Hazard and Operability (HAZOP)

What is Hazard and Operability (HAZOP)?

Hazard and Operability Study also known as HAZOP is a structured and systematic method used to identify potential hazards and operability problems in a process or system. It is normally carried out by a competent and dedicated team. It was one of the method for Process Hazard Analysis (PHA).

HAZOP normally studies and identifies any potential deviations from the design intend, examines their possible causes and assessing the consequences. HAZOP methodology uses guide words as way to systematically assessing the process or system. These guide words are combination of the deviations (No, Less, More, As Well As, Part Of, Reverse, Other Than & etc.) and the parameters (Flow, Tempreature, Pressure, Level & etc.).

As per CCPS definition, a HAZOP is a systematic qualitative technique to identify process hazards and potential operating problems using a series of guide words to study process deviations. It was used to question every part of a process to discover what deviations from the intention of the design can occur and what their causes and consequences may be. This is done systematically by applying suitable guidewords. This is a systematic detailed review technique, for both batch and continuous plants, which can be applied to new or existing processes to identify hazards.

Why Do We Need HAZOP?

We need to perform HAZOP as part of the Process Hazard Analysis (PHA) and risk assessment requirements. 

When to Perform HAZOP?

We need to perform HAZOP to examine the deviations from the design requirements and intents.

How to Perform HAZOP?

HAZOP can be performed by the following steps:

1. Define the Scope & Objectives – Establish the boundaries of the study, including the system or process to be analyzed.
2. Form the HAZOP Team – Assemble a multidisciplinary team of experts, including engineers, operators, and safety professionals.
3. Break Down the System into Nodes – Divide the process into manageable sections (nodes) for detailed analysis.
4. Identify Process Parameters – Examine key variables such as temperature, pressure, flow rate, and chemical composition.
5. Apply Guide Words – Use predefined keywords like “More,” “Less,” “Reverse,” or “None” to explore potential deviations.
6. Analyze Causes & Consequences – Determine the root causes of deviations and assess their impact on safety and operations.
7. Evaluate Safeguards – Identify existing control measures and determine if additional safety mechanisms are needed.
8. Document Findings & Recommendations – Record observations and propose corrective actions to mitigate risks.
9. Review & Implement Changes – Ensure that recommended improvements are applied and periodically reassessed.

Main reference for HAZOP:

1. IEC 61882 Hazard aand Operability Studies.
2. PSM Egypt HAZOP Guideline

Process Hazard Analysis

Process Safety Requirement - Process Hazard Analysis

The process hazard analysis is a thorough, orderly, systematic approach for identifying, evaluating, and controlling the hazards of processes involving highly hazardous chemicals. The employer must perform an initial process hazard analysis (hazard evaluation) on all processes covered by this standard. The process hazard analysis methodology selected must be appropriate to the complexity of the process and must identify, evaluate, and control the hazards involved in the process.

First, employers must determine and document the priority order for conducting process hazard analyses based on a rationale that includes such considerations as the extent of the process hazards, the number of potentially affected employees, the age of the process, and the operating history of the process. All initial process hazard analyses should be conducted as soon as possible, but at a minimum, the employer must complete no fewer than 25 percent by May 26, 1994; 50 percent by May 26, 1995; 75 percent by May 26, 1996; and all initial process hazard analyses by May 26, 1997. Where there is only one process in a workplace, the analysis must be completed by May 26, 1994.

Process hazard analyses completed after May 26, 1987, that meet the requirements of the PSM standard are acceptable as initial process hazard analyses. All process hazard analyses must be updated and revalidated, based on their completion date, at least every five years.

The employer must use one or more of the following methods, as appropriate, to determine and evaluate the hazards of the process being analysed:

• What-if, Checklist,
• What-if/checklist,
• Hazard and operability study (HAZOP),
• Failure mode and effects analysis (FMEA),
• Fault tree analysis, or
• An appropriate equivalent methodology.

A discussion of these methods of analysis is contained in the companion publication, OSHA 3133, Process Safety Management Guidelines for Compliance. Whichever method(s) are used, the process hazard analysis must address the following:

• The hazards of the process;
• The identification of any previous incident that had a potential for catastrophic consequences in the workplace;
• Engineering and administrative controls applicable to the hazards and their interrelationships, such as appropriate application of detection methodologies to provide early warning of releases. Acceptable detection methods might include process monitoring and control instrumentation with alarms, and detection hardware such as hydrocarbon sensors;
• Consequences of failure of engineering and administrative controls;
• Facility siting;
• Human factors; and
• A qualitative evaluation of a range of the possible safety and health effects on employees in the workplace if there is a failure of controls.

OSHA believes that the process hazard analysis is best performed by a team with expertise in engineering and process operations, and that the team should include at least one employee who has experience with and knowledge of the process being evaluated. Also, one member of the team must be knowledgeable in the specific analysis methods being used.

The employer must establish a system to address promptly the team's findings and recommendations; ensure that the recommendations are resolved in a timely manner and that the resolutions are documented; document what actions are to be taken; develop a written schedule of when these actions are to be completed; complete actions as soon as possible; and communicate the actions to operating, maintenance, and other employees whose work assignments are in the process and who may be affected by the recommendations or actions.

At least every five years after the completion of the initial process hazard analysis, the process hazard analysis must be updated and revalidated by a team meeting the standard's requirements to ensure that the hazard analysis is consistent with the current process.

Employers must keep on file and make available to OSHA, on request, process hazard analyses and updates or revalidation for each process covered by PSM, as well as the documented resolution of recommendations, for the life of the process.