Hazard and Operability Study (HAZOP) is a systematic method to identify potential hazards in complex processes, particularly in chemical production. The process involves forming a team, identifying system elements, considering variations, and documenting potential hazards to improve safety and operability. HAZOP can be applied to both new and existing systems, helping prevent accidents by evaluating and addressing risks effectively.

1. What Is HAZOP?
HAZOP, or a Hazard and Operability Study, is a systematic way to identify possible
hazards in a work process. In this approach, the process is broken down into steps, and every
variation in work parameters is considered for each step, to see what could go wrong. HAZOP’s
meticulous approach is commonly used with chemical production and piping systems, where
miles of pipes and numerous containers can cause logistical headaches.

2. Image Credit: Graphic Products
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The task of analyzing hazards in a workplace or system can be daunting. However, without
an effective analysis, potential hazards may not be discovered before they result in injuries
and loss. The cost of an accident is often many times greater than the cost of the analysis that
could have stopped it. It’s the old proverb: “An ounce of prevention is worth a pound of
cure.”
There are many ways to assess a process or workplace for hazards, and each approach has
strengths and weaknesses. For example, the worker-focused Job Hazard Analysis (JHA) is
particularly effective for protecting workers, because it considers each task that a worker
must perform.
However, if you need to assess a long and complex system, rather than individual workers’
safety needs, a broader hazard analysis method may be needed. OSHA lists several common
methods of finding the potential hazards in these systems, including:
• What-If Analysis
• Hazard and Operability Studies (HAZOP)
• Failure Mode and Effects Analysis (FMEA)
• Fault Tree Analysis
HAZOP is a common hazard analysis method for complex systems. It can be used to identify
problems even during the early stages of project development, as well as identifying potential
hazards in existing systems.

3. The HAZOP Study ProcessThe HAZOP Study ProcessThe HAZOP Study ProcessThe HAZOP Study Process
A Hazard and Operability Study systematically investigates each element in a process. The
goal is to find potential situations that would cause that element to pose a hazard or limit the
operability of the process as a whole. There are four basic steps to the process:
1. Forming a HAZOP team
2. Identifying the elements of the system
3. Considering possible variations in operating parameters
4. Identifying any hazards or failure points
Once the four steps have been completed, the resulting information can lead to improvements
in the system. The best way to apply the results of a HAZOP study will depend on the nature
of the system.
1. Form a HAZOP Team
To perform a HAZOP, a team of workers is formed, including 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 people with experience,
knowledge, and an understanding of their part of the system. The key requirements are an
understanding of the system, and a willingness to consider all reasonable variations at each
point in the system.
2. Identify Each Element and its Parameters
The HAZOP team will then create a plan for the complete work process, identifying the
individual steps or elements. This 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. For each element, the team will identify the planned operating parameters of the
system at that point: flow rate, pressure, temperature, vibration, and so on.
3. Consider the Effects of Variation
For each parameter, the team considers the effects of deviation from normal. For example,
“What would happen if the pressure at this valve was too high? What if the pressure was
unexpectedly low? Would the rate of change in pressure (delta-p) pose its own problems
here?” Don’t forget to consider the ways that each element interacts with others over time;
for example, “What would happen if the valve was opened too early, or too late?”
4. Identify Hazards and Failure Points
Where the result of a variation would be danger to workers or to the production process,
you’ve found a potential problem. Document this concern, and estimate the impact of failure
at that point. Then, determine the likelihood of that failure; is there a realistic cause for the
harmful variation? Evaluate the existing safeguards and protection systems, and evaluate their
ability to handle the deviations that you’ve considered.
HAZOP can be used when planning a new process, or for improving an existing process.

4. Results of a HAZOP StudyResults of a HAZOP StudyResults of a HAZOP StudyResults of a HAZOP Study
Because HAZOP is a mental exercise, it can be implemented as part of the planning of a new
work process, even before a facility is built. Existing facilities and processes can also be
assessed with HAZOP.
Where a HAZOP study is performed in the planning stage of a new process, completing the
study means that all potential causes of failure will be identified. The HAZOP team will write
an assessment weighing the potential deviations, their consequences, their causes, and the
protection requirements. From this point, changes to the plan can be made to prevent
problems from arising, or to mitigate their effects.
In existing facilities, a HAZOP may be ongoing, working to improve the process without any
specific end date. Instead of a single, large assessment, the study’s results will be released as
a stream of action items, as each problem is identified and a solution is created.
In both cases, when a hazardous condition is identified, recommendations may be made for
process or system modifications, or further study by a specialist may be required. A HAZOP
study might recommend these typical actions:
• 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
Each of these steps might be recommended as part of the overall Hierarchy of Controls. This
way of addressing hazards is intended to prioritize the most effective steps.
The Role of Labeling in HAZOPThe Role of Labeling in HAZOPThe Role of Labeling in HAZOPThe Role of Labeling in HAZOP
In the complex processes where the HAZOP approach is most effective, the size and intricacy
of the system can be overwhelming. Analysis and maintenance, as well as ordinary, day-to-
day operation, require workers to navigate these systems. To allow effective work, system
components such as pipes, valves, instruments, and vessels must be identified and labeled.
Often, safely maintaining a system will require monitoring. When measurements must be
taken at the same point in a system, it makes sense to clearly mark that point with an
indication of the test to be performed. Bad data will ruin the usefulness of any monitoring
system.
Opening the wrong valve, or cutting into the wrong pipe, have often been the causes of
serious accidents. That’s why the ANSI/ASME A13.1 standard is so widely used for labeling
pipe systems; it requires clear, bold labels in a highly-visible placement scheme.
Where hazardous chemicals are used as part of the process, OSHA’s HazCom labeling rules
apply. The rules are meant to give workers the information they need to be safe, and effective
labeling serves that goal.

5. Labeling and signage are critically important in these cases. The DuraLabel line of printers
from Graphic Products can help your facility create the signs and labels that you need.

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