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What are the Key Stages in a Hazard and Operability Study (HAZOP)?

HAZOP stands for Hazard and Operability Study.

It is a structured and systematic approach to identifying potential hazards and operability problems in complex systems and processes.

This can include chemical plants, oil refineries, and nuclear power plants.

HAZOP analysis is typically conducted by a team of experts from various disciplines, including engineering process design, operations, maintenance, and safety.

This short article aims to provide a comprehensive overview of the stages involved in a HAZOP analysis.

It begins with providing an understanding of what a HAZOP is and its significance in identifying hazards.

It then discusses HAZOP documentation, safeguard identification and package recording.

Finally, this article discusses the difficulties that organisations may encounter when attempting to assess and identify hazards during a HAZOP analysis.

What is a HAZOP and how can it help identify potential hazards?

The HAZOP methodology involves breaking down a system or process into smaller units, called nodes.

The HAZOP team members then systematically analyse each node to identify deviations or possible deviations from the intended design intent or operation.

The HAZOP method typically results in a detailed report that identifies potential hazards and operability problems in process design, along with recommendations for best practices for mitigating or eliminating them.

The HAZOP method is an important management tool used for managing risk and ensuring the safe and efficient operation of complex systems and processes.

An overview of the HAZOP analysis process

The HAZOP analysis process is a structured and systematic approach used to identify potential hazards and operability problems in complex systems and processes. 

The following is a detailed overview of the HAZOP analysis process:

1.     Define the scope and objectives

The first step in the early stages of a HAZOP analysis is to define the scope and objectives of the study. 

This involves identifying the system or process to be analysed alongside the team members involved, and the goals of the study.

2.     Develop the HAZOP team

The HAZOP team should consist of experts from various disciplines, including engineering, operations, maintenance, and safety. 

The team should be trained in the HAZOP methodology and have a clear understanding of the system or process being analysed.

3.     Break down the system or process into nodes

The system or process must then be broken down into smaller units, called nodes, for analysis. 

Each node represents a distinct element of the system or process, such as equipment, a control system, or an operating procedure.

4.     Identify the process parameters

For each node, the team identifies the process parameters, such as temperature, pressure, flow rate, and composition. 

These elements are critical to the safe and efficient operation of a system or process.

5.     Apply deviation keywords

The team systematically analyses each node using a set of standard deviation keywords, such as “no,” “more,”, “less,” “part of,”, “reverse,” and “other than.” 

These keywords are used to identify potential deviations from the intended design or operation of the system or process.

6.     Consider the consequences, causes, and safeguards

For each deviation identified, the team considers the potential consequences, causes, and safeguards.

The team considers each deviation in terms of its potential consequences, causes, and safeguards. 

Consequences can include harm to people, damage to equipment or the environment, or loss of production or revenue.

Causes can include failures in equipment, workplace hazards (such as hazardous chemicals) human error, or external factors like weather or power outages.

Safeguards can include engineering controls, alarms, safety procedures, or training.

7.     Document the findings

The team documents the findings of the HAZOP analysis in a detailed report, which includes a summary of the system or process, the nodes analysed, the deviations identified, and the recommendations for mitigating or eliminating the hazards and operability problems.

8.     Review and implement recommendations

The report is then reviewed, and the recommendations are implemented to improve the safety and efficiency of a system or process.

The HAZOP analysis process may be repeated periodically to ensure that any changes or updates to the system or process are properly analysed for potential hazards and operability problems.

The HAZOP reporting document

A HAZOP report is a document that summarizes the findings of a HAZOP and includes an analysis of process systems. 

This includes potential hazards and operability problems, along with recommendations for mitigating or eliminating them:

1.      Executive summary: A summary of the key findings and recommendations of the HAZOP analysis.

2.      Introduction: A description of the system or process being analysed, the scope and objectives of the HAZOP analysis, and the team members involved.

3.      Methodology: A description of the HAZOP analysis process used, including the nodes analysed, the deviation keywords used, and the criteria for evaluating the consequences, causes, and safeguards.

4.      Results: A detailed summary of the deviations identified, including the process parameters affected, the potential consequences, causes, and safeguards for each deviation, and the severity of the risk associated with each deviation.

5.      Recommendations: A set of recommendations for mitigating or eliminating the hazards and operability problems identified in the HAZOP analysis, including engineering controls, alarms, procedures, or training.

6.      Conclusion: A summary of the main findings and recommendations, along with any limitations or caveats of the HAZOP analysis process.

7.      Appendices: Additional supporting information, such as diagrams, tables, calculations, or references, to provide more detailed information on the system or process being analysed and the HAZOP analysis process.

The HAZOP reporting document should contain clarity, conciseness, and comprehensiveness such that it communicates the findings and recommendations effectively to all relevant stakeholders, including management, operations, maintenance, and safety personnel. This should be the study leader’s aim.

Identifying Safeguards

HAZOP identifies the safeguards, which prevent, control, or mitigate a deviation and/or its consequences. 

Because it identifies not only what is present and must therefore be considered important, it can be used to highlight how those safeguards should be managed to maintain their effectiveness. 

If a relief valve is cited as a safety safeguard against overpressure leading to a vessel failure, for example, then that safety valve must be sized, designed, installed, maintained, and evaluated in accordance with its duty.

 It is these activities that are the ‘risk management’ activities.

Recording Packages

There are specialist HAZOP recording packages e.g., PHA-Pro and HAZOP-Manager. 

Both are good tools, but similar jobs. 

The main advantages of these packages are that, for large studies, they tend to give better control over version control, easier action management and more user-friendly navigation.

Most used, however, are spreadsheets, which, when well-designed, are powerful and flexible. 

With this flexibility comes the danger of data loss, replication and version control that spreadsheet users are familiar with.

Text-based editors like MS Word or even pen and paper can also be used.

The Difficulties of the HAZOP

Few studies require the rigour demanded by the HAZOP and, as a result, they seldom run perfectly smoothly. 

The generic difficulties that have been encountered include:

(1) Whether the study is a new project, a change, or a review, none of the attendees (except for the Chair/Facilitator) are employed specifically to take part in the study. 

They have other jobs to do and getting everyone together in the room simultaneously can be difficult.

 This is especially true when outside expertise e.g., vendors or subject matter experts are required. 

There are only two solutions to a potential problem; either sufficient notice must be provided or there must be concrete plans for the study to be undertaken during a block of time in the future to allow people to plan it into their activities or by edict from a senior manager. 

Planning is the preferable route.

(2) One of the most important attendees, and one that is sometimes overlooked, is the operator. 

Having someone in the room who knows how the plant operates rather than how the design team thought it was going to work, is vital. 

The HAZOP is particularly good at identifying ‘knowledge vs experience’ differences.

(3) Companies have been reluctant to identify the worst-case consequence. Their logic is that, because they know that they have safeguards in place, a potential loss of containment will not happen. 

The HAZOP should look for the unmitigated consequence first, because if that is not known then it is impossible to say what those safeguards need to be, how robust they need to be and therefore what risk reduction they must provide. 

If they are not identified enough during the very early stages, then their importance for risk and hazard reduction can be missed and there is the chance that they will not be recognised and treated as being important.

(4) The HAZOP is rigorous and requires concentration. The team members are human and have human limitations. The more time spent in the meeting room the more tired people become. 

This can lead to tunnel rather than lateral thinking and the quality of the workshop decreases. Do not schedule more than three days of meetings in a block, try to restrict the number of hours in any one day to around six and give people meaningful breaks. A good Chair should be mindful of how people are feeling.

(5) The HAZOP is an identification exercise, not a design exercise. In general, if an identified issue cannot be reconciled within 20 seconds or so of the startup of the discussion, then this disagreement should be resolved outside the meeting. Take an action to resolve the issue and move on.


The Hazard and Operability Study (HAZOP) is a critical process safety methodology that helps identify and mitigate potential hazards in various industries.

Through a systematic and structured approach to risk assessments, a HAZOP allows organizations to thoroughly evaluate their processes and operations, uncovering any potential risks, deviations and vulnerabilities that could result in hazardous situations.

This article provided an overview of the stages involved in a HAZOP analysis, starting from understanding what a HAZOP is and its significance in identifying hazards.

The importance of HAZOP reporting document is a crucial deliverable. 

The reporting document summarises the findings, recommendations, and actions and emphasizes the importance of effective communication and documentation in the HAZOP process.

Additionally, this article shed light on the difficulties that organisations may encounter when identifying problems assessing hazards during a HAZOP analysis. 

This includes challenges related to team dynamics, subjectivity in hazard identification, and the potential human limitations of the method.

A HAZOP analysis is a valuable tool for identifying and mitigating potential hazards in complex processes and operations. 

By following a structured approach and leveraging the expertise of a multidisciplinary team, organisations can proactively identify and address potential hazards, minimise risk and enhance safety across their operations.

However, it is important to recognize and address the challenges and limitations of the HAZOP process to ensure its effectiveness in hazard identification and mitigation.

Implementing a HAZOP analysis can contribute to enhancing safety and preventing incidents in industries where hazards are inherent to a working environment, making it an essential tool in process risk management.

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