Failure analysis on cracking and leakage of 304 stainless steel flange in petrochemical butyl device

Abstract During the pressure test process in a petrochemical butyl device in China, it was found that the 304 stainless steel flange of the ethylene pipeline appeared to be cracking and leakage. This article analyzed the reasons for failure using macroscopic inspection, chemical composition analysis, metallographic structure analysis, scanning electron microscope, energy dispersive spectroscopy, mechanical properties test, and intergranular corrosion test. The results show that the carbon content of the flange base material exceeds the standard, many carbides precipitate at the grain boundary, the material itself is seriously sensitized, and the intergranular corrosion resistance is reduced. At the same time, under corrosive media such as sulfur and chlorine and high stress, the flange displays stress corrosion cracking, which leads to cracking and leakage failure. This article reports the reasons for the failure of the flange, and some reasonable suggestions are put forward to avoid similar leakage accidents.