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CORYTON ENGINEERING
STANDARD
Indicator Number: CES/18/001
SUBJECT:
PIPE FABRICATION, WELDING, ERECTION AND INSPECTION
New:
Re-Issue: (No change): Re-Issue: X (Amended):
Original Issue Date May 1995 Last Issue Date January 2000 This
Issue Date December 2001
SUPERSEDES: NONE
Author
D T Hatfull
Inspection Group Quality Co-ordinator
Authorised by
P Avery Maintenance Engineering &
Performance Superintendent ATTACHMENTS: None REFERENCES: Q3/0059
- Refinery Document Control REVIEW DATE: November 2006
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CES/18/001 (December 2001)
CONTENTS 1.0 SCOPE AND PURPOSE 2.0 REFERENCES 3.0 GENERAL
REQUIREMENTS 3.1 Table 1 - Inspection Classification Requirements
4.0 FABRICATION, ASSEMBLY AND ERECTION
4.1 General 4.2 Figure 1- Fabricated Piping Dimensional
Tolerances 4.3 Figure 2 - Proximity Of Welds 4.4 Carbon Steel 4.5
Low Alloy Steel 4.6 Austenitic Stainless Steel Monel 4.7 Monel 4.8
Nickel And Nickel Alloy 4.9 Assembly And Erection
5.0 WELDING
5.1 General 5.2 Weld Procedures 5.3 Qualification Of Welders And
Welding Operators 5.4 Welding Processes 5.5 Consumables 5.6 Alloy
Cladding And Overlay
6.0 THERMAL HEAT TREATMENT
6.1 Preheat And Interpass Temperatures 6.2 Postweld Heat
Treatment
7.0 NON-DESTRUCTIVE EXAMINATION
7.1 Visual Examination 7.2 Radiographic Examination 7.3
Ultrasonic Examination 7.4 Magnetic Particle Inspection 7.5 Dye
Penetrant Inspection 7.6 Examination Personnel
8.0 HYDRO-STATIC TESTING 9.0 QUALITY APPENDIX A SPECIAL
REQUIREMENTS FOR HF ACID SERVICE APPENDIX B HF SERVICE COUPLING
INSTALLATION APPENDIX C TABLE 2 FILLER METAL FOR WELDING DISSIMILAR
MATERIAL
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1.0 SCOPE AND PURPOSE
This standard defines the Refinery requirements for the
fabrication and installation of metallic piping systems including
welding, inspection, non-destructive testing and post weld heat
treatment.
This standard also defines the requirements for welding pressure
vessels, heater coils, heat exchangers, pumps, compressors, tanks
and other pressure containing equipment
The purpose of this standard is to establish a common quality
level for the fabrication and installation of metallic piping
systems and for the welding of all other pressure containing
equipment.
2.0 REFERENCES - (All References Shall be of the Latest
Revision)
API (American Petroleum Institute) Standard
Std 510 (1997) Pressure Vessel Inspection Code Std 650
(1993-1997) Welded Steel Tanks for Oil Storage Std 653 (1991) Tank
Inspection, Repair, Alteration and Construction ANSI (American
National Standards Institute) / ASME (American Society of
Mechanical Engineers).
B1.20.1 Pipe Threads, General Purpose (INCH.) ASME (American
Society of Mechanical Engineers) Standards Section V (1995) -
Non-destructive Examination Section VIII (1995) Boiler & Vessel
Code Section IX (1995) - Welding and Brazing Qualifications B31.3
(1999) - Process Piping B31.1 -Power Piping
American Society for Non -destructive testing (A.S.N.T.) ASNT RP
SNT-TC-1A - American Society for Non-destructive Testing Inc. -
Recommended Practice For Non-destructive Testing British Standards
BS 2600 Part 1 - Radiographic examination of fusion welded butt
joints in steel: methods or steel 2mm upto and including 50mm
thick. BS 2600 Part 2 - Radiographic examination of fusion welded
butt joints in steel: methods for steel over 50mm upto and
including 200mm thick. BS 2910 - Radiographic examination of fusion
welded circumferential butt joints
in steel pipes.
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BS 1113 (1998) - Design and Manufacturer of Water-tube Steam
Generating Plant BS 5500 (1997) - Specification For Unfired Fusion
welded Pressure Vessels Welding Institute CSWIP - Certification
Scheme For Weldment Inspection Personnel. Coryton Engineering
standards (CES) CES/36/002 - Preparation for materials and shipment
CES/42/001 - Piping Material Specification + Specific Classes
CES/42/006 - Spring Support Installation and Commissioning Standard
CES/32/010 - Pressure Testing Of Refinery Piping and Equipment BP
GSs BP GS 118-5 - The Fabrication, Assembly, Erection and
Inspection of Carbon, Carbon Manganese and Low alloy Steel Pipework
To ASME B31.3 BP GS118-7 - The Fabrication, Assembly, Erection and
Inspection of austenitic and Duplex stainless Steel, Cupro-Nickel,
Nickel Base Alloy, Titanium and Zirconium Pipework To ASME B31.3
Inspection Procedure CRIG/INS/024 - Procedure For Repairs The
Engineering Equipment And Materials Users Association (EEMUA)
Publication No. 153/95 - Chemical Plant and Petroleum Refinery
Piping International Standard Organisation (ISO) ISO 9000 - Quality
Management and Quality Assurance Standards. German DIN 54 109 Part
1 - Non-destructive Testing, Image Quality Radiographs of Metallic
Materials, Definitions, Image Quality Indicators, Determination of
Quality Index
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3.0 GENERAL REQUIREMENTS
The Fabrication, Erection and Inspection of metallic piping
systems shall be in accordance with THIS STANDARD, BP GS 118-5 and
ASME B31. 3 in that order of precedence. The Fabrication, Assembly,
Erection and Inspection of Austenitic and Duplex stainless steel,
Cupro-Nickel, Nickel Base Alloy, Titanium and Zirconium pipework
shall be in accordance with THIS STANDARD, BP GS 118-7 and ASME
B31.3 in that order of precedence.
The use of the Inspection Classification Requirements Table 1
will achieve the required quality level for all installed metallic
piping systems. The inspection classification is also detailed in
each individual Piping Material Class ( See Coryton Engineering
Standard No. CES/42/001).
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TABLE 1
Material, Service and Rating Inspection Required Visual
Radiographic Hydrostatic
Pressure Class Welding
% Test 1. All piping constructed of alloy
material other than carbon steel YES 100% YES A GTAW root
2. All carbon steel piping for the Alkylation unit in piping
class WCZ41 (See note 3)
YES 100% YES A GTAW
3. 900# rating and above YES 100% YES A root/ 4. All
reciprocating compressor piping and discharge KO drums, regardless
of rating and material.
YES
100%
YES
A
Low Hydrogen
5. All 300#, 400# and 600# rating piping other than alloy
material
YES 10% of all welds YES B Low Hydrogen
6. All piping in low temperature service below 0o C (32o F)
YES 10% of all welds YES B Low Hydrogen
7. All 150# rating piping, except as noted below
YES 5% YES C Low Hydrogen
8. Salt water and fire water YES 5% Service Test D E6010 root 9.
Service water YES 5% Service Test D E6013 10. Sewer piping YES 5%
Service Test D Remainder 11. Non -pressurised piping to
atmosphere
YES 5% Service Test D Acceptable
12. MP & LP / condensate and YES 5% Service Test D smallbore
tracing (leads & tails)
Notes : 1. All piping butt welds 2 nominal bore and below shall
be GTAW. 2. All pressure containing fillet welds 1 nominal bore and
below shall be GTAW. 3. Existing piping material classes under this
classification are HP-41S and WCA-7. 4. For pressure testing of
piping reference CES/32/010.
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4.0 FABRICATION, ASSEMBLY AND ERECTION
4.1 General
4.1.1 Where the butt weld ends of piping items are to be joined,
accurate alignment shall be made within commercial tolerances
(within 1.5mm). If the wall thickness misalignment is greater than
1.5mm (1/16 in.) the heavier walled item shall be internally taper
bored at 1:4 taper to give approximately equal finished wall
thickness. In No case shall the wall thickness be reduced below the
nominal - mill under tolerance of the lower thickness pipe.
4.1.2 This misalignment tolerance is not permitted in piping to
and from
reciprocating compressors (through the second change in
direction ) or in piping in severe cyclic conditions as defined in
ASME B31.3. For such services, the inside diameter of the pipe
shall be machined or ground to a close tolerance and the root pass
shall be welded by the GTAW process. When these two service
conditions apply they shall be clearly stated on the isometric
drawing.
4.1.3 Piping fabrication tolerances shall be in accordance with
FIGURE 1, where
the tolerance on linear dimensions indicated as dimension A
shall not exceed 3.0mm. Tolerances shall not be cumulative.
4.1.4 Longitudinal seams in adjoining lengths of welded pipe
shall be staggered
preferably 180o apart and shall be so located as to clear
openings and external attachments. Clearance and stagger shall not
be less than 150mm. Longitudinal seam welds shall be located in the
top quadrant of the pipe wherever possible (See Figure 2).
4.1.5 The toes of adjacent butt welds shall be no closer than
two times the
nominal thickness of the pipe with, in the case of NPS 12 and
below , a minimum acceptable separation of 40mm. For pipe sizes
greater than NPS 12 the minimum acceptable separation shall be 100
mm.
Branch and non pressure part attachment welds shall not cross
longitudinal seams or circumferential butt welds and shall be
subject to the toe to toe separation distance specified for
circumferential butt welds. Where such intersections are
unavoidable the main weld shall be subject to non -destructive
examination prior to making the attachment weld. Joints involving
the intersection of more than two welds shall be avoided. See
Figure 2.
4.1.6 Unless otherwise stated in the piping material class,
fabricated branch
intersections shall be of the set-on type with the branch pipe
prepared to suit full penetration welding. Holes for branch
connections shall be
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prepared by machine or flame cutting dependent on material
except for holes less than 25mm nominal bore which shall be
drilled. Flame cut edges shall be dressed to remove all oxide and
dross (See 4.4.2).
4.1.7 Socket weld connections shall be made up with a 1.5mm to
3mm gap
between the pipe nipple end and the counterbore shoulder of the
fitting, good working practice would be to use spacers/washers.
The weld shall be a minimum of two passes to achieve the
required throat thickness and leg length.
4.1.8 When used, pipe threads shall conform to ANSI/ASME
B1.20.1. Threads
shall be correctly formed and tapered and free from damage. When
male and female threads are engaged and fully tightened to make a
joint, the disengaged length of incomplete or vanishing thread
shall be 2.5 times the thread pitch.
Seal welding of threaded joints, when specified , shall be
performed only when the joint is made dry and is tight and all
surface contaminates have been removed. All exposed threads shall
be covered by the weld deposit with a minimum of two passes to
ensure full fusion to the root of the thread. The welds shall be of
good contour and free from undercut.
4.1.9 Where reinforcing pads are fitted, either for branches or
structural
attachment, they shall be accurately shaped so that no gap
larger than 1.5mm measured before welding shall exist between the
periphery of the pad and the pipe. The gap between the pad and the
branch pipe should be kept to a minimum but adequate to allow
access for welding and fusion to the parent pipe.
4.1.10 Openings for thermowells and other inserts shall be
drilled through the
connection after welding and should be free from obstruction.
4.1.11 For 300# rating and above, the misalignment between branch
pipe/fitting
bore and the parent pipe hole shall not exceed 1.5mm. 4.1.12
Weld neck orifice flanges shall be the same bore as the pipe to
which
they are attached and shall be accurately aligned. All internal
weld protrusion shall be ground flush with the inside diameter.
4.1.13 All meter run lengths shall be good quality round and
checked for ovality
- no welds shall be present along the meter run length. 4.1.14
Seamless pipework 12 NPS and smaller may be fabricated using hot
or
cold formed pulled bends, where the bending radius shall not be
less than 5 times the nominal pipe size. The bending and forming
procedure including preheat and post weld heat treatment shall have
prior BP approval.
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4.1.15 Cold bending shall be performed at a temperature above
the transformation range in accordance with the approved
procedure.
4.1.16 Pulled bends shall be free from cracks, buckling,
wrinkling, flattening and
wall thinning. If flattening of any bend occurs it shall not
exceed 5% of the nominal outside diameter of the pipe when measured
by the difference of the maximum and minimum diameter at any cross
section. The maximum decrease in pipe wall thickness shall not
exceed 10% of the specified nominal wall thickness.
4.1.17 Temporary attachments to the outside surface of the pipe
shall not be
made without prior approval by BP.
Any such attachments which are permitted shall be removed by
grinding, followed by NDE (MPI or DPI dependent on material). BP
may also request for thickness checks to be taken to establish that
the wall thickness is not less than the design minimum, if it is,
the wall shall be buttered, dressed and magnetic particle inspected
or dye penetrant inspected dependent on the material.
4.1.18 For all material grades other than PI all weld repairs
shall be brought to the attention of the Inspection Group.
For PI materials, which are in the PWHT, condition all weld
repairs shall be bought to the attention of the Inspection Group.
One repair attempt is permitted; if unsuccessful the repair shall
be bought to the attention of the Inspection Group.
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FIGURE 1 - FABRICATED PIPING DIMENSIONAL TOLERANCES
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FIGURE 2 - PROXIMITY OF WELDS
DETAILS SHOWN ARE TYPICAL ONLY CLEARANCES = Sp or Sa as
applicable Where Sp = Clearance between any two pressure containing
welds
= the greater of 2t or 40mm minimum.
And Sa = Clearance between an attachment weld and any other weld
= the greater of 2t or 40mm minimum.
NOTE : For Longitudinal seams in adjoining lengths of welded
pipe, the clearance (stagger) shall be 150mm minimum.
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4.4 Carbon Steel
4.4.1 Hot or cold formed pulled bends fabricated on site by the
contractor in accordance with an approved procedure are acceptable
with prior BP Inspection approval.
4.4.2 Machine cutting is preferred but flame cutting and
bevelling is
acceptable if the cut is smooth and true and all oxides are
removed by grinding. The flame cut shall be ground back 1.5mm to
remove hard spots.
4.5 Low-alloy Steel
4.5.1 Hot bending of pipework shall only be performed off-site
(shop) under
strictly controlled conditions to a procedure approved by BP
Inspection where :- a) The bending/forming temperature shall be
580o C to 750oC, and
without cooling down to ambient temperature, thermally stress
relieve at 720oC to 745oC. The holding time shall be half an hour
per 13.0mm of thickness for a minimum of half an hour, or
alternatively:-
b) The bending /forming temperature shall be 950o C to 1030oC
followed
by controlled furnace cooling down to 570oC and then cooling in
still air.
4.5.2 The heating of the pipework shall be by the use of
electric elements or
full circumference gas rings. Local torch heating or quenching
is prohibited with the exception of Section 6.2.13.
4.5.3 Machine cold cutting of pipe and of weld bevels is
preferred but flame
cutting may be employed providing that any cut edge is ground or
machined back 4.0mm, with one individual 3.0mm dimension, to sound
metal.. All cut edges shall then be examined for cracks using dye
penetrant or magnetic particle inspection. Any cracks shall be
removed by grinding. The BP inspector may, at his discretion, allow
the percentage number of cut edges being examined, to be reduced if
the number of cracks found in the material are sufficiently
few.
4.6 Austenitic Stainless Steel
4.6.1 Cold bending is preferred but hot bending is permitted
off-site (shop)
only, under strictly controlled conditions and to a BP approved
procedure. The heating of the pipework shall be the muffle or
semi-muffle type with accurate temperature measurement and control.
Any contact with an open flame is prohibited.
4.6.2 The area used for fabrication needs to be totally
segregated from the
area used for fabrication of carbon steel and other low alloys
steels. Adequate precautions need to be taken to prevent surface
contamination by contact with jigs, vices and other fixtures
manufactured in non-
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compatible materials. Separate sets of clearly identified
equipment i.e. grinding discs (s/s) files, wire brushes (s/s) need
to be in place.
4.6.3 Cutting of pipework and weld bevelling shall be machine
cold cut or plasma
cut.
4.7 Monel 4.7.1 Hot bending of pipework is allowed under
controlled conditions off-site
(shop) only to a BP approved procedure. Cold bending will only
be permitted with prior BP approval. The hot bending temperature
shall be 1010o C to 1175o C. The following controlled conditions
shall apply to the heating medium (furnace atmosphere) :-
Maximum Sulphur Content Reducing Conditions Oxidising
Conditions
GAS 114 mg/m3 503mg/m3 FUEL OIL -- 0.50%
(0.25 % preferred)
4.7.2 Localised heating for bending and forming is not permitted
without prior BP approval.
Where Monel is worked or deformed it shall be re-annealed in
accordance with Section 6.0 of this standard.
4.7.3 Cutting of pipework and weld bevelling shall be machine
cold cut or plasma
cut. The weld bevel surfaces and adjacent areas shall be cleaned
of all extraneous matter and any atmospheric oxide film on the
surface. The cleaning shall be carried out using a fine grinding
wheel or disc followed by vigorous stainless steel brushing and
finally solvent degreasing. This cleaning shall be carried out
immediately prior to welding.
4.8 Nickel and Nickel Alloys
4.8.1 Hot bending of pipework is only permitted off-site (shop),
to a BP
approved procedure, where strictly controlled furnace operation
and conditions apply. The hot bending temperature shall be 1030o C
to 1230o
C. The furnace atmosphere shall be limited as follows :- Maximum
Sulphur Content Reducing Conditions Oxidising Conditions
GAS ZERO 503mg/m3 FUEL OIL -- 0.50%
(0.25% preferred)
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4.8.2 Cold bending and localised heating for bending or forming
will only be permitted with prior BP approval.
4.8.3 Where Nickel or Nickel Alloy material is worked or
deformed it shall
be re-annealed in accordance with section 6.0 of this standard.
4.8.4 Cutting of pipework and weld bevelling shall be machine cold
cut or plasma
cut. 4.8.5 Immediately prior to welding the weld bevel surfaces
and adjacent areas
shall be cleaned of all extraneous matter and any atmospheric
oxide film on the surface. The cleaning shall be performed using a
fine grinding wheel or disc followed by vigorous stainless steel
brushing and then solvent degreasing.
4.9 Assembly and Erection
4.9.1 All flanged piping systems shall be assembled using
service gaskets and
studbolts as detailed in the individual piping material
specifications, except where line blinds are installed. At line
blind locations non-asbestos gaskets shall be installed initially
for hydro-test and shall then be removed and the correct service
gaskets installed.
4.9.2 All studbolts shall be lubricated with high temperature
lubricant; i.e.
Coppercoat or equal, with the exception to the Alkylation Unit
where Coppercoat is prohibited and a Nickel based lubricant should
be used (i.e. Nickel Never Seize). For grade 8 austenitic stainless
steel studbolts care shall be taken that the lubricant used does
not contain chloride, sulphur or any low melting point metallic
compounds. The studbolt shall have a minimum of two threads showing
at each end without being too long. The contractor is responsible
for ensuring joint integrity i.e. correct nuts, bolts, gaskets are
used and that the joint is tight.
4.9.3 The assembly of mis-aligned pipework shall not be
corrected by local
heating, quenching or applying excessive force. 4.9.4 If Cold
Spring is specified on the isometric or piping G.A., extra care
shall be taken with setting up, assembly and supporting of this
pipework. Local heating shall not be used to aid erection.
4.9.5 Temporary and permanent supports shall be installed and
spring supports shall be locked prior to hydro-testing. Temporary
welded supports are to be removed prior to hydro-testing.
4.9.6 Spring supports shall be installed in accordance with
Coryton Engineering
Standard No CES/42/006 - Spring Support Installation and
Commissioning Standard. Note: After hydro-test all temporary
supports shall be removed and the spring supports shall be released
and commissioned in accordance with CES/42/006.
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4.9.7 After hydro-testing where piping systems are required to
be insulated and steam traced, certain corrosive services require
the steam tracer to be clear of the process pipe to prevent Hot
Spots or to prevent the process boiling ; i.e. Amine, Caustic, H2S
etc.
Piping material class KUZ-2 details the specific services and
the spacer layout to be used.
4.9.8 All piping systems, after hydro-test, shall be left in the
ready for
operation conditions except for steaming through or flushing.
4.9.9 Where pipe spools are to be stored prior to installation,
flange faces and
pipe ends are to be capped and protected to prevent damage.
4.9.10 All pipework shall be identified by indelible marking, free
from sulphur,
chloride and other halogens. For spools that will be subjected
to post weld heat treatment a suitable titanium oxide pigmented
heat resisting paint marker containing less than 250 ppm of lead,
zinc or copper shall be used. Vibro-etching techniques may be used
for identification transfer, but adhesive tapes or hard stamping,
other than with low stress stamps, shall not be used. Painted or
corocoated spools shall have metal tags attached to the flanges for
identification. The marking applied shall identify the material and
the fabricator and include an item or spool number enabling the
spool to be traced to the relevant isometric, sketch etc.
5.0 WELDING 5.1 General
5.1.1 All welds, including external attachment welds, shall be
made in
accordance with this standard. 5.1.2 All welders and welding
operators shall be qualified in accordance with
Section 5.3 of this standard. 5.1.3 Semi-automatic or fully
automatic welds shall be made using a multi-pass
welding technique as stated in the qualified weld procedure.
5.1.4 Welding shall not be performed on wet metal surfaces. When
the
atmospheric temperature is less than 0o C, the areas to be
welded shall be pre-heated to 10o C minimum for a distance of 75mm
on both sides of the weld joint before welding commences. All welds
shall be protected from high winds and adverse weather conditions
whilst work is in progress.
5.1.5 The root gap of the joint shall be adequate to ensure full
penetration and
a sound root bead in accordance with the welding procedure. If
required
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back welding after chipping and grinding can be carried out if
safe to do so.
5.1.6 Tack welds shall be made by qualified welders only. There
shall be a
sufficient number of tack welds to maintain alignment during
welding and if these tacks are to be incorporated in the finished
weld they shall be : Full penetration Below the finished weld
surface Twice the wall thickness in length (Minimum) Tapered and
feather edged each end Other acceptable methods would be to bullet
or bridge tack.
5.1.7 If NDE indicates cracks in more than one-quarter
cumulative
circumferential length of any weld, then the entire weld shall
be rejected, removed and remade, less than one-quarter may be
repaired. Note, cracks are not acceptable in any completed weld
(See Table 6).
5.1.8 If any welder produces a weld with defects outside the
code limits two
additional welds shall be fully examined. If more defective
welds by the same welder are found the extent of further NDE will
be at the discretion of the BP Inspector.
5.1.9 All slag shall be removed from welds internally and
externally. 5.1.10 All welds shall be marked with the welders
identification number using
marker pencils or paints which are in accordance with the
restrictions of section 4.9.10 of this standard.
5.1.11 Peening shall not be permitted on any pass. 5.1.12 Unless
otherwise stated in the manufactures installation instructions,
all
welding adjacent to in-line valves shall be performed with the
valve in the fully opened position. Soft seated valves (e.g. butt
welded valves or socket welded ball valves) should not be welded
in-line unless a weld procedure has been qualified to demonstrate
that the soft seats are undamaged or unless the soft seat has been
removed prior to welding.
5.1.13 Pressure containing fillet welds on 1 nominal bore and
smaller pipes shall
use GTAW, with the addition of filler metals for all passes.
5.1.14 All butt welds 2 nominal bore and smaller shall use GTAW on
all
materials, with addition of filler metals for all passes. GTAW
is also the preferred technique for the root pass in all alloy
steels. SMAW may be used for subsequent passes provided the
electrode size does not exceed 2.5mm for the second (hot) pass.
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5.1.15 Back purging shall be employed for all joints involving
alloy steels and/or weld metals with a nominal chromium content of
21/4% or more. Purging shall as a minimum, be maintained for the
root and second (hot) pass.
5.1.16 SAW and, where permitted FCAW and GMAW shall not be used
for pipes
smaller than NPS 6 unless otherwise agreed by BP Inspection.
5.1.17 All welds should be completed without intermediate
cooling, however where this is impractical, intermediate cooling
under an insulating blanket is permitted, but only after 30% of the
final weld depth is completed. In the case of P No. 3,4,5, 6 &
7 materials, the heat treatment cycle in Table 5 shall be applied.
Before welding is re-started on these P Nos the weld surface shall
be subject to magnetic particle inspection and any preheat
established. Pipes shall not be moved or lifted until at least 50%
of the final weld has been deposited.
5.1.18 Vertical down welding is not permitted unless approved by
BP Inspection.
5.2 WELDING PROCEDURES
The Text of ASME IX latest issue applies, except where amended
by the following text or in Engineering Design. 5.2.1 Welding
procedure specifications and procedure qualification test
results
shall be submitted to BP Inspection for approval before
commencement of fabrication together with a matrix showing where
these procedures are to be used, i.e. material, process, Wall
thickness and diameter range etc.
5.2.2 Each weld procedure qualification record (WPQR) shall be
certified by a
recognised independent inspectorate. 5.2.3 It is important to
ensure procedures qualified for FCAW and GMAW that
the particular welding technique proposed for a given
application is well proven and will only be used by qualified and
experienced welders. Training and records of experienced personnel
shall be supplied to BP Inspection for review.
5.2.4 Welding procedure qualification impact testing of welds
and heat
affected zones (HAZ) for ferritic materials is required at the
minimum design temperature :
a) When the base material requires impact testing.
b). When the base material does not require impact testing , but
the
material thickness exceeds 12.7mm (1/2in.) and the minimum
design temperature is -18oC (0oF) or lower.
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CES/18/001 (December 2001)
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5.2.5 When a welding procedure requiring impact testing is to be
used in all positions, separate 2G and 5G qualifications shall be
performed.
5.2.6 Backing rings are not permitted on pipework fabricated to
this standard.
5.2.7 P-Numbers and F-Numbers :
a) The extension of a welding procedure qualification from
the
material on the WPQR to material of a different specification,
even if it has the same P-Number, shall be subject to approval by
BP Inspection.
b) A new WPQR is required for impact tested procedures if there
is
a change of consumable brand name, unless agreed otherwise by BP
Inspection.
c) The P- number shall be considered as an essential variable
for all
welding processes. 5.2.8 The Welding procedure specification
(WPS) shall require re-qualification
if any of the following changes are made:-
a) A change out with the welding parameter tolerance ranges
specified in the qualified procedure specification.
b) Any increase of more than 1 gauge number in the electrode
size
from that used in the qualified welding procedure. c) A change
in the type of current, i.e. AC to DC or, in DC welding, a
change in electrode polarity, except where these changes are
within the electrodes manufacturers recommendation.
d) For impact tested procedures, an increase in either the
maximum
electrode diameter or weave width, or if the maximum interpass
temperature is raised above 250oC.
5.2.9 Procedure qualification tests for welding carbon steel
shall also include a
hardness survey if any of the following conditions exist : a)
Shielded metal arc welding is performed with covered electrodes
of E80XX or higher classification. b) Filler metal contains 1.6%
manganese and silicon exceed 1.4 and
0.8 %, respectively (such as AWS A5.17 filler metal EHXXX or
EC1).
c) Job specifications or data sheets require a maximum
specified
hardness in the weld and/or heat affected zone (HAZ).
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d) Process conditions (Wet hydrogen sulphide, amine, hydrogen
fluoride and caustic) require production hardness testing.
5.2.10 The hardness testing for welding procedure qualification
shall be
performed on the base metal, weld metal and heat affected zone.
The hardness shall be reported as Brinell (HB) Rockwell B or C or
Vickers (HV) equivalent numbers. The type of hardness test
instrument shall be reported and the test results shall meet the
hardness requirement of 225 HB (238 HV10, Rc 20) maximum. For
process conditions wet hydrogen sulphide, amine, hydrogen fluoride
and caustic the maximum hardness shall not exceed 200HB
(212HV).
5.2.11 For gas tungsten arc welding (GTAW), the qualification
record shall
include the composition and flow rate of the shielding gas and
inert gas backing when used.
5.2.12 Welding positions shall be considered an essential
variable for groove
welds in all automatic welding processes. 5.2.13 All welding
consumables not listed in ASME code, section ii, part C shall
be individually qualified. 5.2.14 Post weld heat treatment (time
and temperature) shall be considered an
essential variable for P-3, P-4, P-5 and P-6 materials. A
decrease in time of more than 15 % and/or temperature of 10% or
more from the range qualified will require a separate welding
procedure qualification.
5.2.15 Procedure qualifications for weld overlay deposits shall
include complete
chemical analysis of the overlay, procedure qualification test
record, and sample of the overlay. Specimens taken for chemical
analysis shall be representative of material 2.5mm (0.1in.) below
the surface. The weld metal chemical composition shall be within
the nominal range specified for the alloy.
The procedure qualification tests shall include : a) Dye
penetrant test of the completed weld. b) Side bend tests and
longitudinal face bend tests for weld metal
soundness. Fissures shall not exceed four per specimen , nor
shall they exceed 1.6mm (1/16in.) in length. Cracks at specimen
edges shall not be considered as part of the examination.
5.3 Qualification of Welders and Welding Operators
5.3.1 The performance qualification tests are intended to
determine the ability
of welders to produce sound welds to satisfy the requirements of
the various specifications, standards and codes of practice. The
tests have been designed to recognise variations in welding skills
and welding
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techniques required for the different range of materials and
welding processes that may be encountered. The requirements set
below are mandatory and may only be modified or amended by
agreement with BP Inspection.
5.3.2 All welders on or off the Coryton site shall hold a
current welders qualification test certificate for the relevant
combination of materials and welding processes to be used. These
qualification certificates shall be submitted for review and/or
approval to BP Inspection prior to commencement of work.
5.3.3 All performance qualifications tests shall be carried out
in accordance
with the latest revision of ASME section IX with the following
provisos : a) Qualification may be radiography, provided a WPS,
that is fully
qualified, is strictly followed. b) Subject to the provision of
an authenticated CV and with the
agreement of BP Inspection, welders and welding operators may be
qualified on their initial production welds in the 2G and 5G
positions.
c) Renewal of qualification is required when a welder has not
been
employed on a specific welding process for a period in excess of
six months. However, to obviate the necessity for complete re-
qualification, a welder may retain his certification by
satisfactory radiographic examination of a set piece at six monthly
intervals.
d) A new welder performance test is required if there is a
change of
SMAW brand name unless the brand characteristics do not change
sufficiently to affect performance. Any such change shall be
subject to approval by BP Inspection.
e) Pipe tests shall be conducted in the fixed 450 (6G) or 2G and
5G
positions with the following qualifying sizes ( as stated in
ASME IX) and a thickness range of 1/16 in. To 2t (where t = pipe
thickness) and qualifying over 3/4 in. Maximum thickness can be
welded.
Groove Weld Diameter Limits
Outside Diameter Of Test Coupon Outside Diameter Qualified
Min Max Less than 1 (33.4mm) Size welded Unlimited
1 to less than 2 7/8 (73.02mm) 1 Unlimited 2 7/8 and over 2 7/8
Unlimited
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Thickness Limits on Groove Welds
Thickness Of test coupon Thickness Qualified Max Up to 3/8
(9.5mm) 2t
Over 3/8 but less than (19.05mm) 2t Over Max to be welded
5.3.4 Re-qualification is required for each welding process.
5.3.5 Any Welders qualification tests carried out on site shall be
witnessed
by the BP Inspector or an Independent Inspection Authority.
5.3.6 When qualifying welders for overlays a test shall be
required if the welder is not currently coded for the overlay
material to be deposited.
The following list indicates the range of materials likely to be
encountered on the Coryton site, together with the relevant parent
P number and the filler metal F number. Requirements for materials
other than those listed shall be referred to BP.
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Material Grouping For Welder Performance Qualification
Base Material Material P.No. Welding Rod F.No.
Filler Metal F.No.
Carbon Steel (Iron Powder) 1 1 - Carbon Steel AWS E6013 1 2 -
Carbon Steel AWS E6010 1 3 - Carbon Steel (Low hydrogen) 1 4 -
Carbon Steel (CO2) 1 - 6 C- %Mo 3 4 - 1 %Cr - %Mo 4 4 6 2 %Cr-1% Mo
5 4 6 5%Cr- %Mo 5 4 6 7%Cr- %Mo 5 4 6 9%Cr- 1 %Mo 5 4 6 12/13%Cr
6,7 4 6 18/8 Stainless 8 5 6 25/12 Stainless 8 5 6 25/20 Stainless
8 5 6 Aluminium Alloys 21 - 21-24 Aluminium Bronze 35 - 36 Inconel
600. UNS NO6600 43 44 44 Monel. UNS NO4400 42 42 42 Alloy 20. UNS
NO8020 45 5 6
Notes to Table : i. Re-qualification is required for a change
from one F number to any other F
number, except that a re-qualification upto and including F4
also qualifies to weld any lower F number.
ii. Re-qualification is required for any change in parent
material P number to any other P number with the exception of any P
number upto and including P5 will qualify a lower P number.
iii. 25/20 Stainless steel also qualifies for 18/8 and 25/12
stainless steels.
5.4 Welding Processes
5.4.1 General
Welds shall be made by the shielded metal arc (SMAW), gas
tungsten arc (GTAW), gas metal arc (GMAW) welding processes. All
other welding processes, including submerged arc (SAW),
oxyacetylene, electroslag, require prior BP Inspection approval.
The selection of the welding process to be used will be dependent
upon the following:
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a) The job location, i.e. off-site (shop) or on-site (field) b)
The material to be joined c) The line service, thickness and
rating, especially when MIG/MAG
welding is considered.
5.4.2 All welding parameters shall be substantially the same as
used in the welding procedure qualification.
5.4.3 When using processes other than SMAW and GTAW such as GMAW
and
SAW the following should be considered :
a) The FCAW process is not used for the root pass in single side
welding. b) Production consumables are restricted to the
manufacturer and grade
qualified. c) Service is not hot hydrogen, wet sulphide or
hydrogen fluoride. d) Primary flange rating is Class 300 or lower.
e) Welding components with a large mass where the heat sink may
affect
the integrity of the weld ; i.e. slip -on flanges, socket weld
flanges and fittings, branch fittings.
5.4.4 All welding processes shall be protected from wind, rain
and other
harmful weather conditions that can affect quality. 5.4.5 All
weld passes in the vertical position shall be performed uphill,
unless
specifically approved by BP Inspection. 5.4.6 For butt welds 2
nominal bore and below the GTAW process shall be
used on all materials. However where GTAW on-site welding is not
considered practicable (purge problems, shelter, access) the weld
shall be made with compatible electrodes using the MMA process with
prior BP Inspection approval.
5.4.7 For pressure containing fillet welds 1 nominal bore and
below the GTAW
process shall be used on all materials. However where GTAW
on-site welding is not considered practicable (purge problems,
shelter, access) the weld shall be made with compatible electrodes
using the MMA process with prior BP Inspection approval.
5.4.8 For off-site and on-site welding of low-alloy steels,
austenitic stainless
steels, nickel alloys and non-ferrous metals the GTAW or
GTAW/SMAW shall be used. However where GTAW on-site welding is not
considered practicable (purge problems, shelter, access) the weld
shall be made with compatible electrodes using the MMA process with
prior BP Inspection
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approval. The refinery inspection group must be informed of all
fabrications involving these materials prior commencement of
work.
5.4.9 In an Inert gas shielded welding process, inert gas
backing (argon or
helium) is not required for carbon steels, carbon-molybdenum
steels, or low alloy steels with a chromium content not exceeding 1
% by weight. Inert gas backing shall be used for all other alloy
materials, including aluminium and copper alloys. Nitrogen shall
not be used for gas shielding of stainless steel.
5.4.10 Welded joints shall be made by completing each layer
before succeeding
layers are deposited Block welding is prohibited. 5.4.11 For
carbon steel welding of hot-tap branches, new nozzles in vessels
and
the repair of steel castings etc. A low hydrogen process shall
be used. 5.4.12 Autogenous welding is prohibited when using the
GTAW process unless
approved by BP Inspection.
5.5 Welding Consumables 5.5.1 Filler metals for welding similar
materials shall be of the same nominal
analysis as the base material, except as follows : a) AWS Type
347 filler metal shall be used for welding Type 321
stainless steel material. b) AWS Type 308 filler metal shall be
used for welding Type 304
stainless steel material. (Type 308L shall be used for Type
304L) c) The following filler metals shall be used for welding 11
to 13% steels in
cyclic service, or for design temperatures over 350oC (660o F),
only Inco-weld A, Inconel 82 or Inconel 182 are acceptable.
d) For chromium-molybdenum steel, filler materials such as
Inconel 82
and 182 or Inco-Weld A may be used if approved by BP Inspection
(This does not imply exemption from PWHT).
5.5.2 Filler metal for welds joining dissimilar materials shall
be in accordance
with Appendix C Table 2. Filler metals for combinations of
materials other than those in Table 2 shall be submitted to BP
Inspection for approval.
5.5.3 Filler metals for welds shall meet the same minimum
requirements as
those imposed on the base metal. 5.5.4 In all welding processes,
the filler wire shall contain all alloying elements
and shall meet all chemical compositions requirements for the
wire classification. Exceptions are subject to BP approval.
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5.5.5 All welding consumables shall be used within the limits
recommended by their manufacturers. The welding parameters shall be
subsequently the same as used in the procedure qualification.
5.5.6 Electrodes, filler wires, and fluxes shall be kept clean,
dry and properly
stored according to manufacturers recommendations. No damp,
greasy, or oxidised electrodes, filler wires or fluxes shall be
used.
5.5.7 Since various national specifications for welding
consumables are not
freely interchangeable, equivalence to AWS specifications shall
be indicated. The basis of equivalence shall be subject to approval
by BP.
5.5.8 Carbon, Low Alloy Steel and Austenitic Stainless Steel
5.5.8.1 For gas metal arc welding of carbon steels, base wire
filler metals
shall conform to AWS A5.18 classification ER70S-2, ER70S-3, or
ER70S-6.
5.5.8.2 For gas tungsten arc welding of carbon steels, the
filler metal
shall meet the chemical and physical tests requirements of AWS
A5.18, classification ER70S-2, ER70S-3, or ER70S-6.
5.5.8.3 For flux cored arc welding of carbon steels, the
electrodes shall
conform to AWS A5.20 classification E70T-1 (or E71T-1) or to
E70T-5 (or E71T-5). These electrodes shall be used with an external
shielding gas.
5.5.8.4 Carbon steels shall not be welded with C- Mo weld metal
unless
the weld is postweld heat treated and the procedure
qualification record includes hardness weld data. This data shall
show that the weld and heat affected zone hardness have not
exceeded 225HB (238 HV10).
5.5.8.5 For welding carbon steel, submerged arc welding wires
shall be
limited to AWS classifications ELXX and EMXXX and the submerged
arc welding fluxes shall be limited to F72 and F62, unless
otherwise approved by BP Inspection. Welding wire classification
EH14 may be used, but a hardness test survey of the weld and HAZ,
is required during procedure qualification. Hardness shall not
exceed 225HB. Recycled flux shall not be used.
5.5.8.6 AWS classifications E6012, E7014 and E7024 shall not be
used
for pressure containing fillet welds. These electrodes however
may be used for non-pressure containing fillet welds on P-1
materials. The E7024 electrode may be used for lap joint fillet
welds on tank floors in the flat position.
5.5.8.7 Low-hydrogen electrodes shall be used for all shielded
metal arc
welding when any of the following conditions apply :
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a) Design temperature is below 0oC (32oF). b) Valve or flange
rating is class 150# or higher on process
piping. c) Base metal has a carbon equivalent (CE) exceeding
0.43, based
on weight percent of the elements. d) The carbon content exceeds
0.25%. e) Base metal has a minimum specified tensile strength
greater
than 415 Mpa (60,000 psi). f) Thickness of buttwelds and fillet
welds (throat) exceeds
12.5mm ( in.). g) Castings are to be weld repaired.
5.5.8.8 For welding 5 through 9% nickel steels, the filler
materials shall
be reviewed and approved by BP Inspection and qualified by
procedure testing in the maximum plate thickness specified for the
job.
5.5.8.9 Filler metals and consumable inserts for austenitic
stainless
steels welds shall be selected to produce weld deposits that
fall within the ferrite ranges and numbers given in Table 3. This
restriction is intended to prevent problems associated with
sigma-phase formation and microfissuring in fully austenitic
steels
Table 3
Ferrite Content Of Austenitic Stainless Steel Weld Metal
Weld Material PWHT or Service Temperature Ferrite % Ferrite
No.
308, 308L Less than 4300C (8000F) 5-15 5-17 316, 316L 309, 309L
4300C (8000F) and over 5-9 5-9.8
347
5.5.9 For cryogenic service temperatures of -100oC (-150oF) and
lower, the ferrite content of all austenitic stainless steels
welding materials shall be in the range 2 to 5% (FN2 to FN5).
5.5.10 Filler materials of E309, Inconel 182, or Inco-weld A
shall be used for
welding carbon or low-alloy steels to austenitic stainless
steels. 5.5.11 Permanently installed backing rings or strips shall
not be used.
Consumable inserts shall only be used with BP approval prior
fabrication.
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5.6 Alloy Cladding and Overlay 5.6.1 BP approval is required for
any proposed alloy overlay system. 5.6.2 For both integrally clad
plate and weld overlay, the surface of the base
welds that would be exposed to the corrosive environment shall
be protected by depositing not less than two layers of corrosive
resistant weld metal.
5.6.3 In austenitic stainless steel overlays, the first weld
layer shall be made
with type 309L. Subsequent layers of deposit shall be made with
low-carbon 18Cr-8Ni stainless steel or stabilised grades of
austenitic stainless steel, depending on service conditions.
5.6.4 For monel overlays on carbon or low-alloy steel, the first
weld layer shall
be made with a high nickel consumable (62% nickel minimum). The
second and any successive layers shall be made with a filler metal
that nominally matches the monel chemical composition. The first
layer of high nickel deposit shall be applied over bright, clean
and oxide free steel. Monel overlays shall have a maximum iron
content of 4.5%.
5.6.5 When integrally clad stainless plates are to be joined
:
a) The clad layer shall be stripped for a minimum distance of
8mm
from the bevel. In addition, the base material shall be etched
with nitric acid or copper sulphate to ensure complete removal of
the clad layer. This will prevent contamination of the substrate
weld.
b) When the claddings are removed, the base material
thickness
shall not be reduced below the design thickness by more than
1mm.
c) The procedure for back cladding of internal attachments
and
nozzle welds requires approval by BP Inspection. This procedure
shall include base metal examination, welding sequence and final
inspection.
5.6.6 All internal exposed alloy welds joining clad components
and all alloy weld
overlays inside vessels and heat exchangers shall be fully
examined by liquid penetrant examination.
5.6.7 A certified report of the chemical analysis of production
as deposited
alloy weld overlays or alloy welds covering base metals in clad
plates shall be furnished to BP. The weld metal chemical
composition shall be within the nominal range specified for the
alloy. At least three drillings from each vessel section, each
exchanger, and each channel head shall be made to obtain sample
material analysis. One sample shall be taken at the beginning of
the overlay and two samples at locations to be designated by the
inspector. The samples shall be taken 2.5mm below the surface of
the
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material. BP may reduce the number of analytical samples and
supplement with portable analysers when the manufacturer has
exhibited good QA/QC and previously proven performance.
6.0 THERMAL HEAT TREATMENT
6.1 Pre-heat and Interpass Temperatures
6.1.1 General
The preheat temperatures listed in Table 330.1.1 of B31.3 are
mandatory, with the exception to the following modifications in
this Section. Oxy-fuel gas welding and cutting torches may only be
used for pre-heating when fitted with proprietary preheating
nozzles. Quenching or other means of accelerated cooling from
pre-heat temperature shall not be employed.
The minimum preheat temperatures for thermal cutting, arc-air
gouging, and welding shall be in accordance with the requirements
of the applicable code and weld procedure specification (WPS), the
exceptions are as follows :
6.1.2 No welding shall be performed when material temperatures
are below
0oC, preheat must be applied. 6.1.3 Carbon steel shall be
preheated to 10oC, minimum for an area equal to
6.1.4 (h). 6.1.4 Carbon steel shall be preheated to 100oC when
any of the following
conditions apply :- a) Base metal thickness exceeds 19mm. b)
Carbon content is 0.25% or more irrespective of thickness. c)
Carbon equivalent (CE) 0.43% or greater. d) The material is highly
restrained; for example nozzles or major
attachments. e) All ferritic alloy materials shall be preheated
in accordance with Table
4 f) The maximum interpass temperature for austenitic stainless
steel
shall be 180oC. g) The maximum preheat and interpass temperature
for carbon steel and
low alloy steel shall be 300oC.
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h) The preheat zone shall extend 75mm or a distance equal to
four times the material thickness, which ever is the greater,
beyond each edge of the weld.
i) During the welding of castings, the whole casting or an area
extending
300mm on either side of the weld shall be maintained at the
approved preheat and interpass temperature.
j) Preheat and interpass temperature shall be controlled by
temperature
indicating crayons, contact pyrometers, or thermocouples.
Temperature indicating crayons used on austenitic stainless steels
and nickel based alloys shall not cause corrosive or other harmful
effects. Nor shall they contain more than 1% by weight of total
halogens or sulphur, or 200 ppm by weight of inorganic halogens. It
is the fabricators responsibility to determine suitable brands and
melting temperatures that may be used.
k) When the specified preheat temperature is 150oC or higher,
the metal
shall be maintained at preheat temperature until the weld is
completed. For welds of heavy thickness over 50mm or under a high
degree of restraint the preheat temperature shall be maintained
until the start of post weld heat treatment unless an intermediate
tempering treatment is performed. An intermediate tempering heat
treatment shall consist of heating to 600oC minimum, holding for 15
minutes minimum and cooling slowly to ambient temperature.
6.1.5 When P-4 or P-5 materials are welded to P-1, P-3, P-7,
P-9, P-10, or P-11
materials the preheat temperature shall be a minimum of 175oC.
The welding of P-4 or P-5 to P-8 requires special consideration and
prior BP Inspection approval.
6.1.6 To preheat pipework 2 nominal bore and smaller, on-site,
LPG fired
torches may be used together with temperature indicating crayons
if this method is approved by BP Inspection.
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Table 4
Minimum Preheat Temperatures For Ferritic Materials
Material Minimum Preheat Temperature Nominal Analysis P-No oC
oF
Carbon Steel 1 Refer to 6.1 Manganese - Molybdenum 3 150 300
C- Mo 3 95 200 Cr - Mo 3 95 200 1Cr - Mo 4 150 200
1 Cr - Mo 4 150 300 2 Cr - 1Mo 5 200 300
3Cr - 1Mo 5 200 400 5Cr - Mo 5 200 400 7Cr - Mo 5 200 400 9Cr -
1Mo 5 200 400
12Cr (Martensitic) 6 205 400 CA6NM (0.03% C max.) 6 10 50
12Cr (Ferritic) 7 10 50 2 Ni 9A 150 300 3 Ni 9B 150 300 5 Ni 11A
150 300 9 Ni 11A 150 300
6.1.7 As an alternative, for butt welds only, a dehydrogenation
treatment (DHT) can be substituted for the intermediate tempering
treatment. The hydrogen outgassing procedure shall consist of
raising the preheat temperature to 260oC to 300oC and holding for
four hours, or raising the preheat temperature to 325oC to 400 oC
and holding for two hours. All other pressure welds, such as nozzle
and manhole attachment welds shall be given the full 600 oC
tempering treatment. The aforementioned outgassing procedure does
not apply to 5 through to 9% nickel steels.
6.2 Postweld Heat Treatment
6.2.1 General : Postweld heat treatment of welds, bends and
forgings shall be
in accordance with Table 331.1.1 of B31.3 with the following
modifications:
6.2.2 Minimum PWHT of ferritic steels shall conform to Table 5.
6.2.3 Application of heating resistance heating elements shall be
arranged
circumferentially around the weld. The width of the heated band
shall not be less than 3 times the weld thickness in each direction
from the central point of the weld. Heating elements shall be
supplied to operate on a safe, low voltage (60 Volts A.C.).
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6.2.4 Thermocouples: - a) All temperature readings shall be made
by Nickel Chromium / Nickel
Aluminium, Type K Thermocouples to BS EN 60584 Parts 1 and 2. b)
The thermocouple attachment shall be capacitance discharge,
direct
wire welded. c) The thermocouples shall be connected to a
potentiometric chart
recorder by copper constantan compensating cable. The minimum
number of thermocouples shall be as follows:-
External Pipe Number of Thermocouples Diameter Per Weld
Position
Up to and including 150mm 1 On top Above 150mm to 300mm 2 180o
Intervals Above 300mm to 600mm 4 90o Intervals Above 600mm to
1200mm 6 Equispaced
All thermocouples shall be located on the weld centre line.
6.2.5 Insulation :-
a) Takes the form of mineral wool; 2 thick or ceramic fibre; 1
thick
(non-asbestos). b) The insulation will be a band of width not
less than 5 times the wall
thickness either side of the weld. c) All open ended pipework
shall be temporary plugged during heat
treatment to minimise heat loss. 6.2.6 All post weld heat
treatment shall be completed prior final radiography,
radiography can be carried out before PWHT at the contractors
cost. 6.2.7 All carbon steel piping 19mm and over nominal thickness
shall be post weld
heat treated. (Note: Process conditions such as amine and wet
hydrogen sulphide may require PWHT regardless of thickness). All
other ferritic alloy piping (P-3, P-4, P-5, P-6 etc.) shall be PWHT
for all thickness.
6.2.8 The PWHT for welds joining austenitic stainless steels to
dissimilar
materials shall be as specified in the qualified weld procedure
and approved by BP Inspection prior start of fabrication.
6.2.9 For P-6 materials, the PWHT temperature used shall be the
lowest
possible to avoid overheating and hardening on cooling.
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6.2.10 Heat treatment is required for all carbon steel piping
operating below -29oC. PWHT is also required for all carbon steel
piping in ammonia, amine and H2S services.
6.2.11 If PWHT is performed in a furnace , the temperature shall
be measured
by a minimum of two thermocouples. At least two resistance
welded thermocouples shall be attached to the piping being heat
treated. These thermocouples shall be located at the hottest and
coldest parts of the furnace. Neither temperature shall be outside
the specified PWHT range.
6.2.12 Instrumentation used to verify the PWHT temperatures
shall have been
calibrated within 60 days of the performance of the heat
treatment. 6.2.13 All machined surfaces shall be protected by a
suitable paint or compound
to prevent damage from scaling during heat treatment. 6.2.14 All
piping should be supported (and restrained as needed) in the
furnace
during heat treatment to minimise warpage and other distortion.
Valves shall not be subjected to furnace PWHT without BP approval.
PWHT of ends of welds on valves shall be carefully performed so
that the valve packing, bonnet, gasket and internal trim are not
damaged.
6.2.15 The exothermic method of heat treatment shall not be
used. 6.2.16 The PWHT shall follow immediately the welding
operation without losing
the preheat temperature, unless the weld procedure specification
(WPS) specifies otherwise.
6.2.17 Holding time at PWHT temperatures shall be one hour per
25.4mm of
thickness, with one hour minimum. For Chromium-molybdenum steels
( to 9% chromium) and 12% chromium stainless steels , the minimum
holding time shall be 2 hours.
6.2.18 For P-3, P-4 and P-6 materials the production PWHT (time
and
temperature) shall be essentially the same as in the welding
procedure qualifications. The maximum Brinell hardness in all
steels after heat treatment shall be 225HB (238 HV10). If welds are
furnace heat treated, a minimum of 10% shall be tested to verify
that the hardness criteria has been met. If local heat treatment
has been applied , each weld shall be tested. Welds in critical
service such as amine, wet hydrogen sulphide and hydrogen fluoride,
shall also not exceed a maximum hardness in the deposited weld
metal and the heat affected zone of 200HB i.e. piping material
class WCZ-41.
6.2.19 Hardness readings of the weld and heat affected zone
shall be taken at
two circumferential locations 180o apart. It is the heat
treatment contractors responsibility on-site to record the hardness
readings on the heat treatment chart for each weld, this is to be
verified by the fabrication contractors QA.
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6.2.20 Piping isometrics when required shall be stamped Stress
Relieve. 6.2.21 The soak time for carbon steel shall be one hour
minimum and two hours
minimum for alloy steel. 6.2.22 Rates and rise of fall shall be
as follows :- Unrestricted To 300oC Raise Rate from 300 oC at 200
oC per hour maximum
Cooling Period - 200 oC per hour maximum to 300 o. Air cool to
ambient under insulation.
6.2.23 Post weld heat treatment of austenitic stainless steel is
not required
unless called for in the piping material specification, but for
bending and forming the following heat treatment is required :-
Material Grade Temperature oC
Hot Forming /Bending Solution Annealing 304 1100-900 1050-1000
321 1100-900 1070-1020
316, 316L 1100-900 1100-1050 316Ti - 316Nb 1100-900
1070-1020
309, 310 1100-900 1100-1070 347 (See Note) 835-855 835-855
Note: The heat treatment is for piping material class BCM-32
only and shall be
for a minimum of two hours, then cooled in still air.
Upto 850 oC the heating rate shall be slow and may be faster
thereafter. Cooling shall be in still air for hot forming and
bending but rapid cooling is required for solution annealing.
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Table 5
Post Weld Heat Treatment For Ferritic Materials
Material P-No. PWHT Temperature Range Nominal Analysis oC oF
Carbon Steel 1 610-655 1130-1230
Manganese - Molybdenum 3 620-720 1150-1325 Cr - Mo 3 620-720
1150-1325 1Cr - Mo 4 705-745 1300-1375
1 Cr - Mo 4 705-745 1300-1375 2 Cr- 1Mo 5 720-760 1325-1400 3 Cr
- 1Mo 5 720-760 1325-1400 5 Cr - Mo 5 720-760 1325-1400 7 Cr - Mo 5
720-760 1325-1400 9 Cr - 1Mo 5 720-760 1325-1400
12Cr (Martensitic) 6 720-790 1325-1450 12Cr (Ferritic) 7 None
None
2 Ni 9A 595-635 1100-1175 3 Ni 9B 595-635 1100-1175
5Ni 11A 550-585 1025-1085 9Ni
Monel 11B 42
550-585 590-610
1025-1085 1094-1130
Notes: 1. Temperature of any part of the weldment during PWHT
shall not be less than
shown above. 2. Table does not apply to normalised and tempered
materials or to quenched and
tempered materials. PWHT of such materials shall be approved by
BP and shall be such that the weld and HAZ hardness does not exceed
225HB and mechanical properties are not less than the specification
minimum.
3. Monel - Air cool to ambient from soak temperature.
6.2.24 Recording and Documentation :-
a) Heat treatment commencement and completion shall be
authorised by the client representative by signing and stamping
all charts when required.
b) A chart acceptance certificate or alike shall be submitted
with
each temperature chart with the following information:-
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CES/18/001 (December 2001)
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1. Client name and site details. 2. Order number. 3. Item
reference number or drawing number. 4. Technicians signature and
date. 5. Material type, wall thickness, diameter and line
specification. 6. Line / weld identification. 7. Thermocouples
positions. 8. Recorder serial number and date of calibration. 9.
Chart number. 10. Hardness report numbers. 11. Specification
parameters, reference to weld procedures
or specification s where appropriate. 12. Quality procedure
reference number. 13. Any special requirements.
c) Each temperature chart shall indicate the following :-
1. Client and site. 2. Heat treatment specification details. 3.
Line / weld identification 4. Recorder serial number. 5. Chart
speed. 6. Chart number. 7. Chart acceptance document number. 8.
Technicians signature.
7.0 NON-DESTRUCTIVE EXAMINATION
7.1 Visual Examination :-
All fabricated pipework shall be 100% visually inspected for any
imperfections, cracks, surface breaking defects, mis-alignment or
bad workmanship. If the inspector has any doubts regarding the
acceptability of the finished item, then for any surface defect a
magnetic particle or dye penetrant examination may be performed in
addition to any other test specified.
7.2 Radiographic Examination
7.2.1 Radiographic examination shall be performed using Gamma
radiography
for all pipework upto and including 25mm wall thickness. 7.2.2
The radiographic techniques shall be in accordance with BS. 2910
for
piping butt welds or BS.2600 for butt joints in plate. 7.2.3
Image quality indicators of the wire type to BS 3971 or DIN 54 109
part
1 shall be used.
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CES/18/001 (December 2001)
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7.2.4 Film density shall be 2.0 - 3.0 through the thickest
portion of the weld and the radiographic sensitivity shall be
between 1.2% and 2.4% depending on thickness.
7.2.5 The single wall, single image technique shall be used
where ever possible,
lead intensifying screens and fine grain high contrast film
shall be used. 7.2.6 Interpretation and acceptance criteria of
radiographic results shall be in
accordance with Table 6 in conjunction with ASME B31.3 Table
341.3.2A, for normal fluid service, except where 100% radiography
is specified, the severe cyclic conditions criteria shall
apply.
Table 6
Acceptance Criteria For Welds
Kind Of Imperfection Acceptance Criteria For The Specified
Service Condition
Lack Of Fusion (L.O.F) A for all welds
Incomplete penetration * A shall apply to all welds in severe
cyclic conditions 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, or elongated indication*
F shall apply to all welds irrespective of service condition
Undercutting H shall apply to girth and, where approved, mitre
groove welds in category D fluid service
Concave root surface (suck back) * Not permitted in severe
cyclic or normal fluid service unless a specific limit is set by
engineering design. A maximum of 1.6mm shall apply to welds in
category D fluid service
Reinforcement or internal protrusion
For all welds irrespective of service conditions external weld
reinforcement shall be uniform, 1.6mm to 3mm in height and shall
merge smoothly into the pipe surface. Positive root penetration
shall not exceed 1.6mm for NPS 2 and smaller, or 3mm for larger
pipe
* When these defects are permitted the total cumulative length
of lack of root penetration, slag inclusions or concave root shall
not exceed 10% of the weld joint circumference.
7.3 Ultrasonic Examination
7.3.1 The methods and acceptance criteria for ultrasonic
examination of welds shall be in accordance with ASME B31.3 Table
344.6.
7.3.2 When fabricating pipework having a wall thickness in
excess of 25mm,
consideration should be given to the examination of the root
region when welding is partially complete to a depth of
approximately 30% of the wall thickness. This will minimise the
need for through wall repairs.
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CES/18/001 (December 2001)
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7.4 Magnetic Particle Inspection
Magnetic particle inspection shall be performed in accordance
with BPV code Section V, Article 7.
7.5 Dye Penetrant Inspection
Dye Penetrant Inspection shall be performed in accordance with
the BPV code Section V, Article 6.
7.6 Examination Personnel
7.6.1 Only personnel certified in accordance with PCN, CSWIP or
ASNT
recommended practice SNT-TC-1A, shall be allowed to undertake
the examinations. Other equivalent qualifications shall be subject
to approval by BP Inspection.
7.6.2 All radiographic and ultrasonic operators shall be
qualified in accordance
with one of the following :-
1. Welding Institute Certification Scheme for
Industrial Radiographer Grade 2 And / Or Ultrasonic
Weldment Inspection Personnel (C.S.W.I.P)
practitioner (welds) Grade 2
2. American Society for Non-
Destructive Testing Level 2 (Industrial Radiography)
(A.S.N.T)
3. The Personnel Certificate in NDT (P.C.N)
Industrial Radiographer Level 1
7.6.3 Where the approval does not include Radiation Safety a
separate
certificate in Radiation Safety must be held. 8.0 HYDRO-STATIC
TESTING
8.1 All hydro-testing of pipework and equipment shall be in
accordance with Coryton
Engineering Standard 10. 8.2 All hydro testing or service
testing is to be witnessed by BP Inspection or
nominee. 8.3 The fabricators test procedure, giving details of
test fluid, minimum
temperature , test pressure recording and control method and
holding time, shall be reviewed by BP.
8.4 Subsequent to hydro testing , pipe spools that are to be
stored prior to
installation shall have the ends sealed to prevent ingress of
dirt, moisture or
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CES/18/001 (December 2001)
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other contaminates. Flange faces shall be coated with a suitable
corrosion preventative.
8.5 Hydro-testing shall be carried out after the completion of
any specified heat
treatment. 8.6 Hydro-testing shall be only carried out after
completion of any specified NDT. 8.7 Welds shall not be painted or
insulated prior to hydro-testing or service testing.
9.0 QUALITY 9.1 The Contractor shall operate a quality system
fully in accordance with the
applicable part of ISO 9000. 9.2 All maintenance repair work
shall be in accordance with CRIG/INS024 Procedure
for repairs. 9.3 Before commencing fabrication the fabricator
shall prepare a quality plan and a
set of design documents, both of which shall be subject to
approval by BP. 9.4 These documents shall include materials,
welding and consumable control
procedures, welding and non-destructive testing procedure
specifications together with qualification records and an
illustration of their proposed areas of application. Mechanical
working, heat treatment and leak testing procedures should also be
included.
9.5 The quality plan shall include brief details and the
sequence of all examinations
that will be performed by the fabricator. The names of the
responsible individuals responsible for the implementation of all
quality assurance and quality control functions shall also be
included.
9.6 It shall be the responsibility of the contractor to inspect
all materials upon
receipt to ensure that the correct grade of material has been
supplied and the identifications and dimension, material quality
and end preparation are in accordance with the requisite standards
and specifications.
9.7 Different materials shall be kept in discrete sections of
the storage area and all
material shall be marked in a manner that allows it to be
related to the original manufacturers certification.
9.8 All materials shall be stored above ground and kept free
from dirt, grease and
other contaminants. 9.9 At all stages of fabrication the
contractor is responsible for maintaining all
relevant production records, for maintenance work the minimum
shall be in accordance with CRIG/INS/024.
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CES/18/001 (December 2001)
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These records shall include : 1. Material and welding consumable
certificates.
2. Weld procedures.
3. Welders qualifications and NDT operator qualifications.
4. Weld matrixes, identifying Weld number, size, Welder used,
Inspection and
NDT results.
5. NDT reports.
6. PWHT charts and reports.
7. Drawings.
On completion of fabrication the records i.e. workpacks/data
dossiers shall be transmitted to BP for audit and file.
9.10 BP reserve the right to carry out quality audits at the
contractors and sub-
contractors facilities.
BP also reserve the right to call the contractor to provide a
schedule of Quality audits appropriate to the contractors and
sub-contractors activities and for the contractor to supply reports
of such audits.
9.11 The contractor shall advise of any non-conformances which
affects the ability of
the goods to conform to the purchase order / work order, or
which may affect operation, integrity or inter-changeability of the
goods. The contractor shall also advise details of proposed
corrective actions or concession requests and details of any
consequential affects.
9.12 Any queries related to the work shall be formally submitted
by a technical query
and registered with BP Inspection. 9.13 All concessions raised
by the contractor shall be submitted to BP inspection for
approval or rejection. 9.14 The above quality assurance
requirements shall apply to both on-site and off-site
contractors and all associated welding sub-contractors. 9.15 It
is particularly important that equipment/pipework associated with
Pressure
Systems is treated exactly as specified as there could be legal
implications when specifying future inspection frequencies.
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CES/18/001 (December 2001)
APPENDIX A SPECIAL REQUIREMENTS FOR HF ACID SERVICE FOR PIPING
MATERIAL CLASSIFICATIONS WCP-21 AND WCZ-41
1. Where reference to the carbon steel piping material class
WCZ-41 is made then existing pipe classes WCA-7 and HP-41S may also
be taken to apply. Where reference to the Monel piping material
class WCP-21 is made then existing piping classes WCP-2 and HP-41M
may also taken to apply.
2. Piping and fittings 1 NPS and smaller shall be screwed, not
seal welded and installed using
PTFE tape. 3. Socket weld construction is not permitted. All
piping 1 NPS and larger shall be butt
welded. 4. Couplings welded into lines for vents, drains,
thermowells, branches etc., shall be installed in
accordance with Philips drawing No. HF-1008, see Appendix B.
Alternatively, a set-on fitting; i.e. a thredolet may be used,
provided the attachment weld is full penetration and meets the
requirements of paragraph 8.
5. All thermowells shall be in accordance with standard drawing
No. ST-AK-1551. 6. Piping shall be designed and installed so as to
be self-draining to low points at equipment, i.e.
pumps, exchangers, vessels, control valves etc., to minimise the
number of low point drains. If low point drains are required on
piping they shall be in accordance with the piping material class
details.
7. The edges of all piping flanges, valve bonnets flanges and
gaskets shall be painted with one
coat of HF detecting paint Valsper No. 220-Y-7. 8. The first 5mm
of any weldment in contact with HF acid shall be slag free. It is
therefore,
recommended that the GTAW process is used for the first 5mm of
deposited weld. 9. Post weld heat treatment (PWHT) shall be in
accordance with section 6.2 of this standard for
the piping material classes WCP-21 and WCZ-41. 10. Piping shall
be hydrotested using kerosene or gas oil. Water may be used with
prior BP
approval provided that the piping sections can be blown
completely dry after the Hydrotest. 11. For piping material
classification WCZ-41 the maximum hardness of the weld metal and
heat
affected zone (HAZ) shall be 200HB. 12. For piping material
class WCZ-41 the butt welds shall have a TIG root run. 13. Monel
pipework shall be PWHT.
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CES/18/001 (December 2001)
APPENDIX B HF SERVICE COUPLING INSTALLATION
* See Piping, Heat Exchanger, Pump, and Instrument HF Service
Specifications For Use and Size.
See Appendix A.
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CES/18/001 (December 2001)
APPENDIX C - TABLE 2 FILLER METAL FOR WELDING DISSIMILAR
METALS
Base Nominal Analysis Base Material Number Material Of Number
Base Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24
1 Carbon Steel A A A A A A A A A B B B B B B B B B B B C D C 2
Carbon-Molybdenum steel A E C E E E E E E B B B B B B B B B B B C D
C 3 2 %& 3 % Nickel A E C B B B B B B B B C C C 4 9% Nickel
Steel A C C C C C C C C C C C C C 5 1% Cr- % Mo Steel A E F F F F F
B B B B B B B B C D C 6 1 % Cr - % Mo Steel A E F F F F F B B B B B
B B B C D C 7 2 % Cr - 1% Mo Steel A E F F F G G B B B B B B B B C
C C 8 5% Cr - % Mo Steel A E F F H H H B B B B B B B B C C C 9 7%
Cr - % Mo Steel A E F F G H I B B B B B B B B C C C 10 9% Cr - 1%
Mo Steel A E F F G H I J J B B B B B B B B C C C 11 Type 405
Stainless Steel B B K K B B B B B B B B C C C 12 Type 410S
Stainless Steel B B J K K B B B B B B B B C C C 13 Type 410
Stainless Steel B B J K K B B B B B B B B C C C 14 Type 304
Stainless Steel B B B C B B B B B B B B B L L P L L O O C C C 15
Type 304L Stainless Steel B B B C B B B B B B B B B L M M L M O O C
C C 16 Type 321 Stainless Steel B B B C B B B B B B B B B L M N L M
O O C C C 17 Type 347 Stainless Steel B B B C B B B B B B B B B P M
N P M P P C C C 18 Type 316 Stainless Steel B B B C B B B B B B B B
B L L L P Q O O C C C 19 Type 316L Stainless Steel B B B C B B B B
B B B B B L M M M Q O O C C C 20 Type 309 Stainless steel B B B C B
B B B B B B B B O O O P O O R C C C 21 Type 310 Stainless Steel B B
B C B B B B B B B B B O O O P O O R C C C 22 Alloy 800 (Incoloy
800) C C C C C C C C C C C C C C C C C C C C C C C 23 Monel 400 D D
C C D D C C C C C C C C C C C C C C C C C 24 Inconel 625 C C C C C
C C C C C C C C C C C C C C C C C C
A - AWS A5.1, Classification EXX15, EXX16, or EXX18. J - AWS
A5.4, classification E505-XX B - AWS A5.4 and A5.11, classification
E309-XX, ENiCrFe-3 (Inconel 182), or ENiCrFe-2 (Inco-Weld A) K -
AWS A5.4 and A5.11, classification E410-XX, E410 cb-XX C - AWS
A5.11, classification ENiCrFe-3 (Inconel 182) or ENiCrFe-2
(Inco-Weld A) E309-XX, ENiCrFe-3 (Inconel 182), or ENiCrFe-2 D- AWS
A5.11, classification ENiCrFe-3 (Inconel 182), ENiCrFe-2 (Inco-Weld
A), or ENiCr-7 (Monel 190) L - AWS A5.4, classification E308-XX E -
AWS A5.5, classification E7015-A1, E7016-A1, or E7018-A1 M - AWS
A5.4 classification E308L-XX F - AWS A5.5, classification E8016-B2,
E8018-B2, or E8015-B2L, E8018-B2L N - AWS A5.4 classification
E347-XX G - AWS A5.5, classification E9015-B3, E9016-B3, E9018-B3
or E9015-B3L, E9018-B3L O - AWS A5.4 classification E309-XX or
E308-XX H - AWS A5.4, classification E502-XX P - AWS A5.4
classification E308 -XX or E347-XX I - AWS A5.4, classification
E7Cr-XX Q - AWS A5.4 classification E316-XX or E316L-XX Note : R -
AWS A5.4 classification E309-XX 1. Blank spaces in Table 2 indicate
combinations that are considered unlikely or unsuitable. For these
combinations consult BP 2. Table 2 refers to coated electrodes. For
bare wire welding (SAW, GMAW, Inspection Group. GTAW), use
equivalent electrode classification (AWS A5.9, A5.14, A5.17,