Oil lubrication is considered better suited for high speed and high temperature applications. It is very effective for applications requiring bearing generated heat to dissipate outside.



Under normal operating conditions, spindle oil, machine oil, turbine oil and other minerals are widely used for the lubrication. For temperatures above 150deg;C or below -30deg;C, synthetic oils such as diester, silicone and fluorosilicone are used.



Viscosity of the oil determines the oil's lubricating efficiency. If the viscosity is too low, the oil film will not be sufficiently formed, and if the viscosity is too high, the viscosity resistance will also be high and cause temperature rise. For higher speed, a lower viscosity oil should be used, and for heavy loads, a higher viscosity oil should be used.



Methods of Oil Lubrication



Oil bath

For most horizontal shaft applications, the oil level is maintained at approximately the center of the lowest rolling elements when the bearing is at rest. Here it is important that the housing design does not permit wide fluctuations in the oil leve.



For vertical shafts at low speeds, the oil level should be up to 50% to 80% submergence of the rolling elements. However, for high speeds or for bearings used in pairs or multiple rows, other lubrication methods should be used.



Oil splash

Here an impeller or similar device is mounted on the shaft and it picks up the oil and sprays it onto the bearing. This method can be utilized for high speed applications. Drip lubrication, it is used for high speed and light to medium load applications. An oilier is mounted on the housing above the bearing and allows oil to drip down on the bearing, striking the rotating parts, turning the oil to mist.

Circulating lubrication

It is used for bearing cooling applications or automatic oil supply systems where oil supply is centrally located. Here, cooling devices, filters atc can all be installed within the system.



Disc lubrication

A partially submerged disc rotates at high speed pulling the oil up by centrifugal force to an oil reservoir in the upper part of the housing. The oil then drains down through the bearing. The process is effective for high speed applications.