Investigation of a refinery fire and explosion

A fire and explosion occurred in a refinery desulphurisation unit in which hydrogen was present. Investigation disclosed that several different failure mechanisms had led to failure of the 321 stainless steel piping. Based on detailed metallurgical examination, evidence from the plant operators and operating records, and a fracture mechanics analysis of the cracking, the sequence of failure was determined. The paper describes the investigation, presents the metallographic evidence, and details the causes of failure. It is demonstrated that the piping contained manufacturing defects that caused it to be lacking in structural integrity.