- Guide word
- More
- Applied to flow
- Flow higher than the process was designed for.
- What it flags
- Overpressure, or flooding in the next stage.
Glossary
What Is a HAZOP Study?
HAZOP stands for Hazard and Operability Study: a systematic study that examines an industrial process part by part, looking for deviations from its intended operation. Guide words such as “more”, “less”, “reverse” and “none” are applied to each variable — flow, pressure, temperature — and the question asked each time is: what causes this deviation, what does it lead to, and what control already exists for it?
Glossary Published 3 min read
01Where it applies
Why it is used specifically on continuous processes
HAZOP earns its cost on a process that runs continuously rather than in discrete steps, because a deviation in a continuous process does not announce itself the way a stopped machine does. Flow, pressure and temperature can drift gradually while the process still looks normal on a gauge, and the study's job is to ask, systematically, what happens if each of them moves away from its intended value.
02Guide words
Guide words applied to a variable
- Guide word
- Less
- Applied to flow
- Flow lower than the process was designed for.
- What it flags
- Starvation of a step that depends on it, or a stalled reaction.
- Guide word
- Reverse
- Applied to flow
- Flow moving in the opposite direction.
- What it flags
- Material returning into equipment never designed to receive it.
- Guide word
- None
- Applied to flow
- No flow at all.
- What it flags
- A blockage or a stopped pump that is not noticed immediately.
03The team
Who attends the session
A HAZOP session is run by a multidisciplinary team rather than one person reviewing a drawing alone: process, operations and safety perspectives sit in the same room, because a deviation obvious to an operator can be invisible on a process and instrumentation diagram, and the reverse is just as true.
04Timing
When it is conducted
A HAZOP is carried out at the design stage, before a process is built, and again at any material modification to it: a new line, a changed setpoint, a different feedstock. Running it once and treating the process as fixed afterwards defeats the purpose, because the study is only as current as the process it was run against.
05Context
In a Saudi context
The petrochemicals sector here runs the kind of continuous, interconnected processes HAZOP was built for, where a deviation in one unit can propagate into the next before an operator sees it on a single gauge. That is why the study is standard practice at the design stage of new units and at any material change to an existing one.
From the insights library
Continue in the glossary
Next step
Following a HAZOP action through to the plant floor
Tell us which HAZOP actions depend on people behaving a certain way, and we say which of those behaviours can be observed automatically.
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