Structure a hazard and operability study node by node, with guidewords, causes, consequences, safeguards and actions.
A HAZOP is a structured team review of a process design or operation. It asks, for each part of the process, what could deviate from the design intent and what would happen.
HAZOP studies for hazardous processes are usually led by an experienced facilitator and may be part of regulatory process safety requirements. This worksheet supports the study; it does not replace that expertise.
15 items. Keep it on a tablet, or print a copy for the clipboard.
| Field | What to write |
|---|---|
| Node | Part of the process |
| Parameter and guideword | For example, flow and no |
| Deviation | No flow |
| Causes | Why it could happen |
| Consequences | What would happen |
| Safeguards | What exists now |
| Risk | Per your matrix |
| Action, owner, date | What to add |
For a node covering a transfer pump to a storage tank, the guideword more applied to level gives tank overfill. Causes include a failed level gauge; safeguards include a high-level alarm. The team recommends an independent high-level shutdown and assigns it to engineering.
OSHA’s process safety management standard requires a process hazard analysis for covered processes, and HAZOP is one of the accepted methods. The worksheet records each deviation and the actions, which the standard expects to be resolved and tracked.
| Study | Caustic dilution skid, Unit 2, Baton Rouge LA |
|---|---|
| Drawings | P and ID 2-104 rev C |
| Node | Node 3: 50% caustic feed to mix tank T-201 |
| Deviation | More flow |
| Cause | Feed control valve fails open |
| Safeguards | High-level alarm on T-201; operator response |
| Action | Add flow-limiting orifice; owner process engineer Nate, due Q1 |
The drawing revision is recorded so it is clear which design the team reviewed. The recommended orifice limits flow passively, which does not depend on the operator responding to the alarm.
Hazard and operability study.
Process, operations, maintenance and safety people, with a facilitator.
It depends on the number of nodes.
After significant changes and periodically.
The common guidewords are no, more, less, reverse, as well as, part of and other than. Each is combined with a process parameter, such as more plus pressure, to create a deviation the team then examines for causes, consequences and safeguards. Working through every pairing at each node keeps the study systematic.
A node is a section of the process with a clear design intent, such as a pump and its discharge line to a tank. Use the P and IDs to mark nodes where the conditions or purpose change. Nodes that are too large hide deviations, while nodes that are too small make the study drag.
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