Hazard and Operability StudyHAZOP

A Hazard and Operability Study is a team-based process-hazard-analysis technique that walks the process design node by node — a pipe, a vessel, a reaction step — and applies guide-words (No, More, Less, Reverse, As Well As, Other Than) to each parameter (flow, temperature, pressure, level, composition) to surface deviations, their causes, their consequences, and the safeguards that detect or prevent them. It is the PHA method of choice for processes covered by OSHA 29 CFR 1910.119 and the EU Seveso directive, where the hazard is high-energy or a toxic release and the design has to be challenged line by line.

The output of a HAZOP is a worksheet of deviations ranked by risk, each with a safeguard and an action — and the value is in the team, not the worksheet. The study forces the design engineer, the operator, and the safety engineer to argue the same drawing at the same table, which is where the assumptions that would have failed in commissioning surface instead. The weakness is the follow-through: a HAZOP whose actions are never closed is a study, not a control. A QEHS platform holds the worksheet against the asset, links each action to a corrective action, and carries the residual risk onto the bow-tie and the risk register. See bowtie, PSM, FTA, and LOPA.