The results of severaal wet H2S exposure tests utilizing a large-scale steel pressure vessel containing various welded test panels are described. The goal was to provide guidelines for effective repair procedures for use in remediation of equipment damaged in wet HgS service and to minimize the recurrence of cracking after inspection and/or repair. Variables examined included (1) postweld heat treatment (PWHT) versus as-welded, (2) the use of temper bead as opposed to conventional weld repairs, and (3) local thin areas (LTAs) in the base metal and grooves in the heat-affected zone (HAZ) that result from
removal of cracks found by inspection. One of the most significant findings of the program was the impact of PWHT on reducing the number of toe cracks on both full penetration and attachment welds. Another important finding was the similarity in performance between conventional weld repairs with PWHT and temper bead weld repairs without PWHT.
The serviceability of LTAs and grooves was found to be good, provided the guidelines detailed in the proposed API RP 579 fitness-for-service methodology were followed. Keywords: hydrogen blistering, hydrogen-induced cracking (HIC), stress-oriented hydrogen-induced cracking (SOHIC), sulfide stress cracking (SSC), carbon steel fitness-for-service, postweld heat treatment (PWHT, temper bead, local thin area (LTA), grooves, repair, remediation, wet H2S.