TECHNICAL REQUIREMENTS FOR WELD OVERLAY, CLADDING AND HARDFACING 1.0

General

This specification prescribes the minimum requirements for weld inlay/overlay/cladding and weld hardfacing of piping, fittings, pressure vessels and valves. The requirements for 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 and tested as per ASME BPV Code Section IX, NACE MR0175, API 582, DEP 30.10.60.18, 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, DEP 31.40.20.32 and API 5LD (as applicable).

1.2

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

1.3

Repair procedures which do not require post weld heat treatment shall be qualified to establish the minimum "cushion thickness" of clad material above which 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 full range of work scope in the production of an order.

1.6

Welding of coupons and mechanical testing shall be witnessed by CONTRACTOR/COMPANY or CONTRACTOR/COMPANY appointed Third Party Inspectors.

1.7

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

1.8

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

1.9

Previously qualified welding procedures may be accepted by the CONTRACTOR/COMPANY provided the WPS's, PQR's and ing laboratory test reports are submitted for CONTRACTOR/COMPANY review. In this case, weld mock up tests shall be required and the scope of testing shall be reduced to include NDT, deposit analysis, macro, micro and hardness tests as per 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 procedure and 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 minimum qualified 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, a reduction in the amount of grinding or machining.

3.0

Welding Consumables Filler wires and electrodes intended for Inconel 625 (UNS N06625) overlay or clad shall not contain more than 1% Iron in the all-weld deposit. The purchase specifications for Inconel 625 filler wire/ electrode shall include this requirement in 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 be measured and recorded. Actual values of amperes, voltage and travel spend shall be recorded for each .

4.2

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

4.3

The thickness of the weld deposit shall be measured and recorded after each layer of weld metal is deposited. Details of any inter grinding or machining between any two layers shall be recorded.

5.0

Inspection and Testing.

5.1

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

5.2

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

5.3

Mechanical Tests.

5.3.1

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

a) b) c)

Chemical analysis of the overlay deposit at the "minimum qualified" thickness. Side Bend tests. Hardness Traverse of the parent material, heat affected zone and clad material in Rockwell “C" scale. In addition to 5.3.1 above, the following mechanical tests shall be conducted for weld overlay and hard facing procedure qualifications:

5.3.2

a)

Macro examination of the weld cross section including the clad, heat affected zone and the base material. During macro examination, the layer number (e.g. first. second, third, etc.) in which the specified overlay thickness is located shall be determined. This shall be done by drawing a line on the overlay parallel to the fusion line between the first layer and the base material at a distance equal to the minimum qualified overlay thickness. The layer in which this line is located shall be recorded. A photo macrograph showing this and the details of magnification shall 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 fusion line but not on the fusion line. A minimum of ten indentations shall be made for each line of traverse.

c)

A micro examination shall be performed on the overlay cross section to cover the clad material and the heat affected zone. A report of the details of the metallurgical structure including photo micrographs at suitable magnifications shall be attached. The report shall record the presence of any undesirable microstructures, 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 overlay thickness shall meet the requirements of the WPS. The chemical composition of Inconel 625 overlay shall fully conform to UNS N06625 alloy specification. The iron content of the chemical analysis shall not exceed 5.0%. Failure to comply with the specified composition shall be cause for rejection.

5.4.2

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

5.4.3

The micro examination sample shall be free of micro fissures, cracks and undesirable carbide precipitation in the clad, and free of cracks and hardened microstructure in the heat affected zone.

5.4.4

The Rockwell "C" hardness test results shall comply with NACE MR0175. The maximum Vickers hardness for carbon & low alloy steel shall be 248 HV10, and for 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 chemical analysis and mechanical tests as per Section 5.3 above in full compliance with ASME Section IX, NACE MR0175 and this standard.

6.2

Repair welding procedures which involve post weld heat treatment before and after repair shall be qualified to simulate production repair welds by removing overlay material to reach the base material and re-depositing the weld overlay as per 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 Section 5.2 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 after weld repair shall be qualified as follows.

6.3.1

Start with a test coupon deposited with the overlay as per the WPS for initial weld Overlaying 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 overlay thickness 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 of all 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 new heat- affected zone beyond the initial fusion line between the overlay and the base metal. Failure to comply with this requirement shall be cause for rejection of the "cold repair" procedure.

6.3.6

The samples which represent the "cushion thickness" with successful results following 6.3.4 and 6.3.5 above shall then be subjected to chemical analysis as per 5.3.1(a) above.

7.0

Documentation.

7.1

All documents shall be verified and endorsed by CONTRACTOR/COMPANY or CONTRACTOR/COMPANY appointed TPI and shall be traceable to the original sample(s).

7.2

The following documentation shall be submitted to CONTRACTOR/COMPANY for review.

7.2.1

Material certificates of the test coupon base material and batch certificate of the filler 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 of all 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 and hardness tests, macro and micro examination findings as per section 5.3 above.

 Additional Requirements for Alloy Cladding or Weld Overlay of Pressure Vessels. 

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



Cladded surfaces shall be ultrasonically examined to check the integrity of the bonding 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-layer process in which the first layer is applied using a low heat input process. Single layer weld overlay process is not permitted unless specifically approved by the COMPANY.



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



Production testing of the weld overlay shall be carried out at the minimum qualified overlay thickness (min. depth of 2.5mm from the working surface). The chemical composition of the weld deposit at the minimum qualified overlay thickness shall meet the requirements of the WPS and the UNS alloy designation. Filler wires and electrodes intended for Inconel 625 overlay or clad shall not contain more than 1% Iron in the all-weld deposit. Maximum hardness for Inconel 625 shall be 345 HV10



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



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



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

Welding Electrodes 

The level of testing for all electrodes shall be Schedule K of ANSI/AWS A5.01 which shall be taken as Schedule J plus chemical analysis for the particular electrode sizes which are not required to be chemically analysed by ANSI/AWS A5.5. For alternative electrodes, the level of testing shall be at 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 or DNV.



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



All welding consumables used during production shall be the same manufacturer, brand and AWS type as those used and approved during welding procedure qualifications.