCification are

fulfilled and to ensure proper functioning of components.

c

Where it is necessary for certain structural steel components to be installed offshore,

compliance with

all

the requirements of this Specification shall also mean that such

component shall be trial assembled onshore to ensure subsequent correct fit, whenever

directed by the Company.

d

The

Contractor shall satisfy himself

as

to the details of the scope and requirements

in

the contract and shall be deemed to have included for the above stated and all that

follows

in

this section

o

the SpeCification.

e

This

SpeCification

covers the material selection and welding of mild steels

with

yield

strengths of less than or equal

to

52,000

psi as

defined in the relevant material

speCification.

1 2 Performance

f

Work

a

The Contractor shall have in charge of the

work,

at

all

times, a thoroughly competent

superintendent and a fully qualified welding engineer, who are experienced

in

this

category of steelwork construction and its fabrication. The Contractor shall deSignate a

competent representative with whom

the

company and/or its representative may

communicate at all times.

b The Contractor shall employ only qualified craftsmen to perform all aspects of the work

including testing. Any workman considered unsuitable by the Company shall be

removed from the Works without delay and shall not be re-employed on the Works.

c

The Company shall be advised at least two days before commencement of any work by

the Contractor and his sub-contractors.

d

The Contractor shall demonstrate to the Company that he

is

capable of producing work

to the required standard, with particular respect to his sub-contractors he may wish to

employ. This may be achieved by producing documented past and current types of

work the Contractor/subcontractor has been engaged on.

1 3 Errors

And

Omissions

The Contractor shall be responsible for all errors and omissions

in

the detailing, layout and

fabrication of the Works. It is the obligation of the Contractor to check the Contract

Documents including

the

Contract Drawings immediately upon award of the Contract

and to

notify the Company immediately o any errors or omissions discovered.


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1.4 Referenced Documents

1.4.1 Base Specifications

a

Materials

The BS 4360 has been selected as the basis for materials. All materials shall meet the

requirements o this Code

and

the requirements mentioned

in

this Specification Chapter

2.0.

b Welding

All welding, temporary or permanent, shall meet the requirements

o

the latest edition

o

AWS 01.1 Structural Welding Code-Steel

as

modified by this specification.

c

Inspection

All inspection requirements shall meet AWS 01. 1. and the codes mentioned therein

describing the techniques and as modified

in

this Specification

in

Chapter 10.0.

1.4.2 Standards. Rules And Codes

a

Unless otherwise specifically indicated, the following standards, rules and codes shall

be the guides governing the works. These shall be considered complimentary to and

providing further detailed. requirements and recommendations to those stated in this

Specification and shall be complied with. Where, however, the requirements

o

this

Specification are

in

conflict with or expand the above requirements, this Specification

shall prevail.

b All the standards, rules and codes stated below are to be the latest editions at the

commencement o the contract.

i) American Petroleum Institute (API)

API 5L - Specification For Line Pipe.

API RP 2A - Recommended Practice For Planning, Designing And Constructing

Fixed Offshore Platforms

API 2B - Specification For Fabricated Structural Steel Pipe.

API 2H - Specification For Carbon Manganese Steel Plate For Offshore Platform

Tubular Joints.

ii) American Institute

o

Steel Construction (AISC)

Code

o

Standard Practice For Steel Building And Bridges Specification For The

Design, Fabrication And Erection

o

Structural Steel For Buildings.

iii)

American Welding Society (AWS)

AWS 01.1 - Structural Welding Code-Steel

AWS A.2.4 - Symbols For Welding And Non Destructive Testing

AWS A.3.0 - Welding Terms And Definitions

AWS A.5.1 - Specification For Carbon Steel Covered Arc Welding Electrodes

AWS A.5.5 - Specification For Low Alloy Steel Covered Arc Welding Electrodes

AWS A.5.17 - Specification For Bare Carbon Steel Electrodes For Submerged

Arc Welding

AWS A.5.18 - Specification For Carbon Steel Filler Metals For Gas Shielded Arc

Welding


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iv) American Society For Testing And Materials ASTM)

ASTM

A6

- Specification For General Requirements For Delivery of Rolled

Steel Plates, Shapes, Sheet Piles

And

Bars For Structural Use

ASTM A36 - Specification For Structural Steels

v) British Standards BS)

BS

4360 - Weldable Structural Steels

BS 4 Pt1 Specification For Structural Steel Sections:

Pt1

:

Hot

Rolled

Sections

BS 4848

Pt2

- Specification For Hot Rolled Structural Steel Sections: Pt2

Hollow Sections

BS 5135 Metal Arc Welding of Carbon

And

Carbon Manganese Steel

BS 638 Arc Welding Plant Equipment

And

Accessories

BS

3971

Image Quality Indicators For Radiography And Recommended

Use

vi) Det Norske Veritas DNV)

Rules For The Design, Construction

And

Inspection For Fixed Offshore

Platforms.

vii) Deutsches Institute for Normung DIN)

DIN

17100 - Steels For General Structural Purposes.

viii) International Institute of Welding IIW)

Collection of Reference Radiographs of Welds In Steel

IIW-36-39 - Recommended Practice For The Radiographic Inspection of

Circumferential Fusion Welded Butt Joints In Steel Pipes Up To

50mm Wall Thickness

ix) National Association of Corrosion Engineers NACE)

• Std RP-01-76 - Recommended Practice For Control of Corrosion

On

Steel,

Fixed Offshore Platforms Associated With Petroleum Production

x

Japanese Industrial Standard JIS)

JIS G3106 SM41-B - Rolled Steels For Welded Structures


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1 5 ocumentation

1.5.1 Prior

To

Fabrication

Prior

to

commencement of any part of

the

fabrication, the Contractor shall submit the

following documentation for approval by the Company.

a

Mill certificate for Contractor supplied materials.

b

Fabrication procedures, welding sequence and erection

sequence. This is

to

include

the welding procedure specification to be applied, sequence of plates to be welded, and

number and location of welders at each stage

o

assembly.

c Fabrication drawings including plate seam arrangement drawings, plate cutting

drawings and

weld

details.

d Drawings and calculations of temporary works, inclusive of support points, jacking

points and sling points, approved

by

a qualified engineer.

e List

o

proposed welding consumable and their areas of application including detailed

control procedures for consumable handling, baking, storage

and issue.

f Welding procedures, repair welding procedures with their supporting procedure

qualification records and including weld maps.

g Certificates

o

welders, welding operators and tackers qualified

in

accordance with this

Specification complete with list of welder identification numbers and photographs.

h Key plan showing

an

unambiguous member identification and weld marking scheme.

i

Inspection procedures and detailed report sheets for non-destructive testing and

inspection. This

shall

include separate sheets for Visual, Radiography, Ultrasonic, Dye

Penetrant, Magnetic Particle, Painting

and

Coating.

j) Identification and control procedures for materials.

k Procedures for control of tolerances during fabrication and procedure for distortion

rectification.

I Detail procedures for welding equipment maintenance

and

calibration.

m Qualification certificates for all inspection personnel.

n) Summary sheets for NDT test reports for each joint which are

to be

kept up

to

date as

the work progresses.

1.5.2 puring Fabrication

As the work progresses, the following shall be required :

a As built dimensional survey records which shall be updated continually.

b Where traceability is required, plans marked to relate certificate references for

all

materials to its final position

in the

structure.

c

NDT test reports original only) including radiographs and key plans marked showing

final identification numbering, test report numbers and the results.

d Production mechanical test reports, post weld heat treatment charts, leak reports and

all charts for all items tested.

e As

built drawings and Specifications which shall show

in

detail the manner in which the

facility was constructed and shall reflect all changes, additions, corrections or revisions

made during the course of construction. The objective being to build up a full

documented history of

the

Construction Work.


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1 6 Glossary

1 7

Company - Shall mean PETRONAS

Contractor - The party which entered into contract with the Company for the execution of

activities as mentioned in a written agreement.

Shall - The word shall is to

be

understood

s

mandatory to comply with the requirements of

this specification.

Should - The word should is to be understood as strongly recommended to comply with the

requirements

o

this specification.

Abbreviations

API

ASNT

ASTM

AWS

BS

CSR

CAR

CSWIP

DPI

DIN

GTAW

GMAW

JIS

MSF

NDT

PQR

PWHT

RT

SAW

SMAW

SSB/SSPC

WPS

UT

American Petroleum Institute

American Society For Non-clestructive Testing

American Society For Testing and Materials

American Welding Society

British Standard

Company Site Representative

Company Authorised Representative

Certification Scheme For Welding Inspection Personnel

Dye Penetrant Inspection

Deutsches Institute for Normung

Gas Tungsten Arc Welding

Gas Metallic Arc Welding

Japanese Industrial Standard

Main Structural Frame

Non Destructive Testing

Procedure Qualification Record

Post Weld Heat Treatment

Radiographic Testing

Submerged Arc Welding

Shielded Metallic Arc Welding

Sarawak Shell Berhad/Sabah Shell Petroleum Company

Welding Procedure SpeCification

Ultrasonic Testing


10/52

2 0

MATERIALS

2.1.1

General

a The purpose of this chapter is

to

specify the composition, properties, dimensions,

tolerances, manufacturing process, handling, etc,

o

all materials which will

be

incorporated, both permanently and temporarily as either structural members or

structural appurtenances, into the offshore platform.

b

Company inspection personnel shall

be

permitted free access

to

the Manufacturer s

works for the inspection of any process necessary for the manufacture of these

materials.

c If a material not described in this chapter is required, it shall be brought to

the

attention

of the Company which will decide which Specification shall apply.

2.1.2 Transportation. Storage and Handling of Materials

a The Contractor shall ensure adequate protection to all steelwork during any loading and

transportation activities by providing adequate timber bearers during transport.

b The Contractor shall provide nylon or similar lifting slings during handling or lifting

operations; wire ropes

or

chain slings will not be permitted.

c The

steelwork shall

be

stored

above ground

on

pallets, timber

blocks

or other similar

supports, be kept above the level of any standing water and be kept free from dirt,

grease, paint sprays, etc. and shall

be

protected from harmful environments.

d Damage to any part of the steelwork either before, during or after erection shall

immediately be brought

to

the notice of the Company.

e Particular care shall be taken in storage and handling of parts which have

been

metal

sprayed, galvanised, painted, etc., and should the coating be

damaged,

it shall

be

restored by an approved method at

the

cost of the Contractor, and be compatible with

the particular coating.

2.1.3 Used Materials

Temporary bracing, erection

aids, scaffoldings

and

materials and equipment for testing shall

be

fumished by the Contractor

and

shall

be

safe,

serviceable

and

adequate,

but need

not

be

new.


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2.1.4 Classification of Structural Steels

For the purpose of this Specification, structural steel

is

classified by the following groups.

a) TYPE I

STEEL

Primary Structural Steel- High Strength

Primary structural steel - high strength, is steel with a yield strength of 5 ksi

and

over

used

in

members essential to the overall integrity of the structure and for other

structural members of importance

to

the operational safety of the structure.

b) TYPE II STEEL : Primary Structural Steel - High Strength With Through Thickness

Properties

Primary structural steel - high strength with through thickness properties,

is

steel with

yield strength of

5 ksi

and over

and

used in members essential to the overall integrity

of the structure, where stress concentrations are high and where the stresses

in

the

thickness direction may lead to lamella tearing.

c) TYPE III STEEL: Primary Structural Steel- Mild Steel

Primary structural steel - mild steel, is steel with a yield strength between 36 ksi and 5

ksi

and used in members essential to the overall integrity of the structure and for other

structural members of importance to the operational safety of the structure.

d) TYPE IV STEEL : Primary Structural Steel - Mild Steel With Through Thickness

Properties

Primary structural steel - mild steel with through thickness properties

is

steel with yield

strength between 36

ksi

and 5

ksi

and used in members essential to the overall

integrity of the structure, where stress concentrations are high and where the stresses

in the thickness direction may lead to lamella tearing.

e) TYPE V STEEL : Secondary Structural Steel

Secondary structural steel is steel used in members not essential to the overall integrity

of the structure and/or the operational safety.


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2.2

Weldable Structural Steel And Steel Products

2.2.1 General Provisions

All structural steel for use in offshore structures shall meet the requirements of BS 4360

Specification For Weldable Structural Steel .

a The types

of

structural steel, including the

BS

4360 grade identification which shall

be

used are:-

BS Grade Description

HS 50A,B,C,D,EE High Strength Steel

II

HS TTP 50A,B,C,D,EE High Strength Steel With Improved

Through Thickness Properties

III

MS

43A,B,C,D,EE

Mild Steel

IV

MSTTP 43A,B,C,D,EE Mild Steel With Improved Through

Thickness Properties

V

SEC 40A,B,C,D Secondary Steel

43A,B,C

For through thickness properties, reference is made to BS 4360 clause B29.

The

suffix

Z25 shall apply.

b All

structural steel shall

be

fully killed and fine grained. Acid and Bessemer Steel

making processes are not acceptable. Rimming steel shall not

be

used.

c Through thickness properties materials shall

be

used when the Contract Drawings

require them. They shall always

be

calcium treated. The steel producer may propose

additional processing to reduce

the

occurrence of elongated Inclusions and laminations

as appropriate for the speCified requirements. These may include for example, reduced

sulfur, vacuum degassing and rare-earth-metal treatment. The additional processing

and the casting method, ingot or continuous, shall be clearly defined and will become

part of the basis of purchase.

d) All Contractor supplied steel shall be new stock, free from mill scales, rust, grease or

dirt and free from deformation.

2.2.2 Altemative Specifications

The following material specifications are considered acceptable as

an

altemative to the BS

4360 grades specified in paragraph 2.2.1 above provided that

i the carbon content is always 0.23% maximum

ii) the maximum carbon equivalent (CE) is 0.45% (the applicable expression for C.E. is

defined in BS 4360 clause B.6)

iii) all additional requirements defined in 2.2.1 are met.

Mild Steel High Strength Steel

API 5L Grade B JIS

G3101

Class 4 SS55

API5LX4

ASTMA36

DIN

17100 RSt 37-2

DIN 17100 St 42-2

JIS G3106 SM41-B

API Grade X52

DIN

17100 St 52-3


13/52


14/52

2.2.4.2 Contents Of Certificates

a) All material certificates should state the following:

Name

o

manufacturer and factory symbol

Purchaser order number and date

o

revision

Certificate number and date of issue

Material specification in full

Dimensions

Quantity and/or weight

Charge number - batch number or heat-lot number

Specified chemical, mechanical and physical properties (or reference standards)

Actual chemical, mechanical and physical properties

When applicable, NOT methods and results

When applicable, heat treatment procedure, furnace charge number of heat

treatment records

Supplementary or additional requirements

b

In

addition, the independent third party inspection certificates (DIN 50049.3.IC) shall

state:

That identification

o

the material has been verified by the certification authority

That

all

tests were witnessed by the independent third party inspection agency

Agency or inspectors identification symbol

Certificate number and date

o

Issue

2.2.5 Material Identification

Material marking

o

all Contractor supplied primary structural steel shall be white paint

stencilled letters on black paint background. In addition,

all

materials shall be colour coded

with one

red

and one yellow painted band.

Plate material shall be die stamped with the plate number and heat number by the plate

manufacturer using low stress dot matrix type die stamps.

Materials

in

the Contractors yard shall be clearly identified with piece and item number

painted on the steel.

2.2.6 Bolts. Nuts And Washers

All bolts and nuts shall be the ISO metric thread series. Bolts shall be ASTM A 193 Grade B7

and nuts shall be ASTM A 194 Grade

2H.

Alternatively, bolts to ASTM A325 and A490 may be used provided approval

Is

obtained from

the Company.

Round washers shall conform to American Standard B27

-2

Type B or equivalent, for use with

ISO metric bolts. The diameter of the washer hole shall be 1.5

mm

greater than the bolt size

for bolts larger than 25 mm.

2.2.7 Pile Packer And Pile Gripper Assemblies

Pile packer and pile gripper assemblies shall be as shown in the Drawings and shall be

manufactured by a manufacturer approved by the Company. The assemblies shall be

handled, installed and tested in strict accordance with the manufacturer s Instruction.


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2.2.8 Gratings

2.2.8.1 General

All materials shall be fabricated from secondary steel (type SEC .

Alternatively, ultra violet light resistant glass reinforced epoxy grating with fire retardants may

be

used after approval of the Company has been obtained. The colour of the grating shall be

black or dark grey.

2.2.8.2 Open Steel Stair Treads and Floor Panel (See 8.9.3)

a Stair grating panel shall be of serrated pattern. Floor grating panel should either

be

smooth or serrated pattern type. The cross bars of section 6 mm x 6 mm shall be

twisted, load bearing bars

and end

plates shall

be

constructed

as

detailed Table

2.

The

load bearing bars may be constructed from cold drawn flat bars or I-bars.

b) On the rung of

the

steel ladders and stairs anti-slip ladder

rung

covers of the type

Safemate industrial grade or equivalent

as

approved by the Company shall

be

installed.

2.2.8.3 Galvanizing

All steel grating shall be hot dip galvanised with a minimum thickness according to BS 729 or

ASTM A-123. Where it

is

impossible to galvanize a complete unit which must be joined by

welding after galvanizing,

the

welds shall

be

painted in accordance with

PTS

30.48.00.31-P

2.2.8.4 Installation

All galvanised gratings shall

be

installed after galvanizing

to

check

the

fit.

At the discretion of the Company,

the

grating on any part of

the

structure may have

to

be

removed prior to load out.

In

this case, the Contractor shall mark the grating prior

to

removal

and prepare a placing drawing

in

accordance with Section 11 of this specification.

2.2.9 Deck Plate

The use of chequer plates shall be avoided where possible and only be installed when

indicated on the contract drawings. They shall be of the type where no slippery surfaces will

be

created due

to

standing water or oily products.

For deck plates

in

a working area e.g. drill floors or walkways, heavy duty anti-slip surfaces

shall be installed of the type Safemate or equivalent as approved by the Company. These

anti-slip surfaces shall be bolted on.

2.2.10 Timber

a Timber for the

mud

mat shall

be

of a medium hardwood, keruing or equivalent, with

an air dry density of approximately 740 kg/cu.m (46 Ib/cu.ft). The required allowable

static bending strength of the timber shall be 11 MPa (1.6 ksi) determined in

accordance with ASTM 0143-52.

b) Launch runner timber shall be a hardwood, (Selangan Batu) or equivalent, with an air

dry density of approximately 960 kg/cu.m (60 Ib/cu.ft). The required allowable

compressive strength (parallel

to

the fibre) o the timber shall

be 13 MPa

(1.9 ksi)

in

accordance with ASTM 143-52.

c) Timber of drilling decks shall be as b) above.


16/52

3.0 WELDING

3.1

General

a Welding

All

welding, temporary or permanent, shall meet the requirements of the latest

edition of AWS 01.1 Structural Welding Code-Steel ,

as

modified by this specification.

b

The following sections of AWS 01.1 are not applicable:-

10.1-10.6,10.8-10.11,4.6,4.7,4.9-4.11,4.14-4.20. Section 8 and 9 of AWS

01 1

are

only applicable when specifically referenced in AWS 01.1 sections 1-6. Where

alternative provisions apply in AWS 01.1, those of section 10 shall apply for tubulars

and section 9 shall apply for plates, girders and sections, with the exception of the non

destructive testing acceptance criteria which shall

be as

per

AWS

01.1. section 10.

c All welding shall be carried out by qualified welders and welding operators using

qualified welding procedures in accordance with this specification.

4.0 WELDING CONSUMABLE

4.1

Types

Of

Electrodes, Wires And Fluxes

4.1.1 General

a) The electrodes, wires and fluxes used

in

fabrication shall

be

selected to produce welds

with mechanical properties equivalent

to

those required for the base metal or as

specified by the Company.

b)

When

steels of different strengths are joined,

the

tensile properties of the weld metal

shall

be

matched

to

the lower strength steel.

4.1.2 Covered Electrodes

a

All covered electrodes for welding of structural steels shall

be

low hydrogen electrodes.

The hydrogen content shall not exceed 10 ml per 100 grams of deposited weld metal.

b) Electrodes shall

be

selected from a list of approved types of electrodes, such a list

to

be

submitted

to

the Company for approval prior

to

selection being made.

c) Electrodes shall only be used under conditions,

in

positions, and using the welding

parameters recommended by the manufacturer.

4.1.3 Wire And Flux For Submerged Arc Welding

Wire and flux shall be carefully selected and the flux shall be of the fully basic type. The

storage

and use

of wire and flux shall be

as

recommended

by

the manufacturer. The flux

supplier shall define the range

of

chemical composition of wire

to be

used for his particular

flux.

No

low-alloy wires shall be accepted. The proposed wire and flux shall

be

submitted for

approval by the Company.

4.1.4 Wire For

Gas

Metal Arc Welding

The gas metal-arc process may only be used on mild steel in enclosed shop fabrication

conditions, and provided that the filler wire selected is such that the welds produced have

the same mechanical properties as the base metal.


17/52

4 2 Conditions nd Storage

a Electrodes shall be supplied in hermetically sealed cartons and stored in a dry storage

room where the minimum temperature is 20 Centigrade. All manual type electrodes

shall be properly identifiable see AWS A5.1 and 5.5)

up

to the time of usage, each

electrode being distinguishable by colour code marking. If colours are destroyed

by

baking, handling or other causes, the electrodes shall not

be

used. Batch numbers shall

be recorded.

b) Low hydrogen electrodes shall not be stored in heated cabinets containing electrodes

of other types,

such as

rutile or organic type electrodes.

c Wire spools for automatic and semi-automatic processes shall be stored in cabinets

with supplier wrapping not removed and remain clearly identifiable up to the time of

usage. Unidentifiable wire shall not be used.

d) Flux shall

be

supplied and stored in accordance with paragraph 4.1.3.

e Each batch of flux and wire shall be labelled with the information from the supply

container. The labels with batch number shall be recorded for reference.

f All unidentifiable, damaged, wet, rusty or otherwise contaminated consumable shall be

scrapped.

g) A consumable handling, storage and issuing procedure shall be submitted to the

Company for approval prior to the start of any fabrication.

4 3 Heating nd Baking Requirements

a All low hydrogen electrodes shall

be

baked at 270°C

to

330

°C

for one hour prior

to

use.

b

On completion of baking, the electrodes shall be transferred to a holding oven at 150

°C.

When later removed from the holding oven, the electrodes shall be transferred to

heated quivers or containers at

75°C

and used within 8 hours.

c Electrodes not used within 8 hours or for some reason exposed to adverse atmospheric

conditions shall be reba ked for one hour and then transferred to the holding oven for

later

use.

Electrodes shall

be

rebaked only once.

d) Flux for submerged arc welding shall be issued

as

required for immediate use. They

shall be held

in

a heated silo at 70°C


18/52


19/52

5.3 Welding Procedure Qualificat ion Test

a) Welding Procedure Qualification tests shall

be

carried out at the cost of the Contractor,

to verify the WPSs and shall simulate,

as

far

as

is practicable, the conditions and

materials

to be

used for production welding. Limitations imposed by

the

essential

variables of the procedure qualification shall

be

adhered

to

in production welding.

b) Changes

in

any of the essential variables (See 5.4) will call for a new qualification

test.

c)

Changes

in

one or more of the non-essential variables will not call for a new

qualification test, but a new WPS is required.

d) A qualified procedure is valid for materials

and

thicknesses

in

accordance with

paragraph

5.5.1 and

Tables

5.10.1 and

5.10.3 of

AWS D1.1

e) Qualification of a fillet weld by a groove weld is not acceptable.

5.4 Essential Variables In Qualification

f

Welding Procedures

Any changes

in

the essential variables listed

in

AWS

D1.1

para 5.5.2 and/or the following

shall require the submission of a new WPS and a complete qualification of the procedure.

i)

A change in base metal type or grade outside

the

range defined in 2.2.1 above.

ii) A change in welding process from that qualified

to

any other welding process or

combination of welding processes.

iii) A change

in

the welding groove or a change

in the

root

gap

outside

of

the allowable

tolerances.

iv) A change of consumable trade name, group, grade, classification or source of origin.

v) A change in wire/flux combination.

vi) An increase of electrode diameter by more than 1.0 mm over that used in the procedure

qualification.

vii) A change

in

shielding gas composition of any constituent of more than 5 of the total

flow.

viii) The omission or inclusion of backing strips These shall

be

avoided wherever possible.

ix) A change from multipass

to

single pass or vice versa.

x) A change

in

type of current or the polarity.

xi) The omission or inclusion of back gouging.

xii) A deviation in the preheat and/or post-weld heat treatment procedure.

5.5 Procedure Qualification Record

The specific facts from the WPS and test results from the welding procedure qualification test

shall

be

recorded

in

the procedure qualification record (PQR). The PQR shall be submitted

to

the Company for approval before any production welding is commenced. Test results from

previous jobs or contracts may be acceptable but only at the discretion of the Company.

The form used for the WPS and PQR shall be such as described

in

AWS D1.1. However, the

parameters stated in

5.2

above shall

be

recorded. Other alternatives are acceptable and on

request,

the

Company s forms can be made available.

5.6 Non Permitted Welding Processes

High heat input welding processes such as electrogas, electroslag or high power density

welding will not normally

be

permitted.


20/52

5.7 Testing Requirements For Procedural Qualification Test

5.7.1 Non Destructive Testing

Each test specimen shall

be

non-destructively tested for soundness using the following

methods:

a) Visual inspection.

b)

Radiography for butt welds.

c) Ultrasonic inspection for thick walled butt welds and T-K-Y connections.

d) Magnetic particle or dye penetrant inspection.

5.7.2 Destructive Testing

5.7.2.1 Tensile

And

Bend Test

a) Complete Penetration Groove Welds:

The type and number of specimens that must be taken to qualify a welding procedure

are as shown in Table 5.10.1 of AWS 01.1.

b) Partial Penetration Groove Welds:

The type and number

o

specimens that must

be

taken

to

qualify a welding procedure

are

as shown in Table 5.10.2 of AWS 01.1.

c) Fillet Welds:

The

type

and number of specimens that must be taken to qualify a welding procedure

are as shown in Table 5.10.3 of AWS 01.1.

5.7.2.2 Macroetch Cross-Section Test Specimen

Macroetch tests are required for all welds. For plate welds, one piece shall be selected. For

tubular welds, one test piece in the 6 O clock and one test piece in the 9 O clock position shall

be selected.

For T-K-Y connections, a macroetch test piece shall

be

selected from the 3, 6 and 12 O clock

positions. For fillet welds, refer to AWS 01.1

Fig

5.1 0.3A.

5.7.2.3 Hardness Test

A hardness survey shall

be

carried out

on

one of the macroetch cross-section test specimens.

5.7.2.4 Impact Test

This shall

be

required if ambient temperature at the fabrication yard

is

likely

to

fall below

20

°C. See

also para 2.2.3 above)

5.8 Acceptance Criteria

5.8.1

Visual Inspection

The weld shall be inspected in accordance with 10.17.1 of AWS 01.1

5.8.2 Radiographic Inspection

The

weld

shall be Inspected in accordance with 10.18 and 10.17.3 of AWS 01.1

5.8.3 Ultrasonic Inspection

The weld shall be inspected in accordance with 10.19 and 10.17.4 of AWS 01.1.

5.8.4 Magnetic Particle/Dye Penetrant Inspection

Inspection shall

be

evaluated on the basis o the requirements for visual inspection above.

5.8.5 Tensile Test

The tensile strength shall not be less than the minimum of the specified tensile strength of the

base metal used.

5.8.6 Bend Test

The specimen shall

be

Inspected

In

accordance with 5.12.2 of AWS 01.1


21/52

5.8.7 Macroetch Test

The specimen shall be inspected in accordance with 5.12.3 of AWS D1.1

5.8.8 Hardness Test

The maximum hardness allowed shall

be

325 Hv

10.

5.8.9 Impact Test

Impact requirements shall be as per 2.2.3 of this Specification.

5 9 etest

5.9.1

When

Retest

Is

Not Allowed

Unacceptable defects evaluated by visual, MPI, DPI, radiographic, ultrasonic and macroetch

testing shall be cause for rejection. A new test weld shall be required.

5.9.2 When Retest Is Allowed

When one of the following mechanical test specimens fail

to

meet the required acceptance

criteria, two additional specimens shall

be

prepared for retesting. The location of the

two

additional specimens shall reflect the location of the failed specimen. If one or both of the

retest specimens fail, then this shall be cause for rejection. A new test weld shall be required.

a) Tensile test

b

Bend test

c Impact test when applicable)

d) Hardness test


22/52

6 0 QU LIFIC TION OF WELDERS ND WELDING OPER TORS

6 1

General

6.1.1 Qualifications Required

Welders and welding operators shall

be

qualified in accordance with the requirements of

WS

01.1 and this Specification. Only qualified welders shall

be

employed during the fabrication

including tack welding structural welding

and

repair welding of any structural steel part. They

shall only perform welding for positions and processes for which they are qualified. Backing

materials

shall

not be used during testing. The Contractor shall ensure that welders of any

sub-contractor or of any otherwise nominated contractor are qualified in accordance with this

Specification. The purpose of a welder qualification test is

to

verify that the welder can apply a

qualified welding procedure making welds of satisfactory quality.

6.1.2 Witness nd Approval

f

Test Before Welding

ll

welders and welding operators tests shall

be

witnessed

and

approved by the Company

before the welder or welding operator is permitted

to

work on the structure. The decision by

the Company regarding qualification of any welder or welding operator shall

be

final.

Evidence of previous qualification tests may

be

accepted solely at the discretion of the

Company Representatives.

6.1.3 Provisions Of Equipment And Costs

f

Test

The Contractor shall provide equipment for the welder qualification tests

and

shall bear

all

costs for

the

non-destructive testing the cutting

and

machining of test specimens

and

mechanical testing. of specimens.

6.1.4 Welder Identification System

n identification system shall be worked out for welders

and

welding operators. The system

which shall include a numbering and identification card index shall

be

established and agreed

with the Company. Whilst

on

the Works the welder/welding operator shall always

be

identifiable by a badge bearing his name his photograph and his identification number.

Welders

and

welding operators not wearing their badges will

be

dismissed

from

the Works

by

the Company Representatives.

In

the event that a welder leaves the Works his mark shall not

be assigned to another welder employed on the Works.

6.1.5 Marking Of Welds

Each qualified welder and welding operator shall

be

supplied with

an

identification marker.

The welder shall clearly mark the plate or pipe adjacent

to

his weld using soft die stamps with

the identification mark assigned to him in his qualification certificate. Tack welding of

components need not be marked.

6.1.6 Applicability Of Qualifications

The Contractor shall ensure that qualified welders and welding operators are employed during

fabrication only on welding the type process and positions of weld for which their qualification

test so qualifies them.

6.1.7 Base Material

As far as

is

practicable welders and welding operators shall

be

qualified

on

the same material

to be

used for fabrication. Similar types of materials may

be

substituted at the discretion of the

Company provided that it can clearly

be

demonstrated that the weldability

is

equivalent to the

material intended for use in the fabrication. Refer also to para 2.2.1.

6 1 8

If the test joint does not meet the requirements the welder or welding operator may at the

discretion of the Company carry out a new test joint of the same type as the one rejected.

Failing of both these tests shall result in the welder or welding operator not being employed

further

on

the work. The welder shall only be considered for requalification after 14 days

provided proof is given of proper training of the welder over that period.


23/52

6.1.9 Welder Qualification Record

A record of the welders qualification test, including a reference to the corresponding

WPS

number, the essential variables according to

AWS

01.1 para 5.1.2, and the test results, shall

be issued for

each

welder or welding operator for

each

test they pass.

6.1.10 Period Of Effectiveness

a)

Welders

and

welding operators who will perform welds

in

the process/position

combinations for which they were previously qualified need not requalify for those

combinations if both

o

the following requirements are met

i) The Contractor can show that the welder s performance has been monitored

and proven satisfactory since

the

qualification test.

ii) The welder certificate has been endorsed by a Company recognised Certifying

Authority at a date less than six months before construction starts.

b) Ouring construction, the Contractor shall provide evidence indicated in a) above to the

Company so that the welder certificates can

be

re-endorsed within six months of the

previous endorsement date. Any certificate not endorsed every six months shall

be

considered invalid.

c)

A qualified welder or welding operator may, at

the

discretion of the Company,

be

required

to

requalify if inspection reveals that

an

unacceptable number of repairs are

necessary.

6.2 Qualification Test For SM W With Covered Electrodes

6.2.1

Welding Test And Position

Welders shall be qualified

in

the 6GR position as shown in Figure 5.21A of AWS 01.1 This

will qualify him to perform groove or fillet welds in

all

positions

on

both pipes and plates

including groove welds for T-K-Y connections. Other types of tests may

be

allowed at the

discretion of the Company.

6.2.2 Inspection

And

Test

Each

test weld shall

be

subjected

to the

following inspection and tests:

a)

Visual inspection

b) 100 Ultrasonic test

c)

100

Radiographic testing where possible

d) Bend

tests.

See

para 5.26 of AWS 01.1

6.2.3 Qualitv Requirements

Quality requirements are as defined by AWS 01.1 chapter 6 Part C.

6.3 Qualification Test For S W

6.3.1

General

Welding operators shall be qualified

in the

flat position

and

where this is done on pipes, the

pipe shall be mechanically rotated.

6.3.2 Welding Procedure

A multipass technique shall be used.

6.3.3 Inspection And Test

Each

test weld shall be subjected to the following inspection and tests:

a)

Visual inspection

b)

100

Ultrasonic test

c)

100

Radiographic test

d) Bend tests. See para 5.26

o

AWS 01.1

6.3.4 Qualitv Requirements

Quality criteria are

as

defined by AWS 01.1, Chapter 6 Part

C.


24/52

7 0

PRODU TION WELDING

7.1 General

a Preparation and welding of structural members shall be in accordance with the

appropriate qualified welding procedure specifications. Manual electrodes, wires and

flux shall be of the same type and manufacture as those used in the procedure

qualification tests.

b Welding equipment shall conform

to

the appropriate sections of BS 638. Any equipment

found not

to

comply with these requirements shall

be

replaced.

c Welding current and voltage shall be the same as the test values, or within the range

specified in the welding procedure.

d)

No

welding shall

be

done until

as

much of the structure

as

will be stiffened thereby has

been properly aligned.

7 2

Welding Sequence

The Contractor shall develop welding sequences to control warping, creeping and the build-

up of excessive internal stresses

in

the

structure. The sequences shall be submitted to the

Company for approval before the assembly of any components. The Contractor shall furnish

the necessary supervision to ensure that the planned sequences are followed.

Sequences shall include:

a Welding procedure speCification to be applied.

b Sequence of plates

to be

welded.

c Any differences from the specified welding procedures, such as areas of preheating,

reinforcements, etc.

d) Post weld heat treatment, heating and cooling rates.

e Number and location of welders at each stage of assembly.

f Tack welds and spacers used in the assembly of components.

7 3

Weld Preparations

7.3.1

Alignment

a

At Splices butt welding)

The offset at butt joints shall not exceed

T 10

where T is the thickness of

the

thinner

material) or 6mm, whichever is less. The offset in longitudinal seams shall not exceed

T 10 or 3mm, whichever is less. All offsets greater than 2mm shall be given a 1:4

transition.

b) At Welded Intersections

The utmost attention shall be paid to good alignment of the structural parts on opposite

sides of the through member.

7.3.2 Surface Cleaning Before Welding

Surfaces

to be

welded shall

be

free from loose scales, slag, rust, grease, paint

and

any other

foreign material.

7.3.3 Edge Preparation

Preparation of weld edges by gas cutting shall, wherever practicable, be done with a

mechanically guided torch. Edges shall be left free of slag and the cut surface shall be ground

to a smooth uniform surface by removing approximately 0.5 mm of metal. After grinding, the

weld edges shall be visually examined

to

ensure freedom from defects.

7.3.4 Cleaning During And After Welding

Upon completion o each welding pass, the weld shall

be

cleaned of spatter, slag and flux

deposits. After welding is complete, adjacent surfaces shalf be thoroughly cleaned of all

spatter and deposits.


25/52

7 4

eld

Execution

7.4.1 Welding Position And Progression

a) SMAW Welding

Electrodes shall only

be

used in the position recommended by the manufacturer. Weld

progression in vertical joints shall utilise the uphill method. For the 1

G, 2G,

1F

and 2F

positions, the maximum size of electrode allowed

is

6.4mm. For any other position, the

maximum size of electrode shall

be

5.0mm. The capping passes shall always

be

done

with a 4.0mm maximum electrode.

b) SAW Welding

This shall

be

done in the flat position and in the case that it is done on pipe, the pipe

shall

be

mechanically rotated.

7.4.2 Size Of Welds

a) To obtain optimum toughness, a small bead multipass technique shall

be

used. The

weave width for SMAW, i.e. maximum oscillation of the electrode, shall not exceed two

and

a half times the electrode diameter or 12mm whichever is the least.

b

The width of SAW beads shall not exceed six times the electrode diameter

and

the

welding speed shall

be

375

mm

per minute minimum.

c Fillet welds shall

be

completed in three or more runs except for seal welds which may

be done in one run. Two

run

fillet welds are not permitted.

d) The Company shall have the right

to

limit the thickness of each weld bead or pass

when this exceeds those given in the weld procedure qualification test.

7.4.3 Intermittent Welding

Stitch welding i.e. partial seal welds shall not

be

allowed.

7.4.4 Seal Welds

Where stress bearing welds are required

by

contract drawings

to

extend only partially around

a member, including plates joining another member, a seal weld of 4mm minimum fillet shall

be

applied continuously to the remainder, but note should

be

taken that a hardness of HV

325

maximum shall not

be

exceeded.

7.4.5 Tack Welds

Bridge tacking is the preferred method

to

avoid the tack becoming part of the final weld.

If another method is selected, tack welding shall

be

performed with the same qualified

welding procedure as will

be

used for structural welds. These tack welds shall

be

ground

(feathered)

and

checked before actual welding commences. Tack welds are

to be

a minimum

of approximately 50 mm long and spaced so that shrinkage forces cannot cause cracking.

i See 7.5.2 (c) for preheat requirements .

.4.V

Butt Welds

.....

- a) Design of the groove and performance of welding shall be in accordance with the

approved WEB However, in general, the groove shall

be

bevelled

to

give

an

included

angle of not less than 60 degrees

and

shall

be

of the V or X type (single bevel or double

bevel). The root openmg shall not

be

less than 2mm and not greater than 5 mm

and

the

root face, if any, shall not

be

greater than 2

mm.

b

Where access to both sides is possible, double bevel groove welds shall

be

used

to

minimise welding stresses

and

shrinkage effects.

When different thicknesses are

to be

butt welded, a 1:4 taper shall

be

provided

on

the

thicker member starting at the toe of the weld cap.

At any joint, no butt weld shall

be

located such that

an

incoming member will result in a

weld overlapping the butt weld.


26/52

7.4.7 Plate and Tubular. T or Y Joints

Design of the groove

and

performance of welding shall be in accordance with the approved

WPS.

However, in general, Table

10.13.1A

of AWS 01.1 shall

be used as

a guide for all T-K-Y

connections. The bevel shall preferably

be

feather edged and the root opening shall be 3 -

5mm

or according to

an

approved procedure.

Welding of minor members shall

be

a full penetration type weld and

where

fabrication method

permits, welding from both sides shall

be

carried out.

7.4.8 Weld Compatibility

All weld joints shall develop the mechanical properties specified for the steel being welded.

Where different grades of steel

are

joined, the weld metal shall

be

matched

to

the lower

strength steel. The procedure shall

be

such

as

to safeguard the mechanical properties of the

higher strength member.

7.4.9 Weld Finish

Welds shall be left

as

welded

and

not

be

doctored with a torch or by any mechanical means

to

change their appearance. Any grinding or other mechanical dressing shall only

be

permitted after inspection and authorisation by the Company.

7.4.10 Weld Interruption

Welding o each weld shall be a continuous operation, with the exception of manually welded

root runs for submerged arc welding.

In

the case that welding must

be

discontinued, this shall

not take place before at least half of the final weld thickness is achieved. The maximum time

that a production weld will remain part welded is two days. The maximum number of heat

cycles that will be used in a production

weld

shall be two. Slow cooling of the weld area shall

be

ensured. Before continuation of welding, the weld shall

be

inspected for cracks visually

and

by MPI.

7.4.11

Weather Protection

Shelters shall be provided at

all

times

to

give protection to the weld areas

from

wind, rain and

moisture. No welding shall be carried out when the weld surface is wet or the work area is

exposed to high winds.

Precautions required :-

a) The weld surfaces shall

be

thoroughly dried by preheating not above 300 ·C).

Temperature control shall

be

carried out.

b Special precautions made to provide conditions maintaining a satisfactory surrounding

temperature and freedom from the effects of winds, all subject

to

the approval of the

Company.

c If any fabrication is

to be

carried out in the vicinity of eqUipment already installed in

connection with the Work, then, before such fabrication work commences, the

Contractor shall provide adequate protection to prevent any damage from weld spatter,

flame cutting droplets and the like. Such protection shall be subject

to

the approval of

the Company.

7.4.12 Peening

The peening

o

welds is not permitted.

7.4.13 Arc

Strikes

Arcs shall be struck only on fusion faces and contact o the electrodes or the non-insulated

parts of the electrode holder with the assembly shall be avoided. Places where any stray arcs

have accidentally occurred shall

be

subject to repair or rejection at the discretion of the

Company.

Where permission to repair arc strikes mechanically has been given, the procedure shall

Include, but not necessarily be limited to, the mechanical removal of the defective material,

blending o the excavation, checking by MPI and confirmation that the thickness o the

repaired material

Is

within permitted tolerances.


27/52

7.5 Preheating And Interpass Temperatures

7.5.1 General

a Preheating shall

be

carried out

by

electrical resistance induction equipment or with gas

burners specifically made and shaped for this type of operation. Torches for flame

cutting or gouging shall not be used.

b

The preheating temperature shall

be

established to a distance of at least 75mm

on

either side of the weld line and throughout the wall thickness prior to welding and be

maintained over

the

full length of

the

weld joint until the weld is completed unless

specifically agreed otherwise

by the

Company.

c

The weld area shall

be

protected

from

draughts

and

lagging shall

be

provided on

adjacent areas, if necessary, to maintain the required temperature of preheating during

welding.

d The temperature measurement for preheating may be by thermocouples or temperature

sensitive crayons, or a combination of both as may be appropriate for the type of joint

being heated and the method of heating.

e

At all joints where preheating is required, the joint shall be subjected to temperature

checks by the Company before welding commences.

f

During welding particularly where preheat has been used

and

for high heat input

processes, care shall

be

exercised

to

control the interpass temperature and

in no

event

should it exceed 300°C or as indicated in the

WPS.

The interpass temperature shall be

monitored by means of thermo sticks or another approved method.

7.5.2 Temperature Requirements

a

Preheat temperatures shall be as indicated in the approved

WPS.

b Preheat temperatures for lifting lugs or padeyes shall be 150°C minimum.

c For tack welding where the tack becomes part of the main weld, the preheat

temperature shall be 5 °C higher

than

specified

on

the WPS with a maximum of 300

°C.

7.6 Stress Relieving Post Weld Heat Treatment

7.6.1

General

a

The Contractor shall inform the Company prior to any PWHT operation so that the

proposed format can be reviewed and inspected as a prerequisite for Company

approval to proceed with the PWHT operation.

b PWHT of nodes shall

be

carried out following complete assembly of

the

node.

c The requirements for PWHT shall be determined from the thickness of the thickest

component of

the

welded assembly. For tapered sections, the thickness at the weld

shall be taken as the base metal thickness.

d Assemblies with different maximum thickness but not exceeding a ratio of 2:1) may be

post-weld heat treated

in the

same furnace charge

in

accordance with the heat

treatment requirements for the thickest assembly in the charge.

e Following PWHT,

the

temperature charts shall

be

marked with a clear identification

and

shall be retained for the quality control dossier. A copy shall be forwarded to the

Company.

7.6.2 Requirements For PWHT

PWHT is required when any of the following conditions apply:

a PWHT is indicated on drawings.

b PWHT is indicated

in the

WPS.

c The base metal thickness exceeds 65 mm.


28/52

7.6.3 Temperature Requirements

a) When PWHT is required the following temperature ranges shall apply:

i) 540 - 580 ·C for as-rolled

and

controlled-rolled steel.

ii) 580 - 620 ·C for normalized steel.

The soaking time shall be 1 hour per 25 mm of the maximum thickness occurring in the

assembly

to be

heat treated.

b) For furnace heat treatment, the fumace temperature at the time the assembly enters

the furnace shall not exceed 300 ·C.

c) The rate of heating shall not exceed 220 ·C/hour.

During the heating period, there shall not

be

a greater variation

in

temperature

throughout the portion of the assembly being heat treated than:

i) 150°C within any 4500 mm interval of length and

ii) 50°C

between inside and outside surfaces.

d) Cooling

to

400°C shall be at a rate not exceeding 275 °C/hour.

Below

400°C

the fabrication may be cooled to ambient temperature in still air.

7.6.4 Method

a) Post-weld heat treatment shall

be

done in a suitable furnace or using proper induction

or electrical resistance equipment.

b) Where it is impracticable to heat the whole assembly in a furnace,

the

Contractor shall

propose, in writing,

an

adequate method of PWHT for the approval of the Company.

This procedure shall include the following information:

•

•

•

•

The number, dimensions, locations and method of attachment of heating elements

The location, type and thickness of insulation.

Thermocouple types and their calibration procedures.

Method of attachment of thermocouples, locations and number.

• Types of temperature recorder

and

the calibration procedures.

• Standard information

to be

recorded on the chart.

c) The procedure for PWRT shall comply with the following:

An assembly may be heat treated in sections in an enclosed fumace, providing the

overlap is at least 5 SQRT Rt) R is the internal radius and t is the base metal

thickness) with a maximum of 1500mm. Where this method

is

used, the portion outside

the furnace shall be insulated so that the longitudinal temperature gradient is such that

the distance between the peak and half peak temperature is not less than 2.5 with a

minimum of 750

mm.

Circumferential seams in tubulars may

be

heat treated locally by electrically heating a

shielded band around the entire circumference. The width of the heated band shall not

be less than 5 , the weld being in the centre. For plate the width of the band shall

be

20t. Sufficient insulation shall

be

fitted

to

ensure that the temperature at the edge of the

heated band

Is

not less than half the peak temperature. The ends of the tubulars shall

be covered to avoid draughts inside the tubular.

In

addition, the adjacent portion of the tubular outside the heated zone shall

be

thermally insulated such that the temperature gradient is in accordance with the above.

A minimum total insulated band width of 10 for tubulars, or 40t for plate,

is

recommended for the purpose of meeting this requirement.

Welded attachments may

be

locally heat treated by electrically heating a shielded

circumferential band around the entire surface.

In

such cases, the above requirements

for circumferential seams in tubulars shall apply with the exception that the width of the

circumferential band 2.5 Rt minimum or 750mm for plate) shall be measured from the

edge of the weld which connects the attachments to the main fabrication.

In cases where these requirements cannot be strictly applied, modifications may be

agreed between the Contractor and the Company.


29/52

8.0 FABRICATION

8.1 General

8.1.1 Erection Loads and Stability

a)

During site assembly,

the

Contractor shall take account of

all

temporary erection loads

imposed on the structure

from

supports, jacking

and

slinging at each stage of the

structure assembly.

b) At each stage of the structure assembly, the Contractor shall take account of the local

or overall stability from self weight and environmental loads; inclusive of scaffolding,

staging, welding shelters

and

temporary works. The Contractor shall ensure that

all

stresses induced in

the

structure during fabrication and load out are within acceptable

limits.

c) The Contractor shall take due consideration of the effect of wind induced vortex

shedding on

the

structure or parts of the structure during construction.

d) The Contractor shall demonstrate

to

the satisfaction of the Company that he has

considered all relevant erection

and

temporary loads.

e) The Contractor shall produce a procedure for each erection or transport activity where

the item under consideration exceeds

50

tonnes

in

weight,

and

at other times when

requested

by the

Company. The procedure shall cover

all

aspects detailed in this

Clause and shall satisfy the requirements of the Malaysian Factory and Machinery Act

and the SSB/SSPC Safety Manual.

8.1.2 Material Identification

a) All components shall

be

clearly marked in accordance with the approved scheme for

the identification of members, welds and welders. (See 2.2.5, 6.1.5).

b) The Contractor shall maintain full identification of primary structural steel throughout

fabrication and

the

Contractor s reference number shall

be

die-stamped, using round

nosed dies or

by

paint marking, on cut sections of plate, sections

and

tubulars, in a

manner

to be

approved by the Company.

8.2

Material Preparation

8.2.1 Straightening

All rolled plates, bars and sections shall be flattened and straightened and made free from

twist, without damage, before marking and cutting. The limit on the amount of strain induced

by cold working shall

be

3 .

8.2.2 Cutting And Edge Preparation

The plate shall

be

cut

to

size

by

thermal cutting or machining in accordance with approved

procedures except that for plates less than 15 mm thick, cold shearing may

be

used provided,

that the sheared edge is dressed back by machining or grinding for a distance of not less than

1.5mm. All cut edges shall be prepared to the satisfaction of the Company.

The hardness of flame cut edges shall be limited to 325 HV10 maximum either by controlled

speed flame cutting, by preheat, or by grinding back or machining after cutting.

The cut edges shall

be 100

visually examined for laminations, cracks,

and

other defects. If

such defects are detected,

the

extent shall be established. A repair procedure shall

be

agreed

with the Company. At the discretion of the Company, the material component may be

rejected.

Any bevelled edge that has been damaged shall be restored to the minimum tolerances.

Where such restoration involves welding, only welding procedures approved by the Company

shall be used.

8.3

Forming

Of

Tubular And Cones

f

the Contractor decides

to

produce structural tubulars and cones, the end products shall

meet the requirements of

BS

4360

and

procedures for forming and welding shall

be

approved

by the Company. Only

one

longitudinal seam is allowed for tubulars. Cones shall be formed

with a minimum number of longitudinal seams.


30/52

8 4 Spacing

f

Seams nd Splices

8.4.1 Nodes

Circumferential seams shall in principle not

be

allowed.

If,

however, they cannot

be

avoided

the distance between circumferential seams in node barrels shall not

be

less than 2.5 metres.

Circumferential seams shall not

be

permitted in the node stubs or cones.

Longitudinal seams of the

node

barrels shall

be

offset

by

more than

90

0

•

Longitudinal seams in stab in assemblies shall not be located closer than 150

mm

to

longitudinal stiffeners.

Longitudinal seams of node barrels shall not

be

positioned within

75 mm

of the brace/stub

to

barrel weld or within the perimeter of the brace/stub

to

barrel welds.

Where the foregoing requirements cannot

be

met as a result of the complexity of the node

then the locations of weld seams shall

be

agreed in advance of fabrication with the Company.

The longitudinal seam weld of the stub shall not be within 200 mm on both sides of the centre

of the toe

and

heel of stUb. See Figure 6.

8.4.2 Other Tubular Structure And Piling Assembly

No two circumferential seams shall

be

located closer together than 1m or the pipe diameter,

whichever is less. There shall

be

no

more than two circumferential welds in any three metres

length. Longitudinal seams shall, wherever practicable be 9 ° radially offset.

In

general the number of seams in any tubular shall

be

kept

to

a minimum; they shall

be

either

as indicated

on

the contract drawings or the restrictions outlined above shall apply.

8.4.3 Stiffeners

a) Where required, transverse splices shall

be

located not closer than 120

0

intervals

around the ring stiffener flange or web. Web seams shall not

be

located closer than

150mm

to

the node barrel or tubular circumferential seams unless noted otherwise in

the Contract drawings.

b

Stiffeners shall

be

fitted accurately and neatly between the flanges of beams,

and

where tight fits are required

to

transmit bearing, the ends of the stiffeners shall be milled

or ground, as detailed on the Contract drawings, to secure an even bearing against the

flange faces, or shall

be

bevelled and fully butt welded to the flange. Cope holes shall

be

used only when indicated on the design drawings (see 8.5.4).

8.4.4 Splices

8.4.4.1 General

a) Splices shall be kept to a minimum by making individual sections as

l rge

as possible

consistent with the size of the plate supplied and the Contractor's approved assembly

sequence.

b) Splices shall be arranged

to

minimise overhead welding. Spliced materials of different

widths and thicknesses shall have smooth transitions as specified

in 7.3.1

.

c Lapped jOints are not permitted.

d) Unless speCified otherwise on the drawings, when two or more members Intersect or

overlap at a

jOint,

the order

In

which each member comes Into the joint will

be

determined by wall thickness and/or diameter. The member with the thickest wall will be

the continuous or through member, and the sequence for framing the remaining

members shall

be

based

on

the order of decreasing wall thickness.

8.4.4.2 Beams

Segments of beams with the same cross-section may

be

spliced. The use of the beam shall

determine the location

and

frequency of spliCing.

In

cantilever beams there shall be no splice

located closer

to

the

pOint

of support than one-half the cantilevered length. For beams

employed in any span between supports, there shall be no splice in the middle one-fourth of

the span. Splices shall not

be

located closer together than twice the depth of the beams, or

900 mm, whichever is larger.


31/52

8.4.5 Camber

When members are required

to be

cambered, the amount shall

be

specified and shown on

the Construction drawings, and the means of achieving the correct amount of camber shall be

agreed with the Company.

8.5 Laying-out Alignment nd Fit-up

8.5.1

Laying-out

a At all stages during fabrication, the Contractor shall ensure correct positioning,

alignment and levels

in

accordance with the required datums.

b) During layout

and

assembly of each node, the Contractor shall permanently mark

and

identify all wrap lines, working

pOints

and centre lines.

c) Overloading, damage or any permanent deformation of any of the structural

components at any stage of the erection shall be rectified in accordance with a

procedure approved by the Company.

d)

No

structural welding shall commence until the members

to be

joined have been

properly aligned and braced

to

prevent distortion.

8.5.2 Alignment

And

Fit-up For Welding

And

Tack Welding

a

Whenever practicable, clamps, holding devices or other setting

up

fixtures shall

be

used

in

assembling parts of the structure

to

avoid temporary welded attachments or

tack welding.

In

fit-up where clamps cannot

be

used, temporary spacer strips shall

be

used to ensure the correct root gap prior to tack welding.

b) Ring stiffeners, stiffeners

and

diaphragms shall be close fitted

to the

shape of the

surface

to

which they are attached either by machining or by flame cutting

and

grinding.

c) At intersections, the utmost attention shall be paid to good alignment of the structural

parts where members meet

on

opposite sides of a through member. As-built

dimensions shall

be used to

align such plates

and

not theoretical dimensions.

d) Where powered manipulations are used

in

conjunction with Mechanised Welding

Machines for the production of circumferential seams

in

tubulars, the tubular shall be

set to turn at a constant angular velocity to ensure uniform deposit of weld metal.

8.5.3 Temporarv Attachment Welds

Temporary weld attachments

and

their removal shall meet the requirements of Clause 8.6

below.

8.5.4 Cope Holes

Cope holes for

ring

stiffeners, stiffeners and diaphragms shall

be

permitted

to

a maximum

radius of 50 mm. The cut edges of the cope holes shall be ground smooth to remove all

notches, prior

to

fit-up of

the

member s). The fillet portions of all welds are

to

be returned

through the cope hole.

Cope holes shall be used only with the permission of the Company

and

may have

to be

filled

to an approved method.


32/52

8.6 Temporary nd Non-structural Attachments nd Cut-outs

8.6.1 Welding

Temporary and non-structural attachments shall be fitted to the shape of the surface to which

they are attached, and welding shall be to a qualified and approved procedure by qualified

welders. Temporary or non-structural attachments shall not be welded within 75mm of any

other structural weld measured from weld toe to weld toe.

Locations and fixing details of

all

temporary attachments are subject to the prior approval of

the Company.

8.6.2 Removal

The removal of temporary attachments shall be either by thermal cutting or by grinding. If

thermal cutting is employed, the attachments shall be cut off at a minimum distance

of

5mm

from the surface

of

the material and then ground flush. Following removal, the area

of

the

attachment weld shall be subjected to 100 magnetic particle inspection.

Temporary attachments shall not be removed by hammering, or by any other technique which

may cause mechanical damage to the surface of the steel forming the main structure.

Following removal, any damaged area shall be ground to merge smoothly with the original

surface, and the surface is to be magnetic particle inspected. Where gouges up to 20 of the

steel member thickness have been made, then after grinding and testing they shall

be

repair

welded to an approved procedure. Where gouges exceed 20

of

the material thickness, the

repair procedure or alternative solution shall be proposed by the Contractor and be subject

to

the approval

of

the Company.

8.6.3 Temporary Cut-Outs

The need for temporary cut-outs shall be subject to approval by the Company

in

each

instance unless they are detailed on the Contract drawings.

When temporary cut-outs are necessary, they shall be prepared with the same degree of care

as for permanent cut-outs and shall be cut-out prior to erection of the member(s).

Special care shall be taken to ensure that the weld preparation applied to the cut-out is

appropriate to the final erected orientation

of

cut-out at the time

of

rewelding. The cut-out shall

be trial fitted prior to erection

of

the member. An approved welding sequence developed such

that welding will be minimized shall be followed. All cut-outs shall

be

prepared with radius

corners not less than 50 mm.

8.7 Finishing

Of

Surfaces

a) Prior to completion, Contractor shall remove all burrs, tack welds and other marks

made by welding, scaffolding or temporary bracing used in the fabrication procedures.

b

Any plate defects resultant from handling or fabrication works shall be repaired

mechanically or to an approved welding procedure in accordance with the requirements

of this SpeCification. The method applied for plate repairs shall be subject to the

approval of the Company and shall comply with the limits of BS 4360.

c) For areas with arc strikes see 7.4.13.


33/52

8 8 Repair nd Remedial Procedures

8.8.1

Repair Welding

Weld repairs shall be carried out in accordance with an approved welding procedure. See

5.1g.

In

the case of repairing cracks, the cause of cracking shall first

be

established satisfactorily

before repair

is

allowed.

8.8.2 Straightening Of Distorted Members

a) Prior to straightening of a distorted member, calculations of the strains involved shall be

submitted

to

the Company for approval. Members may

be

straightened

cold

if

the

deformation does not exceed

3

strain.

b) When carried out hot, the temperature of heated areas, measured by methods

approved by the Company shall not exceed 600 °C.

The part

to

be heated shall

be

substantially free of stress

and

from external forces

except those stresses imposed resulting

from the

mechanical straightening used

in

conjunction with

the

application of heat.

c) Flame heating rectification shall be carried out only in accordance with appro