HAZID and HAZOP studies share a number of key similarities. Both of them are:
- Formal processes to uncover workplace hazards
- Qualitative risk assessment methods
- Carried out by multidisciplinary teams
- Aimed at creating a set of recommendations to mitigate risks and improve safety
But they also have some important differences. HAZID and HAZOP are not interchangeable processes, but each has its own specific purpose and methodology.
In this article, we’ll lay out the basic features of HAZID and HAZOP studies and tease apart the differences between the two.
What Is HAZID?
HAZID stands for Hazard Identification, and it is a structured method for doing just that – identifying hazards.
It is typically conducted in the early stages of a project and focused on identifying potential hazards in a design or process before it is implemented. HAZID studies can also be useful for identifying issues and hazards when planning changes to an existing facility.
Since it tends to be used at the design and planning stage, HAZID studies often rely on 3D models and renders to get a better sense of a facility’s design and the hazards that could arise within it.
HAZID Teams
HAZID studies are conducted by multidisciplinary teams. These teams are often relatively small, consisting of four or five people. Although the exact number and composition of the team will depend on the type of facility being designed and the complexity of the project.
HAZID teams might include:
- A project manager
- Engineers with relevant expertise (depending on the project, this could include chemical engineers, electrical engineers, or other specialists)
- A safety professional, industrial hygienist, or other EHS specialist
- A facilitator to record the minutes of the meetings
HAZID Methodology
HAZID is, broadly, a three-step process.
Step 1. Identify the Hazards
To ensure the HAZID study is thorough but manageable, the facility and its operations are divided into sections.
The HAZID team then considers one section at a time, identifying the potential hazards that could arise from it.
These hazards are each assigned a guideword, which is essentially a hazard category, like “Equipment Malfunction” or “Natural Hazards.” Each of these guidewords will have a set of considerations that the HAZID team will then run through. For instance, if they identify the potential for a “Hazardous Substance” hazard, that guideword might indicate that they should the consider factors like flammability, corrosivity, and toxicity.
For each of these considerations, the team will then identify possible causes for these events what their consequences might be.
Step 2. Assess the Risks
After all the hazards have been identified, the next step is to assess just how much risk they pose.
This involves the creation of risk matrices for each identified hazard. A risk matrix is a simple graph with two axes:
- The likelihood that the adverse outcome will occur
- The severity of the outcome
Plotting each hazard on the graph will determine the level or risk they carry (Low, Medium, or High).
Suppose, for instance, that the team assesses a dry materials container and finds that it is likely to spill some of its contents occasionally, but that each spill is unlikely to cause any slips or injuries. In that case, the combination of high likelihood and low severity would likely result in the issue being marked as a Low Risk.
On the other hand, a rare systems failure that could cause a large explosion might be deemed a Medium Risk. Although it’s unlikely to occur during the facility’s lifetime, the potential catastrophic outcome still makes it a very serious concern.
Step 3. Recommend Safeguards
Once all the hazards have been identified and assessed, the HAZID team then recommend safeguards that should be put in place to eliminate or minimize the risks.
The results of the risk assessments guides the team’s recommendations. The higher the risk, the more safeguards might be needed.
It also helps them categorize each of these recommendations, with priority placed on safeguarding High Risk hazards.
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What Is HAZOP?
HAZOP stands for Hazard and Operability. Right off the bat, that name highlights one of the differences between the two processes. Unlike HAZID, HAZOP studies are not only focused on uncovering hazards, but also inefficiencies in a plant’s operations that could cause delays, shutdowns, and quality issues.
These studies are carried out after the planning and design stages, once the facility is running and operations are in full swing.
HAZOP is used to evaluate complex and often high-risk systems, like chemical manufacturing plants or nuclear facilities. The goal is to closely evaluate the operations of the system to identify actual or possible deviations from the intended process.
HAZOP Teams
A HAZOP team has at least four members, but can be larger depending on the complexity of the system under review.
The team should include:
- A facilitator or team leader
- A scribe or secretary
- A process engineer
- An electrical, controls, and instrumentations engineer
- A process safety expert
- A senior member of the operations team
Depending on the type of system under review, other specialists might also be required. For example, a chemical engineer might be recruited to take part in a HAZOP study of a chemical production plant.
If the HAZOP team is small, some of the members will need to fulfill multiple roles. The representative for the operations team might act as the scribe, for instance. Or the process engineer may also have the right background to also act as the process safety expert.
For large-scale HAZOP studies, there might also be multiple people with the same areas of expertise (e.g. a team with two process engineers rather than one).
HAZOP Methodology
A HAZOP study can be outlined in four key steps.
Step 1. Identify the Nodes
First things first, the HAZOP team will break down the complex system into manageable parts.
This will involve looking at the processes and dividing them into smaller nodes that can be considered closely and carefully. The nodes can be components of the facility (e.g. a segment of a pipeline) or individual operational processes.
Step 2. Outline the Parameters for Each Node
Once the nodes have been identified and listed, the team will then define the process parameters for each node. These parameters are descriptions of how each process needs to function in order to be safe and efficient. They might include, for example, the acceptable temperature range for a machine component or how much voltage should be coursing through an electrical system.
Step 3. Apply Deviation Guidewords
Once the parameters are set, the HAZOP team will then identify potential deviations from them. This is done by applying a set of standard guidewords to each process, such as:
- More
- Less
- Higher
- Lower
- No
- Reverse
- Other than
For instance, for a process that involves pressure, the team will apply the guidewords “Higher” and “Lower” to represent the process operating at pressure levels that deviate from the safe parameters.
Then, for each of these deviations, the team will outline:
- Possible causes of each deviation (what events could lead to the pressure being too high or too low?)
- The consequences of each deviation (what is expected to happen if the safe pressure is exceeded? What about when the pressure falls under the safe operating range?)
- How to prevent these deviations (including monitoring, detection, and control measures)
Step 4. Evaluate Safeguards and Recommend Actions
After all of this has been laid out, the HAZOP team will then look at each possible deviation and note the current safeguards that are in place.
If any of these safeguards are not sufficient to prevent these deviations and their undesirable outcomes, the team will recommend a set of actions to remedy the issue.
These actions could be improvements on existing safeguards (such as regular inspections, maintenance, or upgrades) or the implementation of new control measures.
HAZID vs. HAZOP: What’s the Real Difference?
As you can see, there are more similarities than differences when it comes to HAZID and HAZOP. But the differences are there nonetheless.
To briefly summarize them, the main differences between HAZID and HAZOP studies are:
- When the studies are conducted
- HAZID studies are typically done at the planning and design stages of a process
- HAZOP studies are typically done when the facility is operational and the system is running
- The aims of the studies
- HAZID studies aim to identify safety hazards
- HAZOP studies aim to identify both safety hazards and operational inefficiencies
- What the studies look for
- HAZID studies look for hazardous situations or events
- HAZOP studies define parameters and look for deviations from those parameters
- The guidewords used
- HAZID studies employ a wide set of guidewords to identify a variety of hazards
- HAZOP studies focus on a more restricted set of guidewords to identify process deviations
- The proposed actions
- HAZID notes the safeguards that should be put in place to control potential hazards
- HAZOP takes existing safeguards into consideration and only recommends actions if those safeguards are insufficient
Both are essential. Both are complementary and can be used to ensure the safety and integrity of high-risk facilities. Despite their differences, they fundamentally serve the same purpose: guiding teams of experts through a complex process to ensure that no hazards are overlooked.
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