Causes of Cracking of Stainless Steel Pipes under Insulation in Coastal Environment

Cracks appeared on the surface of stainless steel pipe under the insulation layer in a coastal refinery. The causes of cracking were analyzed by chemical composition analysis, fracture morphology observation and hardness test, combined with the production environment feature of the failed pipeline. The results show that the crack of the pipeline originated from the outer surface, and transgranular cracks propagated from the outside to the inside in a dendritic shape. Chloride ion accumulation under the insulating layer caused stress corrosion cracking of austenitic stainless steel, and corresponding preventive measures were proposed.