Corrosion failure analysis of the condensate collector vessel head of evaporation system in ethylene glycol device

Lots of cracks have been found on both internal and external surfaces of the straight flange on the reboiler’s condensate collector vessel head of the ethylene glycol device’s evaporation system in a glycol factory. The composition, microstructure, corrosion status, and cracking of the vessel head have been systematically investigated. It has been found that the material of the vessel head is stainless steel 304. The results show that the cracking on the internal and external surfaces can be attributed to the pitting caused by the enriched Cl− existing in the deformed martensite of the straight flange of the vessel head, which subsequently results in the stress corrosion cracking of the material. In addition, the selective dissolution of the martensite promotes the cracks to propagate. Based on the analysis, several reasonable proposals for heat treatment, and material selection have been put forward.

► Deformed martensite formed during the cold spinning process of stainless steel 304.
► Deformed martensite induces the stress concentration and the increased hardness.
► Deformed martensite results in the stress corrosion cracking in the Cl− media.
► The selective dissolution of the martensite promotes the cracks to propagate.