(22a) Advanced QRA Methodology-Quantifying Risk Reduction Measures to Minimize Economic Investment

Quantitative Risk Assessment (QRA) has been accepted as a process safety management tool in many countries throughout the world for the risk management decision-making process. QRA enables the comparison of a facility's risk levels with either country-wide or corporate risk tolerability criteria. When required, recommendations are generated during the QRA, in order to reduce the risks to a tolerable level. However, one evidenced limitation of QRAs has always been the lack of a quantitative evaluation of the required Risk Reduction Factors (RRFs) associated with the proposed QRA recommendations. This paper proposes a detailed methodology to resolve this shortcoming by illustrating a real case study.

Given a target location being impacted with an intolerable risk level, ioMosaic Corporation has developed a methodology to fully identify and quantify the most suitable, practical, and economic risk reduction measures. Based on QRA results, the methodology requires the completion of the following key steps: (1) calculation and collection of dedicated risk profiles for every process equipment item and piping segment with identified Loss Of Containment scenarios (LOCs); (2) identification and risk-ranking of the equipment which contributes the highest risk to a target location, using specific risk indices statistics; (3) estimation of the required RRF for each piece of equipment identified in step 2. This is determined by evaluating the ratio of the actual risk index value and a desired constant target risk index threshold; and (4) definition of the target risk index threshold through an iterative procedure consisting of applying the guesstimated RRFs and then re-evaluating the QRA risk profiles. The iterative procedure is completed when the target location is confirmed to be within a tolerable risk level.

The proposed methodology allows companies to focus efforts on safeguards which guarantee specific levels of risk reduction, rather than implementing generic safeguards which may yield minimal benefit. This information minimizes the risk reduction economic investment during the decision-making process, and maximizes the effectiveness of the safeguards to be implemented.