Many processes today require an indirect method of heating, which implies the use of a heat transfer medium instead of circulating the process directly into a heater. Thermal oil, water, glycol mixtures and steam are the most commonly used heat mediums for indirect heating. Thermal oil often is preferred over steam for high temperature applications because there is less maintenance such as water conditioning and blowdown systems. Steam processes require higher pressures when compared to oil systems at comparable temperatures as well as more ongoing regulatory oversight.
Thermal oil heaters typically are used in a non-pressurized, closed-loop system. Primary components include a pump, heater, piping and an expansion tank. Many factors govern the size and selection of the heater and associated equipment. The following guidelines will help navigate sizing and selection, which can be a challenging and time-consuming task.