Failure Cause Analyses on the Material of Deaerator/Surgas Stripper in Synthetic Ammonia Installation

For the leakage accident in the cylindrical shell′s material of the deaerator/sourgas stripper in the synthetic ammonia equipmeut,the chemical composition,microstructure,corrosion condition,crack and fracture of the cylindrical shell′s material were analyzed.The results show that the material of the cylindrical shell is 316L stainless steel,and the failure of the material was due to stress corrosion cracking which was induced by the regional enrichment of Cl- in the cylindrical shell to cause pitting consequently.Besides,the acid media,such as H2S,CO2,HCOOH and CO,O2 in the cylindrical shell had accelerated the propagation of stress corrosion cracking.A corresponding improvement measure of using duplex stainless steel is suggested.