Investigation of the Susceptibility of Conventional Astm A516-70 Pressure Vessel Steel to Hic and Sohic in H2s-containing Dga Solutions

Hydrogen Induced Cracking (HIC) and Stress Oriented Hydrogen Induced Cracking (SOHIC) tests were conducted on a conventional ASTM A516-70 pressure vessel steel exposed to H2Scontaining diglycolamine (DGA) gas-sweetening environments. Baseline HIC and SOHIC tests were conducted in NACE TM0284-96 solution A. For the SOHIC tests, four-point double beam specimens were stressed to 60%, 80% or 100 % of the yield strength of the steel in order to study the effect of applied stress. Test conditions included solutions containing 70 wt. % DGA and 500 ppm H2S to 0.45 or higher mole-H2S/mole-DGA and temperatures of 25, 45 and 80 ° C. Corrosion rates of the steel were calculated from weight loss of the HIC specimens in order to compare the severity of the test environment with the actual service environment. Cracks were characterized in terms of crack length ratio (CLR), crack thickness ratio (CTR) and crack sensitivity ratio (CSR). Results indicate that conventional ASTM A516-70 pressure vessel steel is not susceptible to HIC or SOHIC in various H2S-containing DGA solutions at the temperatures studied.