Abnormal Modes of Operation – a Risk-Based Focus

Per PII, US OSHA, and CCPS, at least of major process safety incidents have occurred during abnormal modes of operation. Abnormal modes of operation include startup, shutdown, temporary operations, emergency, and maintenance activities. Yet much of the focus in process safety is during steady-state operation. This paper summarizes the approaches that focus on the control of risk during abnormal modes of operation, including:

• Focusing PHAs on abnormal modes of operation by PHA of procedures (using 2 guideword HAZOP and What-If), per Chapter 9 of Guidelines for Hazard Evaluation Procedures, 3rd Edition, 2008, CCPS. This paper will recap the approach and list examples of how these approaches were successfully applied. Usually, PHAs find that recommendations for reducing risk during abnormal operations account for 80% of the risk reduction from a PHA overall.
• Learning scenarios that are unique to abnormal modes of operation that help a company understand what can be found, and what PHA teams and investigation & audit teams should focus on.
• Unique remedies (many are IPLs) for scenarios specific to startup, shutdown, and online maintenance. Over the years, a list of typical remedies to accident scenarios unique to abnormal modes of operation have been developed. These have proven value in reducing risk. The paper will list 10 of the most common remedies.
• Optimizing human factors. Since most of the scenarios for abnormal modes of operation start with a human error initiating event, the paper provides a recap of how to optimize each human factor. Other papers and books discuss these in more detail.