gis 42-101 - fabrication assembly erection and inspection of carbon and low alloy steel pipework.pdf
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Guidance on Industry Standard forFabrication, Assembly, Erection, and
Inspection of Carbon, Carbon Manganese,and Low Alloy Steel Pipework (ASME B31.3)
GIS 42-101
BP GROUPENGINEERING TECHNICAL PRACTICES
Document No. GIS 42-101
Applicabi li ty Group
Date 3 May 2005
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Foreword
This is the first issue of Engineering Technical Practice (ETP) BP GIS 42-101. This Guidance onIndustry Standard (GIS) is based on parts of heritage documents from the merged BP companies as
follows:
British Petroleum
GS 118-5 The Fabrication, Assembly, Erection and Inspection of Carbon, Carbon
Manganese and Low Alloy Steel Pipework to ASME B31.3.
Amoco
A PN-PLT-31.3-C PipingPlantASME B31.3Construction Specification.
A PN-PLT-31.3-CG PipingPlantASME B31.3Construction and Fabrication Guide.
A PN-PLT-31.3-P PipingPlantASME B31.3Fabrication Specification.
ARCO
ES 200 Piping Design.
Copyright2005, BP Group. All rights reserved. The information contained in thisdocument is subject to the terms and conditions of the agreement or contract under whichthe document was supplied to the recipients organisation. None of the informationcontained in this document shall be disclosed outside the recipients own organization
without the prior written permission of Director of Engineering, BP Group, unless theterms of such agreement or contract expressly allow.
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Table of Contents
Page
Foreword ........................................................................................................................................ 2
Introduction..................................................................................................................................... 5
Chapter I Scope and definitions ..................................................................................................... 6
300 General statements................................................................................................................ 6
300.1 Scope ......................................................................................................................... 6
Chapter V Fabrication, assembly, and erection.............................................................................. 7
327 General.................................................................................................................................. 7
327.1 Quality assurance and positive material identification ................................................. 7
327.2 Material control ........................................................................................................... 8
327.3 Pipework marking ....................................................................................................... 8
327.5 Fabrication facilities .................................................................................................... 8
328 Welding.................................................................................................................................. 8
328.2 Welding qualifications ................................................................................................. 8
328.3 Welding materials ..................................................................................................... 11
328.4 Preparation for welding ............................................................................................. 11
328.5 Welding requirements............................................................................................... 12
330 Pre-heating.......................................................................................................................... 15
330.1 General..................................................................................................................... 15
330.2 Specific requirements ............................................................................................... 16
331 Heat treatment..................................................................................................................... 16
331.1 General..................................................................................................................... 16
331.2 Specific requirements ............................................................................................... 17
332 Bending and forming............................................................................................................ 18
332.1 General..................................................................................................................... 18
332.2 Bending .................................................................................................................... 18
332.4 Required heat treatment ........................................................................................... 18
335 Assembly and erection......................................................................................................... 19
335.1 General..................................................................................................................... 19
Chapter VI Inspection, examination, and testing .......................................................................... 20
341 Examination......................................................................................................................... 20
341.3 Examination requirements ........................................................................................ 20
341.4 Extent of required examination.................................................................................. 20
342 Examination personnel ........................................................................................................ 20
342.1 Personnel qualification and certification .................................................................... 20
343 Examination procedures ...................................................................................................... 20
344 Types of examination........................................................................................................... 21
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344.2 Visual examination.................................................................................................... 21
344.5 Radiographic examination......................................................................................... 21
344.6 Ultrasonic examination.............................................................................................. 21
345 Testing................................................................................................................................. 22
345.4 Hydrostatic leak test.................................................................................................. 22
347 Weld repairs ........................................................................................................................ 22
Appendix E Reference standards................................................................................................. 29
Bibliography.................................................................................................................................. 30
List of Tables
Table 1 Acceptance criteria for welds (to be read in conjunction with Table 341.3.2 ofASME B31.3) ....................................................................................................................... 23
Table 2 Acceptable radiographic sensitivity levels (using wire type IQI to ASTM E747 orBS EN 462-1)....................................................................................................................... 24
List of Figures
Figure 1 Charpy notch locations................................................................................................. 25
Figure 2 Dimensional tolerances for fabricated pipework ........................................................... 26
Figure 3 Local heat treatment for branch connections................................................................ 27
Figure 4 Segmental bends ......................................................................................................... 28
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Introduction
a. Guidance for fabrication, assembly, erection, and inspection of carbon, carbon manganese,and low alloy steel pipework is based on American Society of Mechanical Engineers
(ASME) B31.3, Process Piping, 2002:
1. Chapter I Scope and definitions.
2. Chapter V Fabrication, assembly, and erection.
3. Chapter VI Inspection, examination, and testing.
b. Guidance statements of this GIS are modifications to ASME B31.3.
c. Modifications to ASME B31.3 are identified as Add, Modify to Read, or Delete.
d. Paragraph numbers in this ETP correspond to ASME B31.3.
e. Paragraphs of ASME B31.3 that are not revised remain applicable.
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Chapter I Scope and defini tions
300 General statements
300.1 Scope
300.1.3 Exclusions
Add
(e) Sea transport.
(f) Transmission pipelines in land or subsea locations, including risers.
(g) Pipelines of significant length and diameter, e.g., transfer lines between processing units,
storages, and jetties that are specified by BP to be engineered as main pipelines.
(h) Production piping systems, as designated by BP.
Production piping is covered by BS EN 14161 and ASME B31.4.
(i) Underground drainage systems.
(j) Steam piping systems within plot limits of power stations and steam generating stations
outside process areas.
Steam piping is covered by ASME B31.1 and BS EN 13480.
There is no ETP currently available to cover this category. However, guidance on
these systems can be found in ACES A PN-BLR-31.1-E and BP OUS RP 5-5-4.
(k) Heating, ventilating, and domestic water systems within buildings, including offshore
accommodation modules.
(l) Hydraulic systems.
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Chapter V Fabrication, assembly, and erection
327 General
Add
327.1 Quality assurance and posi tive material identification
327.1.1 Initial documentation
a. Before commencing fabrication of pipework, fabricator shall prepare:
1. Quality plan.
2. Set of design documents.
b. Both documents shall be subject to BP approval.
c. These documents should normally include:
1. Procedures for:
a) Storage and control of materials and welding consumables (Refer to GP 18-02).
b) Welding and nondestructive testing.
c) Mechanical working, heat treatment, and leak testing.
2. Supporting qualification records.
3. Illustration of proposed areas of application.
d. Previously qualified welding procedures may be considered for use if they comply with
this GIS document and are appropriate to proposed scope of work.
e. Simplified welder instruction cards based on qualified welding procedures should be
prepared for each welding process/material combination and issued to each welder.
f. Quality plan shall include brief details and sequence of examinations that will be
performed for fabricator.
g. Names of individuals responsible for implementation of quality assurance and qualitycontrol functions shall be included.
Fabricators involved in simultaneous fabrication of carbon steel and alloy piping
should submit positive material identification (PMI) document setting out how they
maintain and verify identification of materials during fabrication. GIS 36-103 sets
out requirements for a PMI system.
327.1.2 Product ion docu mentation
a. Fabricator shall maintain production records using recording system approved by BP.
b. Production records shall include:
1. Material and welding consumable certificates.
2. Post weld heat treatment records.
3. Visual and dimensional inspection.
4. NDT and pressure test records.
5. Isometric drawings marked up with weld numbers.
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6. Welder and welding operator qualification test records.
7. Authenticated copies of NDT operators certificates.
8. Records of agreed concessions to fabrication standards.
c. Upon completion of fabrication programme, records shall either be passed to BP or storedby fabricator, as directed by engineering design or fabrication contract.
327.2 Material cont rol
a. Fabricator shall inspect materials upon receipt and ensure that correct grade of material has
been supplied and that identification, dimensions, material quality, and end preparation are
in accordance with the requisite standards and specifications.
b. Different materials shall be kept in discrete sections of storage area, and material shall bemarked in a manner that allows it to be related to original manufacturers certification.
c. Procedures for transfer of material identification marks shall be agreed with BP prior to
commencement of fabrication.
d. Material that is not readily identifiable shall be removed from worksite and quarantined
until material grade and source can be confirmed.
Positive identification and segregation of materials is an important issue.
327.3 Pipework marking
a. Pipework shall be identified by indelible marking that is free from sulphur, chloride, and
other halogens.
b. If spools are subject to postweld heat treatment, suitable heat resisting paint shall be used.
c. Vibroetching techniques may be used for identification transfer, but adhesive tapes or hard
stamping, other than that with low stress stamps, shall not be used.
d. Marking shall have minimum life of 1 year in covered, unheated, storage.
e. Marking shall identify material and fabricator and include item number, enabling spool tobe traced to relevant isometric drawing.
Guidance on suitable colours for identification of piping materials is in BS 5383.
327.5 Fabrication facili ties
a. Area used for fabrication shall be totally separate from that used for carbon and low alloy
steel.
1. Each alloy type shall be segregated during fabrication.
2. Precautions shall be taken to prevent surface contamination by contact with jigs and
fixtures manufactured in non compatible materials.
3. Separate sets of clearly identified cleaning and grinding equipment shall be provided
for each material.
b. Shop layout, equipment, and production procedures shall be subject to BP approval.
328 Welding
328.2 Welding qualifications
328.2.1 Qualification requirements
(a) Add
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1. Welding procedure specifications and procedure qualification test results shall besubject to BP approval before commencement of fabrication.
2. Each procedure qualification record (PQR) shall be certified by recognised
independent inspectorate.
SMAW, GTAW, and SAW processes are frequently employed for pipework
fabrication and are considered to be acceptable welding techniques if used inaccordance with this ETP. GMAW and FCAW processes are also often applied to
piping fabrication. However, there are many variants of these two processes. In
addition to ensuring adequate procedure qualification, it is important to ensure that
the particular welding technique proposed for a given application is well proven
and will only be used by qualified and experienced welders.
(d) Add
1. For design temperatures below 0C (32F), Charpy V notch impact testing shall be
required on carbon, carbon-manganese, and 3 1/2% nickel piping materials, fittings,
and weldments in accordance with EEMUA 153, Appendix SA.
2. Weld metal, fusion line, and HAZ testing are required.
3. Charpy specimens shall be cut transverse to weld with axis of notch perpendicular tosurface of test piece.
4. Specimen and notch locations shall be as shown in Figure 1.
5. Weld metal, fusion line, and HAZ impact results shall, as a minimum, meet
requirements of parent material.
6. If only subsize charpy specimens can be taken, the following standard energy
reduction factors shall be applied:
Specimen Size (mm) Specimen Size (in) Reduct ion Factor
10 x 7.5 0.394 x 0.295 0.833
10 x 5 0.394 x 0.197 0.667
7. If welding procedure requiring impact testing is to be used in all positions, separate2G and 5G qualifications shall be performed.
EEMUA 153, Table SA 6.1.3, gives guidance on service conditions where
nonimpacted materials may be used.
(e) Modify to Read
Backing rings are not permitted.
(f) Add
P-Numbers (also F-Numbers)
1. Extension of welding procedure qualification from material on PQR to material of
different specification, even if it has same P-Number, shall be subject to BP approval.2. New welding procedure qualification is required for nonimpact tested procedures, if
there is a change of consumable classification.
3. Unless agreed otherwise, new welding procedure qualification is required for impacttested procedures if there is a change of consumable brand name.
4. New welder performance test is required if there is a change of SMAW electrode
brand name, unless brand characteristics do not differ sufficiently to affect
performance. Such change shall be subject to BP approval.
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Add
(g) Welding procedure specification (WPS) shall require requalification if any of the following
changes are made:
1. Change outside welding parameter tolerance ranges specified in qualified weldingprocedure specification.
2. Increase of more than 1 gage number in electrode size from that used in qualifiedwelding procedure.
3. Change in type of current, e.g., ac to dc or, in dc welding, change in electrode
polarity, except where these changes are within electrode manufacturer
recommendations.
4. For impact tested procedures, increase in either maximum electrode diameter or
weave width or if maximum interpass temperature is raised above 250C (480F).
5. For critical applications, as directed by the engineering design.
(h) If a limitation on weldment hardness is specified in engineering design, macrographic
examination and hardness measurements shall also form part of welding procedure
qualification (WPQ).
Depending on service duty, weld metal and HAZ hardness may be subject to specific
limitations. Perhaps the best known limitation is 22 Rc (248 HV 10) placed on
carbon and low alloy ferritic steel weldments in sour duty in accordance with
GP 06-20. Hardness limit of 200 HBN (210 HV 10) is also often placed on carbon
steel weld metals in corrosive refinery environments (NACE RP0472). Guidance on
need for hardness limitation should be provided by engineering design.
A hardness test may also be used to determine effectiveness of heat treatment
procedures. In absence of specific restrictions on hardness, requirements of
Table 331.1.1 of ASME B31.3 may be used for guidance.
(i) In addition to mechanical testing, welding procedure test samples shall be subjected to
radiographic examination.
(j) Magnetic particle/dye penetrant and ultrasonic examination shall be applied to test samples
if they are to be used in evaluation of production welds.
(k) Nondestructive examination shall be completed prior to machining of test pieces.
(l) Ideally, welder performance tests for positional welding should be performed in both 2G
and 5G positions. However, subject to agreement of BP, welder performance test may be
undertaken in 6G position. In that case, each welder shall also demonstrate his ability to
deposit acceptable root runs in both 2G and 5G positions. With the agreement of BP, this
may be achieved by radiography of welders first production welds in 2G and 5G
positions.
(m) Welders and welding operators shall be qualified by visual examination and radiography.
Subject to provision of authenticated CV and with agreement of BP, welders andwelding operators may be qualified on their initial production welds.
(n) Welder and welding operator qualification tests shall be witnessed by inspector.
The above additions and modifications to qualification requirements have been
made on basis of fabrication experience and allow welding to proceed with
improved level of confidence in both procedural qualification and welder skill.
Ultrasonics may be used in lieu of radiography if material thickness restricts
suitability of radiography due to decreased sensitivity or extended exposure time.
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Add
328.2.5 Test joints
a. Welding procedure qualification tests for impact tested P1 steels and all higher P-Numbermaterials shall be performed on pipe.
b. On nonimpact tested P1 materials, testing shall be performed on pipe for sizes DN 200
(NPS 8) and below.
c. On sizes greater than DN 20 (NPS 8), plate qualified welding procedures may be approved
by BP.
d. Welder performance tests shall be performed on pipe.
328.3 Welding materials
328.3.1 Filler metal
Add
a. In general, deposited weld metal shall be of similar composition to parent material, except
that in case of:1. Carbon steel carrying injection water or wet hydrocarbons, where specific guidance
shall be provided by engineering design in order to minimise possibility of
preferential weld metal corrosion.
2. Carbon steels in service at or below 0C (32F), where a consumable containing
nominally 1% nickel may be required to meet impact toughness requirements.
3. 1/2 Cr 1/2 Mo 1/4 V steels, where 2 1/4 Cr 1 Mo consumables shall be used to
minimise risk of stress relief cracking and ensure adequate creep ductility in service.
b. Consumables for repairs to C 1/2 Mo steels shall be of 1 1/4 Cr 1/2 Mo composition.
Selection of austenitic stainless steel or high nickel alloy weld metal for steels
containing 5% chromium can minimise potential for hydrogen cracking and may
permit some relaxation of preheating requirements. However, use of such
consumables must be compatible with service requirements, specifically approved
by BP and qualified by procedure testing.
Final guidance on special requirements for weld metal selection, including selection
of weld metal composition for dissimilar metal joints, should be provided by
engineering design.
328.3.2 Weld backing material
Modify to Read
As stated in 328.2.1(e), backing rings shall not be used.
328.3.3 Consumable inserts
Modify to Read
Consumable inserts may only be used with BP approval.
328.4 Preparation for weld ing
328.4.2 End preparation
(b) Circumferential welds
(4) Modify to Read
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Use of deposited weld metal to correct misalignment shall be subject to agreement byBP.
Add
(6) Prior to fitup, weld bevels shall be visually inspected.
This visual inspection, if considered necessary by either fabricator or BP inspection
or welding personnel, may be supplemented by either magnetic particle or dyepenetrant examination.
(7) Unless approved by BP, end bevels and holes for branches shall be prepared by
machining or machine flame cutting, except for holes for branches less than 25 mm
(1 in) nominal bore, which shall be drilled.
(8) Flame cut edges shall be dressed to remove oxide and dross.
328.4.3 Alignment
(a) Circumferential welds
Add
(3) Bore misalignment in circumferential butt joints shall not exceed 1.5 mm (1/16 in)without BP approval.
(c) Branch connection welds
(3) Add
Weld metal shall not be deposited to correct contour, shape, or tolerances without
permission of BP.
Add
(e) Fabrication tolerances
1. Unless approved otherwise, fabrication tolerances shall comply with Figure 2.
2. Category M tolerances shall be used:a) For service temperatures greater than 460C (850F).
b) PN 150 (Class 900) ratings and above.
c) If specified by engineering design.
328.5 Welding requirements
328.5.1 General
(b) Modify to Read
Welds shall be marked with welder/welding operator identification symbol using marker
pencils or paints that comply with 327.3.
(c) Add
Tack welds that are to become an integral part of root weld shall be ground to feather edge,
while those not intended to become part of final weld shall be removed as weldingproceeds.
(d) Modify to Read
Peening shall not be permitted on any pass.
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(r) If practical, fillet welded joints for pressure containment should have minimum of threeweld passes, two of which should be showing for visual inspection.
The above additions and modifications to welding requirements have been made on
the basis of fabrication experience and allow welding to proceed with improved
level of confidence in workmanship and practice.
328.5.3 Seal welds
Modify to Read
a. Threaded joints should be assembled in such a manner that a maximum of three threads are
exposed prior to welding.
b. Joints to be seal welded shall be made up clean and without use of tape or compound.
c. Welding shall be performed in accordance with qualified procedure by qualified welder.
d. Welding shall not cause damage to threaded fitting.
e. Exposed threads shall be covered by seal weld.
328.5.4 Welded branch connections
Add
If designing angled branch connections, in addition to considering stress concentration effects,
sufficient access shall be provided for welding in acute angle section.
If set on integrally reinforced branch connections are used, it should be noted that
the wall thickness of the connection may well be in excess of that necessary to
provide the required level of reinforcement. Consequently, no reinforcement
contribution is necessary from the weld metal, and the deposition of a branch weld
with an excessive throat thickness may lead to unacceptable distortion of the main
run pipe. The engineering design should provide guidance on the sizing of branch
welds if using this type of fitting and on the need for controlled weld profiles if the
branch is on severe cyclic duty.
If set in integrally reinforced branch connections are used, fit up, jigging, and
developing an overall welding sequence, should minimise the extent of any
"sinking".
328.5.5 Fabricated laps
Add
Fabricated laps shall not be used without agreement of BP.
328.5.6 Welding for severe cyc lic cond itions
Add
a. Weld reinforcement shall be smooth and regular.b. Weld reinforcement shall blend smoothly with external surface of pipe to minimise
possible stress concentration effects.
The engineering design should provide specific guidance considered necessary for
weld profiles in severe cyclic duty.
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Add
328.5.7 Proximity of welds
a. Toes of adjacent circumferential butt welds shall be no closer than four times nominalthickness of the pipe.
b. For pipe sizes of DN 300 (NPS 12) and below, minimum acceptable separation shall be
50 mm (2 in).
c. For pipe sizes greater than DN 300 (NPS 12), minimum acceptable separation shall be
100 mm (4 in).
d. Branch and non pressure part attachment welds shall not cross longitudinal seams orcircumferential butt welds and shall be subject to toe to toe separation distance specified
for circumferential butt welds. If such intersections are unavoidable, the main weld shall be
subject to nondestructive examination prior to making attachment weld.
e. Joints involving intersection of more than two welds shall be avoided.
330 Pre-heating
330.1 General
Add
a. Oxy-fuel gas welding or cutting torches may only be used for preheating if fitted with
proprietary preheating nozzles.
b. Quenching or other means of accelerated cooling from preheat temperatures shall not be
used.
330.1.1 Requirements and recommendations
Add
If the carbon content of P1 material is greater than or equal to 0.25%, minimum preheattemperature of 80C (175F) shall be required, irrespective of thickness or minimum tensile
strength.
When establishing preheat temperatures, advantage may often be taken of the lower
hydrogen potential of the GTAW process, relative to the SMAW process, in setting a
lower preheat temperature for welding. However, adequacy of the selected
temperature must be proven by welding trials/procedure qualification testing.
330.1.3 Temperature verifi cation
(b) Add
Thermocouples may not be directly attached to pressure parts without agreement of BP.
330.1.4 Preheat zone
Modify to Read
The preheat zone shall extend 75 mm (3 in) or a distance equal to four times the material
thickness, whichever is greater, beyond each edge of weld.
Add
330.1.5 Interpass temperature
Maximum interpass temperature shall not exceed 250C (480F).
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330.2 Specifi c requirements
330.2.4 Interrupted welding
Add
If welding is interrupted, the requirements of 328.5.1(m) shall apply.
331 Heat treatment
331.1 General
331.1.1 Heat treatment requirements
Add
(e) Post weld heat treatment shall be applied if required by the engineering design.
(f) Post weld heat treatment is required if carbon content of P1 material is greater than 0.25%.
(g) Low melting point metals, such as aluminium, lead, tin, copper, zinc, cadmium, and
mercury, and their alloys, shall not be permitted to contact steel surfaces that will undergo
hot forming, welding, or post weld heat treatment.
Possible sources of such contamination include solder, galvanised components,
clamps and fixtures, and certain types of paint.
331.1.3 Governing thickness
The engineering design should provide necessary clarification of paragraphs (a)
and (b) in the event that specific service conditions, e.g., low temperature
applications or sour duty, require alternative guidelines on governing thickness.
331.1.4 Heating and coo ling
Add
a. If furnace heat treatment is applied, furnace temperature shall not exceed 400C (750F)
when pipework is loaded or removed.
b. Maximum heating or cooling rate above 400C (750F) shall not exceed 200C (400F)
per hour, and for wall thickness, t mm greater than 30 mm (1 in) shall not exceed
6000/t C (430/t F) per hour.
The above additions are made to define heat treatment requirements more closely.
331.1.6 Temperature verifi cation
Add
a. If practical, thermocouples shall be attached to spool pieces at minimum of six equally
spaced locations, adjacent to welds, prior to heat treatment.b. Procedures for attachment of thermocouples by capacitor discharge welding shall be
subject to BP approval. Use of this technique shall be carefully monitored.
331.1.7 Hardness tests
Add
Additional requirement for hardness testing may be specified by engineering design.
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331.2 Specifi c requirements
331.2.2 Exceptions to basic requirements
Some examples of where the engineering design may deviate from the basic
requirements are:
Use of P1 materials in low temperature piping systems designed for use below0C (32F), where requirements of EEMUA 153, Appendix SA, and
paragraph 328.2.1(d) of this document should be followed.
Use of P1 materials in low criticality applications at temperatures above 0C(32F), where limiting thickness for post weld heat treatment may be relaxed
from 19 mm (3/4 in) up to maximum of 35 mm (1 3/8 in).
If materials are employed on sour duty or in environments liable to induce stresscorrosion cracking, reference should be made to GP 06-20.
331.2.4 Delayed heat treatment
Modify to Read
If a weldment in material of P-Numbers 3, 4, 5, 6, or 7 is to be allowed to cool to ambient
temperature prior to final post weld heat treatment, intermediate post weld heating shall beapplied, as required by the following:
a. On completion of welding, joints of thickness in excess of 10 mm (0.4 in) deposited by
processes other that GMAW or GTAW shall be immediately raised to 300C (570F) for1 hour per 25 mm (1 in) of thickness, with a minimum of 30 minutes. Subsequently, the
joint shall be cooled slowly under dry insulation.
b. For joints in materials containing in excess of 4% chromium and having wall thickness
exceeding 25 mm (1 in), the temperature shall be raised immediately after welding to a
value within range specified for post weld heat treatment and held at that temperature for
30 minutes. Subsequently, the joint shall be cooled slowly under dry insulation.
The above modification is made to clarify requirements related to delayed heat
treatment.
The thermal cycle associated with intermediate post weld heating is designed to
allow dispersion of potentially dangerous hydrogen concentrations in weld metal
and HAZ. This heat treatment may also result in microstructural softening in some
alloys that often further reduces the potential for hydrogen induced cracking.
331.2.6 Local heat treatment
Modify to Read
a. If local heat treatment is applied, weld shall be sufficiently heated and insulated to ensure
that (for a pipe of DN (NPS) D and wall thickness t):
1. Specified heat treatment temperature is achieved at weld.2. Within distance of 1.8 Dt on both sides of the weld, temperature of not less than
half of specified heat treatment temperature is attained.
b. In the case of branch attachments, temperature gradient shall be such that length of
material from each crotch heated to temperature equalling half heat treatment temperature
shall be 1.8 Dt (where D and t are the nominal diameter and thickness of the main
pipe and branch as appropriate) (Figure 3).
c. In a. and b., D is expressed as DN (NPS), t is expressed in mm (in), and temperature isexpressed in C.
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The above modification is made to clarify the requirements for local post weld heat
treatment.
332 Bending and forming
332.1 General
If designing pipe spools, particularly in P1 materials, the potential of induction
bending should be considered to avoid use of large numbers of individual elbows
and minimise extent of fabrication welding. Multiple bends of varying angles may be
included in spools made from single lengths of parent pipe using this technique.
Engineering design should consider manufacturing tolerances and need for heat
treatment following pipe bending. Bend manufacturer procedures should be
reviewed to confirm that adequate control is being exercised in heating, cooling,
and inspection of bends.
Typical tolerances on completed bends should be:
Ovality at cross section of bend should not exceed 5%.
Wall thickness after bending should not be less than nominal design thickness.
Angle of bend should be within 0.009 radians (0.5 degrees) of nominal.
Following heat treatment of cold pulled bends in low alloy steels, it is recommended
that a quality control check by means of hardness testing be performed, at least in
the early stages of production. The hardness testing should be performed on one
bend per heat treatment batch at four locations around pipe circumference using
portable hardness tester of a type approved by BP. In the absence of specific
restrictions on hardness, requirements of Table 331.1.1 may be used for guidance.
332.2 Bending
332.2.3 Corrugated and other bends
Add
a. Fabricated mitre (segmented) bends are not generally permitted.
b. Subject to agreement of BP, limited use of mitred bends in accordance with Figure 4 may
be proposed.
c. Cut and shut design shall not be used.
332.4 Required heat treatment
332.4.1 Hot bending and forming
Add
a. The engineering design shall state requirements for heat treatment of P1 materialsfollowing hot bending and forming.
b. The fabricator shall be required to retest materials following thermal treatment to confirm
that requirements of engineering design are satisfied after such heat treatment.
Heat treatment of P1 materials may not be necessary if hot forming is completed at
a temperature above 900C (1650F), and material is allowed to cool in still air.
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335 Assembly and erection
335.1 General
335.1.1 Alignment
(a) Piping distortions
Add
1. Application of heat for correction of minor distortions shall only be undertaken with BP
approval.
2. Such heating shall be performed in accordance with approved procedure, and maximum
temperature employed shall not exceed 450C (840F).
3. Spot heating techniques shall not be used.
4. Under no circumstances shall materials be quenched to correct alignment.
Add
335.1.2 Bolt ing proceduresa. Bolting procedures should be provided for each joint or group of joints to be assembled.
b. As a minimum, these procedures shall contain the following information:
1. Required bolt load or stress.
2. Tightening method.
3. Tightening sequence.
4. Elongation measurement requirements.
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Chapter VI Inspection, examination, and testing
341 Examination
341.3 Examination requi rements
341.3.1 General
(a) Modify to Read
Final examination shall be performed after completion of heat treatment.
341.3.2 Acceptance crit eria
(a) Modify to Read
Acceptance criteria for welds are stated in ASME B31.3, Table 341.3.2, and Table 1 of this
GIS.
341.4 Extent of requi red examination
Add
a. For all fluid categories, extent of required examination and inspection method employed
shall depend on criticality rating of individual piping system.
b. Method of determining criticality rating shall be specified by engineering design. Assigned
values shall be recorded in piping line lists.
342 Examination personnel
342.1 Personnel qualification and certification
Add
a. Only personnel certified in accordance with PCN, CSWIP, AWS QC1, ASNT CP-189, or
ASNT recommended practice SNT-TC-1A shall be allowed to undertake examinations.
b. In the case of ASNT SNT-TC-1A, assessment of operator competence should have been
undertaken by an external authority.
c. Other equivalent certification may be accepted at discretion of BP.
d. Personnel qualifications shall be subject to BP approval.
Under most circumstances, equivalent certification will only be considered if the
body issuing certification meets the requirements of ISO 9712 or BS EN 473.
343 Examination procedures
Add
Examination procedures shall comply with 327.1.1.
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344 Types of examination
344.2 Visual examination
344.2.1 Definition
Add
Visual examination shall include examination of internal surface of weld, if possible, using
suitable optical instruments.
344.5 Radiographic examination
344.5.1 Method
Modify to Read
a. X-ray techniques are preferred for shop radiography of pipework up to 25 mm (1 in) wall
thickness.
b. If use of X-rays is impractical, gamma ray isotopes may be used, subject to BP approval.
c. In each case, prior to production radiography the technique shall be qualified using sourceside image quality indicator (IQI) of wire type to ASTM E747 or BS EN 462-1, whichever
is applicable.
d. Single wall, single image technique should be used if possible.
e. Lead intensifying screens and fine grain high contrast film shall be used.
f. Film density shall be 2.0-3.0 through thickest portion of weld.
g. IQI specified in accordance with BS EN 462-1 shall have radiographic sensitivity that
complies with Table 2.
h. If complete joint circumference is radiographed in a single exposure, four IQIs placed at
/2 radian (90 degree) intervals shall be used.
i. Set on branch connections if permitted by engineering design, should be subject tointermediate radiography.
1. Film shall be on bore side of joint.
2. Radiography shall be performed when weld depth is similar to wall thickness and
before reinforcing fillet is applied.
344.5.2 Extent of radiography
(c) Spot radiography
Modify to Read
Spot radiography shall not be used for girth, mitre, or branch welds.
344.6 Ultrasonic examination
Add
a. If ultrasonic examination is required, procedures for each joint configuration and thickness
shall be subject to BP approval.
b. Such examination will normally be restricted to wall thicknesses greater than 10 mm
(3/8 in).
If fabricating pipework having wall thickness in excess of 25 mm (1 in),
consideration should be given to examination of root region if welding is partially
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complete to depth of approximately 30% of wall thickness. This minimises the need
for through wall repairs.
Following repairs to the root and reexamination, the weld should be completed and
subjected to final examination.
Add
344.6.3 Post weld heat treated join ts
a. On joints subject to post weld heat treatment, if examination is necessary both prior to and
after heat treatment, the use of a dual NDT technique may be considered.
b. While radiography might be the most appropriate form of examination during fabricationprior to heat treatment, ultrasonics may be more relevant in some locations after heat
treatment.
c. If ultrasonics is applied following post weld heat treatment it should also be applied beforeheat treatment.
Access to perform radiography may become restricted as fabrication proceeds. In
such cases, it may be appropriate to perform radiography and ultrasonics prior to
completing fabrication and apply ultrasonics after heat treatment to those areas that
are inaccessible for radiographic inspection.
345 Testing
345.4 Hydrostati c leak test
Add
a. Fabricator hydrostatic test procedure shall include:
1. Details of test fluid.
2. Minimum temperature.
3. Test pressure.
4. Pressure recording.
5. Control method and holding time.
b. Hydrostatic test procedure shall be reviewed by BP.
c. After hydrostatic testing, pipe spools that are to be stored prior to installation shall have
ends sealed to prevent ingress of dirt, moisture, or other contaminants.
If piping spools are to be stored prior to installation, due consideration should be
given to the need for the introduction of a suitable vapour phase inhibitor/biocide.
d. Flange faces shall be coated with suitable corrosion preventive.
Hydrotesting should be performed after completion of heat treatment.
Add
347 Weld repairs
a. Before starting fabrication, the fabricator and BP shall agree which types of weldingdefects are to be regarded as notifiable prior to rectification.
b. Fabricator shall subsequently advise BP of need to perform such repair, which shall be
subject to approval prior to commencement of further work on defective welds.
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c. Detailed records of repairs shall be retained by fabricator.
d. Repair welding shall comply with approved repair procedures, unless use of original
procedure has been agreed with BP.
e. As a minimum, repair welds shall be inspected to their full extent using techniques usedfor inspection of initial weld.
f. If cracking has occurred in either weld metal or heat affected zone and a repair has beenagreed:
1. The full extent of the original weld shall be re-examined on completion of the repair.
2. BP may require that additional inspection techniques be applied to the joint following
repair.
g. Weld repairs shall, if practical, be performed prior to post weld heat treatment. If a second
heat treatment is necessary, details of procedure qualification requirements shall be agreed
with BP.
Application of a second heat treatment may have adverse effects on the properties of
weld metal and some base materials. Thus, it may be necessary to consider a
qualification test using previously welded and heat treated material for qualification
of repair techniques. In such cases, additional testing of parent material should be
performed.
Table 1 Acceptance crit eria for welds (to be read in conjunction w ith Table 341.3.2 of ASME B31.3)
Type of Imperfection Acceptance Criteria for the Specified Service Condition
Lack of fusion 'A' for all welds.
Incomplete penetration (1) 'A' shall apply to all welds in severe cyclic or normal fluid service.
Internal porosity 'D' shall apply to all welds in severe cyclic or normal fluid service.'E' shall be applicable to category D fluid service.
Slag inclusion, tungsten inclusion, orelongated indication (1)
'F' shall apply to all welds irrespective of service condition.
Undercutting 'H' shall apply to girth and, if approved, mitre groove welds in category Dfluid service.
Concave root surface (suck back) (1) Not permitted in severe cyclic or normal fluid service unless a specificlimit is set by the engineering design. A maximum of 1.6 mm (1/16 in)shall apply to welds in category D fluid service.
Reinforcement or internal protrusion For all welds irrespective of service conditions external weldreinforcement shall be uniform, 1.6 mm (1/16 in) to 3 mm (1/8 in) inheight and shall merge smoothly into the pipe surface.
Positive root penetration shall not exceed 1.6 mm (1/16 in) for DN 50(NPS 2) and smaller or 3 mm (1/8 in) for larger pipe.
Note:
1. If these defects are permitted, total cumulative length of lack of root penetration, slag inclusions, or concave root shall
not exceed 10% of weld joint circumference.
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Table 2 Acceptable radiographic sensitivity levels(using wire type IQI to ASTM E747 or BS EN 462-1)
Thickness1 X-Radiography Gamma Radiography
mm in SWSI DWSI DWDI SWSI DWSI DWDI
4.5 0.177 Note 3 Note 3 Note 3 Note 3 Note 3 Note 3
4.5 6.0 0.177 0.236 2.0% 2.5% 3.2% 2.6% 2.7% 3.5%6.0 9.0 0.236 0.354 1.7% 2.0% 3.0% 2.4% 2.5% 3.2%
9.0 14.0 0.354 0.551 1.5% 1.8% Note 3 2.4% 2.5% Note 3
14.0 18.5 0.551 0.728 1.4% 1.7% NA 2.0% 2.2% NA
18.5 26.0 0.728 1.024 1.3% 1.7% NA 1.7% 2.0% NA
26.0 40.0 1.024 1.574 1.1% 1.7% NA 1.5% 1.8% NA
>40.0 >1.574 Note 3 Note 3 Note 3 Note 3 Note 3 Note 3
1. Thickness for SWSI and DWSI is estimated single weld thickness. Thickness for DWDI is one wall thickness plus one
estimated weld thickness.
2. Sensitivity shall be no worse than the values given in this Table. Sensitivity values are based on IQI placed on film sidefor SWSI and DWSI exposures and IQI on source side for DWDI exposures. Sensitivity shall be calculated using the
formula:
Sensitivity =1Thickness
areaweldinvisiblewirethinnestofThickness
3. Sensitivity requirement to be agreed with BP following production of test radiographs.
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Figure 1 Charpy notch locations
WELD CENTRE
LINE NOTCHES
2mm MAX
2mm MAX
FL + 1mmFL + 2mm
FL + 5mm
FUSION LINE (FL) AND HAZ
NOTCH POSITIONS
Weld metal centre line, FL and FL+2 mm testing is mandatory. The need for other notch locations to be tested shall be identified
by the engineering design.
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Figure 2 Dimensional tolerances for f abricated pipework
CL
CL
CL
CL
A
A
A
A
A
E
D
C/L FLANGE OR BRANCH
C
B
A
Maximum Allowable Dimensional Tolerance
Item Category D and Normal Service ConditionsCategory M and Severe Cycli c Temperature
450C (850F) Rating PN 150 (Class 900)
A 3 mm (1/8 in) maximum from indicated dimension: from face to face, centre to face, location ofattachments, etc.
B 8% maximum (for internal pressure)3% maximum (for external pressure)
2% maximum
Flattening measured as difference between maximum and minimum O.D. at any cross section
C 3 mm (1/8 in) maximum lateral translation ofbranches or connections
1.5 mm (1/16 in) maximum lateral translationof branches or connections
D 1.5 mm (1/16 in) maximum rotation from the indicated position, of flanges measured as shown
E 0,75 mm (0.03 in) maximum out of alignment of
flanges from the indicated position, measuredacross any diameter
0.4 mm (0.016 in) maximum out of alignment of
flanges from the indicated position, measuredacross any diameter
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Figure 3 Local heat treatment for branch connections
1 11.8 D t
1.8 D t2 2
SHADED AREAS TO BE HEAT TREATED
D NOMINAL O.D OF MAIN PIPE
D NOMINAL O.D OF BRANCH PIPE
t THICKNESS OF MAIN PIPE
t THICKNESS OF BRANCH PIPE
1
2
1
2
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Figure 4 Segmental bends
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Appendix E Reference standards
ASNT
Add
CP-189 Qualification and Certification of Nondestructive Testing Personnel.
ASTM
Add
E 747 Standard Practice for Design, Manufacture and Material Grouping
Classification of Wire Image Quality Indicators (IQI) Used for
Radiology.
AWSAdd
QC1 Standard for AWS Certification of Welding Inspectors (1996 or lateredition).
Add
BSI Standards
BS EN 462-1 Non-destructive testing - Image quality of radiographs - Part 1: Imagequality indicators (wire type) - Determination of image quality value.
EEMUA StandardsEEMUA 153 Process Piping-Supplement to ASME B31.3.
BP
GP 18-02 Guidance on Practice for Storage and Control of Welding Consumables.
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Bibliography
American Society of Mechanical Engineers (ASME)[1] ASME B31.1 Power Piping.
[2] ASME B31.4 Pipeline Transportation Systems for Liquid Hydrocarbons and other Liquids
BP
[3] GIS 36-103 Guidance on Industry Standard for Positive Material Identification (PMI).
[4] GP 06-20 Guidance on Practice for Sour Service (GS 136-1).
British Standards Institute (BSI)
[5] BS EN 473 Non-destructive testing - Qualification and certification of NDT personnel - Generalprinciples.
[6] BS 5383 Material identification of steel, nickel alloy and titanium alloy tubes by continuouscharacter marking and colour coding of steel tubes.
[7] BS EN 13480 Metallic industrial piping.
[8] BS EN 14161 Petroleum and natural gas industries Pipeline transportation systems.
International Organization for Standardization (ISO)
[9] ISO 9712 Non-destructive testing - Qualification and certification of personnel.