Explosion suppression with water curtains between congested regions

Abstract

Vapour cloud explosions (VCEs) are rare events but can lead to severe consequences in terms of harm to people and damage to onshore and offshore facilities. Research conducted in the latter part of the 20th century demonstrated the key role of congestion, such as process pipework, within the flammable cloud in accelerating the flame to high speeds. In recent years it has also become accepted that at least some major VCEs have involved flame acceleration to the point where deflagration to detonation transition (DDT) occurred (Chamberlain et al., 2019). Limiting the size of congested regions can potentially reduce the chance of DDT, however in addition the regions need to be adequately separated to avoid a fast flame from one region entering a second. Previous research into explosion safety gaps at large scale has shown that the introduction of gaps between regions can significantly reduce the magnitude of an explosion (Skjold, 2016).

However, on facilities where space is at a premium, the provision of sufficient gaps may be impossible or incur high costs. The DOWSES (Development Of Water Spray Explosion Suppression) experimental research programme studied the effect of water curtains installed in the gap between congested regions. To establish the benefit provided by the water curtains, baseline explosion experiments without water sprays were performed (with either methane- or propane-air mixtures), one of which resulted in DDT in the second congested region (Allason et al., 2019), one giving a high-pressure deflagration and one with low interaction between the congested regions.

This paper extends the reporting of results to include the experiments with water spray mitigation, not available at the time of the last publication. The experiments involved variation in water spray configuration, the type of congested region and the spacing between the congested regions. In addition, an experiment was conducted with a particulate added to the water. Detailed results from the experiments are presented: in every instance where water was introduced into the vapour cloud, the baseline explosion was significantly mitigated. In the configuration where DDT had occurred in the baseline experiment, the water sprays prevented DDT.