A primary plus secondary local PWHT method for mitigating weld residual stresses in pressure vessels

Local post-weld heat treatment (PWHT) is often used for mitigating welding-induced residual stresses in pressure vessels and piping systems. As large and ultra-large pressure vessels are increasingly used in petrochemical and power generation industries, traditional local PWHT procedures stipulated in Codes and Standards become difficult to implement for some of the ultra-large vessels due to their very large diameter and overall length. In this paper, a new method referred to as primary-secondary heating based local PWHT technique (PS-PWHT) is proposed. Both finite element residual stress modeling and experimental residual stress measurements were performed for both validating the effectiveness of the proposed technique and elucidating the underling mechanisms. The results show that the PS-PWHT method can reduce welding-induced residual stresses in a significant manner, even leading to some level of compressive residual stresses at the vessel weld region.

Automated summary

With the increasing use of large and ultra-large pressure vessels in petrochemical and power generation industries, traditional local post-weld heat treatment (PWHT) procedures are no longer feasible, prompting the introduction of a new primary-secondary heating based local PWHT technique (PS-PWHT). Both finite element residual stress modeling and experimental residual stress measurements have shown that the PS-PWHT method can significantly reduce welding-induced residual stresses, even leading to some level of compressive residual stresses at the vessel weld region.