General Specification for Welding and Weld Inspection [EIL]

GENERAL SPECIFICATION FOR WELDING AND WELD INSPECTION

DOCUMENT No. 3959-00-06-41-SP-04 Rev. 0 Page 1 of 19

GENERAL SPECIFICATION FOR WELDING AND WELD INSPECTION

0

11.08.03

Issued for bid

Rev. No

Date

Purpose

Format No. EIL 1641-1924 Rev. 1

Prepared by

Checked by

Approved by

Copyright EIL – All rights reserved

DOCUMENT No. GENERAL SPECIFICATION FOR WELDING AND WELD INSPECTION

3959-00-06-41-SP-04 Rev. 0 Page 2 of 19

CONTENTS

1.0

SCOPE

2.0

CODES AND STANDARDS

3.0

WELDING PROCESSES

4.0

MATERIAL

5.0

QUALIFICATION

6.0

WELDING PRACTICES AND REQUIREMENTS

7.0

INSPECTION AND TESTING OF WELDS

8.0

REPAIR DEFECTS




1.0

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SCOPE This section modifies and/or supplements the referenced codes, which apply to all piping, pressure vessels, skid, and structural welding. These requirements cover welding done at Supplier’s fabrication plants, Contractor’s yards, or field installations, either onshore or offshore. -

2.0

The company shall review the adequacy of all welding procedures to assure compatibility with the accepted offshore structural fabrication practices and the service requirements. The company reserves the right to reject all such procedures which, in its opinion, conflicts with sound fabrication practices or pose a hazard to good service performance.

CODES The following codes/specification shall be the minimum acceptable standards for welding and inspection. The latest editions, addenda, and supplements available at the time of bidding will be used. Any part of any other non-listed code referred to in these listed codes as augmentation is to be considered applicable.

2.1

Structural a) b) c) d)

2.2

American Welding Society Structural Welding Code D1.1. ASTM E 94 and E 142. ASME Boiler and Pressure Vessel Code, Sections V, VIII and IX, Latest Edition. API RP 2X.

Pressure Vessels ASME Boiler and Pressure Vessel Code:

2.3

Section VIII Division I

Pressure Vessels

Section IX

Welding and Brazing Qualifications

Section V

Non-destructive Examination

Piping on Platforms, or Skid Mounted Assemblies Refer to ANSI B 31.3.

3.0

WELDING PROCESSES

3.1

All welding required in the fabrication of the offshore structures and on-deck facilities shall be carried out by low-hydrogen processes.

3.2

In general, Shielded Metal Arc Welding (SMAW), Flux Cored Arc Welding (FCAW), Gas Tungsten Arc Welding (GTAW), Gas Metal Arc Welding (GMAW) and Submerged Arc Welding (SAW) are acceptable in the fabrication of structure, vessels, and piping coming under the scope of this specification.




4.0

MATERIAL

4.1

Electrodes, Welding Wire and Flux

4.2

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a)

All welding consumables will be suitable for the position and for the conditions of its intended use and be suitable for use with the particular base metal to which they are applied and shall be bought from reputed approved manufacturer. All welding consumables like welding electrodes, filler wires and fluxes shall be individually approved by the Company.

b)

All electrodes and filler wires shall be bought in hermetically sealed containers and stored in suitably heated humidity controlled storage ovens until issued for use. Temperature of storage shall be to manufacturer’s recommendations. After removal from storage ovens, the electrodes shall be transferred to portable holding ovens kept at about 100°C and shall be drawn one at a time for immediate use. These materials shall be identifiable by means of their original colour coding (or factory labelling, in the case of wire) until the time of use.

c)

If submerged arc welding is utilized, the flux shall be the neutral type. It shall be kept on humidity controlled storage and used in accordance with the manufacturer’s recommendations regarding the temperature and humidity limitations. Flux shall be screened and filtered before reuse. The wire flux combinations used in SAW shall be specifically approved by the Company.

d)

Electrodes and filler wire showing signs of damages or deterioration shall not be used.

Inspection of Welding Materials a)

All welding materials furnished by the Contractor shall be subject to inspection and test at the site by the Company. Inspection and tests of materials will be conducted without expense to Contractor only when such inspections and/or tests are in addition to those required by these specifications.

b)

Inspection at the mill, shop, and/or fabricating sites will not relieve the Contractor of the responsibility of furnishing welding materials satisfactory to the specification requirements. In the event that these materials do not perform on site to the requirements of these specifications Company reserves the right to reject such materials at any time.

5.0

QUALIFICATION

5.1

Welding Inspectors Irrespective of any stipulations in the Codes, the Company’s inspectors shall be the qualified welding inspectors for the contract resulting from these bid documents.

5.2

Procedures a)

Prior to commencing welding work, Contractor shall submit the proposed welding procedures, including the repair welding procedure specification,




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for the Company’s approval, in accordance with ASME SEC IX. Test results of procedures previously qualified should be submitted and if satisfactory will form the basis for approval of these procedures without further testing. b)

Any procedures not previously qualified, and any pre-qualified procedure whose test results are not satisfactory, shall be qualified as required by the particular code applicable to the work for which the fabrication or assembly of structural members will have these requirements for qualification in addition to the requirements of AWS D1.1. “Structural Welding Code” and ASME SEC IX.

1.

Impact Requirements If AWS specifications do not require minimum Charpy V-Notch impact properties, for the electrodes and fluxes, that are to be used for procedure qualification, then Charpy V-Notch test specimens shall be obtained and tested according to ASTM A370 and E 23. The as-deposited weld metal is required to have a minimum impact strength of 27 Joules or 2.75 kgm. (20 ft – lb) at - 18 °C (0°F) for welds in tubular joints and other key points. Company is the sole judge of what is a key point.

2.

Radiographic Inspection In addition to the above requirements, the welding procedure qualification testing must include the provision for the radiographic inspection, by a testing Agency acceptable to Company. Radiographic Inspection of complete penetration groove tests welds shall be carried out prior to the removal of impact test specimens.

3.

Hardness Testing Hardness testing shall be carried out with acceptance criteria as set forth in DNV Rules (1977) and with procedure as given in Appendix C.8.3.6 to the same rules.

4.

Fabrication of Welded Tubular Members (Structural) For qualifying procedures for fabricating welded tubular members, the transverse tensile strength of the welds shall be determined by tests on weld specimens conforming to the requirements of ASTM Methods and Definitions A 370 “Mechanical Testing of Steel Products, Supplement II, Steel Tubular Products”. Weld tensile test specimens shall be taken 90 degrees to the weld, with the weld at the centre as shown in Figure 23 (Tensile test specimen) of ASTM A 370. the bend test specimen as shown in Fig. 31(a) of ASTM A 370 shall withstand being bent 180 degrees in the jig for guided bend test, substantially in accordance with Fig. 32 of ASTM A 370. A bend specimen shall be considered as having passed if no crack or other open defect exceeding 3 mm. (1/8 inch) measured in any direction is present in the weld metal or between the weld and base material after bending. The position and number of test specimens shall be subject to approval by Company’s representative.




5.

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Stress Relievers Should Contractor desire to use ultrasonic or other mechanical stress relieving apparatus he shall completely define their method of application in the welding procedures submitted. This definition will be complete with proof of the effectiveness of the apparatus and its effect on weldments produced during its usage.

5.3

Welders and Welding Operators a)

Welders and welding operators must be qualified as required by the ASME SEC IX or any other code covering the work they are to perform, by passing a welder/operation qualification test. This qualification shall be at the Contractor’s expense.

b)

Prior to commencement of work Contractor must submit records of welder/operator qualifications to the Company. If the work turned out by a welder or welding operator shows repetitive defects, Company reserves the right to ask for the retesting of the welder or welding operator at any time. The decision of the Company regarding the qualification and requirement of qualification of the welder shall be final. Retesting of the welder shall be at Contractor’s expense. Qualification based on solely radiography shall not be permitted unless specifically permitted by the Company’s representative in exceptional cases.

c)

All welders shall be qualified for the type of weldment and grade of steel they are employed to weld. Welders qualified to weld only part of materials utilized shall be restricted to welding on only that portion of the work for which they are qualified.

d)

All welders working on the project shall wear identification cards made at Contractor’s cost, which shall contain the photograph and name of the welder, procedure qualified and Company’s Representative’s signature.

6.0

WELDING PRACTICES AND REQUIREMENTS

6.1

Pressure Vessels

6.1.1

Welding

6.1.2

i)

Only welders and procedures qualified as per ASME Code, Section IX shall be used for fabrication. Qualification papers for these welders shall be made available on request.

ii)

Non-consumable backing rings shall be used only with Company’s approval.

iii)

Temporary attachment welds shall be removed. The affected surface shall be restored by adding weld metal, grinding or both.

Heat Treatment i)

Minimum preheat temperature for thermal cutting, welding and tack welding shall be as specified in ASME Code, Section VIII, Division 1, Appendix R except as follows:




a)

b)

6.1.3

6.2

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Materials in the P-1 group shall be preheated to 80°C (175°F) and maintained during welding when (i) under a high degree of restraint (such as closely spaced nozzles), or (ii) when any one of the following conditions exist : i)

The specified carbon content is 0.25% or more.

ii)

Minimum specified tensile strength exceeds 60,000 psi (414 Mpa)

iii)

Metal thickness at the joint exceeds 25 mm (1-inch).

All other P-1 group materials, other than those included above, shall be preheated to maintain a minimum temperature of 10°C (50°F).

ii)

All welding including internal and external structural attachments shall be completed prior to post weld heat treatment.

iii)

P-1 group materials requiring postweld heat treatment which contain lining or internals of unstabilized austenitic materials such as AISI type 304 or 316 shall be heat treated at 510° ± 10°C (950°F ± 50°F) for a period of 10 hours per 25 mm (1-inch) of thickness.

iv)

Machined surfaces shall be protected against scaling during heat treatment.

v)

Cold formed dished ends i.e. formed below the normalisation temperature range shall be stress relieved.

Cleaning i)

Prior to testing, vessels shall be cleaned of all weld spatter, loose scale and foreign matter. Liquid used for testing shall be completely drained.

ii)

Vessels of thickness greater than 20 mm (3/4-inch) shall be cleaned externally by a No.6 Commercial blast. SSPC-SP 6-63, to ensure freedom from embedded foreign matter. Any defects discovered shall be repaired.

Piping and Pipelines a) b)

No chill rings or backup rings are to be used. All welds shall be allowed to air cool to a temperature of not over 52°C (125°F) prior to being placed in the water, and to a temperature below 204°C (400°F) prior to pipe tensioning.

6.3

Structural Welding

6.3.1

General a)

All structural welding shall conform to the Company approved welding procedures. The Contractor shall post copies of the procedures in a conspicuous location in each fabrication area and shall provide adequate supervision to ensure strict adherence to the qualified procedures.




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b)

All member intersections including those between floor grating or deck plate and its supporting structural members, shall be seal welded in all areas where strength welds are not required. Steel doubler plates shall be completely seal welded.

c)

Preheating of the base metal prior to welding shall be in accordance with the AWS D1.1 “Structural Welding Code” for those materials not having been heat treated during their manufacture for the purpose of increased strength or notch ductility. Such heating should be accomplished by devices which produce uniform heating of all the critical zones around the entire welded zone, such as resistance heating flexible pads. When materials intended for joining by welding have been heat treated in manufacture, Contractor shall strictly adhere to heating requirements to the qualified welding procedures pertinent to the specific type of material used and to their thickness.

d)

It is extremely important that the finished structure be as free from distortion as possible. The Contractor shall be responsible for preventing or for correcting distortion and maintaining perfect alignment as per the detailed approved drawings. The Company will have the right to stop the work should excessive distortion become evident. Stiffener plate edges and bevels shall be ground smooth prior to installation.

e)

Welders shall be supplied Tempil sticks – Thermal Crayons or contact thermocouple instruments, so that welders and inspectors can accurately check and control the preheat temperatures at the weldments.

f)

Circumferential butt welds joining pipes of the same diameter shall be welded by the automatic submerged arc process wherever possible. If the joint preparation is such that welding is done from both sides of the welding groove, the inside weld shall be deposited first excepting the case of clad pipes. The depth of the weld deposited from the inside shall not constitute more than 1/3 of the thickness of the members being joined. The backside of the first pass of the inside welding shall be gouged, ground, or chipped to clean weld metal before deposition of any of the outside weld metal. The inside weld may be deposited by the manual arcwelding process if desired.

g)

Butt welds in jacket legs, piles, braces and conductor pipes shall be background and re-welded from both sides. Welding backup rings shall not be used for butt welded joints of structural tubular members. In joints where welding is possible from only one side, the members shall be carefully contour fitted and bevelled to achieve complete weld penetration.

h)

If pipe contains logitudinal weld seams, the logitudinal seams shall be staggered a minimum of 90 degrees at the circumferential butt weld joints. Longitudinal seams shall not be placed within 50 mm. (2-inch) of any point on the intersection seams between members at tubular joints.

i)

Grooves shall be bevelled to give an included angle of 60°. The groove shall be of single-`V’ or double-`V’ type Root openings shall be not less than 1.5 mm (1/16-inch) and not greater than 3.2 mm (1/8 inch) Root face shall not be greater than 1.5 mm. (1/16 inch).




6.3.2

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j)

The covered electrodes for manual welding shall only be used in the positions recommended by the manufacturer. The submerged arc welding shall be done in a flat position. If submerged arc welding is required on tubular, the tube shall be rotated. A multiple pass technique shall be used.

k)

No fit-ups and associated joint intersection placement operation for major structural joints, especially tubular ones, shall be permitted to occur before one hour after sunrise and after one hour before sunset, unless otherwise specially authorized by company. All such joining operations, to include placement of at least the root pass weld can occur at night, provided the operating conditions and preheats are satisfactory to the Company.

l)

All fitted members shall conform to the straightness and alignment specified in the bid specification and approved drawings. Correction of improperly fitted parts shall be accomplished by disassembly and refitting. Thermal straightening shall not be permitted unless specifically approved in writing by the company as an exception.

Structural Plates, Shapes, and Stiffeners a)

All welded fabrication involving structural shapes and/or plates shall be joined in the manner designated on the drawings and may require shop drawings. Weld sizes and notes on drawings shall be strictly adhered to, or if not specified shall joint section in such a manner as to develop not less than the net area of the sections joined. Where full penetration welds are specified, the back side of the first pass of welding on double butt welds shall be gauged and ground smooth to sound metal before depositing weld metal to the opposite side. Company shall have the right to nondestructively test the root of this weld before deposition of weld filler metal. Where welding can only be done from one side, the joining member shall be prepared with proper angle of bevel and shall not contain a root face.

b)

Where strength welds are required by the drawings, or otherwise, to extend only partially around a member of plate joint, a 6 mm (1/4-inch) fillet seal weld shall be deposited continuously throughout the remaining distance around the member or plate. Company places special emphasis on the complete seal welding of all intersections (where there is no strength welds) between steel members. Of special note are the beam-to-deck plate and the beam-to-beam intersections on the superstructure.

c)

Sections of beams with the same cross section may be splice welded in the interest of material economy. The number of splice welds and their locations, with respect to beam ends, shall be dictated by the design function of the beam(s) under consideration. Generally, in cantilever beams, there shall be no splice weld located closer to the point of support than one-half of the cantilevered length. For beams employed in any span between supports, there shall be no splice weld in the center one-fourth of the span distance nor in one-eighth segment of the beam nearest any support. No two splice welds shall be located closer together than two times the beam depth, or a minimum of three feet whichever is smaller.

d)

Joints between deck plate and bar grating sections shall be fully strength welded.




6.3.3

6.4

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e)

Stiffeners shall be accurately located and neatly fitted between the flanges of the beam or the girders when full surface contact is required. The ends of stiffeners shall be millled or smoothly ground to conform to the geometry of the member to which it is being attached, or bevelled in such a manner as to assure 100 percent fusion in the root of the attachment weld, as dictated by the drawings, and/or by the Company s Representative.

f)

When members are slotted to receive gusset plates, the slot must be 300 mm (12 inches) or 12 times the member wall thickness, whichever is greater, from any circumferential weld. The slotted member shall be drilled at the end of slot with a drill diameter at least 3 mm (1/8 inch) greater than the width of the slot. Where a gusset plate passes through a slot, the edge of the gusset plate shall be ground to an approximately half round shape to provide a better fit-up and welding conditions. Slots shall be atleast 12 inches away from longitudinal seam welds.

Finishing of Surfaces a)

The completed structures shall be free of all scars, grooves, random arc striker, burrs, and any other imperfections introduced by handling, scaffolding, lugs, dogs, or other welding aids. Fillet welds attaching lugs, dogs, scaffold supports or other temporary attachments shall be so located that their removal can be accomplished without the removal of parent metal. These attachments must be removed by cutting with a flame torch, then by power grinding them to the original plate surface. Removal of these attachments by arc gouging will not be allowed. Repair welds shall not be less than 50 mm. (2 inch) in length.

b)

If, in the opinion of the Company’s Representative, welded joints contain geometric irregularities contributing to stress concentrations or notch effect, Contractor shall eliminate the condition by grinding. Over-welding will not be permitted to correct such conditions. If additional welding will assist in correction, it shall be done with the Company s approval.

General Welding Requirement a)

No weld is to be cooled by quenching or by any means other than natural convection by air.

b)

No weld is to be coated before it has been inspected and accepted.

c)

Welders’ identification stamping for piping and pressure vessels shall be done using low-stress type dies. This identification on all structural and pipeline welding shall be done by a paint marking or a tagging system which will avoid die-stamping. The system is to be submitted to the Company for approval.

d)

Proper grounding of all welding machines is necessary to prevent underwater corrosion damage. The welding machine should be located on and grounded to the structure whenever possible. If this is not possible, the welding machine should be insulated from the barge and the vessel and an adequately sized cable should be used to ground the structure to the welding machine. Ground clamp connection to the component shall be steel not brass.




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e)

All surfaces or joint faces to be welded shall be free of loose scale, paint, oil or other foreign material. Cleaning shall be accomplished by grinding, power wire brushing, or by sandblasting.

f)

Components may be cut and shaped by machining, grinding, chipping, flame or plasma-arc cutting or shearing. Mechanically guided equipment shall be used wherever practical. Sheared edges not subsequently fused by welding shall be trimmed by grinding or machining to a minimum depth of 3 mm (1/8 inch) to ensure complete removal of cracked or cold work metal. Components may generally be flame or plasma-arc cut without preheat.

g)

All plate edges or pipe wall ends to be welded shall be examined for laminations before assembly into the structure.

h)

The entire area to be welded shall be warmed before welding is started to a minimum temperature of 21°C (72°F). Preheat and interpass temperatures shall conform to those given in AWS D1.1, or Contractor s qualified welding procedure.

i)

Welding shall not be done when the quality of the completed weld would be impaired by the prevailing weather conditions including, without limitation airborne moisture, blowing sands, or high winds. Windshields may be used when practical. Company Representative shall decide if weather conditions are suitable for welding.

j)

No welding shall be performed in any area when the base metal temperature is above 260 ° C (500 ° F).

k)

Arc-air gouging shall be an acceptable method for random metal removal and back gouging only when followed by grinding to bright metal. The temperature and weather limitations specified above for welding shall apply to all arc-air gouging.

l)

All low hydrogen flux coated electrodes shall be heated before use by holding in a drying oven for a minimum period of 24 hours at a temperature of 149°C minimum to 204°C (400°F) maximum, or strictly as per the electrode manufacturers recommendations. They shall then be stored in heating quivers at about 70°C (158°F) till use. All low hydrogen flux coated electrodes shall be used within 4 hours after removal from the oven. Welding materials left unnecessarily exposed to moisture contamination shall be discarded.

m)

The root (or second) side of all joints to be back welded shall be back gouged to clean, sound metal. The back gouged weld root shall be subject to inspection (for porosity, unfused metal and cracks) by magnetic particle methods, until the gouging operation has been demonstrated to be capable of consistently producing a sound weld surface for subsequent weld passes.

n)

Weld detail, for fillet weld contour and reinforcement of butt welded joints, shall conform to the requirements given in AWS D1.1. Full or partial penetration groove-welded tee joints shall be contoured smoothly into the upstanding member by building up a filler reinforcement in the inner corner with a minimum transition radius equal to 1/2 the thickness of the thinner member joined, but not more than 3/16 inches unless otherwise specified for joint strength.




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o)

Partial or deep penetration welding joints are not generally acceptable. However, if such joints are unavoidable and permitted by the Company representative, then the root pass of all partial penetration groove welds shall be visually inspected for adequate penetration into the joint before the welding is continued.

p)

Root openings in the welding joint wider than permitted by AWS D1.1 and as qualified but not greater than the thickness of the thinner member shall be built up by welding to the specified groove dimensions before the parts are joined.

q)

Root openings in the welding joint less wide than that permitted by AWS D1.1 shall be chipped or gouged in a manner as to maintain the specified groove dimensions.

r)

All welding shall be accomplished by an approved bead deposit sequence. Weave passes in a excess of 2.5 times the electrode diameter shall not be acceptable.

s)

Care shall be exercised to keep arc-strikes and Weld Scars to a minimum. Temporary fit-up and erection attachments shall be welded with the same care and the same procedures as applicable for the structural connections. Radiographic or other inspection operations shall be maintained concurrent with weld completions. All general clean up surface repairs shall be completed before final inspection.

t)

u)

Welding on primary strength members shall not be permitted on any galvanized surfaces or any surface coated with a lead or zinc bearing paint, unless otherwise specified.

v)

Unless otherwise indicated on the Contract Drawings, the weld joint groove preparation for joining members less than 50 mm. (2 inch) thickness through the center line of the weld shall be AISC type B-L2. Weld in excess of 50 mm (2 inch) throat thickness shall be welded with AISC type BU-3B or B-1. 3-S joint preparation whenever possible. If a single groove preparation is employed for welds in excess of 50 mm. (2 inch) thickness, qualification of a welding procedure is required as proof that the welding groove is satisfactory.

w)

Electric ovens shall be provided at job sites for baking of electrodes. The bake electrodes shall be transferred to a portable holding oven kept at about 100°C, and shall be drawn one at a time for immediate use on the job. Any welder shall draw electrodes from oven not more than one at a time for use in immediate welding works.

x)

With the exception of manually welded root runs for submerged arc welding, interruptions shall not take place until at least half of the final weld thickness is achieved all around the joint. In the event of interruptions, controlled cooling of the weld area shall be ensured. Before resumption of welding, the weld shall be inspected visually for cracks and, if required by Company, shall be tested by MPI or liquid penetrant examination.

y)

Contractor shall develop and submit for Company’s approval welding sequences to control warping, creeping, or build up of excessive residual




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stresses in the structure. Contractor shall ensure that these planned sequences are fully adhered to during fabrication. z) 6.5

6.6

All seal welding shall be done using minimum 6 mm. size fillet welds.

Pipe Welding a.

Piping joints shall be butt welded or filet welded using the appropriate qualified welding procedures by qualified welders.

b.

GTAW or P- GMAW is preferred for the root welding. Fill and cap passes can be by GTAW or GMAW or SMAW or FCAW process. For shop welding of longitudinal joints and circumferential joints, SAW using an approved wire/flux combination may be used with the approval from the Company.

c.

The weld area and the neighbourhood shall be cleaned both by mechanical and solvent cleaning procedures to remove any adherent paint, oil, grease, oxides and other contaminants.

d.

All bevelled edges shall be checked for cleanliness and accuracy of dimension as per the approved drawing before fit up.

e.

The proposed edges shall be inspected for laminations at the ends on a band of 50mm. All defective ends shall be cut and removed to prepare fresh edges. The discarded ends shall not be used anywhere.

VESSEL WELDING a)

Welding on vessels could be carried out by SMAW, SAW or FCAW process. The rest could be welded with GTAW process or Pulsed-GMAW process.

b)

All pressure containing welds such as longitudinal welds, circumferential welds and nozzle attachment welds shall be full penetration welds. Wherever approach exists from both sides, the welding shall be done by using a double `V’ groove edge preparation, the weld detail employed shall be such that it ensures a full penetration joints.

c)

Back up strips shall not be used, even in closure joints in heads.

d)

All nozzles, couplings and manholes shall be attached to the vessel wall with full penetration butt welds through the vessel walls.

e)

All bevelled edges shall be mechanically prepared by grinding smooth to sound material and shall be cleaned by mechanical and solvent cleaning procedures to remove oily/greasy substances, paints and other oxide scales.

f)

All longitudinal seams shall clear nozzles, clips and other external attachments by a minimum of 6” distance. Longitudinal seams for the vertical vessels shall be located 180° approximately from each other. Longitudinal seams for horizontal vessels shall be located 80° apart and shall be minimum of 30° above the horizontal plane through the centreline of the vessel.




6.7

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g)

All welds in the vessels shall be ground flush with the neighbourhood on the inside of the vessel to facilitate easy installation of trays and baffles. Remelting of the weld metal to impart smooth finish shall not be permitted.

h)

All external attachments to the vessels, both in the shell as well as in the head, shall be made by continuous seal welding, unless prohibited by the ASME code or the approved drawings.

i)

The welded vessels shall be stress relieved in accordance with the requirements of the codes and approved welding procedures. The heat treatment procedures, including the schemes for the heating arrangements, thermocouple placements and insulation, shall be specifically qualified and approved by the Company prior to their deployment on the job. Flange facings shall be protected against oxidation during heat treatment. No welding shall be permitted after the stress relieving, unless specifically permitted in writing in exceptional cases.

Temporary Welds Temporary welds (for temporary handling attachments, lugs etc.) shall be minimized. When a temporary weld is necessary, the welding will be performed with the same care, materials, electrodes, preheat, and procedures as for the permanent weld installations with a doubler plate whenever possible. However temporary attachments to permanent members like sea fastenings shall be through a doubler plate. The temporary welds shall subsequently be removed with an oxy-acetylene torch by severing the attachment slightly above the surface of the structural member and by grinding the remainder of the weld deposits flush with the member. Temporary welding shall not be removed by arc-air gouging, hammering or other mechanical means.

7.0

INSPECTION AND TESTING OF WELDS

7.1

Pressure Vessel

7.1.1

Company reserves the right to inspect vessels at any stage during fabrication and testing to assure compliance with this specification, the vessel specification and the ASME Code. Adequate advance notice shall be given for the inspection prior to start of fabrication and scheduled time of hydrostatic testing.

7.1.2

All examination methods shall be ASME Code, Section VIII. Division 1 with the following additional requirements : (a) (b) (c)

7.1.3

Radiograph film shall be equivalent to Type 1 or 2 per ASTM E94. Type 1 film shall be used on steel less than 20 mm (3/4 inch) thick. Company reserves the right to approve the radiographic method employed. Ultrasonic examination and acceptance Criteria shall be per ASME Code Section VIII, Division 1, Appendix 12.

For fully radiographed vessels greater than 20 mm (3/4 inch) thickness, in addition to Code requirements, the followings examinations shall be performed:




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(a)

All circumferential and longitudinal butt welds joining heads, shells, and nozzles shall be radiographed.

(b)

All welds attaching nozzle necks to shell or reinforcing pads (Category D, other than butt welds shall be examined by one of the following methods : (i) (ii) (iii) (iv)

Radiography Liquid penetrant examination of every 10 mm (3/8 inch) of weld build up. Magnetic particle examination of every 10 mm (3/8 inch) of weld build up by both the prod and coil methods. Ultrasonic examination.

7.1.4

For spot radiographed vessels, a minimum of 10% spot radiography on all main weld seams and 100% at all tee junctions of welds shall be carried out. The film length for each spot shall be 250 mm minimum. At least 10% length of welds other than the main circumferential and longitudinal seams shall, in addition be examined by magnetic particle or liquid penetrant, method. For cylindrical vessels, one spot shall be examined at each shell seam intersection.

7.1.5

All reinforcing pads shall be air tested to 1.05 kg/cm2g (15 psig) prior to post weld heat treating and/or hydrostatic test and all welds inside and outside inspected during the test. Test holes shall be open during the hydrostatic test and plugged with a non-hardening sealant or heavy grease after the hydrostatic test.

7.1.6

Pressure Testing A shop hydrostatic test shall be applied as per paragraph UG-99C ASME Code Section VIII, Division I, Test requirements are : (a)

No testing shall be performed before post weld heat treatment.

(b)

No pre-testing shall be performed before the code hydrostatic test.

(c)

Time period of testing shall be 1 hr. per 25 mm (1 inch) of the greatest thickness with a minimum of 4 hour.

(d)

Minimum test water temperature and metal temperature shall be 16°C (60°F) except if the design temperature is below 16°C (60°F), the minimum water temperature may be equal to the design temperature.

(e)

Test fluid shall contain no more than 500 ppm chlorides. However, for stainless steel vessels it shall not contain more than 25 ppm chlorides.

(f)

All cover plate hinge pins shall be in place during the test and shall not bind on the hinges.

(g)

Service bolting and ring joint gaskets to be finished with the assembly may be used for shop tests. Any materials damaged during testing and all types of gaskets other than ring joints shall be replaced by fabricator with new material. Gaskets used for tests shall be of the same material and design as those to be furnished with the vessel.




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7.2

Piping

7.2.1

Random radiography shall be performed on one weld in each 10 welds for each welder on the following: Water (in case of carbon steel) Air Chemicals Diesel Closed drain Relief Hydraulic oil Oily water Slops

7.2.2

25% radiography shall be performed on the following: Glycol and Therminol Vent gas Lube oil & Seal oil

7.2.3

100% radiography shall be performed on size 2” and above and 25% on sizes below 2” for the following: a) b) c) d) e) f) g) h) i)

Crude oil Jet fuel Fuel gas/Instrument gas Process gas Production flow lines (well fluid) Injection water Hydrocarbons (Process) Water (in case of 90/10 Cu-Ni) H.P. and LP Flare lines

7.2.4

For fillet welds and brazed joints where carrying out radiography is not possible, magnetic particle test or dye penetrant test shall be carried out. The extent of inspection shall remain same as for radiography.

7.2.5

All the lines which are stress relieved or have design pressure more than 50 kg/cm2 shall be fully radiographed (100%) even if not required as per 5.1 to 5.3.

7.2.6

RADIOGRAPHIC PROCEDURE shall be as per ANSI B31.3.

7.2.7

ACCEPTANCE CRITERIA based on visual, radiography and other types of examination shall be as per ANSI B31.3 with the following modifications: i)

The internal weld protrusion on “pigged lines” shall not exceed 1.6mm (1/16 inch).

ii)

Orifice flange butt welds shall be internally ground smooth and flush.

iii)

For 90-10 Cu-Ni Piping, radiographic examination of welds shall be as per ASME Section VIII, UW 51.




3959-00-06-41-SP-04 Rev. 0 Page 17 of 19

7.2.8

HYDROSTATIC TESTING is not required for shop fabricated piping where the pipe is to be field tested. Hydrostatic testing is required on skid mounted assemblies or if called for on an individual specification. Pressure tests shall be performed per ANSI B31.3 and the appropriate piping material specification class chart.

7.2.9

Those field welded joints, which cannot be leak-tested due to unavoidable reasons, shall always be 100% radio graphed.

7.3

Structural a)

All welds will be visually inspected as instructed in Section-6 of AWS D1.1. The Company will be vitally concerned with welds relative to quality, geometry, fit-up, and size, and will impose the use of gauges and/or nondestructive test procedures when and where they deem necessary. It shall not be construed as unreasonable for the Company to request proper repair of any defects in welds or materials that they consider to be detrimental to the strength and usefulness of the facility. If random NDT, as specified in this specification, indicates non-acceptable defects in a weld, the identification of the weld to the respective welder(s) shall be established and testing of other welds made by the same welder(s) shall be extended to the discretion of the Company, up to 100% at no extra cost to the Company.

b)

Radiographic examination shall be performed in accordance with ASTM E94 and E142 at the following weld areas: 1.

100% of all girth welds in tubulars.

2.

At the intersection of all tubular member girth and logitudinal seams, minimum 6 inches on either side of seam.

3.

In addition to clause 7.3(b2) above, 10% of each longitudinal seam of all tubulars.

4.

Any questionable weld defect.

5.

100% of all beam splices in skid beams, main truss beams and deck beams.

6.

20% of all full section splices in minor beams.

7.

100% for all pad-eyes to main structural attachment welds. AWS D1.1 shall be the standard of acceptance for all the welds inspected by radiography.

c)

All longitudinal seams of factory manufactured welded pipes shall be examined by 100% ultrasonic inspection during production, as directed in ASTM E-273, “Ultrasonic Inspection of longitudinal Welds of Welded Pipe and Tubing” or ASTM E164, “Ultrasonic Contact Inspection of Weldments”.

d)

100% ultrasonic testing and magnetic particle inspection of following weld areas shall also be performed :




7.4

3959-00-06-41-SP-04 Rev. 0 Page 18 of 19

1.

All T, K & Y, X and TK joint welds of jacket legs, skirt sleeves and deck frame work including truss chord to brace joints (beam to pipe).

2.

Welds and areas upto 100mm all around the weld of 10% of all remaining joints (Location of joints to be decided by Company’s representative).

3.

All pad eyes to main structural member attachment welds deck leg to girder welds, deck leg to ring stiffeners or diaphragm welds and intercostal deck beam to truss chord butt welds.

e)

100% ultrasonic and magnetic particle inspection shall be carried out on all welds in built-up girders.

f)

Rejection criteria for UT specified in 6.3.d above, shall be as per the “Rejection Criteria Level C” of API RP 2X. Rejection criteria for UT as in 6.3.c shall be as per the “Rejection Criteria Level A” of API RP 2X. Acceptance criteria for MPI shall be in accordance with ASME Section-VIII Div. I.

g)

The area of structural steel plates where attachments like padeyes, temporary supports, etc. are to be welded, shall be ultrasonically tested for laminations upto a distance of 100mm from the weld areas on all sides, prior to welding.

Inspection (General) a.

The mandatory inspection methods specified in Paragraph 6.1 through 6.3 above shall be at the Contractor’s expense, Company shall have the right to ask for the inspection of any weld (not previously accepted) by either nondestructive or destructive methods. This optional inspection can be for the purpose of routine quality control or to further investigate apparent defects detected visually. Defective welds found during a Company-optional inspection shall be repaired and the cost of removal, repairs, and re-inspection shall be at the Contractor’s expense. Welds found to be satisfactory shall be repaired and the cost of removal and repairs shall be at the Company’s expense under the provisions of the “Extra Work” clause in the Articles of Agreement. Company shall not be held liable by the Contractor for loss of time during these tests.

b.

Contractor will provide complete facilities for radiographic inspection of welds, including the equipment for development of films and full time services of a qualified technician familiar with radiographic inspection techniques, who will be competent to operate the above equipment.

c.

Contractor is responsible for rendering the surface of all welds clean and satisfactory for non-destructive testing.

d.

The Company retains the final right to determine the acceptability of any weld. Interpretation of test results will be in accordance with the guidelines set forth in the applicable codes.




8.0

REPAIR OF DEFECTS

8.1

Method

8.2

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a.

Defects shall be repaired as specified in the code governing the type of weld involved, in accordance with an approved repair welding procedure duly qualified along with the production welding procedures.

b.

Repaired defects shall be re-inspected by the same criterion as used for the original inspection.

Notification a.

The Company shall be notified before repairs are made on defective material and/or welds. Repairs made without a reasonable notice shall be subject to any form of testing (both destructive and non-destructive) to assure adequacy of the repair, and all removal, repair, and retesting deemed necessary by Company shall be at the Contractor’s expense.

b.

Welding Procedures shall be developed by vendor based on broad guidelines provided in the AWS Welding Specification Charts.



General Specification for Welding and Weld Inspection [EIL]

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