Consequence severity-probability importance measure for fault tree analysis

Fault Tree Analysis (FTA) has realized substantial application for safety engineering; however, the method is not without limitations. Traditional FTA requires substantial time and effort, even for single fault assessment, and focuses solely on the probability of event occurrence without considering the severity of consequences. A constrained literature review and examination of functions available in commercial-off-the-shelf FTA software revealed current implementations to lack a structured functional approach to account for severity of intermediate events to a fault as well as severity of fault outcomes. To address this limitation, a novel Consequence Severity-Probability Importance Measure (CSPIM) is proposed as an extension of static FTA. The CSPIM approach is demonstrated through a case study comparing results to those of traditional FTA. Results from a numerical example show that the CSPIM approach effectively prioritizes risky events for safety controls by taking into account both the likelihood and severity of consequences. The CSPIM algorithm calculates a composite risk value and importance of fault tree initiators, revealing those initiators that pose serious risk and should be the focal point for control measures. This approach provides a higher resolution solution than traditional FTA.