Comparison between thermal fluid and steam



In previous posts we informed on the thermal fluid transmitters that can be used in an industrial installation. In this blog we want to make a comparison between the use of the thermal fluid versus the steam, both perhaps the most extended systems world-wide.

The requirements for the steam facilities are more restrictive than those of thermal fluid:

  • Steam boilers of a certain size and water volume have to be installed in a separate boiler room. In many countries the boiler room cannot be located within the main building or production site, but has to be separated at a certain minimum distance. Moreover, protection walls of such boiler room have to be of a minimum thickness, depending on the category of the boiler.
  • Water treatment is an absolute requirement for every type of steam boiler, whether of the coil type, water tube or fire tubes. Water treatment consists of a water softening plant (which should be a twin system in most of the cases) in combination with a chemical treatment of pH control and oxygen scavenger. A water softener “Twin” system consists of two cylinders to hold the resin in order to allow a regeneration of one column whilst the other resin column remains in service. A twin softener is an absolute must in production plants with a continuous operating cycle of 24/24 h.
  • Oxygen removal and pH control can be done by means of a chemical dosing system (dosing pump with dosing tank). With some type of boilers, especially of the coil type, special care has to be given during “stand-still” periods. If no measures have been taken to keep the coil either completely dry or completely filled by means of a time controlled “post-run” system, the risk of oxygen corrosion during standstill period is very high. (Note: Post-run means that the water pump has to remain in operation to keep the coil filled with water whilst the system cools down, in order to prevent air pockets to be formed in the upper part of the heating coil which would introduce oxygen in the heating coil and cause a typical form of “pit corrosion”).
  •  With too much concentration of TDS (Total Dissolved Solids), a carry over of chemicals will take place. Too high concentration of dissolved solids (example over 3.000 mg/l) can be caused either when blow down periods are not being strictly adhered to or during “peak-loads” which demand momentarily more steam than the average nominal capacity of the boiler size. This carry-over will result into wet steam and the chemicals which will remain in “wet steam” can block steam traps, steam regulating valves etc. Hence, high maintenance costs and waste of energy in case steam traps do not function properly and do not shut off properly.
  • Some more details are referred to in the section “Corrosion” hereafter. Especially in fire tube boilers, because of the larger water content, explosion risk remains despite added automation on modern boilers.


The thermal fluid does not require any special treatment once the installation has been filled up. Its life oscillates between 10 and 12 years. This means that the cost of this element is really insignificant.

The thermal fluid, which comes out of equipment after having heated it, will enter into the generator with only 1 or 2 ºC less temperature. This shows that the loss of heat during its way in the line is situated at the minimum.

There has to be taken into account, that the outcoming steam of a purge has an average temperature of 120 ºC, whereas when it reaches the tank of condensed it usually does not exceed 90 ºC, and in many occasions it does not even reach this low temperature. On the other hand it should also be taken into account, that there always remain a flow of steam in the purges which gets lost through evaporation and these calories are never more recovered.

Thermal fluid systems suffer none of the above-described losses.

Legal requirements

These are generators working WITHOUT HIGH PRESSURE. This fact exonerates them of the walls, distances to neighborhood, and all the other norms which have to be taken inTO account and accomplished for the steam type boilers. Thermal fluid boilers may be installed in any place, even just besides the manufacturing machines.


Neither the generator nor the pipeline suffer from wearing away, as the function is done with lubrication liquid, NOT CORROSIVE like water.


Any kind of dragging, such as for water, of salts, of oxides, or of any other indissoluble solids is not necessary. This means that nothing can affect the goodness of heat transmission through thermal oil. This type of installations are practically free of maintenance.

Fuel saving

When heating is done through thermal fluid, we are able to obtain a level of temperature regulation till ± 2 ºC in the machines. When using steam heating this is completely unthinkable, as the differences in a normal installation are situated around ± 10 ºC.

This is of course also a very important factor in saving fuel, as it allows organizing a very regular temperature average, without any fear that the quality of the product may get spoiled due to the ups and downs which could occur when treated with steam.

The sum of the related factors results on a fuel saving around a minimum 12 to 18% according to concrete data taken in facilities which are working for a long time to total satisfaction of our clients.


Another advantage when using thermal fluid, is that all problems concerning passing preferences, as usually they appear in steam installations, are completely cancelled: When working with steam all the machines, which are located nearer to the boilers, they will receive the full amount of flow which they need. Those machines which are at a greater distance very often have a lack of flow.

With the thermal fluid and through our system of ballast check valves we assure to each individual machine the whole quantity of necessary hot oil, ensuring a temperature stability.


No risk of explosion, because there is no high pressure inside and neither hot oil storage.

Cavitations do not appear in the recirculating pump of thermal oil.

In steam installations they may arise when the feeding water which is recovered from the condensed surpasses a temperature of 90 ºC, at that stage either it is cooled down with water entering in the line or part of the condensed are thrown away, but this last supposition is really absurd in view of the cost of the fuel.

With the details we have mentioned above, we intend to offer you a global view on the subject of the thermal fluid installations. However in order to get a more precise knowledge it is necessary to enter deeper in this kind of equipment, for this purpose we remain at your entire disposition.

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