Bearing / Ease / Oil Lubrication

BEARING LUBRICATION

Rolling bearings have to be adequately lubricated for satisfactory operation. The main purposes of rolling bearing lubrication are :
- To prevent direct metallic contact between the rolling elements, raceways and cages.
- To prevent the bearings from corrosion and wear.
- To prevent the ingress of contamination.
- Cooling of the bearing.
Rolling bearings may be lubricated with grease or oil, the choice of which depends primarily on the temperature range, operating speeds and loading conditions of the bearings concerned. However in special cases solid lubricant may also be used.
The limiting speeds for both grease and oil lubrication are given in the bearing tables.

EASE LUBRICATION

In majority of the applications under normal operating conditions, grease lubrication is generally used. Grease has certain advantages over oil, of being easily retained in housing as well as its sealing effect against the entry of the moisture and other foreign particles.
Excessive grease is detrimental to satisfactory bearing performance and will cause rapid temperature rise, particularly if speeds are high. In general, the quantity of grease necessary to ensure that the bearing operates well should be equal to approximately 25 to 40 % of its free internal volume. However, when bearing is operating at slow speed,it should be filled fully with grease in order to have good protection against corrosion.

OIL LUBRICATION

Oil lubrication is generally used when high speeds / operating temperatures are beyond the range of application of greases, or where oil is also used as coolant, or where bearings are integrated into a mechanism that is already lubricated with oil (Gear Box).
Viscosity of the lubricating oil is the main factor to be considered to suit the diverse applications with respect to speed, temperature and loading conditions. Mineral oils are mostly used for lubricating bearings.