Development of a risk informed quantitative decision making framework for major accident hazards installations in Sri Lanka

Abstract

This paper proposes a risk informed decision-making framework for siting Major Accident Hazard Installations in Sri Lanka. It is named the “Upper Bound FN curve” method. Generic failure rate data are utilized as country specific data are not available. FN Curves are derived for each process node of a Major Accident Hazard Installation using different failure rate data sets available in literature. The data sets giving the “worst case” FN Curve for each process node is identified. These FN Curves are called the Upper Bound FN Curves. Using these curves, a composite FN Curve is developed which is compared against the country specific risk acceptance criterion line. If the risk is not acceptable, further safety barriers are introduced. Safety distances are then determined using a scaling factor developed in this study called the relative risk reduction factor (RRRF). The RRRF is determined based on the comparative position of the composite FN curve with respect to the criterion line. The proposed methodology was applied in a case study of liquefied propane storage tank. Guidelines for application of the proposed framework, interpretation of the “Upper Bound FN Curve” method and estimation of safety distances are presented.