Heat transfer plants – contrary to hot water or steam plants – are characterized in particular by the fact that they can provide process heat almost pressure-less in a very wide temperature range.

So for the standard application up to a maximum inflow temperature of 300 °C a design as per PN 16 is sufficient, up to 350 °C this is as per PN 25 and up to 400 °C as per PN 40. Although it is to stress that a temperature of 350 °C can be reached basically pressure-less with a suitable heat transfer fluid (“thermo oil”). Solely the pressure caused by the circulation pump is to be considered.

Heat transfer plants are suitable nowadays in almost all producing branches. Owing to their working fluid (the so-called „heat transfer medium“, named generally also “heat transfer oil”, “thermal oil” or “thermo oil”) these plants are designated in many cases also as “thermal oil plants”, “hot oil plants” or “thermo oil heating plants”or “hot oil units”.

In the Asian area these plants are often embraced by the term “Dowtherm heater” or “HTF boiler”.

The advantages of indirect heat transfer against the direct heating are various. So e. g. with one heater several heat consumers can be supplied; for a central heat supply it means a greater efficiency – by the spatial separation of heater and consumer there is no explosion hazard with the consumer and the maintenance effort at a central unit is lower than with many individual consumers.

Significant for the design and the construction of heat transfer plants is the DIN 4754 (Heat transfer systems operating with organic heat transfer media – safety requirements and testing. Beuth Verlag Berlin, last Edition March 2015), for the operation and maintenance the directive VDI 3033 is decisive.

In addition to this the Pressure Equipment Directive 2014/68/EC, the Maschinery Directive 2006/42 EC as well as the AD-Merkblätter are to be observed.

Heat transfer oil plants are divided according to the type of the primary heating, so e.g. as electric heater, as fired thermo oil boiler, as heating-cooling plant (also named “temperature control unit”). Although the general assignment of tasks is almost the same everywhere: It is about the temperature control of industrial manufacturing processes (“process temperature control“).

In the plant engineering, also waste heat boilers (as hot gas / thermo oil heat exchanger – also called Waste Heat Recovery unit “WHRU”) come into operation in many cases. Primary aim here are the utilization of residual heat (thus waste heat recovery, e.g. behind gas turbines), an increase of the efficiency of industrial manufacturing processes and the reduction of emissions.