Further Lessons Learned on How to Efficiently Perform the Necessary PHA of Startup, Shutdown, and Online Maintenance

Hazard evaluations, also called process hazard analysis (PHAs) have been performed formally in gradually improving fashion for more than five decades. Methods such as HAZOP and What-If analysis have been developed and honed during this time. Some weaknesses identified 30 years ago still exist in the majority of PHAs performed around the world. Critically, most PHAs do not thoroughly analyze the errors that can occur during startup, shutdown, and other non-routine (non-normal) modes of operations; sadly the commonly used approaches for PHA of continuous mode of operation only find about 5 - 10% of the accident scenarios that may occur during startup, shutdown, and online maintenance. This is true even though about 80% of major accidents occur during non-routine operations. Instead of focusing on the most hazardous modes of operation, most PHAs focus on normal operations (e.g., HAZOP of equipment nodes). In a majority (perhaps more than 80%) of both older operations and new plants/projects, the non-routine modes of operations are not analyzed at all. This means that perhaps 70% of the accident scenarios during non-routine operations are being missed by those PHAs. If the hazard evaluation does not find the scenarios that can likely occur during these non-routine operations, the organization will not know what safeguards are needed against these scenarios.

One reason that many companies do not perform PHA of Procedures is because they believe the time required for such analysis will be excessive. This paper shows clearly the best practices for (1) screening and ranking which procedures/tasks are most critical for analysis, (2) deciding on the method to optimize the investment of time, and (3) streamlining the documentation of the results of the PHA of procedures. Following the steps outlined in this paper reduces the time needed for PHA of procedures by about 40% with noticeably effecting the number of accident scenarios found during PHA of procedures. The result should be more sites completing PHA of procedures.