Abstract
Hydrogen cracking, as expressed in sulfide stress cracking and other hydrogen induced cracking/blistering (HIC) corrosion mechanisms, was found in a de-ethanizer column employed in sour service. The extent of the failure, root cause, mitigation steps and the longer term remedial action are discussed in this paper. A risk matrix was determined, resulting in a final decision made to effect repairs with tray ring repair and replacement and use a high velocity thermal spray process to mitigate further corrosion. Due to constraints with the scope of effected areas, and risks associated with extant HIC, whole vessel post weld heat treatment was not viable. A NiCrMo-XX alloy, developed specifically for a high velocity thermal spray process, was employed in cladding all shell and tray support ring internal surfaces to isolate susceptible areas of non-HIC resistant material and weld repairs. The vessel was returned to service. The initial success of this application was determined at the first subsequent turnaround inspection.
