Critical Review of Recent Vapor Cloud Explosion Incidents and the Newly Proposed "Episodic Nature" Theory

A recent report by the UK's Health and Safety Executive postulated that severe explosions can propagate at subsonic speeds but generating overpressures of several bar in open areas and this "new" type of explosion is episodic in nature. The HSE paper based their findings on a specific interpretation of historical data and "empirical evidence" from previous incidents and selected experimental data. They indicate that their results should guide plant design and risk assessment. The study completely discounts certain key experimental evidence determined in recent events studies as well as key findings from incident investigations in proposing a hypothetical explosion mechanism over those that are known to occur and are well understood. This has the potential to significantly misdirect efforts to manage such events.

This paper will review a number of incidents and demonstrate that each of these incidents can indeed be explained by fast deflagrations or transition to detonations, in complete contradiction to the HSE findings. These will include findings from Buncefield, Jaipur, Capeco and the Skikda Algeria explosion. The results found at the incident sties will be directly compared against results from DDT work and the resulting damage. In addition, new experimental results will also be presented that further support the idea that explosions can transition more easily than expected when the "width" of the region plays a role in impeding the side venting of the deflagration event.