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HAZOP, how it is done in Process Industries?

HAZOP is a qualitative method to analyze Process Hazards. It is a very popular technique in Manufacturing Industries which stores processes or manufactures Hazardous chemicals.

Node Selection and Marking

Node is a part of process for which we are analyzing hazards. For example if we are doing HAZOP for a Distillation Tower then feed pump to feed tray can be taken as a Node. As I have observed, there are two basic criteria for Node selection,

  • One, change in Design Intent. That is transportation of fluid, processing of fluid, or storage of fluids or solids.

  • Two, significant change in Pressure, Temperature, Phase, Flow rate or any other process parameters.

Parameter Selection

After Node is marked , we need to select the right parameter to the Node. This requires operating knowledge of that process. Let's say if the fuel injection system is our Node then Pressure can be a parameter. What I have observed that HAZOP is not done with all process parameters, but with those which are important to the process.

Guide word Selection

Once we settle with parameters , we need to apply Guide Words to it. HAZOP has some defined Guide Words to it. Notably , not all the guide words are required but those which represent the change in Design Intent. Like Low fuel Pressure poses a significant risk in choking the reactor coils, then Low Guide Word is important here.

Cause and Consequences Mapping

Once we find the right combination of Parameter and Guideword we can map the cause and consequence to it. Like what can be the cause of high temperature to a reaction, and what are the possible consequences to it.


After the Consequences are listed , we tend to find the existing safeguard to mitigate those Consequences. Like the High Temperature Alarm of reaction process and attached Shut Down logic to it once it crosses a certain value.


Recommendations are must where there is no existing or insufficient safeguard for a Hazardous Consequence. This usually becomes the responsibility of plant owner.

Risk Matrix Mapping

Most of the organizations have their own Risk Matrix. During HAZOP the Consequences are mapped with their Risk Matrix to measure the impact of the consequences to organization.

If you are interested in exploring how real time HAZOP is done in Process Industries, please Register for 30 min Live HAZOP Workshop on 23rd September, 2021 from 2:30 pm to 3:00pm.

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