Definition:
Hazard and Risk Assessment (H&RA or HARA) is the formal process of identifying hazards, assessing associated risks, and determining necessary risk reduction to achieve tolerable risk levels. It is the formal terminology used in IEC 61508 and IEC 61511. There are many ways to achieve these requirements which can be confusing. Broadly, it can be qualitative (QLRA), semi-quantitative (SQRA), or quantitative (QRA). More specifically, these could include HAZOP, HAZID, or a Risk Graph. Additional choices are ETA, FTA, and a bowtie with a what-if checklist.
In other words, there are lots of ways to skin this cat. It can be a bit confusing even for experienced practitioners on the best approach. SIL Safe’s mental model is there is the “H” portion where the hazards are identified. Now there’s the “A” portion where the risks are analyzed. Some tools do this all together. Some tools really apply more for the “H” and others apply more for the “A”.
See a much broader article about the ways this can be structured.
- H&RA Foundation
- Process Hazard Analysis Methods
Methods overview: For an overview of the hazard and risk analysis methods used in an H&RA — HAZOP, What-If, LOPA, risk graph, FTA, ETA, and bowtie — see Hazard and Risk Analysis Methods.
Key Points:
- H&RA is an umbrella term that includes qualitative, semi-quantitative, and quantitative methods.
- Required early in the safety lifecycle to define Safety Instrumented Functions (SIFs) and assign Target SILs.
- Broader and more formal term compared to “Process Hazard Analysis (PHA)” used under OSHA regulations.
Example:
A Hazard and Risk Assessment done via a HAZOP identifies overpressure scenarios in a reactor system, determines the initiating event frequency and its consequence. Later, a LOPA evaluates the existing protection layers, and assigns a SIL 2 requirement for a high-pressure shutdown SIF.
See Also: QLRA, SQRA, QRA, PHA, HAZOP, HAZID, risk matrix, risk graph, dispersion analysis, IDLH
Cited Source:
- IEC 61511-1:2016, Clause 8.