This topic has always been one that seemed to be controversial in the ammonia refrigeration sector, with decades of denial that Stress Corrosion Cracking could occur in an ammonia refrigeration process due to the water content in the ammonia. But last month, Technical BC (British Columbia) discussing their SCC concerns related to pressure vessels in a refrigeration process. I know, that ammonia in Canada is different than ammonia in the USA (sarcasm), but seriously, please consider checking out their concerns and their discussion of Post-Weld Heat Treatment (PWHT) as a means to manage this concern.
The ammonia refrigeration trade groups only “recommend” Post-Weld Heat Treating (PWHT) of the pressure vessels in the ammonia refrigeration process. But when we look at pressure vessels in ammonia service within other processes, we can find RAGAGEPs that specifically call for the vessel to be PWHT’ed…