WELD REPAIRS & RESIDUAL STRESS & DISTORTION
WELD REPAIRS:
Two types: production repair; in-service repair.
Repair welding is more often difficult than production welding due to
- Material being mixed with in-service contaminations during welding.
- Restricted access with repair area.
- The possible position of the weld.
- any one of the above.
A repair has been detected after PWHT: Repair, NDT/ Checking & PWHT.
RESIDUAL STRESS & DISTORTION:
- Use minimum number if runs to control distortion.
- Use minimum volume of weld to control distortion.
- Back step welding & skip welding : weld run sequence to control distortion in thin plates.
- Double sided preparation is preferred over single sided preparation for distortion control.
- Single U-preparation is preferred over single V-preparation.
Control cooling and heating is done above 300°c to control distortion