By Krishni Arumugam and Enrico Lammers

There are many types of risk analysis techniques such as: HAZOP, LOPA, SWIFT and many more. Academic articles such as Hazard Evaluation Techniques, on selecting appropriate process safety risk assessment methods, are interesting reading for a process safety engineer. For convenience, let's abbreviate this long term to PHA(Process Hazard Analysis). (Process Hazard Evaluation (PHE) is also a commonly used abbreviation, but we choose the former here...)

As we have noted many times before, this is one of the biggest challenges within the process safety profession: selecting the right PHA method for assessing risks and then applying that method correctly. Because even if you've selected the best technique, that doesn't give you a guarantee that all risks are correctly assessed. More is needed for that.

To measure is to know

As with any research, a literature search provides an overwhelming source of information on PHA techniques. Many of the references compare PHA studies in a particular application. But it is not always clear how to apply them. And as useful as these comparisons are, it is impractical to say that every possible technique is listed.

A subjective assessment of the advantages and disadvantages can be made, especially in the case of qualitative methods such as a HAZOP (HAZard & OPerability) study (connoisseurs will recognize the deliberate contradiction in this sentence). But the real question about the right PHA method has to do with its ability to identify all relevant hazards. To measure is to know! Because you cannot guard against a hazard until you have identified that hazard.

What is the right PHA technique?

In practice, this is the weakest point (one of the holes in the swiss cheese model). Selection of the appropriate PHA technique should be a formal step prior to any PHA study (but, in our opinion, almost never happens...).

Once the appropriate technique has been selected, the value of the outcome depends not only on the application, but also on the available resources (such as the expertise and experience of the team and the quality of the documentation). It is pointless to run a HAZOP without an experienced chairman (facilitator) or without as-built documentation.

The poorer the quality of the documentation, the more is required of the team's expertise and experience. And vice versa: if the documentation is and span and reflects the situation exactly as it is present in the field, then you can also get good results with less experience in the team. The outcome of a study with less common techniques can probably be more valuable if the expertise of the team is used optimally compared to the correct PHA method with less good resources.

The comparison in the literature attempts to match techniques at different types of facilities, taking into account not only the probability on available resources to perform the assessment, but also the magnitude of the hazards present.

With the exception of the widely used HAZOP technique, there are few formal documents available on the application of such techniques. The most common method to learn how to apply a technique is to follow one of the many training courses or to work with a more experienced colleague.

The lack of formal guidelines for a series of techniques that need to be very flexible can be explained. Their application to a wide range of circumstances must remain possible, without discouraging free thinking. The available guidelines seem to focus on providing a description of the technique rather than setting quality standards for the application of the technique.

And here lies the real challenge ...

To gain more uniformity in the outcome of PHA studies, we have developed a number of standardized scenarios as a test. Take for example the scenario: high level leads to overfilling of a tank. This is a scenario that comes up (or should come up) in every PHA study where a liquid is stored in a tank. Depending on the properties of the spill, according to a standardized scenario, you can then determine how to protect against this scenario. This significantly increases the efficiency and effectiveness of a PHA study and with this we want to continuously (further) increase the value of the outcomes of a PHA study.

What are you doing to optimize the outcome of your PHA study?

What are the challenges your PHA team faces?

Do you have an opinion on this? If so, give the editors a tip and we can write a blog about it or respond to it and we can all learn something from it.