RR1190: Factors Affecting the Severity of Vapour Cloud Explosions - Flame Propagation from Hinging Enclosures
The UK Buncefield incident in 2005 was a severe Vapour Cloud Explosion (VCE) causing widespread destruction. The ignition source was likely to have been an arc from switch gear within an electrical control box located in a fire pumphouse submerged in the vapour cloud. The pumphouse was mainly constructed from a steel frame, clad with lightweight steel panels.
The purpose of this experimental research was to understand the effects on explosion severity caused by the explosion propagating from the enclosure; and then from the building into the cloud within which it was submerged.
Results using n-propane (C3H8) as a fuel showed that the explosion propagation process from an enclosure with a hinging door, resulted in very high flame speed acceleration as the expanding gas flowed out of the door as it opened. However, the high flame speeds reduced quickly as the flame moved away from the opening. Results also showed that lightweight steel panels (such as those used in construction of the pump house) can act as turbulence inducing elements, as they are displaced by the burning/expanding cloud. This results in a significant increase in explosion severity, compared to an explosion in an enclosure with an equivalent vent area.
This information is of great importance as buildings of a similar construction to the Buncefield pumphouse are commonly used to enclose processes on high hazard sites. These effects may become increasingly important with more reactive fuels, such as hydrogen.
This report and the work it describes were funded by the Health and Safety Executive. Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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