Scenario identification and evaluation for layers of protection analysis

The identification and screening of scenarios has been identified as a source of variation in Layers of Protection Analysis (LOPA). Often the experience of the analyst is a significant factor in determining what scenarios are evaluated and the worst credible consequences. This paper presents a simplified chemical process risk analysis that is effective in providing a semi-quantitative measure of consequence that may include human harm and is independent of the analyst. This process may be used in evaluation of Management of Change, inherently safer design decisions for capital projects and LOPA re-validation. Conditional and relational logic may be captured with the use of simple spreadsheets to further improve overall efficiency. For example, this method minimizes the overall time required for scenario development and re-validation relative to Hazard and Operability studies (HAZOP).The technique simplifies established models used by engineers engaged in the operation or design of a chemical manufacturing facility without special software or training. The results of this technique are realistic and may be directly compared with corporate or regulatory guidelines for risk of fatality or injury. At each step in the risk analysis process, more detailed or sophisticated methods may be used to refine the technique. Furthermore, results from any step may indicate that the hazard from a specific scenario case is not sufficient to continue with subsequent analysis steps.