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answered Aug 20, 2014 by franchaze (1,150 points)

Backwelding should not be permitted unless it meets at least one of the following conditions:

  • With proper PWHT at a sufficiently high temperature and adequate holding time to reduce residual stresses and lower hardnesses to less than 248 HV10 (Diamond Pyramid).
  • The adequacy of the PWHT procedure should be demonstrated during welding procedure qualification testing
  • By performing the backweld repair before the second pass is applied