Not every project needs a HAZOP, and not every project is ready for one. A HAZOP needs firm P&IDs, a full team and several days of everyone’s time. Ask for one at concept stage and you will either be told to come back later, or you will run a study against drawings that are about to change. Meanwhile the decisions that matter most, such as which route, which solvent, where it sits on the plot and how it will be controlled, are being taken with no structured hazard review behind them.
A Process Hazard Review fills that gap. It is a structured but proportionate examination of the process description, the credible deviations and the safeguards being relied on, producing a risk register a project can actually use. We run PHRs for process manufacturers across the UK at concept and early design stage, on modifications going through management of change, and as periodic reviews of operating plant where a full HAZOP revalidation is not yet due.
What the study involves
A PHR works from whatever definition exists: a process description, a block flow or process flow diagram, a mass balance, a draft layout, a materials list. The team works through the process steps rather than node by node, asking what hazards each step introduces, how the process could credibly deviate from what is intended, what the consequences would be, and what is being relied on to prevent or mitigate them. Each finding is recorded with a qualitative risk ranking against your own criteria, and an action with an owner.
Because the review is proportionate to the definition available, it costs a fraction of a HAZOP and can usually be run in a day or two rather than a week. That is the point of it. A PHR is a study you can afford to run early, and repeat when something changes, rather than one you defer until the design is fixed.
The term is used loosely across the industry. Some sites call this a hazard study 2, some a preliminary hazard analysis, and in North American practice process hazard analysis covers the whole family of studies including HAZOP. If you are unsure which you have been asked for, describe what the project needs and we will tell you which study actually fits.
Where it sits between HAZID and HAZOP
A HAZID asks what hazards this project carries at all, looking across chemicals, layout, utilities, access, egress and external events. A HAZOP examines a defined design node by node against design intent, using guide words and mature drawings. A PHR sits between the two: more structured than a hazard brainstorm, less granular than a HAZOP, and tied to the process rather than to a finished drawing set.
On smaller projects and straightforward modifications a PHR is often the only process hazard study needed. On larger schemes it is the right place to decide what else is required, because the review will show which parts of the process carry enough risk to justify a HAZOP, and which scenarios are likely to need LOPA and SIL determination behind them.
What you get
- A planned and chaired review with the right disciplines in the room
- A risk register covering each hazard, credible deviation, consequence and existing safeguard
- Qualitative risk ranking against your own matrix or tolerability criteria
- Actions and recommendations with owners, recorded in an auditable format
- A clear recommendation on whether a HAZOP, LOPA or DSEAR assessment is required, and when
- Input to concept and early design decisions while those decisions can still be changed
- Documentation that supports management of change, project gate reviews and internal governance
- Follow-up to confirm the actions are addressed and closed out
When clients typically call us
- A project is at concept or early design and a HAZOP cannot yet be run against the drawings
- A modification is going through management of change and needs a proportionate hazard review
- A small project does not justify a full HAZOP but cannot proceed with no study at all
- Operating plant is due a periodic process safety review between HAZOP revalidations
- A corporate standard, insurer or funding gate requires evidence of structured hazard review
- Nobody is certain which study is required and a decision is needed before budget is committed
Frequently asked questions
Is a Process Hazard Review the same as a HAZOP?
No. A HAZOP is a detailed node-by-node examination of firm drawings against design intent, using guide words. A PHR is a structured review of the process description, its credible deviations and the safeguards relied on, run at a level of detail that suits the information available. A PHR often identifies where a HAZOP is needed. It does not replace one where the risk warrants it.
Can a PHR satisfy our management of change requirement?
For many modifications yes, and that is one of the most common reasons clients ask for one. Whether it is sufficient depends on the change and on your own procedures. We will say plainly if a change needs a full HAZOP rather than a review, and we would rather tell you that before the work than after it.
What do you need from us to run one?
Whatever exists. A process description, a block or process flow diagram, a materials list and a rough layout are enough to start. We prepare from your documents beforehand, so the session is spent on analysis rather than on explaining the process to the chair.
How long does it take?
Most reviews are a day or two of workshop, plus preparation and reporting, against a week or more for a HAZOP on the same plant. Scope and complexity drive it, and we will give you a firm estimate once we have seen the documents.
Related: Part of our process safety services. See also HAZID studies, HAZOP facilitation and LOPA.
If you need a hazard study that fits the stage your project is actually at, rather than the one the procedure happens to name, we can scope and chair it. Talk to us about your project. Request a call