RR1206: Fire safety: hydraulic systems used in underground work
Fire is a significant hazard in underground workings because heat, smoke and harmful gases produced by a fire are confined in the same enclosed areas occupied by people.
During the 20th century, most of the mining in Great Britain was carried out for coal extraction. Handling a combustible product and managing the risk from methane gas trapped in the coal-bearing seams led to a very tightly controlled safety regime, particularly for fire safety. This often required the use of procedures, equipment and materials that were unique to coal mining, even when equipment performing similar tasks was available from other industries.
One area where this was particularly noticeable was in the fluids used in hydraulic machinery. Most hydraulic systems in use above-ground use mineral oil-based hydraulic fluids, which are combustible and can be ignited relatively easily. Hydraulic systems used in coal mines were specifically built to use fluids that were an emulsion containing a high proportion of water to reduce their flammability (ie HFA, HFB, and HFC fluids). This does result in increased costs however, due to specialist components, higher maintenance and shortened working life for the fluids and the machinery.
Today, coal forms a minute fraction of mining in Great Britain and most mines now have a very different risk profile. As a result, specialist underground equipment has been based on standard hydraulic system designs that use either mineral or HFDU hydraulic fluids. HFDU fluids are based on fatty acid esters and were developed to provide a more fire-resistant alternative to mineral oil following a number of serious underground incidents.
Findings from this report will be of interest to the users and managers of hydraulic systems underground.
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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