Bowtie analysis

A bowtie diagram is a risk-visualisation method that puts a central top event in the middle — the loss of containment, the release, the ignition — with preventive barriers on the left that keep threats from triggering it, and mitigative barriers on the right that keep the consequence from escalating once it has. The diagram is the picture an operations team and a regulator can read at the same level: the threats, the barriers, the degradation factors that weaken a barrier, and the consequences the barriers are there to stop. It is used heavily in process safety and major-hazard facilities, where a single top event can cascade into a catastrophe.

The value of a bowtie is not the diagram; it is the barrier register it produces. Each barrier on the diagram has an owner, a performance standard, and a verification — the human action, the instrumented function, the physical relief — and the audit tests the barrier, not the drawing. A bowtie built from a HAZOP carries the top events and the safeguards forward in a form the operations team can manage, and the management-of-change process re-touches the bowtie when a barrier is modified. The weakness is the static diagram: a bowtie drawn once and never reviewed is a poster. See HAZOP, process safety management, and risk.