TECHNICAL REQUIREMENTSFOR WELD OVERLAY, CLADDING AND HARDFACING

1.0 General

This specification prescribes the minimum requirements for weld inlay/overlay/claddingand weld hardfacing of piping, fittings, pressure vessels and valves. The requirementsfor weld cladding of wellhead equipment are outside the scope of this specification.

1.1 All weld overlay, cladding and hard facing procedures shall be qualified andtested as per ASME BPV Code Section IX, NACE MR0175, API 582, DEP30.10.60.18, DEP 30.10.02.31 and the requirements stated in this document,plus SHELL MESC SPE 77/313, SPE 74/38, SPE 74/008, SPE 76/48, DEP31.40.20.32 and API 5LD (as applicable).

1.2 Welding procedure qualifications shall include repair procedures which requirepost weld heat treatment (PWHT) after repair.

1.3 Repair procedures which do not require post weld heat treatment shall bequalified to establish the minimum "cushion thickness" of clad material abovewhich PWHT may not be required.

1.4 All welding operators shall be qualified as per ASME BPV Code Section IX.

1.5 Welding procedures and welding operators shall be qualified to cover the fullrange of work scope in the production of an order.

1.6 Welding of coupons and mechanical testing shall be witnessed byCONTRACTOR/COMPANY or CONTRACTOR/COMPANY appointed ThirdParty Inspectors.

1.7 A minimum of two layers of weld should be deposited to reach the "minimumqualified" overlay/clad thickness.

1.8 Mechanical testing shall be carried out at a reputed, independent laboratoryhaving IS0 9000 or "UKAS" or equivalent accreditation.

1.9 Previously qualified welding procedures may be accepted by theCONTRACTOR/COMPANY provided the WPS's, PQR's and supportinglaboratory test reports are submitted for CONTRACTOR/COMPANY review. Inthis case, weld mock up tests shall be required and the scope of testing shall bereduced to include NDT, deposit analysis, macro, micro and hardness tests asper Sections 5.2, 5.3.1(a) and 5.3.2.

2.0 Essential Variables.

2.1 The essential, supplementary and non-essential variables for welding procedureand welding operator qualifications shall be as per ASME BPV Code Section IX.

2.2 In addition to 2.1 above, the following shall be considered as essential variables:

a) A decrease in the number of layers of weld deposit to achieve the minimumqualified thickness.

b) Addition or deletion of grinding or machining between weld deposit layers.

c) Where a procedure was qualified with inter layer grinding or machining, areduction in the amount of grinding or machining.

3.0 Welding Consumables

Filler wires and electrodes intended for Inconel 625 (UNS N06625) overlay orclad shall not contain more than 1% Iron in the all-weld deposit. The purchasespecifications for Inconel 625 filler wire/ electrode shall include this requirementin addition to AWS classification A 5.11 E NiCrMo-3 and A 5.14 ER NiCrMo-3.Every batch of welding consumable shall have a batch test certificate.

4.0 Welding of Test pieces

4.1 During welding of test pieces, the actual values of all variables (essential,supplementary essential and non-essential) as per ASME Section IX shall bemeasured and recorded.Actual values of amperes, voltage and travel spend shall be recorded for eachpass.

4.2 Where pulsed arc welding is used, actual values of pulse current, backgroundcurrent, pulse time and non-pulse time shall be recorded for each pass.

4.3 The thickness of the weld deposit shall be measured and recorded after eachlayer of weld metal is deposited. Details of any interpass grinding or machiningbetween any two layers shall be recorded.

5.0 Inspection and Testing.

5.1 Following completion of the weld overlay, the test coupon shall be permanentlymarked, preferably with a metal die stamp duly witnessed byCONTRACTOR/COMPANY or CONTRACTOR/COMPANY appointed TPI.

5.2 The test weld overlay shall be subjected to surface NDE by wet dye-penetrantinspection (PT) and then ultrasonic examination. During ultrasonic examination,the reference standard for examining and evaluating the weld bond integrity shallbe 1/8" Flat Bottomed Hole (FBH) and for evaluating the volumetric defects withinthe overlay/clad material shall be 1/16" FBH. Indications above the referencelevel shall be cause for rejection. The acceptance criteria for PT method shall beas per ASME Section IX.

5.3 Mechanical Tests.

5.3.1 The test coupon for weld overlay shall be sectioned and test samples machinedto carryout the following tests as per ASME Section IX.

a) Chemical analysis of the overlay deposit at the "minimum qualified" thickness.b) Side Bend tests.c) Hardness Traverse of the parent material, heat affected zone and clad material in

Rockwell “C" scale.5.3.2 In addition to 5.3.1 above, the following mechanical tests shall be conducted for

weld overlay and hard facing procedure qualifications:

a) Macro examination of the weld cross section including the clad, heat affectedzone and the base material. During macro examination, the layer number (e.g.first. second, third, etc.) in which the specified overlay thickness is located shallbe determined. This shall be done by drawing a line on the overlay parallel to thefusion line between the first layer and the base material at a distance equal to theminimum qualified overlay thickness. The layer in which this line is located shallbe recorded. A photo macrograph showing this and the details of magnificationshall be attached to the final documentation.

b) A Vickers (HV10) hardness survey shall be carried out in the heat-affected zone(HAZ), base metal and on each layer of overlay up to a maximum of two layers.The impressions on the heat affected zone shall be within 0.5mm of the fusionline but not on the fusion line. A minimum of ten indentations shall be made foreach line of traverse.

c) A micro examination shall be performed on the overlay cross section to cover theclad material and the heat affected zone. A report of the details of themetallurgical structure including photo micrographs at suitable magnificationsshall be attached. The report shall record the presence of any undesirablemicrostructures, micro fissures and carbide precipitation.

5.4 Acceptance criteria for Nickel based overlays.

5.4.1 The chemical composition of the weld deposit at the minimum qualified overlaythickness shall meet the requirements of the WPS. The chemical composition ofInconel 625 overlay shall fully conform to UNS N06625 alloy specification. Theiron content of the chemical analysis shall not exceed 5.0%. Failure to complywith the specified composition shall be cause for rejection.

5.4.2 The macro examination sample shall be free of any under clad cracks. Theminimum required/qualified overlay thickness shall have at least two layers ofoverlay.

5.4.3 The micro examination sample shall be free of micro fissures, cracks andundesirable carbide precipitation in the clad, and free of cracks and hardenedmicrostructure in the heat affected zone.

5.4.4 The Rockwell "C" hardness test results shall comply with NACE MR0175. Themaximum Vickers hardness for carbon & low alloy steel shall be 248 HV10, andfor Inconel 625 overlay the maximum hardness shall be 345 HV10.

6.0 Repair Welding procedures.

6.1 All repair welding procedures shall be qualified by full testing including chemicalanalysis and mechanical tests as per Section 5.3 above in full compliance withASME Section IX, NACE MR0175 and this standard.

6.2 Repair welding procedures which involve post weld heat treatment before andafter repair shall be qualified to simulate production repair welds by removingoverlay material to reach the base material and re-depositing the weld overlay asper the repair procedure and repeating the post weld heat treatment after repair.The repaired welds after heat treatment shall be subjected to NDT as per Section5.2 above and mechanical tests as per Section 5.3.1 and 5.3.2 above.

6.3 Repair welding procedures which do not require post weld heat treatment afterweld repair shall be qualified as follows.

6.3.1 Start with a test coupon deposited with the overlay as per the WPS for initial weldOverlaying and duly post weld heat treated as per the "initial WPS".

6.3.2 Then remove, by machining, the clad material such that the final overlaythickness equals 1.0mm,1.5mm, 2.0mm, 2.5mm … etc.

6.3.3 Then deposit weld overlay as per the "repair WPS" recording the actual values ofall relevant variables such as amperes, voltage, travel speed etc.

6.3.4 Carry out NDE as per 5.2 above.

6.3.5 Remove samples for macro, micro and hardness tests as per 5.3.2 above.During micro and macro examinations, there shall be no evidence of any newheat- affected zone beyond the initial fusion line between the overlay and thebase metal. Failure to comply with this requirement shall be cause for rejection ofthe "cold repair" procedure.

6.3.6 The samples which represent the "cushion thickness" with successful resultsfollowing 6.3.4 and 6.3.5 above shall then be subjected to chemical analysis asper 5.3.1(a) above.

7.0 Documentation.

7.1 All documents shall be verified and endorsed by CONTRACTOR/COMPANY orCONTRACTOR/COMPANY appointed TPI and shall be traceable to the originalsample(s).

7.2 The following documentation shall be submitted to CONTRACTOR/COMPANYfor review.

7.2.1 Material certificates of the test coupon base material and batch certificate of thefiller wire/electrode to be used for welding procedure qualifications.

7.2.2 Welding Procedure Specifications (WPS's).

7.2.3 Procedure Qualification Records (PQR's) including the record of actual values ofall relevant variables used during welding of the test coupons.

7.2.4 Post Weld Heat Treatment chart and report.

7.2.5 Dye-penetrant (PT) and UT examination reports.

7.2.6 Laboratory test reports detailing chemical analysis, tensile, bend, impact andhardness tests, macro and micro examination findings as per section 5.3 above.

Additional Requirements for Alloy Cladding or Weld Overlay of PressureVessels.

Alloy cladding for shell and heads shall be made using integrally andcontinuously bonded, clad plate or weld deposit overlay. Clad plate shall besubjected to shear test.

Cladded surfaces shall be ultrasonically examined to check the integrity of thebonding in accordance with ASTM A 578, with an acceptance level of S7

In case of weld overlay, the same shall be carried out using normal two-layerprocess in which the first layer is applied using a low heat input process. Singlelayer weld overlay process is not permitted unless specifically approved bythe COMPANY.

Where cladding or overlay is specified, the use of solid alloy is not allowedunless it is specifically accepted by COMPANY.

Production testing of the weld overlay shall be carried out at the minimumqualified overlay thickness (min. depth of 2.5mm from the working surface). Thechemical composition of the weld deposit at the minimum qualified overlaythickness shall meet the requirements of the WPS and the UNS alloydesignation.

Filler wires and electrodes intended for Inconel 625 overlay or clad shall notcontain more than 1% Iron in the all-weld deposit. Maximum hardness for Inconel625 shall be 345 HV10

Incoloy 825 (UNS N08825) clad material shall be welded to each other (full jointthickness) or repaired by using Inconel 625 welding consumables.

The chemical composition of Incoloy 825 overlay at the minimuim qualifiedoverlay thickness shall fully conform to UNS N08825 alloy specification.

For stainless steel overlay, the ferrite content shall be as per API 582 andproject specification requirements (measured at the depth of 2.5mm from theworking surface).

Welding Electrodes

The level of testing for all electrodes shall be Schedule K of ANSI/AWSA5.01 which shall be taken as Schedule J plus chemical analysis for theparticular electrode sizes which are not required to be chemically analysedby ANSI/AWS A5.5. For alternative electrodes, the level of testing shall beat least the same.

The batch classification shall be C3 of ANSI/AWS A5.01.

Electrodes shall have type approval by a certifying authority such as Lloyd’s orDNV.

Each electrode shall have the AWS or other appropriate classification markedon the flux near the grip end. Electrodes which do not have this marking shall beremoved from the job site to the satisfaction of the Company.

All welding consumables used during production shall be the samemanufacturer, brand and AWS type as those used and approved during weldingprocedure qualifications.