How can impurities arise in the thermal oil and which reasons does this have?

Especially in new systems, it often happens that shavings and metal particles of the inner wall of the pipes and the abrasion of pumps and fittings pollute the oil from the beginning. Therefore, it is optimal to filter the thermal oil already from the beginning.

Later – during the running operation of the system – oxidation products occur already from 80 °C and reaction products are generated from 250 °C. These particles (> 40µm), e.g. oil coal or coke, are clearly visible without a microscope as well.

Many of these mentioned particles are too small for the strainers upstream the pumps and control valves.

Which effects do these small particles have in the thermal oil?

In the long term, these particles, contained in the oil, impair the operating safety and the efficiency of the heat transfer oil systems. Impurities and deposits reduce the flow rate and increase wear. In the worst case, defects on heaters, pumps, sealings and valves will be the consequence. In addition, the core function – heat transfer – will be impaired strongly.

How do I determine the degree of pollution of my oil?

The degree of pollution can be determined by an oil analysis as per DIN 51551. In this analysis, the coke residue is determined as per Conradson. This value is a very good indicator for the pollution with fine particles of the oil and the system.

What can I do about the contamination?

The conventional method to remove – at least a part of the contamination – from the thermal oil system is the partial replacement of the used thermal oil. In this case, part of the oil is replaced by fresh oil, whereby a certain percentage of the particles in the oil will be discharged out of the system. However, this solution does not replace the filtration and is only a short-term solution, mostly in case of an emergency. Already “cracked” or not discharged particles further remain in the system. In addition, in some circumstances, the oil change is associated with a standstill of the system and – depending on the oil used – it causes high running costs.

A fine filter with a mesh size smaller than the standard strainer , e.g. 1000-1600 μm, can remove most particles from the system. For comparison: The standard mesh size of the NESS Fine filter stations is 15 μm, i.e. only a fraction of the normal strainer. With this, the particles will be filtered out excellently. Correctly intergraded, this solution has the advantage that it can be carried out during the running operation of the system.

Oil filtration as preventive action against deposits in the system?

Exactly! The integration of a Fine filter station in your thermal oil system ensures that particles are removed from the beginning and with this, the formation of deposits, e.g. in heat exchangers, on inner pipe walls, etc., will be avoided in the best possible way.

Using the method, continuous filtration constantly provides for operating safety and efficiency and actively counteracts defects on heaters, pumps, sealings, and valves.

What do the NESS Fine filter stations do?

The NESS fine filter station is a product in the NESSessities concept which constantly increases safety, availability, durability and efficiency in thermal oil systems. One of the 3 most important factors for a good quality is a low Conradson value. The NESS Fine filter station helps you ensuring this permanently.

Besides acid figure and flashpoint, the
Conradson value is an important factor for good oil quality

How do I integrate the NESS Fine filter station in my system?

No problem at all! Like all NESSessities, also the NESS Fine filter station is part of the modular concept. As it applies to many other NESSessities, the fine filter station can be retrofitted in each system. Existing processes are not influenced. because the fine filter station filters in the bypass flow. This concept allows the relatively easy retrofitting also for already existing systems.

NESSessities work independently
in the bypass flow of the system

Are there different fine filter stations available? And if yes, do we have to consider something?

Generally, NESS is offering two sizes of systems for the filtration in thermal oil systems. However, their functions do not distinguish in principle. If selecting the right size, beside the actual oil volume of the system, the pollution factor must be considered also for retrofitting of the system.

FF300Used oil: < 50.000 litres
New oil: < 80.000 litres
FF500Used oil: < 150.000 litres
New oil: < 200.000 litres

What product solutions are available for your system, you will read here

Do I need additional infrastructure for the operation of the fine filter station?

Beside a certain intake pressure of the thermal oil, of course an adequate power supply is needed for the own pump and the own control unit of the station. Additionally, a washing station or a similar cleaning equipment is recommended for cleaning of the filter baskets.

Oil is filtered through filter baskets. Are there any differences and what is to be considered?

Depending on the age of the thermal oil system and the heat transfer oil, particles are solved in the oil to a greater or lesser extent. For this reason, for the first filtration we recommend starting with a little wider mesh size (200 µm) of the filter insert – mainly for already running systems. The following mesh sizes / filter basket variants are available:

Mesh size in 15, 90 or 200 μm
Scope of applicationExternal filterInternal filter
First filtration200 μm–
Transition filter90 μm –
Normal operation90 μm 15 μm

The filter basket for normal operation includes an additional internal filter. We recommend always having a second filter of this variant in store, for instance to be able to insert the second filter while the first filter is being cleaned to avoid standstill during filter cleaning.
Furthermore, each basket can be completed by a temperature-resistant magnetic bar, to better remove iron particles from the heat transfer oil.