How do I choose the right bearing lubricant?

Why is it important to lubricate a bearing?

Many industrial applications use metal parts whose surfaces are constantly touching and rotating. One of the many mechanisms used in industry for this function are ball bearings. However, adequate lubrication must be provided to prevent undesirable failures.

In fact, over 60% of premature bearing failures are due to poor or insufficient lubrication, which will result in contamination or excessive heat build-up in contact. Therefore, lubrication between the ball or roller of the bearing, the ring and the cage becomes important because it simultaneously extends the life of the bearing and minimizes excess heat generated during friction.

In addition, it ensures contact with a carrier film between the rolling elements and the rings, which helps to minimize the impact of wear, while preventing moisture penetration and corrosion.

How to choose a good lubricant?

Selecting the right lubricant for any specific application requires a complete understanding of the operational and environmental conditions to which the bearing will be subjected. There is a wide range of equations and diagrams in the literature that can be used to determine a life adjustment factor for lubrication.

This factor results from the evaluation of the lubricant based on the operating conditions relative to the fatigue life of the bearing. Typically, this factor is multiplied by the L10 life to obtain the bearing life adjusted for the effects of lubrication. L10 life is the number of hours a bearing will last under a given load and speed with 90% reliability.

Some bearings are already pre-lubricated by the manufacturer and do not require additional maintenance. This can be advantageous in certain cases where relubrication is not practical or is a problem. In addition, there is no risk of contamination by external agents and maintenance costs are lower.

On the other hand, for bearings that are not pre-lubricated, either grease or oil can be used. In this case, the decision to change the type of lubricant to increase or decrease the life adjustment factor depends on the needs of the machine. However, there are also trade-offs and concerns other than service life to consider.

What are the important parameters in choosing a good lubricant?

The viscosity and type of lubricant used depends on the bearing design and operating conditions. Most importantly, when selecting an oil or grease, the most important aspect to consider is that the main role of the lubricant is to separate the metal surfaces in contact, lubricate them and provide cooling and corrosion protection. In addition, the choice of base oil viscosity depends on the load, temperature and speed requirements of the machine.

For example, if the application requires low speeds, high loads and high temperatures, a lubricant with a higher viscosity will be preferred. On the contrary, if the machine operates at high speeds, low loads and low temperatures, then a lubricant of lower viscosity should be used.

The correct viscosity will, for a given load, speed and temperature, develop a complete oil film between the moving surfaces. When the optimum film thickness is reached between the rolling elements, no contact between the surfaces is ensured and there is a minimum friction value. However, when the viscosity is insufficient, it can lead to mixed or boundary lubrication and, as a result, wear and heat generation.

Samaro and its partners Molykote and Krytox offer perfectly adapted lubricants for :

High-speed lubrication of bearings

Lubrication of bearings under heavy loads

Le graissage à Hautes températures des roulements ou paliers

Lubrication of bearings and sintered steel bearings

Krytox™ Synthetic greases and synthetic oil used in bearings and steel/sintered metal bearings provide longer-lasting lubrication, reducing the frequency of relubrication. This not only reduces operating costs through reduced maintenance, but also minimizes waste and environmental impact.

Krytox™ high-performance lubricants applied to bearings and bearings made of steel/sintered metal provide :

• Superior film-forming ability: Oil forms a thicker reduced layer, which limits wear.
• Extreme oxidation resistance: Krytox™ oil, combined with an advanced high performance polytetrafluoroethylene (PTFE) thickener, will not oxidize, will not erase with age and will not shear off.
• Extreme Temperature Performance: Lubricants will not break down at the high temperatures of electric motor applications (can operate over a wide temperature range of -75 to 350°C).
• Optimum stability: Krytox™ Lubricants are water resistant, non-flammable and chemically inert.
• Lifetime filling: It is generally not necessary to relubricate bearings during the lifetime of a product.
• Corrosion Protection: These additives protect against corrosion and rust during storage and in humid environments.

More information :

Needs more information on Molykote or Krytox ?
Contact our technical services by phone to +33 426 680 680 or fill our contact form.

You can also download our lubricants selector guide :