Broken Pipe Hazop

HAZOP – Hazard and Operability Study


The HAZOP method was initially developed in the 1960s to analyze chemical process systems. Later, it has been extended to other types of systems such as nuclear power plant operation and software development.

1. What is HAZOP?

HAZard and OPerability Study (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.

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2. HAZOP Analysis Step by Step

Let’s start with a simple HAZOP template. HAZOP document is a relation structure table with the relationships between its columns.

1 Study Node
The first step in HAZOP is breaking down the overall process into a number of simpler elements that are called nodes. Nodes could be the item in the Process Flow Diagram (PFD) or the Piping and Instrument Diagram (P&IDs).
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 hazards at one. If too many nodes, each node may be too simple for the team meeting.

2 Parameter
Lists all related process parameters for an individual node. The parameters are physical or chemical characteristics of the machine, equipment that is used in the node.

3 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 the following list:

Guide WordMeaning
NONone of the designed parameter
MOREQuantitative increase of the parameter
LESSQuantitative decrease of the parameter
AS WELL ASAdditional activities
PART OFPart of the designed intent is achieved
REVERSEOpposite of the design intention
OTHER THANAnother activity takes place
EARLYEarlier than a design intention
LATELater than a design intention
BEFORERelating to the sequence in the process
AFTERRelating to the sequence in the process
FASTERHappen but in a less time
SLOWERHappen but in a longer time

When conducting the study, the team questions every element of a (new or existing) process with suitable guide-words to discover what can deviate from design intention can occur and what their causes and consequences may be.

4 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: The process parameter is Air Flow Rate, Guide word is Low -> Deviation (potential) is Low Air Flow Rate.

Not all combinations of parameter and guide word have a meaning, some combination deviation that does not exist or never happens, the team needs to eliminate these deviations.

5 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.

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

7 Action Required
If there is 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.

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

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

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

3. When you should use it?

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 is a team effort

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.

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DFMEA stands for Design Failure Mode and Effects Analysis, and PFMEA stands for Process Failure Mode and Effects Analysis. They are both FMEA and use

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