(120b) Lessons Learned from Scenarios Found during PHA of Startup, Shutdown, and Online Maintenance

Hazards may go unrecognized or underappreciated due to a variety of influences. Ignorance of the hazard is a convenience excuse after an incident. And many incidents are touted as black swan events when actually they are quite predictable. This paper shows examples from many PHAs of scenarios found for startup, shutdown, and online maintenance modes of operation for which there were no or not enough IPLs. These include (1) introducing cryogenic liquids in columns or vessels before ensuring proper pressurization with gas, (2) valves being left in the wrong position despite many double checks, (3) valves opened or closed in the wrong sequence, despite checklists and significant emphasis, (4) purges being left off despite frequent checks by multiple shifts, and other similar incidents. Some of these have led to significant losses and fatalities. Some could lead to catastrophe tomorrow.

The paper describes how these scenarios are found and how they can be prevented. The paper build on the foundation of human reliability and risk assessment of abnormal modes of operations covered in other papers and textbooks.