possible damage in thermal fluid heater

Normal System Operation

During the normal operation of a thermal oil system, the radiant and convective heat provided by the thermal fluid heater to the heater tubing positioned in the firebox is transferred to the film layer of the fluid through the tube wall. As the fluid is in a turbulent state, its film layer constantly mixes with the bulk of the fluid and swiftly transfers the heat. By means of the high flows provided by the circulating pump, the heat is quickly carried to the user by the fluid, which returns at a lesser temperature to carry more heat.

At normal working temperatures, the temperature of the refractory and structural metal parts of the heater may be equal to that of the flame itself. When the thermal oil system is shut down, it takes some time for the heat in these materials to entirely radiate and exit the stack. As certain heaters are equipped with more refractory parts than others, although the firebox temperature may be the same, it takes more time to radiate the additional stored heat.

If the fluid circulates even after the heater is shut down, it continuously carries these BTUs from the heater and distributes them to the entire system.



Improper Shutdown

On the contrary, if the entire thermal oil system is shut down instantaneously, the heater stops firing and the pump does not circulate the fluid. Consequently, heat stored in the refractory and structural metal parts of the heater is transferred to the firebox.

As the blower is turned off, this heat does not exit the stack immediately, resulting in the experiencing of intense heat by the heater tubing comprising the heat transfer fluid. As the fluid is stagnant, it cannot remove the heat and starts to boil once its skin temperature surpasses the recommended limit. The occurrence of this boiling can be clearly heard when listened carefully.