Process safety performance indicators are the metrics a facility tracks to know whether its process safety is actually holding, rather than inferring it from injury rates. API RP 754 is the framework nearly everyone uses, and it sorts indicators into four tiers. The part that trips people up is that only the top two are process safety events (PSEs), meaning real losses of containment split by consequence. Tier 3 and Tier 4 involve no release at all.
Key Points
- Tier 1 and Tier 2 are PSEs, ranked by how bad the outcome was: fatalities and serious injuries at Tier 1, recordable injuries and smaller losses at Tier 2.
- Tier 3 counts challenges to the safeguards with nothing released, including demands on safety instrumented functions (SIFs), relief valve lifts, and excursions past safe operating limits.
- Tier 4 measures operating discipline. API intends Tiers 1 and 2 for public reporting, while Tiers 3 and 4 stay internal because they are specific to how a given facility runs.
Example
A unit logs eleven high-level trips on a knockout drum over a year. Nothing spilled and nobody was hurt, so there is no PSE to report anywhere. But that is eleven Tier 3 demands on a SIF that was sized assuming roughly one demand a year, which means the protection layer is working far harder than the risk assessment ever assumed.
See Also: PSE, process safety
Cited Sources
- API Recommended Practice 754, Process Safety Performance Indicators for the Refining and Petrochemical Industries, 4th edition (2026)
- API — Guide to Reporting Process Safety Events