A set pair analysis based layer of protection analysis and its application in quantitative risk assessment

As an effective risk assessment method, layer of protection analysis (LOPA) is widely used in the evaluation of protection measures, i.e., independent protection layers (IPLs). However, traditional LOPA can only make semi-quantitative assessments for risk. Thus, assessment results with respect to risk will not be accurate or detailed enough, and the evaluation for IPLs may not be scientific or reasonable. By taking advantage of the quantitative analysis of the set pair analysis (SPA), a quantitative LOPA called the set pair analysis-layer of protection analysis (SPA-LOPA) is proposed in this study. The severity of the risk is judged by experts, and expert judgements are reflected by the connection degree (CD) while the corresponding algorithm for the CD is developed. In addition, the diversity degree (DD) and its algorithm are presented to process the CD with respect to the severity, and the assessed severity is measured by the calculated value of the DD. Next, the risk is quantified by the value of the DD and its frequency. Subsequently, the steps of the SPA-LOPA and corresponding assessment flowchart are provided. The SPA-LOPA and semi-quantitative LOPA are utilized to evaluate risks of gas leakage in biomass gasification. It is proved that the SPA-LOPA is more scientific and reasonable in the evaluation for IPLs, based on the comparison results.