Barrier Health Check

This check sits downstream of a bowtie and upstream of the risk review, and assumes the barrier list exists and is agreed. Where the list itself is in question the work belongs in the analysis — the wrong template reports cleanly on a diagram nobody trusts.

Bowtie method is not a standard, so the obligations this check discharges come from the management-system and major-hazard instruments around it.

Barrier management is written into law mainly where major-hazard regimes apply, and the wording differs enough to matter. These three shape most programmes.

Filling this in is mechanical. What makes the record defensible, or worthless, is four judgements the person holding the pen has to make.

The same findings recur across sites and industries. Each has a clause behind it and a fix cheaper than the argument about whether it matters.

A packaging line at a food plant carried a bowtie for entanglement during jam clearing. The preventive side named an interlocked guard, a lockout procedure and operator training. Every six-monthly check for four years recorded all three present and functioning, health above ninety per cent. Nobody recorded that the interlock had been strapped out in a commissioning trial and never reinstated — the check was done by walking the line with the shift lead who had strapped it out.

A near miss finally forced a physical test. What would have caught it earlier was not a better checklist but three fields kept apart. Barrier Present was legitimately Pass; the guard was there. Barrier Functioning was Fail the moment anyone opened it and watched the line run on. Barrier Verified Recently had no answer at all, because the interlock had no proof-test interval. The correction was small: a defined interval, a test record as Evidence, and an assessor who is not the barrier's owner.

The barrier list changes between checks, and that is where the effort goes: keeping the diagram, the maintenance regime, the contractor scope and the schedule on the same barriers.

KnowSafe

Holds the bowtie and the check together, so each opens with the current barrier list rather than last cycle's copy, and unactioned Bowtie Needs Updating flags surface before the walk.

KnowMaintain

Supplies the proof-test and calibration history behind engineered and detection barriers, so Barrier Verified Recently is answered from asset records and overdue tests appear as barrier findings, not breakdowns.

KnowContractor

Tracks which barriers depend on contractor scope — isolation, guarding, standby crews — so a change of contractor is flagged as a barrier event and triggers a check.

Ella

Pulls degraded barriers across every bowtie into one view, spots the same escalation factor recurring at different sites, and drafts follow-up actions for approval.

Material unwanted event

The top event at the centre of a bowtie — the loss of control preventive barriers stop and mitigating barriers limit. An event, not a consequence: loss of containment, not fatality.

Threat line

One path on the left of a bowtie, running from a specific threat to the top event with its own preventive barriers. Barrier health is meaningful per line; averaged across lines it is not.

Barrier degradation

Gradual loss of a barrier's ability to perform, through bypass, deferred maintenance or drift rather than outright failure. It is what periodic checks exist to detect.

Performance requirement

The specification a barrier must meet — availability, response time, test interval, competence — against which verification is judged. Without it, Pass and Fail are opinion.

Compensating measure

A temporary substitute while a barrier is impaired, with its own end date. Under barrier-management regimes an impaired barrier without one is reportable.