FIRE AND EXPLOSION HAZARDS WITH THERMAL FLUID SYSTEMS

"Incidents relating to thermal fluid systems are unfortunately more common than we might realise,
and can be extremely serious. The fire and explosion hazards with thermal fluid systems have been
re-emphasised by recent incidents. These incidents have a direct bearing on the estimated 4,000 UK
companies that operate thermal fluid systems.
Water or steam can be used as heat transfer fluids, but when high temperatures are needed
organic fluids, which are capable of forming explosive atmospheres, are often used. Although
fire and explosion hazards of low flash point flammable liquids are generally recognised, similar
hazards with high flash point materials, such as thermal fluids, are often missed. These heat transfer
fluids are often handled at temperatures above their flash point.
However, many people are unaware that heat transfer fluids based on mineral oils
degrade over time. This degradation can cause the fluid’s flash point to decrease dramatically, so
that thermal fluids which were not flammable at the operating temperature when they were initially
installed may, over time, become flammable at the operating conditions. Also, high flash point
materials (such as thermal fluids), can form explosive mist atmospheres when handled under
pressure, even at temperatures below the flash point".

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