Abstract: The application of LOPA, a semi-quantitative risk assessment method, in the assessment of chemical hazards is restricted. It cannot fulfill the requirement of scientific and precise evaluation for safety measures in the chemical industry. In order to make quantification of LOPA, a quantitative LOPA called the set pair analysis-layer of protection analysis (SPA-LOPA) was worked out by taking advantage of the SPA. The severity of the risk can be determined quantitatively by using the proposed method. Moreover, a concept of diversity degree (DD) was introduced to make quantitative description of the severity, and corresponding algorithm of the DD was worked out. Therefore, the risk can be calculated, and the quantitative LOPA can be achieved. A case study for the high pressure incident of a certain toluene tank was made by using SPA-LOPA. The traditional LOPA was employed to make comparison and verify the effectiveness. The results show that the quantitative LOPA for chemical hazards can be made by using the proposed method, and the quality of assessment results also can be ensured.

Key words: layer of protection analysis(LOPA), set pair analysis(SPA), quantitative risk assessment, chemical hazards, risk reduction