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Hazop Analyses Often Fail to Address Human Factors and Equipment Operability Issues


Although Hazops are a useful tool for reducing process risks and increasing safety, they often fail to address equipment operability issues and human factors. In the course of benchmarking plant operations, Beville has observed many plants that conducted Hazop analyses, and yet numerous human factors deficiencies and equipment operability issues still existed. Now, some regulatory agencies are mandating that human factors be included in Process Hazard Analyses. In counties, such as Contra Costa County in California, failing to properly address human factors as part of Hazop studies will result in studies that are out of regulatory compliance and plants in danger of citation.

The reason Hazops fail to address human factors issues is tied to how they are structured. Most Hazops focus on equipment rather than operator tasks (eg. Is this relief valve sized correctly?). A traditional Hazop analysis involves several operations and engineering personnel systematically reviewing equipment drawings and evaluating each piece of equipment in terms of failure modes. What is missing from the analyses are realistic assessments of the equipment’s operability and how the equipment’s controls conform to ergonomic and human factors principles. What often happens is that a manual valve on a drawing that is supposed to be operated during a shutdown is actually up in a pipe rack and inaccessible or mislabeled and causes the operator to close the wrong valve. When equipment operability assumptions made during Hazop studies fail to reflect reality, the result is a false sense of safety and an under estimation of process hazards.

To ensure human factors are included in Hazop studies, those conducting the studies need to validate equipment operability assumptions. Reviews of equipment operability and compliance with ergonomic and human factors principles need to be done as part of the equipment drawing reviews. This combined approach will ensure that Hazop studies do in fact address human factors and comply with regulatory demands.

Assessing equipment operability and ergonomic/human factors issues is best done via walkthroughs of the process with process operators. During the walkthroughs, the equipment can be examined and operators queried for their experiences with the equipment. Human factors issues, such as job aids and labeling, can also be assessed as part of the walkthroughs. Based upon the findings, the equipment can be classified in terms of its usability and effort needed to operate. Addressing equipment operability issues and human factors as part of a Hazop will help identify and control the process hazards and reduce the rates of operational error.

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