Failure Analysis of a Long Term Serviced Cr-Mo Steel Coke Drum

Abstract Coke drums are critical pressure vessels used in the delayed coking process in petroleum refineries. Over the past two decades, Cr-Mo steel coke drums have increasingly replaced carbon steel drums in China. However, in recent years, several Cr-Mo steel coke drums have experienced severe cracking failures, and the underlying causes and influencing factors remain unclear. This study investigated the failure mechanisms of a Cr-Mo steel coke drum exhibiting through-wall cracking. Nondestructive inspections and miniature sampling tests were conducted to analyze the failure morphology and tensile properties of the material. Laser scanning inspection was employed to reconstruct the deformation profile of the shell. An integrated finite element analysis procedure, incorporating both the quenching process and cold spot effects, was performed to study cyclic strain under various conditions. The results indicated that structural discontinuities, weld weakening, cold spot effects, and process instability are critical factors contributing to catastrophic failures. Recommendations were provided to stabilize process operations and enhance inspection protocols to prevent future failures in Cr-Mo steel coke drums.