(104z) Risk-Based Inspection As a Tool for Managing Risks - Beyond Inspection Plans

Risk based inspection (RBI) is defined as a risk based analysis for assessment loss of containment scenarios, assuming that risk is managed thru inspection activities or inspection plans. Besides the main goal of an RBI study which is identify high risk equipment and piping, to focus inspection resources, it can be used as a risk management tool, because of its consistency and straightforward methodology for risk calculation. Risk, for Risk-based inspection, can be expressed in many indicators, either qualitative or quantitative. On the quantitative side, financial risk (dollars/yr) and/or area risk (m²/yr) can be used, but also individual and societal risk could be used, just to say some; this risk indicators will help to prove the benefits of the actions taken to manage risk inside a process plant, refinery or petrochemical facility; also will help owners and stakeholders to demonstrate, that they are making enough efforts to keep their facilities safe for workers and for the people who live surrounding the plant and the rest of the community.

The intention of this paper is to show a full risk management application for the RBI methodology beyond the inspection plans as well as to propose a methodology for risk index calculation, taking advantage of the large amount of information generated by the risk analysis developed in inspection planning. This paper will show the risk reduction in terms of risk to the population and people inside a process plant (workers), represented by the risk contours and F-N curves. The study was developed for several chemical process plants inside a 190 MBPd crude oil refinery, surrounded by an urban area with high population density and a shoreline. Once we have identified the high risk components (pressure vessels and piping) as a result from the RBI study, we evaluated them to assess the inspection plans impact and benefits for managing (reduce) the risk, specifically individual risk and societal risk.

This methodology consists in both, a consequence analysis and a frequency of failure analysis. The consequence assessment for the high risk components, require a definition for the conditions that will be used on the scenario modeling, just to keep consistency on the expected results. The scenario was defined as a single leak scenario, represented by a 2 in hole diameter; this scenario was modeled to get as an outcome the affected area. The frequency analysis requires the failure rates results from the RBI study, evaluating the frequency of failure without the inspection plan and after that, the frequency of failure with the inspection plan. The inspection plan is the risk mitigation action. So, we calculate two risk values, one for the “without plan” option and other for the “with plan” option. Then we compare both risk values to evaluate the benefits.

Results are showed graphically using risk contours for individual risk, F-N curves for societal risk, and mathematically in m²/yr. Individual risk are used to identify places of particular vulnerability around the facility, like hospitals, neighborhoods or commercial areas. Societal risk was evaluated to assess how many people may be affected by the release of hazardous materials, meanwhile, risk in area was used to rank high risk components and focus management efforts on them.