Call us now

00 44 (0) 1298 815862


What can cause a fire in your thermal fluid system?

Thermal fluid systems include fuel, air and an ignition source - so the risk of fire is always present. Fire safety in thermal fluid systems can be enhanced through a number of measurements, including flash point, fire point and auto-ignition temperature.  

  • Flash point - the temperature at which sufficient vapour is generated for the fluid to flash when exposed to an ignition source.
  • Fire point - the point at which a fluid generates sufficient vapour to support continued combustion.
  • Auto-ignition temperature - the temperature at which a fluid will ignite without any external source of ignition.

Relatively few fires originate in thermal fluid systems, but they can be very serious and the majority of those that do occur are insulation fires, or are caused by cracked heater tubes or leakage.


Insulation fires occur when thermal fluid leakage from valves, gaskets, welds or instrument ports infiltrates porous insulation. The insulation’s open structure allows the fluid to spread which can lead to spontaneous ignition if the fluid is suddenly exposed to air if, for example, the protective covering is punctured. When the leak is within the insulation, it may not be discovered immediately.

Cracked heater tubes

Cracks are formed by excessive thermal cycling or hot spots that develop from internal fouling or flame impingement. Leaking fluid will burn off immediately while the heater is operating, however, when the system is not in operation, fluid will continue to leak into the combustion chamber. In the most serious cases the fluid can form a large pool inside the heater during prolonged shutdown and when the heater is restarted the entire pool will ignite and destroy the heater.

Large volume leaks

Large volume leakage from the thermal fluid system can be a direct cause of fire if the liquid contacts an ignition source. Most major leaks result from component failure, including expansion joints, flexible hose and rotary unions. If the ignition source is part of the failing component or is the source of a leak, a significant fire may occur.

If you’d like to find out more about the causes of fire in thermal fluid systems and how to prevent them, get in touch on 01298 815862 or visit our contact page