Assessing Consequence of Failure
Build the scenario first
Consequence analysis starts from a release scenario: what is the contained fluid, at what pressure and temperature, through what hole size (small, medium, or rupture), and for how long before isolation? From that you derive release rate, total inventory released, dispersion or pool behavior, and the resulting effect zone.
The four consequence categories
- Safety and health – potential injuries or fatalities, on site and off site, considering population and occupancy within the effect zone.
- Environmental – volume, toxicity, and persistence of the release; proximity of water, soil, and sensitive receptors; cleanup burden.
- Economic – property damage, equipment replacement, lost production and business interruption, cleanup cost, and potential regulatory penalties.
- Sometimes business/reputation – treated as a separate category in some owner/user criteria.
Note that the cost of the inspection itself is never part of COF.
Time dependence
Unlike POF, consequence usually does not grow with service time; it changes when the process, inventory, population, or environment changes. Assessment intervals for consequence should therefore track management-of-change events rather than inspection intervals.
Traps
- Confusing consequence with likelihood - a large inventory with an effective isolation system may still have a modest consequence.
- Ignoring business interruption and only counting hardware damage.
- Applying a release scenario that ignores the actual failure mode identified by the POF analysis (a pinhole leak does not produce a rupture effect zone).
Rule of thumb
Consequence is governed by the amount of hazardous material that can escape before isolation, multiplied by what it reaches. Reducing inventory or speeding isolation is often cheaper than reducing failure frequency.