Pipe Fabrication
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Indicator Number: CES/18/001
CORYTON ENGINEERING STANDARD SUBJECT:
Original Issue Date May 1995
New:
PIPE FABRICATION, WELDING, ERECTION AND INSPECTION
Re-Issue: (No change):
Re-Issue: X (Amended):
Last Issue Date January 2000 This Issue Date December 2001
SUPERSEDES: NONE
Author
Authorised by
D T Hatfull Inspection Group Quality Co-ordinator
P Avery Maintenance Engineering & Performance Superintendent
ATTACHMENTS:
None
REFERENCES:
Q3/0059 - Refinery Document Control
REVIEW DATE:
November 2006
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
CES/18/001 (December 2001)
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 British Standards
American Society for Non-destructive Testing Inc. Recommended Practice For Non-destructive Testing
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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CES/18/001 (December 2001)
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 CES/42/001 CES/42/006 CES/32/010
- Preparation for materials and shipment - Piping Material Specification + Specific Classes - Spring Support Installation and Commissioning Standard - Pressure Testing Of Refinery Piping and Equipment
BP GS’s 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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CES/18/001 (December 2001)
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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CES/18/001 (December 2001)
TABLE 1 Material, Service and Rating
Inspection Required Visual
Radiographic
% 1. All piping constructed of alloy material other than carbon steel 2. All carbon steel piping for the Alkylation unit in piping class WCZ41 (See note 3) 3. 900# rating and above 4. All reciprocating compressor piping and discharge KO drums, regardless of rating and material. 5. All 300#, 400# and 600# rating piping other than alloy material 6. All piping in low temperature service below 0o C (32o F) 7. All 150# rating piping, except as noted below 8. Salt water and fire water 9. Service water 10. Sewer piping 11. Non -pressurised piping to atmosphere 12. MP & LP / condensate and smallbore tracing (leads & tails)
Hydrostatic Pressure
Class
Welding
Test
YES
100%
YES
A
GTAW root
YES
100%
YES
A
GTAW
YES
100%
YES
A
YES
100%
YES
A
root/ Low Hydrogen
YES
10% of all welds
YES
B
YES
10% of all welds
YES
B
YES
5%
YES
C
YES YES YES YES
5% 5% 5% 5%
Service Test Service Test Service Test Service Test
D D D D
YES
5%
Service Test
D
Low Hydrogen Low Hydrogen Low Hydrogen E6010 root E6013 Remainder Acceptable
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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CES/18/001 (December 2001)
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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CES/18/001 (December 2001)
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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CES/18/001 (December 2001)
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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CES/18/001 (December 2001)
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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CES/18/001 (December 2001)
4.4
4.5
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.
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 air.
4.6
cooling down to 570oC and then cooling in still
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.
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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CES/18/001 (December 2001)
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
4.7
Cutting of pipework and weld bevelling shall be machine cold cut or plasma cut.
Monel 4.7.1
GAS FUEL OIL
4.7.2
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 114 mg/m3 503mg/m3 -0.50% (0.25 % preferred)
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
4.8
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.
Nickel and Nickel Alloys 4.8.1
GAS FUEL OIL
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 ZERO 503mg/m3 -0.50% (0.25% preferred)
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CES/18/001 (December 2001)
4.9
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.
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. 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.
4.9.5
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 No’s 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)
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 :
5.2.8
5.2.9
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.
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.
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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CES/18/001 (December 2001)
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 requalification, 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 Less than 1” (33.4mm) 1” to less than 2 7/8 (73.02mm) 2 7/8 and over
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Outside Diameter Min Size welded 1” 2 7/8
Qualified Max Unlimited Unlimited Unlimited
CES/18/001 (December 2001)
Thickness Limits on Groove Welds Thickness Of test coupon Up to 3/8” (9.5mm) 3 Over /8” but less than ¾” (19.05mm) Over ¾”
5.3.6
Thickness Qualified Max 2t 2t 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.
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 Carbon Steel (Iron Powder) Carbon Steel AWS E6013 Carbon Steel AWS E6010 Carbon Steel (Low hydrogen) Carbon Steel (CO2) C- ½ %Mo 1 ¼%Cr - ½%Mo 2 ¼ %Cr-1% Mo 5%Cr- ½ %Mo 7%Cr- ½ %Mo 9%Cr- 1 %Mo 12/13%Cr 18/8 Stainless 25/12 Stainless 25/20 Stainless Aluminium Alloys Aluminium Bronze Inconel 600. UNS NO6600 Monel. UNS NO4400 Alloy 20. UNS NO8020
Material P.No.
Welding Rod F.No.
Filler Metal F.No.
1 1 1 1 1 3 4 5 5 5 5 6,7 8 8 8 21 35 43 42 45
1 2 3 4 4 4 4 4 4 4 4 5 5 5 44 42 5
6 6 6 6 6 6 6 6 6 6 21-24 36 44 42 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 ½ % 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- ½ 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 (½ 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 308, 308L 316, 316L 309, 309L 347 5.5.9
PWHT or Service Temperature Less than 4300C (8000F)
Ferrite % 5-15
Ferrite No. 5-17
4300C (8000F) and over
5-9
5-9.8
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 lowcarbon 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 preheating 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 Nominal Analysis Carbon Steel Manganese - Molybdenum C- ½ Mo ½ Cr - ½ Mo 1Cr - ½ Mo 1 ¼ Cr - ½ Mo 2 ¼ Cr - 1Mo 3Cr - 1Mo 5Cr - ½ Mo 7Cr - ½ Mo 9Cr - 1Mo 12Cr (Martensitic) CA6NM (0.03% C max.) 12Cr (Ferritic) 2 ¼ Ni 3 ½ Ni 5 Ni 9 Ni
6.1.7
6.2
P-No 1 3 3 3 4 4 5 5 5 5 5 6 6 7 9A 9B 11A 11A
Minimum Preheat Temperature o o C F Refer to 6.1 150 300 95 200 95 200 150 200 150 300 200 300 200 400 200 400 200 400 200 400 205 400 10 50 10 50 150 300 150 300 150 300 150 300
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.
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 Diameter Up to and including 150mm Above 150mm to 300mm Above 300mm to 600mm Above 600mm to 1200mm
Number of Thermocouples Per Weld 1 2 4 6
Position On top o 180 Intervals 90o Intervals 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 ( ½ 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 304 321 316, 316L 316Ti - 316Nb 309, 310 347 (See Note)
Temperature oC Hot Forming /Bending Solution Annealing 1100-900 1050-1000 1100-900 1070-1020 1100-900 1100-1050 1100-900 1070-1020 1100-900 1100-1070 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 Nominal Analysis
P-No.
Carbon Steel Manganese - Molybdenum ½ Cr - ½ Mo 1Cr - ½ Mo 1 ¼ Cr - ½ Mo 2 ¼ Cr- 1Mo 3 Cr - 1Mo 5 Cr - ½ Mo 7 Cr - ½ Mo 9 Cr - 1Mo 12Cr (Martensitic) 12Cr (Ferritic) 2 ¼ Ni 3 ½ Ni 5Ni 9Ni Monel
1 3 3 4 4 5 5 5 5 5 6 7 9A 9B 11A 11B 42
PWHT Temperature Range o o C F 610-655 620-720 620-720 705-745 705-745 720-760 720-760 720-760 720-760 720-760 720-790 None 595-635 595-635 550-585 550-585 590-610
1130-1230 1150-1325 1150-1325 1300-1375 1300-1375 1325-1400 1325-1400 1325-1400 1325-1400 1325-1400 1325-1450 None 1100-1175 1100-1175 1025-1085 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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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. c)
Each temperature chart shall indicate the following :-
1. 2. 3. 4. 5. 6. 7. 8. 7.0
Client name and site details. Order number. Item reference number or drawing number. Technicians signature and date. Material type, wall thickness, diameter and line specification. Line / weld identification. Thermocouples positions. Recorder serial number and date of calibration. Chart number. Hardness report numbers. Specification parameters, reference to weld procedures or specification s where appropriate. Quality procedure reference number. Any special requirements.
Client and site. Heat treatment specification details. Line / weld identification Recorder serial number. Chart speed. Chart number. Chart acceptance document number. Technicians signature.
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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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 ‘D’ shall apply to all welds in severe cyclic or normal fluid service. ‘E’ shall be applicable to category D fluid service. ‘F’ shall apply to all welds irrespective of service condition
Internal porosity Slag inclusion, tungsten inclusion, or elongated indication* 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 For all welds irrespective of service conditions external protrusion 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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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 Weldment Inspection Personnel (C.S.W.I.P)
Industrial Radiographer Grade 2 And / Or Ultrasonic practitioner (welds) Grade 2
2. American Society for NonDestructive Testing (A.S.N.T)
Level 2 (Industrial Radiography)
3. The Personnel Certificate in NDT (P.C.N)
Industrial Radiographer Level 1
7.6.3
8.0
Where the approval does not include “Radiation Safety” a separate certificate in Radiation Safety must be held.
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
Page 37 of 39
CES/18/001 (December 2001)
other contaminates. Flange faces shall be coated with a suitable corrosion preventative.
9.0
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.
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.
Page 38 of 39
CES/18/001 (December 2001)
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 subcontractors 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-conformance’s 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.
Page 39 of 39
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 ½ ” 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.
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.
CES/18/001 (December 2001)
APPENDIX C Base Material Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
-
TABLE 2 FILLER METAL FOR WELDING DISSIMILAR METALS Nominal Analysis Of
Base Materials Carbon Steel Carbon-Molybdenum steel 2 ¼ %& 3 ½ % Nickel 9% Nickel Steel 1% Cr- ½ % Mo Steel 1 ¼ % Cr - ½ % Mo Steel 2 ¼ % Cr - 1% Mo Steel 5% Cr - ½ % Mo Steel 7% Cr - ½ % Mo Steel 9% Cr - 1% Mo Steel Type 405 Stainless Steel Type 410S Stainless Steel Type 410 Stainless Steel Type 304 Stainless Steel Type 304L Stainless Steel Type 321 Stainless Steel Type 347 Stainless Steel Type 316 Stainless Steel Type 316L Stainless Steel Type 309 Stainless steel Type 310 Stainless Steel Alloy 800 (Incoloy 800) Monel 400 Inconel 625
Base Material Number 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
B
C
D
C
E
C
E
E
E
E
E
E
B
B
B
B
B
B
B
B
B
B
B
C
D
C
B
B
B
B
B
B
B
B
C
C
C
C
C
C
C
C
C
C
C
C
C
C
B
B
B
B
B
B
B
B
C
D
C
A A
E
A
C
A
E
A
E
F
A
E
F
F
A
E
F
F
H
A
E
F
F
G
H
A
E
F
F
G
H
B
B
B
B
C C F
F
F
F
F
F
F
F
F
B
B
B
B
B
B
B
B
C
D
C
F
G
G
B
B
B
B
B
B
B
B
C
C
C
H
H
B
B
B
B
B
B
B
B
C
C
C
I
B
B
B
B
B
B
B
B
C
C
C
C
C
C
I J
K
J
J
B
B
B
B
B
B
B
B
K
K
B
B
B
B
B
B
B
B
C
C
C
K
B
B
B
B
B
B
B
B
C
C
C
B
B
B
B
B
B
B
B
C
C
C
L
L
P
L
L
O
O
C
C
C
M
M
L
M
O
O
C
C
C
N
L
M
O
O
C
C
C
P
M
P
P
C
C
C
Q
O
O
C
C
C
O
O
C
C
C
R
C
C
C
C
C
C
B
B
J
K
K
B
B
B
C
B
B
B
B
B
B
B
B
B
B
B
B
C
B
B
B
B
B
B
B
B
B
L
B
B
B
C
B
B
B
B
B
B
B
B
B
L
M
B
B
B
C
B
B
B
B
B
B
B
B
B
P
M
N
B
B
B
C
B
B
B
B
B
B
B
B
B
L
L
L
P
B
B
B
C
B
B
B
B
B
B
B
B
B
L
M
M
M
Q
B
B
B
C
B
B
B
B
B
B
B
B
B
O
O
O
P
O
O
B
B
B
C
B
B
B
B
B
B
B
B
B
O
O
O
P
O
O
R
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
D
D
C
C
D
D
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
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. B - AWS A5.4 and A5.11, classification E309-XX, ENiCrFe-3 (Inconel 182), or ENiCrFe-2 (Inco-Weld A) C - AWS A5.11, classification ENiCrFe-3 (Inconel 182) or ENiCrFe-2 (Inco-Weld A) D- AWS A5.11, classification ENiCrFe-3 (Inconel 182), ENiCrFe-2 (Inco-Weld A), or ENiCr-7 (Monel 190) E - AWS A5.5, classification E7015-A1, E7016-A1, or E7018-A1 F - AWS A5.5, classification E8016-B2, E8018-B2, or E8015-B2L, E8018-B2L G - AWS A5.5, classification E9015-B3, E9016-B3, E9018-B3 or E9015-B3L, E9018-B3L H - AWS A5.4, classification E502-XX I - AWS A5.4, classification E7Cr-XX Note : 1. Blank spaces in Table 2 indicate combinations that are considered unlikely or unsuitable. For these combinations consult BP Inspection Group.
C
C C
C
J - AWS A5.4, classification E505-XX K - AWS A5.4 and A5.11, classification E410-XX, E410 cb-XX E309-XX, ENiCrFe-3 (Inconel 182), or ENiCrFe-2 L - AWS A5.4, classification E308-XX M - AWS A5.4 classification E308L-XX N - AWS A5.4 classification E347-XX O - AWS A5.4 classification E309-XX or E308-XX P - AWS A5.4 classification E308 -XX or E347-XX Q - AWS A5.4 classification E316-XX or E316L-XX R - AWS A5.4 classification E309-XX 2. Table 2 refers to coated electrodes. For bare wire welding (SAW, GMAW, GTAW), use equivalent electrode classification (AWS A5.9, A5.14, A5.17,
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