30 November 2022

Procedure of Failure welding Joints repairing

Procedure of Failure welding Joints repairing

Sub: Repair procedure to be followed for replacing the failed tubes in Radiant wing Super heaters
REPAIR PROCEDURE
The following methodology is recommended to be followed for the repair works as discussed with various departments.
  1. The failed location shall be thoroughly checked for erosion / discoloration
  2. The fins shall be smoothly cut and ground flush in the tube locations where butt welding is planned.
  3. Clearly mark the butt weld locations after measuring the thicknesses.
  4. Identify the tubes with damages, mark top and bottom, number of tube, panel number and elevation before cutting the damaged tubes.
  5. Fins shall be slit open for a length of 50-60 mm at the weld locations both at bottom and top.
  6. Do not damage the tubes while slit opening the fins.
  7. Do not damage the failed locations which are required for laboratory analysis.
  8. Once the locations are decided, the damaged tubes shall be cut and removed, preferably as a panel.
  9. Replace tubes one by one with proper alignment after edge preparation for butt welding and after ensuring no internal blocks. Clamps shall be used at weld locations for proper alignment.
  10. Correct WPS shall be followed with preheating temperatures maintained.
  11. After butt welding necessary NDT checks followed with radiography shall be done and ensure healthiness of the welds.
  12. Place the fins of proper material, in this case SA387 Gr.22 Cl.2
  13. Preheat to the required temperature as per WPS. It is better to heat the area to 150 deg C prior to the start of welding as specified.
  14. Only HP welders are to be used for fin welding and butt welding.

 

  • As such  edge preparation(chamfering) of fin need not to be carried out. The sharp edges, scales and other contamination shall be completely removed before taking up of repair welding.
  • Proper care should be taken by the welder not to damage the tubes during the fillet welding.
  • As a special requirement heat the welded area after welding to 150-200 deg C and keep for 15-20 minutes, being T22 material.
  • Attached  Welding Procedures are to be followed.
  • This procedure is only meant for this repair work and shall not be used as a standard.

 

1.) SA 213 Gr. T11 + SA 213 Gr. T22 : Butt joints
Process : GTAW
Filler wire : ER80S-B2
Preheating : 150°C
  1. SA 213 Gr. T22 + SA 387 Gr.22 Cl2 : Fillet joints
Process : SMAW
Filler wire : E9018-B3
Preheating : 150°C
Wherever fin welding is to be done with existing T11 tubes follow the procedure given below:
  1. SA 213 Gr. T11 + SA 387 Gr.22 Cl2:Fillet joints
Process : SMAW
Filler wire : E8018-B2
Preheating : 150°C

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