Risk-Based Ranking in Inspection of Industrial Facilities

Inspection can play a significant role in reducing the likelihood of unexpected structural failures. However, for many critical components and systems that are required to maintain pressure boundary integrity or that are subjected to severe service conditions, inspection requirements for these vital components are either established based upon prior experience and engineering judgment or are nonexistent. Most inspection requirements or guidelines, if they exist, are usually established with only an implicit consideration of risk.Recent catastrophic structural failures over the past decade highlight the societal need to relate more explicitly risk and uncertainty with inspection programs. In this study, risk-based methods with uncertainty evaluation and propagation were developed for the purpose of developing inspection strategies. Interval analysis was used for this purpose which is a form of fuzzy arithmetic. The methods result in establishing priority ranking lists for failure modes and components where actions need to be taken accordingly. The ranking priority lists for inspection purposes were based on the assessments of the probabilities of failure, resulting consequences, expected human and economic risks and the uncertainties associated with these assessments.