10 Tips for Getting the Most from a HAZOP Workshop

How to get the most from your HAZOP Workshop

Although extremely valuable in terms of identifying potential hazards associated with a plant’s design and operation, HAZOP studies can be time consuming and resource intensive. We have therefore compiled a list of 10 tips to help HAZOP Workshops run more smoothly and efficiently, thereby ensuring that you get maximum value from your HAZOP.

HAZOP Session1) Limit the number on teams to between 6 and 12 people.
Circumstances may not always allow this, but the most effective HAZOP teams tend to comprise 6-12 people; fewer than six and you may not have the diversity of expertise to get full benefit from the HAZOP Workshop, more than 12 and attendees may not feel that they are bringing any additional value to the exercise.

2) Circulate an Advance Information Pack.
The HAZOP Leader will almost certainly require a set of Piping and Instrumentation Drawings at least a week in advance of the HAZOP Workshop, together with a Process Description of the system being analysed. By circulating this information to all HAZOP participants they will also have the opportunity to familiarise themselves with the system in advance, reducing the amount of time required within the Workshop to review the process and its critical features.

3) Split the system into nodes in advance of the HAZOP Workshop.
You can save a lot of study time by planning the nodes in advance of the HAZOP (possibly in consultation with the Process Engineer). It can also be helpful to put together an initial draft description of the functional intent of each node for review prior to HAZOPing that node. However be prepared to alter the node start and end points if required based on input from the team, particularly for batch or sequence operations.

4) Tailor your list of parameters.
Standard lists of parameters can be found in many HAZOP textbooks. However, not all of them will be relevant to every system and consideration of irrelevant parameters will prolong the HAZOP Workshop with no additional benefit. Equally, there may be other parameters that are not generally applicable but which should be included within certain industry sectors or when analysing particular types of system. Therefore, agree with the HAZOP team at the start of the Workshop which parameters are relevant to the system being analysed.

5) Keep nodes small.
It is tempting to think that by selecting ‘larger’ nodes we can save a lot of time. However, with large nodes there may be several elements involved, each of which has its own range of flow, temperature and pressure characteristics and each of which needs to be tested for deviations. We need to list all causes of each deviation for every element within the node, and for larger nodes this needs to be done carefully to avoid confusion – otherwise the required level of rigour may not be applied. It usually ends up being quicker and easier to avoid these issues by considering smaller nodes and avoiding the temptation of defining larger ones.

6) Consider ALL operating modes.
If you are studying a batch or sequence process then you will need to consider all of the nodes and their modes of operation during each step within the sequence. Under each mode of operation the same physical equipment is studied, but from a different perspective in terms of its design intent. It is of paramount importance that all of these design intents are studied separately. The causes of deviations may be the same for each “mode node” (e.g. valve closes), but the consequences may be less, or more, or completely different depending on the current mode of operation.

7) Use the egg-timer rule.
One of the hardest things for a HAZOP Team Leader can be to decide when to allow a discussion to run on in the hope that it leads to something useful, and when to cut it short. One piece of advice I received (and which I have found to be a good guide) is to allow the conversation to continue for about three minutes – if it doesn’t lead to anything useful after this time then it is unlikely that it will, so consider moving the discussion on.

8) Refer design issues back to the Design Review.
The process design should have been challenged in a Design Review prior to HAZOP. When the Design Review has been inadequate or not done at all it slows down the HAZOP process. HAZOP should not be an opportunity to discuss alternative designs.

9) Keep the same HAZOP Team for the duration of the HAZOP Study.
If a HAZOP continues over several days there may be circumstances where various members are unable to attend and wish to send a substitute. Provided that the substitute has the required expertise and is sufficiently familiar with the system then this should not cause any major issues so long as substitution is the exception rather than the rule. However, if too many people are substituted then there can be real issues in terms of consistency and completeness. The HAZOP Leader should therefore discourage substitution and rearrange Workshop sessions where necessary to enable the original team members to attend.

10) Be prepared to stop the HAZOP.
Hopefully it will not come to this but as a last resort a HAZOP Leader should always be prepared to draw the analysis of a node (or even the full HAZOP) to a halt if necessary. Likely reasons for doing this are:

  • Lack of complete or current information; e.g. where a control philosophy has not yet been adequately defined
  • Lack of a necessary expertise on the team; e.g. where the knowledge resides with a sub-contractor

Usually it is possible simply to move on to the next node and to revisit the uncompleted one at the next HAZOP session when the missing information or expertise is available. However, if this is not the case it will be necessary either to arrange an additional session for when the information is available or to record in the HAZOP report that certain nodes have not been analysed, together with the reasons for this.

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