September 2014

Eurotubi Pressfittings for conducting lubricating oils

The pressfitting system can also be used to create distribution systems for lubricating oils. Let's take a look at the advantages in using it and what specifics we need to consider.

Carbon steel or AISI 316L Stainless steel?

Carbon is physiologically less resistant to corrosion than stainless steel, by and large. It can only be used for closed circuit systems. In systems where oil is intended for dispensing, it is very easy for air or other substances to infiltrate the circuit. Therefore, AISI 316L stainless steel fittings must be used.

It is often erroneously presumed that the oil conducted inside a carbon steel system can protect the internal walls of the system itself from corrosion. There are two observations that can be made contrary to this hypothesis:
  1. There is no guarantee that the oil film will entirely cover all surfaces.
  2. Some oils contain potentially aggressive additives to which carbon steel is not suitably resistant.
A stainless steel system ensures clearly superior life compared to one in carbon steel. The latter also requires more frequent wear and corrosion inspections in comparison to stainless steel.

Press Fitting for the conduct of lubricating oils

Which O-ring is best?

The best O-ring is the Red FPM commonly associated with industrial applications. The fluorine rubber present in FPM o-rings offers better performance than any other synthetic rubber currently on the market. Besides excellent resistance to lubricants, it also offers excellent performance in the presence of hydrocarbons and mineral acids.

FPM red o-ring
Temperatures: between -20 and + 180 °C
Pressures up to a maximum of: 16 bars
Available in diameters ranging: from 12 to 108 mm

Are there limits to the temperature of the oil that is transported?

Yes, the physical limits of the o-ring mixture. When the oil that is put in the pressfitting circuit is not at room temperature (for example, old oil from an engine that was just shut down) you must ensure that its temperature does not exceed 180° C.

Standard EPDM gaskets should be avoided because they are heavily eroded by the chemical components in the oils. The molecules in the EPDM are destroyed and the o-ring swells up and loses its elastic capacity, inevitably leading to leaks..


Oil, and especially its vapours, is inflammable. The pressfitting joint technique does not use open flames, unlike joints that use soldering. For this reason, it is highly recommended for use in systems for circulating oil, fuels and other flammable liquids.

When using pressfittings for conducting fluids other than water or air, we remind our customers to refer to Table 14 in the Eurotubi technical manual for the primary generic indications. You can also contact the Eurotubi Technical Office for more information.
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