Integrity Assessment of Pressure Vessels Subjected to Hydrogen Induced Damages

Hydrogen damage to pressure vessels in a Crude Oil Production facility is not uncommon. The intriguing question is about the decision to continue affected vessels in safe operation if such decision is supported by an accurate engineering assessment of the damage and the impending risk. Engineering assessments of the vessels instill confidence for safe operation and help in minimizing production loss & capital expenditure. This paper presents the integrity assessment undertaken during the years 2004–2005 for pressure vessels of an upstream oil production facility (Gathering Centre) of Kuwait Oil Company (KOC), where high H₂S (hydrogen Sulfide) levels in the process streams have made the pressure vessels susceptible to hydrogen induced damages. These carbon steel pressure vessels were manufactured to ASME Section VIII Div 1 during the years 1961–1968. As part of elaborate Inspection Program of the pressure vessels in the Gathering Centre, ultrasonic testing was conducted on all the hydrocarbon pressure vessels. Several vessels were found with significant embedded flaws including hydrogen induced crack-like defects & blisters. These defects were further evaluated by Automated Ultrasonic Testing (AUT) which comprised of C-Scan and Time-of-Flight Diffraction (ToFD) techniques. AUT was used for the precise detection & sizing of the embedded flaws which is important for Fitness-For-Service (FFS) Evaluation. Subsequently, the affected vessels with critical flaws were evaluated by FFS assessment as per API-579. While some vessels were found unfit for further safe operation, others were retained in operation with periodic monitoring.