INDUSTRY INSIGHTS ARCHIVE

Dissimilar metal welds (DMWs) are often specified in process plants as an alternative to bolted mechanical joints and are successfully used in many corrosive and severe services. However, these welds can be subject to major weldability challenges and may lead to failures due to inherent material differences. In this article, the author examines these failure mechanisms, offers best practices for weld repairs and joint designs, and discusses a recent case study where laboratory analysis was used to identify the cause of a repeat DMW failure.

In-service welding as part of a maintenance program is a practical and economical way to address leak repairs or new nozzle installations; however, it does come with a few risks, including burn-through and hydrogen-induced cracking. In this article, Raj will discuss the risks involved with in-service welding, thermal analysis to quantify the risks, and practical in-service welding considerations to ensure safe and successful hot tap connections.