Contaminated Lubricants and Tapered Roller Bearing Wear

When antifriction bearings operate in a “clean” environment, the primary mode of damage will be the eventual fatigue of the surfaces where rolling contact occurs. This type of damage is a function of load, alignment, bearing setting, speed, plus temperature and quality of the lubricant. However, when dirt from the outside or metallic debris worn from some mechanism in the application is allowed to contaminate the lubricant, wear will become the initial form of damage to the bearings. In most commercial applications, bearing wear in some magnitude is inevitable because of the difficulty in completely eliminating contaminants from the lubricant, and because elasto-hydrodynamic lubricant film conditions normally exist within the bearing. If, due to the presence of contaminants in the lubricant, the amount of bearing wear becomes significant, changes will occur to critical bearing dimensions which could have adverse effects on the bearing operation and, ultimately, the application. This paper presents an evaluation of three contaminant parameters; namely, a) Concentration Level in the Lubricant, b) Particle Size, and c) Particle Hardness, and their effects on tapered roller bearing wear. Also discussed are other variables that became important during the test program such as, 1) Effect of Time and 2) Effect of Type of Lubricant and Lubricant Viscosity.