Susceptibility of conventional pressure vessel steel to hydrogen-induced cracking and stress-oriented hydrogen-induced cracking in hydrogen sulfide-containing diglycolamine solutions

Hydrogen-induced cracking (HIC) and stress-oriented hydrogen-induced cracki ng (SOHIC) tests were conducted on a conventional type A516-70 (UNS K02700) pressure vessel steel exposed to hydrogen sulfide (H2S)-containing diglyco lamine (DGA) gas-sweetening environments. Base-line HIC and SOHIC tests wer e conducted in NACE TM0284-96 Solution A. For the SOHIC tests, four-point d ouble-beam specimens were stressed to 60%, 80%, or 100% of the yield streng th of the steel to study the effect of applied stress. Test conditions incl uded solutions containing 70 wt% DGA and 500 ppm H2S to greater than or equ al to 0.45 M-H2S/M-DGA and temperatures of 25 degrees C, 45 degrees C, and 80 degrees C. Corrosion rates of the steel were cal culated from weight los s of the HIC specimens to compare the severity of the test environment with the actual service environment. Cracks were characterized in terms of crac k length ratio (CLR), crack thickness ratio (CTR), and crack sensitivity ra tio (CSR), Results indicated that conventional type A516-70 pressure vessel steel was not susceptible to HIC or SOHIC in various H2S-containing DGA so lutions at the temperatures studied.