HAZOP

HAZOP, short for Hazard and Operability study, is a structured and systematic technique for identifying hazards and operability problems in industrial processes, especially in chemical, petrochemical, and related facilities. It originated in the 1960s at Imperial Chemical Industries (ICI) and has since become one of the most widely used process safety reviews.

The study is conducted by a multidisciplinary team following a guide-word based approach. The process is divided into nodes corresponding to sections of the process description or piping and instrument diagrams (P&IDs). For each node, the team considers potential deviations from design intent using guide words (for example, No flow, More pressure, Less temperature). For each deviation, potential causes, potential consequences, existing safeguards, and recommendations are documented. The outcome is a HAZOP report with action items and owners.

Inputs include the process description, P&IDs, process flow diagrams, and operating procedures. Outputs include a written report, a list of recommended actions, and sometimes risk rankings or prioritization.

Used during design, construction, or modification stages; applicable to chemical, oil and gas, pharmaceutical, and other process industries. Strengths include a systematic, thorough examination that considers human factors and equipment reliability. Limitations include dependence on facilitator and team expertise, potential to be time consuming, and occasional gaps in identifying highly unlikely events; it is often complemented by quantitative methods such as Layers of Protection Analysis (LOPA).

Related methods and variations include HAZOP with modifications, HAZOP-LOPA integration, and software-specific HAZOP studies.