Service Life of Lubricating Grease in Ball Bearings (Part 1) Behavior of Grease and Its Base Oil in a Ball Bearing

Abstract

The life of rolling bearings can be limited by sudden increase in friction torque due to exhaustion of lubricant after long-term operations. With the purpose of developing grease having long “service life”, research has been conducted with angular contact ball bearings lubricated with urea greases, and the present First Report describes experimental work. The life was determined on FAG-FE9 rolling bearing grease testers, and considerable difference in the life was found among the greases with different type thickeners. Observation of bearings by interrupting the run inferred the following scenario. In a short churning period, grease was re-distributed to form a lump on the front face of the outer ring and thin layers on some other parts of the bearing. The lump served as an oil reservoir, and the oil bled from it infiltrated through the thin layer on the outer ring to lubricate the raceways. A part of the oil was then carried by the balls to lubricate the sliding interface between the cage and the balls and, when this lubrication became insufficient, seizure initiated to limit the life.

Keywords

• ball bearing
• service life
• grease
• thickener
• feed and loss