What Is Hazop

A hazards analysis can be time consuming, be highly sophisticated, and involve a detailed in-depth analysis. If there is the potential for significant injuries or damage, then it may be essential to put an extensive on-going effort into the hazard analysis.

With many types of processes a Job Hazard Analysis (JHA) is sufficient to reveal potential hazards within the process. However, if the process is complex, or there is the possibility of a disaster should there be a problem in the process, a more powerful hazard analysis method should be used. OSHA lists several accepted methods, such as:

• What-If Analysis
• Checklist
• Hazard and Operability Study (HAZOP)
• Failure Mode and Effects Analysis (FMEA)
• Fault Tree Analysis

A Hazop Study is the most commonly used process hazard analysis method. It can be used to identify operability problems even during the early stages of project development, as well as identifying potential hazards in operating systems.

What is a Hazop Study?

A Hazard and Operability Study (HAZOP) is a systematic approach to investigating each element of a process to identify all of the ways in which parameters can deviate from the intended design conditions and create hazards or operability problems.

A Hazop Study typically involves using the piping and instrument diagrams (P&ID), or a plant model, as a guide for examining every section and component of a process.   A hazop team, consisting of experienced and knowledgeable people, brainstorms potentially hazardous situations that could arise in each section of pipe, each valve, and each vessel in the system.

The hazop team should be led by someone with an in-depth knowledge of the process, but they do not need to be an expert in the technology used in the process.  The hazop team should include people with a variety of expertise such as operations, maintenance, instrumentation, engineering/process design, and other specialists as needed.  These should not be “newbies,” but be people with experience, knowledge, and an understanding of their part of the system.

The Hazop Study Process

In a Hazop Study the hazop team works through the P&IDs examining the impact of potential changes to parameters such as flow, temperature, pressure and time. Using their experience they determine the effects of deviations from design conditions.  This means that a Hazop Study is a systematic, step-by-step approach to brainstorming possible deviations; determining the likelihood of the deviation (is there a realistic cause); evaluating existing protections; and estimating the resulting impact and potential catastrophic result of the deviation.

The process system is evaluated as designed and noting the potential for deviations. All potential causes of failure are identified. Existing safeguards and protection systems are identified and their ability to handle the deviations evaluated. An assessment is written weighing the potential deviations, their consequences, their causes, and the protection requirements.  When a hazard condition is identified, recommendations may be made for process or system modifications, or further study by a specialist may be required.

What Do You Do With the Hazop Study Results?

A Hazop Study may be a one-time study of limited duration, or it may be ongoing, not having a specific end date. Study results should be released as action items as they are identified. Typical actions a Hazop Study might recommend include:

• A review of existing protection system designs by a specialist
• Adding or modifying alarms that warn of deviations
• Adding or modifying relief systems
• Adding or modifying ventilation systems
• Increasing sampling and testing frequency
• Implementation of additional engineering controls

The Role of Labeling in Hazop

Process system components such as mixers, vats, piping, valves, sample points, instruments, and vessels must be identified and labeled in accordance with the P&IDs. Being able to correctly and reliably locate the component identified on the P&IDs is important both for an effective Hazop Study, as well as for operational safety. Opening a wrong valve, or starting to cut a wrong pipe, have often been the causes of serious accidents.

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