The holes in James Reason’s Swiss cheese model can be represented through escalation factors in the bowtie method.
Although, theoretically, that may be true. Practically, it might be of more added value if they are considered to be activities that are part of your safety management system. This blog will show you how to make the distinction between escalation factors and activities, and also on when it might be more useful to change an escalation factor to an activity.
Escalation factors and how to use them: sparingly
An escalation factor is a condition that reduces the effectiveness of a barrier. An escalation factor cannot directly cause an event but increases the chance that a certain threat or top event will, by taking out a barrier. Escalation factors can be things that are not part of usual business such as abnormally strong winds, the loss of power or operating outside the design envelope. For example, cost & time cutting on maintenance management can eventually lead to the deterioration of the integrity of many hardware barriers within a system. Escalation factor modeling enables organizations to gain insights into the specific conditions under which barriers are degraded or defeated. In other words, it adds a failure analysis to a barrier.
Theoretically speaking these are the holes in Reason’s Swiss cheese model. However, if we are to map all the holes onto a bowtie diagram as escalation factors, it could quickly lead to clutter. This reduces its readability and practical use. The strength of the bowtie method lies in its visual communicative value. Bowtie diagrams large enough to wallpaper a room will miss this purpose. Therefore, practically speaking, we recommend making use of activities. With proper use of activities, the number of actual escalation factors on the diagram will remain low, and the diagram will remain readable.
Activities and how to use them: generously
Activities refer to the doings which are part of the management system and are executed to ensure that the barriers will function as intended when challenged. Activities must be performed for the barrier to stay healthy and the responsible personnel will be linked for said activities. Examples of activities are: Maintenance and/or inspection of equipment. By linking the relevant parts of our management system onto the barriers, we create insight into how we as a company are supporting our barriers – what do we do to ensure their adequate operation and availability.
Transforming escalation factors into activities
To demonstrate the practicality of transforming escalation factors into activities, consider this next example: Most organizations have a safety management system that implements and maintains barriers. If an activity such as maintenance is important to keep a barrier working, omitting that activity will reduce the integrity of the barrier. We could identify an escalation factor such as “maintenance not done” to communicate this, and the escalation factor barrier would be to do the maintenance (see Figure 1, left-hand side).
Figure 1: Activities instead of escalation factors
It is possible to do this, but only to highlight a real problem in your organization. It should be avoided if it is only a possible problem. For instance, if the maintenance manager says that he is not doing the required maintenance because he does not have enough personnel available, it is possible to highlight this problem using an escalation factor. However, if he is confident the maintenance is being done, still putting an escalation factor in will lead to an explosion of similar escalation factors (because you are not focusing on the critical issues, but on every possible issue).
It is important to understand that no real information is lost by doing this. Both communicate the need to do maintenance. One just highlights that need as a problem.
To conclude, although theoretically, it makes sense that the holes in the swiss cheese are represented as escalation factors, practically speaking, it is much more useful to divide the holes of the Swiss cheese between escalation factors, and activities.
How would you go about this?
For more information or if you’d like to exchange thoughts on this topic, feel free to leave a comment below.