Enhancing offshore process safety by selecting fatigue critical piping locations for inspection using Fuzzy-AHP based approach

Topside piping is the single largest source of the hydrocarbon releases (HCRs) on the offshore oil and gas (OOG) platforms in the North Sea region. Consequently, if the leaked hydrocarbons from the process pipework are ignited, it may lead to a catastrophic event, thereby causing significant economic losses, environmental damage, and posing serious threat to the safety of the onboard personnel. In order to avert such a fateful event and to enhance process safety, it is vital to maintain the technical integrity of the topside piping. In regard to this, risk based inspection (RBI) plays a vital role, as the inspection locations and frequency are decided based on the risk of potential failure. However, international standards such as API 570, API 581 and DNV RP-G101 provide limited guidance in regard to inspection of the fatigue degradation of the offshore topside piping. Due to the aforementioned, selection of the fatigue critical piping locations for inspection, is currently done either on the ad-hoc basis or using the three staged Risk Assessment Process (RAP) mentioned in the Energy Institute (EI) guidelines. Nevertheless, it has been revealed that the methodology for stage 1 of the RAP is laborious and time consuming. Thus, to reduce the toil of the practicing inspection engineer and with the aim of mitigating the dearth of RBI methodologies for topside piping fatigue, this manuscript proposes a Fuzzy-Analytical Hierarchy Process (FAHP) centered approach for selecting the fatigue critical piping locations for inspection and repair. The usability of the proposed approach is demonstrated by an illustrative case study.