Impact of oxidation on grease life in rolling bearings

In this paper the lubrication mechanism of lithium grease lubricated ball bearings in the bleed phase is described. Oxidation plays an important role and therefore grease life in airand grease life in nitrogenis studied in real bearings. It is shown that grease life is strongly dominated by oxidation but that this is by far not deterministic. Oxidation starts up at a certain time, the induction time, which is the point at which the anti-oxidants have been consumed. This induction time is a function of the bearing operational conditions and the oxygen concentration. Oxidation leads to loss of base oil and loss of lubricity, partly repaired by replenishment and oil release from the grease reservoirs (bleed).

Automated summary

This paper describes the lubrication mechanism of lithium grease lubricated ball bearings in the bleed phase. The role of oxidation is highlighted and the grease life in air and nitrogen is studied in actual bearings. The study shows that grease life is mainly influenced by oxidation, but this is not deterministic. The induction time, which is the point when the antioxidants are depleted, plays a crucial role in the onset of oxidation. Furthermore, oxidation leads to the loss of base oil and lubricity, which are partially repaired through replenishment and oil release from the grease reservoirs (bleed).