Marine applications need heat transfer fluids that can perform at the required temperatures for prolonged periods. All heat transfer oils tend to degrade over time, and the rate of degradation increases when the operational temperature exceeds that of the oil’s recommended use.
At high temperatures, the bonds between hydrocarbon chains start to break. The result is the production of carbon in a process called fouling. As the carbon concentration in the fluid increases, it deposits as a sludge into the pipes, reducing the efficiency of the heat transfer system. If action is not taken, this sludge can obstruct the pipes and lead to serious safety hazards.
It’s important to choose a thermal fluid with a high thermal stability, which can better resist high temperatures and occasional temperature peaks. This can slow down degradation, preventing the formation of sludge.
Degradation also contributes in reducing the fluid’s flash point, which is the temperature at which the vapours produced by a fluid will ignite in the presence of an ignition source. When an HTF degrades, its molecules decompose to low boiling fractions known as light ends, resulting in reduced flash and fire points.
As a consequence, it’s important to choose a heat transfer fluid with a high flash point, as in hard-to-monitor applications such as large vessels, it’s essential to minimise the risk of fire.