Oil and grease for low temperatures
Reduce mechanical wear down to -90°C

The smooth operation of a rolling bearing, a chain, a gear motor or any mechanical device already at -20° C and above cannot occur without a specific low-temperature lubricant solution.

The film of lubricant must provide the best compromise between the lowest possible viscous friction and the lowest possible frictional loss due to wear under all operating conditions.

Depending on its consistency (oil, grease or paste), a lubricant is composed of varying degrees of the following elements:

• Base oil
• Thickener
• Solid lubricants
• Additives

The main constituent directing and characterising the evolution of the lubricant's behaviour at low temperatures is the base oil that, depending on compositions, is present in percentages usually above 60% by weight.

The materials and parts that comprise an electro-mechanical device are, like lubricants, affected by temperature.  Depending on their composition, plastics, metals, rubbers or composites can undergo one or more of the following alterations:

• Deformation – contraction of metals and polymers (elastomers, plastics and composites)
• Embrittlement – decrease in the elastic properties of polymers, since some elastomers such as Nitrile Butadiene Rubber (NBR), if not properly additivated, embrittle and suffer permanent cracking when subjected to low temperatures
• Mutually-sliding surface adhesion – cohesive effects may occur due to crystallisation phenomena
• Increased static and dynamic friction – owing to increased dynamic viscosity of lubricants
• Change in mechanical properties of materials – such as elongation at break

Once the minimum operating temperature of a mechanical device has been established, two parameters must be accurately identified for the correct formulation of the lubricant able to protect during operation:

• Viscosity
• Chemical composition of the base oil (mineral or synthetic)

Viscosity identifies the internal friction of a lubricating fluid and thus its resistance to sliding.  The viscosity of an oil increases with decreasing temperature and is measured in cSt (centistokes) or cPs (centipoises). It is essential that its value at minimum operating temperature does not exceed the critical threshold, which would cause an excessive increase in friction.

Base oils used in the formulation of industrial lubricants can be divided into two categories:

•  Mineral
•  Synthetic

Mineral oils are those obtained by refining and distillation of crude oil, being cheap and unable to perform particularly well at low temperatures  Belonging to the family of synthetics are oils obtained by direct synthesis through chemical reactions and processes. Synthetic oils provide superior performance at low temperatures, as shown in the graph comparing freezing points at the same viscosity.

If we imagine the lubrication of a rolling bearing operating at up to -50° C, it is natural to think that the choice of base oil cannot fall to a grade with a mineral composition!