Bow tie diagrams are useful for visualizing process safety risks and safeguards. Although typically used after an incident has occurred, bow tie diagrams can also be employed during a process hazard analysis.
Bow tie diagrams visually depict the safeguards or barriers put in place to prevent and mitigate a loss-of-containment (LOC) incident. Although bow tie diagrams are typically constructed after an incident has occurred (1), they can also be useful during a process hazard analysis (PHA) to identify deficiencies in a process safety program and help to prevent the occurrence of an incident. Instead of simply showing what went wrong, bow tie diagrams can be used proactively to keep things from going wrong.
This article introduces the bow tie method and explains how bow tie diagrams can assist in preventing incidents and developing corrective actions needed to effectively mitigate any incidents that do occur. The article also illustrates how bow tie diagrams might have been used during a PHA of the Bhopal facility — the site of the world’s worst industrial disaster.
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