RR1107 - Area classification for oil mists - final report of a Joint Industry Project

Many types of industrial equipment can potentially produce an explosive oil mist if a fault develops. As part of controlling the risk, the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) require risk based 'area classification' in places where oil mists can be produced. However, information on the conditions in which a mist can be ignited and continue to burn is limited. This report summarises the outcome of research done by Cardiff University and HSE researchers in a Joint Industry Project co-funded by 14 industry sponsors and HSE.

The research covered: a literature review which showed that existing information was relatively sparse and sometimes contradictory or inconclusive (RR980); development of a draft scheme to group combustible fluids (RR1108); experimental work which showed that fluids from each group gave significantly different combustion behaviour (RR1109, RR1110); computational fluid dynamics (CFD) modelling (RR1111) which identified that droplet size and concentration can only be predicted with reasonable accuracy for some fluid groups and operating conditions.

An important finding from this research has been that existing models (and industry guidance that uses those models) only cover a subset of the ways oil leaks can break up to form mists and how readily those mists can then be ignited.

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Updated 2021-04-15