tdc-10a rev 3 upgradation by welding of c12a steel castings

Technical Delivery Condition Doc. No. TDC-10A Rev 3 Up-gradation by welding of C12A Steel

Castings Date 12-May-12 Page 1 of 3

Prepared by Approved by C Raja R Muruganantham

Form No: GP-010-R1

1.0 Scope:

This procedure covers the technical requirements to be ensured during up-gradation of ASTM A217 GR C12A castings by welding.

2.0 Welding process and consumables:

2.1 Welding Process: Shielded Metal Arc Welding (SMAW) with electrical characteristic of

DCRP (Direct Current with Reverse Polarity).

2.2 Base Metal: ASTM A217 Gr. C12A

2.3 Filler Metal: ASME SFA / AWS A5.5 E9015 B9. Approved Welding consumable manufacturers is Chromo 9V of M/s. Bohler Thyssen

2.3.1 Electrodes shall be stored in a clean dry room without opening the manufacturers packing.

2.3.2 After receipt of electrodes from stores, they shall be baked at 300 350 C for 2 hours.

2.3.3 After baking, the electrodes shall be transformed to holding oven/flask which is maintained

at 125 150C.

2.3.4 All the electrodes shall be kept in holding oven/flask at the temperature of 125 150C till usage. Welder shall take the electrodes from holding oven / flask whenever required and he shall ensure that the electrodes are not allowed to cool to room temperature.

2.3.5 If the electrode is cooled to room temperature, then these electrodes shall be baked again and kept (As per the steps 2.3.3 to 2.3.4)

2.3.6 Used electrodes and studs shall not be kept in oven/flask and scrapped immediately. 2.3.7 The details of the batch number of electrode, Baking, holding time & date, welder name

shall be recorded and maintained.

3.0 Classification of Repairs

Defects shall be classified in to following categories:

3.1 Cosmetic Repair: Surface and Sub surface repairs of 1.6 mm depth maximum and less than 10 inch2 (65 cm2)

3.2 Major Repair: Casting containing any repair weld that exceeds 20% of the wall thickness or

1 inch [25 mm], whichever is smaller, or that exceeds approximately 10in2 [65cm2] in area.

J Viswanath 08/06/2013




Form No: GP-010-R1

4.0 Weld map

The upgraded or weld area shall be marked on the sketches with dimensions for easy identification and inspection of the weld location.

5.0 Preheat and Interpass Temperature: 5.1 Prior to welding, the defect shall be completely removed and ensured by Liquid Penetrant

Examination (NDE-03) or Magnetic Particle Examination (NDE-02).

5.2 Before welding, base metal shall be preheated to 200C minimum

5.3 Interpass temperature shall be 400C maximum.

5.4 This shall be ensured through thermal chalk or Thermocouple with temperature indicator, measuring 1 inch away from the weld zone.

6.0 Welding Technique: 6.1 Maximum weld bead thickness shall be 4 mm and weaving not exceeding the three times of

the diameter of the electrode shall be used.

6.2 The variables of welding process (voltage, current for example) shall be set as per welding procedure specification (WPS) or electrode manufacturer specification.

7.0 Post heating

7.1 Post heating shall be done at the temperature of 350C 400C and to be held for 4 hours. Then is to be covered with blanket/hood and cooled up to 80C then PWHT to be done.

7.2 Heating method: In furnace or by electric resistance coil method for all major & minor repairs.

8.0 Post Weld Heat Treatment

8.1 During Post Weld Heat treatment, an additional test bar shall be placed along with the components. Even if no weld repairs are carried out, the test bar shall be heat treated as per the PWHT cycle. Then Mechanical testing shall be done on the test bar and shall meet the requirements of TDC-10.

8.2 Post Weld Heat Treatment shall be carried out as per procedure TDC-10B (Heat treatment Procedure for C12A Castings).





Form No: GP-010-R1

R3

9.0 Inspection

9.1 The weldments shall be visually inspected and observations shall be recorded.

9.2 Positive Material Identification (PMI) check shall be performed as per RIP-03 on all the welded areas as mentioned in weld map and recorded. The chemical composition to the material specification shall be ensured.

9.3 The chemical composition shall be analysed on the test coupon where welding is performed

similar to the repair welding on casting, and x factor shall be calculated using the below equation and which shall not exceed 20.

x = (10P + 5Sb + 4Sn + As) / 100,

where, P, Sb, Sn & As are expressed in ppm.

9.4 Hardness on the weld location and Heat Affected Zone (HAZ) shall be checked and

recorded. It shall be ensured to the base metal hardness levels (185 - 226 HBW)

9.5 The welded area shall be evaluated by Magnetic Particle Examination (NDE -02), Liquid Penetrant Examination (NDE-03) or Radiographic Examination (NDE-01), whichever is applicable. Any NDE Examination shall be performed at least 48 hours after PWHT.

10.0 Qualification of Procedures and Welders

10.1 The welding procedures and welders shall be qualified in accordance with Section IX of

ASME Boiler and Pressure Vessel Code.

10.2 Welding procedure shall be qualified with impact requirements at a temperature not greater than +20C and test piece single value not less than 27J.

11.0 Records

The following reports shall be forwarded to L&T along with casting during despatch for acceptance of casting.

a. WPS, PQR and WPQ b. Welder identification, Date & time of welding c. Electrode Batch No, Baking temperature, Holding temperature details and No. of

electrodes used. d. Preheating and Post heating records. e. Visual inspection report f. Weld map and corresponding PMI, Hardness inspection results. g. NDE Reports and Films ( prior and after repair)


tdc-10a rev 3 upgradation by welding of c12a steel castings

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