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SUMMARY

This report reviews theoretical and experimental research into confined vented explosions and it is only relevant to the problem of essentially empty volumes.

It is concluded that the majority of "classical" methods for predicting peak vented explosion overpressures are inappropriate to the general offshore explosion problem. There are two reasons for this. First, they do not usually allow for the turbulence created by the fuel leak into the volume. Second, they are based upon results of relatively small-scale experiments in which the explosion processes may be very different from those at a more realistic scale. In the absence of a more fully developed theoretical understanding of the detailed mechanism involved, there can be little confidence in the accuracy of models which have been based upon, or validated against, small-scale experimental data when applied to the prediction of explosion overpressures at a much larger scale.

There is a need for further work to identify the effects of turbulence and the scale dependence of the combustion processes which give rise to the different behaviour of full-scale explosions when compared to small-scale experimental data.

Attention is drawn to the significance of the external explosion of vented gases, studied originally in the simpler environment of the empty vented module but also applicable to the more complex case of "obstacle" filled modules.

It is concluded that whilst studies of explosion behaviour in confined but essentially empty vented volumes provide part of the necessary understanding to build up a better picture of explosion behaviour in general, it is unlikely that methodologies developed for empty enclosures will be of much direct value in assessing explosion hazards offshore. The situation when significant obstacles are present is reviewed separately in Work Package BL3.

The full report is publicly available from the HSE Website at www.hse.gov.uk/research/otipdf/oti92592.pdf.