Thermal oil scores on this point. Even at temperatures of 350 °C, the pressure requirements are just sufficient to overcome the system pressure drops. This also decreases the pumping cost.
The system is simple in that it requires only a pump, an expansion and storage tank and the heat exchangers. A steam system on the other hand requires demineralized makeup water supply, drains, traps, safety valves, chemical additions and blow downs.
Using thermal oils eliminates all these complications along with issues of corrosion, scaling, fouling, and deposits in the heat transfer areas.
This is why thermal oil finds many uses in the process industry. All this leads to considerable reduction in cost.
Unlike steam, thermal oils also find use in applications where the temperatures are below zero °C.