Analysis of Blind Flange and Thermowell Assembly from Wilsonville, Alabama, Solvent Refined Coal Plant Dissolver Tank

摘要

A type 316 stainless steel blind flange and thermowell assembly rated at 17 MPa (2500 psi) was removed from service at the Wilsonville Solvent Refined Coal (SRC) plant when cracks were observed on the flange face. Metallographic examination revealed a system of cracks that penetrated a repair weld and extended into the base metal on the face where it was exposed to the process media. The cracking in the weld metal appeared to follow substructural boundaries. A second crack network initiated in the disturbed base metal beneath a ground surface and extended through a tenth of the flange thickness. Cracking in the base metal was transgranular. Neither the corroding species nor the local stress level responsible for the cracking can be specified. (ERA citation 03:054307)