Failure Analysis on the Leakage of Methanator

Abstract

The leakage of a methanator that made by 304H was analyzed. Near the lugs of the reactor, two cracks without any ductility were found in the hoop direction. From the cross-sectional view of the reactor pipe, more cracks were observed. The cracks were all initiated from OD and propagated to ID along the grain boundaries. “ASTM A262 method A” examination showed the microstructure of the cracked region had been sensitized seriously. And on the surface of the intergranular fracture, high content of sulfur was detected. These phenomena indicate the 304H reactor had suffered the intergranular stress corrosion cracking (IGSCC). According to the analysis reports on the rain pollution at the site, the most possible source of the corrosive medium should be ${\text{SO}}_{4}^{2 - }$ from acid rain. The root cause of the IGSCC should be the insufficient consideration during design that only the strength in high-temperature service was considered, but the possibility of corrosion during downtime in the open-air environment was neglected.