RR1210: Investigation of Mist Explosion Hazards (MIST2) - Vertical ignition test report
Many types of industrial equipment can potentially produce an explosive oil mist if a fault develops. This includes almost all equipment where oil is under pressure, such as hydraulic systems, pressurised lubrication, oil-based heat transfer systems among others. These are in widespread use and appear in areas such as service plant rooms and production facilities in many industries. As part of controlling the risk of oil mist explosions, 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 an oil mist can be ignited and continue to burn is limited.
A previous programme of work, called MISTS, had shown that both the fluid being released, and the leak conditions could have a marked effect on whether a flammable mist was produced. Although MISTS only studied a limited range of leak scenarios, it was found that some fluids produced no ignitable mist across a wide range of release pressure, but that other fluids were readily ignited, even during low pressure leaks. This was particularly seen with kerosene, the fluid tested in MISTS that was most likely to create ignitable mist.
This report presents experimental work carried out by HSE researchers working at HSE’s Buxton laboratory. This work was one work package in a larger programme about oil mist risks called MISTS2. The overall MISTS2 project is summarised in a separate report (RR1207).
This report will be of interest to anyone who is planning further mist ignition testing or has a specific need to better understand the underlying test data when they carry out risk assessment for mists.
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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