(83d) Quantifying the Effectiveness of Explosion Protection Measures

Facility owners and operators are challenged to assess and ascribe efficacious explosion protection measures for industrial processes that handle combustible products. The authors have set out a methodology to guide Industrial Explosion Safety system design by ascribing the residual risk of an unmitigated explosion occurrence when pertinent explosion protection is installed.

This methodology considers the entire process and the elected explosion protection measures as a whole, and facilitates trade-off decisions between viable protection options. This permits a risk based decision process in determining the most appropriate explosion protection solution. Given the complexity of the design challenge, it is inevitable that any such decision support tool can only go so far in guiding the final explosion protection system design. This paper will consider the assumptions implicit in such a tool, and argue that the implicit uncertainties do not detract from the benefit of such an approach.

In industrial practice most design practitioners consider each vessel of the process in isolation, and ascribe explosion protection based on a presumed ignition occurrence within that vessel. Where vessels are interconnected, however, an ignition in one component can lead to flame propagation into a connected vessel that gives rise to an explosion occurrence in that vessel which is more intense than was expected when the explosion protection of this interconnected vessel was ascribed. The paper will show how the risk to these interconnected vessels can be very significant contributors to the overall risk of a failure to mitigate an explosion.

By applying this methodology to a specific application, the paper will demonstrate how a risk based approach leads to a more informed decision basis. For the example application we will quantify the overall residual risk that an elected safety solution fails to mitigate an explosion occurrence, and then extend the analysis to consider this risk in the context of ignition location within the process, and also in the context of failure within a specific plant component of the system.

Industrial practice relies on the knowledge of the design engineer to specify safety measures targeted at the higher risk elements of the process. It inevitably raises the challenging question ? what is the relative risk and consequence of an ignition at location A versus location B? It will be shown that by adopting a deterministic process of ascribing risk based on the duty cycle of each component in a given process it is possible to fully quantify the efficacy of any elected safety alternative, and to use such a quantification to assist in making an informed decision on the provision of efficacious industrial explosion protection measures.