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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
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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
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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.
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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.
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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
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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.
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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
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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