A Hazard and Operability (HAZOP) Study is a systematic and structured evaluation of an existing or proposed operation. Its primary objective is to identify and evaluate potential hazards during both the design and operational stages of a process. This study is conducted by a group of engineers with diverse expertise. The team conducts a comprehensive examination of individual segments of a plant, system, or operation, commonly referred to as nodes.

They evaluate the likelihood of any deviations from the intended operation and assess their potential consequences in light of any existing safeguards. The assessment of the impact of identified hazards on safety, assets, and the environment is conducted. The HAZOP methodology is a brainstorming technique that is driven by the use of guidewords. The team members make contributions based on their combined experience and knowledge gained from previous projects.

The HAZOP study procedure documents the hazards that have been identified, refraining from suggesting any solutions unless a clear solution presents itself. Potential resolutions could comprise supplementary measures or functional protocols as deemed essential. The study record functions as a tool for identifying the Health, Safety, and Environment (HSE) concerns that require resolution throughout the project.

The objectives of the HAZOP study are:

These steps will lead to a better design/ operation of the facility to mitigate the potential hazards identified. Following are the documents required:

The HAZOP study proceeds systematically by examining each node of the plant in succession. The Facilitator makes the selection of the node sizes and the route through the plant before the study.The node ought to be explicated in terms of:

Guidewords refer to uncomplicated terms or expressions utilized to specify or measure the purpose and related parameters, with the aim of proposing deviations.

Typical parameters/elements considered for HAZOP Study are as follows

Deviation refers to the instances where the process design intent is not followed.  The combination of parameters and guidewords in sequence are identified all the deviations (no flow, more temperature etc.). It is possible that there exists a noteworthy degree of overlap among the deviations under consideration, such as the possibility that the absence of flow could produce an effect equivalent to that of increased pressure.

The team will engage in a collaborative process of ideation to identify all plausible factors contributing to the observed deviation. All potential causes should be identified and discussed, as the consequences and actions may be different. Causes are always local or within the node only. If possible, it has been consolidated and limited to the node under discussion.

There exist three primary classifications of causes, ranked in descending order of likelihood:

It may be noted that “cause” in worksheet is explicitly worded including one tag. This implies/ includes other corresponding tags for parallel equipment.

The potential consequences for each cause are discussed and assessed within the limits of the information available and the expertise of the team. There may be several consequences involving escalation to other pieces of equipment. All important consequences anywhere in the facility, resulting from the cause are listed out. Worst-case consequences are described assuming that no safeguards are in place or working.

“Safeguards” are the Controls that prevent the cause from occurring, and/ or alert the Operator when deviations occur, and/ or mitigate the consequences of the cause occuring. They include, for example:

It is further noted that, positive isolation procedure is followed while handling over any facility for maintenance work such as control valve maintenance, which requires breaking the flange, etc. Once the key safeguards are listed, the team then evaluates the listed Safeguards based on adequacy to eliminate or maintain the potential risks within tolerable limits.

During the HAZOP study session, the study team engaged in a systematic brainstorming process to evaluate the process under review in the scheduled meeting. This was accomplished through the use of a set of Guidewords, which were employed to structure the review. The study team is composed of individuals representing a variety of departments/specialties.

The following procedure is adopted during the HAZOP Study workshop:

The recommendations (action items) identified during the HAZOP Study are included in the HAZOP Report and later tracked to closure using the worksheet. Each recommendation suggested by the HAZOP team was proposed to reduce the risk of a hazard scenario to an acceptable level of risk (as determined by the HAZOP team). Should a recommendation not be implemented, the HAZOP Action sheet must identify an alternate action to achieve the required risk reduction or document the basis for reassessing the risks and determining that the risk without the recommendation is within acceptable levels.

It should be noted that the responses to the HAZOP study recommendations should provide a clear audit trail including the reasons for taking or not taking action.