The Impact of Water on the Yield Stress and Startup Torque of Lubricating Greases

Water is one of the most common contaminants in grease lubrication. There are numerous applications where bearings are susceptible to water ingresses such as in the steel, food, and pulp and paper industries. A grease can absorb water to different degrees depending upon the type of grease. The ability of a grease to either absorb or reject water can influence the service life of rolling bearings. Two parameters that determine the performance of a grease at very low temperature are the yield stress and startup torque. Water was found to influence the yield stress and startup torque depending on the operating temperature, grease type, and percentage water in the grease.