What a HAZOP is
HAZOP stands for hazard and operability study. A small team goes through the process drawings section by section and asks what could go wrong if the process drifts from its intended design, and whether the plant is protected against it.
How the study runs
The plant is split into nodes, usually a vessel, a line or a piece of equipment with its connections. For each node the team applies guide words such as no, more, less, reverse and other than to parameters such as flow, pressure, temperature and level. Each deviation is discussed for its causes, its consequences and the safeguards already in place.
Who should be in the room
A good study needs the design engineer, a process engineer, someone who will operate the plant, and an instrument or electrical specialist, led by an experienced facilitator who is not the designer. Mixing people who built it with people who will run it finds problems that either group alone would miss.
What comes out of it
The result is a record of deviations, causes, consequences and safeguards, plus a list of actions: a relief valve to add, an alarm to change, a procedure to write. Each action has an owner and a due date, and the design drawings are updated as they close.
When to hold one
The main study is held when the process drawings are firm enough to review but before detailed design and purchasing are locked, so that changes are still cheap. Modifications to an existing plant should be reviewed again, even small ones, because small changes are a common source of incidents.
Common mistakes
Rushing the session, reviewing drawings that are not final, skipping start-up, shutdown and maintenance situations, and leaving actions open after the study are the usual weaknesses. A study that finds nothing is not a sign of a perfect design. It is often a sign the team did not look hard enough.
If you are planning a new plant or a modification and want a hazard study organised, tell us about the project and we will outline the approach.