HAZOP

Petroleum Plant
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HAZOP

1. What is HAZOP?

A Hazard and Operability (HAZOP) is a systematic risk assessment method that analyzes a process or operation to identify and evaluate problems that may represent risks to human or equipment by using a series of guidewords.
In practical, HAZOP team questions every element of a (new or existing) process with suitable guide-words to discover what can deviations from design intention can occur and what their causes and consequences may be.

2. HAZOP purpose?

A complex process always hides potential risks to human and operation. The purpose of HAZOP is to review the process design to pick up design and engineering issues that may not have been found.

3. When to perform HAZOP?

With a new process: The team should conduct a HAZOP study as early in the design phase as possible to ensure the design quality. After the design phase has been completed, the team should conduct the HAZOP again as a final check for the design.

With the existing process: The team can conduct HAZOP to identify the risk and corrective action needed to eliminate or reduce the possibility of the risk occurs.

4. HAZOP Team and Teamwork

HAZOP is carried out by a cross-functional team during a set of meetings. The success of the HAZOP study depends on the alertness and concentration of the team members.
The team leader is an independent trained HAZOP who is responsible for the overall quality of the review.

5. HAZOP Step and Step

5.1. Break down the process

The first step in HAZOP is breaking down the overall process into a number of simpler elements that are called as nodes.
The number of the nodes sometimes needs a balance between “too many” and “too few.” If a complicated process is broken down into too few nodes, each node may be too complex and hard to cover all the hazard at one. If too many nodes, each node may be too simple for the team meeting.
Node: nodes could be the item in the Process Flow Diagram (PFD) or the Piping and Instrument Diagram (P&IDs).

5.2 Define the process deviation

Parameter
Before defining the deviation, the team lists all related process parameters for an individual node. The parameters are physical or chemical characteristic of the machine, equipment that is used in the node.
Example:
Air flow rate
Temperature
Atmosphere.
Concentration

Guide Word
The guide words are adjectives or adverbs used with the parameters to direct the deviation. Below is a list of guide-words, that include but not limited to:
Guide Word Meaning
NO None of the designed parameter
MORE Quantitative increase of the parameter
LESS Quantitative decrease of the parameter
AS WELL AS Additional activities.
PART OF Part of the designed intent is achieved
REVERSE Opposite of the design intention
OTHER THAN Another activity takes place.
EARLY Earlier than a design intention
LATE Later than a design intention
BEFORE Relating to the sequence in the process
AFTER Relating to the sequence in the process
FASTER Happen but in a less time
SLOWER Happen but in a longer time

Deviation
The team determines the deviation by combine guide-words and process parameters. Not all combinations exist in an actual process. Process deviation is a combination of process parameters and guide-words.
Combine a guide-word with a parameter to identify the deviations of the process parameter form the design intent.
Example: Process parameter is Air Flow Rate, Guide word is Low -> Deviation (potential) is Low Air Flow Rate.
Combination Example, see the matrix for the combination deviation:
Note that not all combination has meaning, some combination deviation that does not exist or never happens, the team need to eliminate these deviations.

5.3 Find the deviation cause

Possible Cause
“Cause” is always the hard part of HAZOP. Finding the cause of a potential failure mode requires experience and a deep understanding of the process being analyzed. This is also where the team knowledge is needed the most. That is why the previous HAZOP document is re-used to analyze a new process.

5.4 Analyze deviation consequence

Possible Consequence
The consequence of the deviation is defined to determine the severity of the risk if the deviation happens.

5.5 Current control

Current Control
Define the existing control for the potential deviation if any. The control can prevent or detect the deviation if it happens or about to happen.

5.6 Action needed

Action Required
If there are no existing control for the deviation or existing controls is not enough to prevent or detect the deviation. The action is required to reduce the chance of deviation occur or consequence of the deviation.

Responsibility
A person who has the responsibility for the required actions. The team should clarify the name of the person to prevent vague understand about responsibility.

Target Finished Date
The date that the responsible person plans to finish the action.

Actual Finished Date
The date that the responsible person finishes the action.

6. HAZOP Software

A small chemical plant can be broken down into hundreds of nodes, moreover, each node can have more than 10 deviations. Thus, HAZOP study becomes complicated with a standard excel worksheet. You might need features that are not the part of Excel to handle large HAZOP worksheets. That is why ABC comes and helps the users of Excel work with HAZOP faster and more effective.

7. Conclusion

The HAZOP method was initially developed in the 1960s to analyze chemical process systems and have been obtaining great success in obtaining safer, more efficient and more reliable plants. Later, it has been extended to other types of systems such as nuclear power plant operation and software development.

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