The method
HAZOP (Hazard and Operability study) is a qualitative, multidisciplinary team review based on piping and instrumentation diagrams (P&IDs). The plant is divided into nodes; for each node, guide words (no, more, less, reverse, other than…) are applied to parameters (flow, pressure, temperature, level…) to reveal deviations.
For each deviation the team records causes, consequences, existing safeguards and recommendations. The method also covers operability problems, not only safety.
It is described in IEC 61882. The most severe scenarios are often taken further with LOPA.
When to use it
- Design or modification of a process unit, once P&IDs are stable enough.
- Periodic revalidation of existing plants (major-hazard, chemical and oil & gas sites).
- Continuous processes; a step-by-step variant exists for batch processes.
Watch out for
- Quality depends mainly on the team and facilitation: software structures the worksheet, it does not replace expertise.
- Up-to-date P&IDs are essential: a HAZOP on outdated drawings misses real deviations.
- Long sessions tire the team; shorter, regular sessions work better.
Steps
- Define the scope, gather the team (process, operations, instrumentation, safety) and an independent facilitator.
- Divide the plant into nodes on the P&IDs and state the design intent of each.
- Apply guide words to parameters; record deviations, causes, consequences, safeguards and recommendations.
- Rank scenarios by severity and pass the most severe ones to LOPA.
- Track recommendations until closure.
HAZOP software
List from the Aurorisk catalogue, links checked on 2026-09-26. Confirmed free access is listed first; unknown information is labelled.
| Tool | Source · licence · access | Scope | Description |
|---|---|---|---|
| Kenexis Open-PHA ↗ | Commercial publisherFree | United States | HAZOP scenarios linked to LOPA scenarios. |
| Polyodos ↗ | Commercial publisherFree for teaching | International | HAZOP and LOPA with action tracking. |
| BakerRisk PHA-Tool ↗ | Commercial publisher | United States | Suite for facilitating PHA studies. |
Standards and references
- IEC 61882 — Études HAZOP
- CCPS — Layer of Protection Analysis (2001)
- IEC 61511 — Sécurité fonctionnelle des systèmes instrumentés de sécurité