The Welding Research Council (WRC) Bulletin 452 titled “Recommended Practices for Local Heating of Welds In Pressure Vessels”(1) was first published in June 2000. This document considers various issues associated with the local heating of welds in pressure vessels and addresses the application of controlled heat in the weld metal, heat affected zone (HAZ) and a limited volume of base metal around the weld.
ASME Boiler and Pressure Vessel Code Section VIII Division 1, paragraphs UW-40, (a) 3 and 8 require that post weld heat treatment (PWHT) be carried out in a manner such that the thermal gradients are not harmful. WRC Bulletin 452 provides guidelines for local PWHT to satisfy this requirement.
This paper provides examples of local PWHT (if not heated as a whole vessel in a furnace) based upon utilizing a soak band and calculated heated band and gradient band widths based upon WRC 452 recommendations. The paper addresses both circumferential and spot PWHTs and demonstrates that the guidelines provided in WRC 452 can also be used as a starting point for determining the band widths for spot PWHT.