Evaluation of antifriction bearing lubrication methods on motor life-cycle cost

The main cause of induction motor failures is bearing failure. Antifriction bearing failures most commonly are the consequences of inadequate lubrication. Antifriction motor bearings are found in four lubrication configurations: re-greasable, sealed, oil mist, and oil lubricated. Bearings are oil lubricated when the operating conditions (i.e., bearing size, speed, thrust, etc.) require it. However, there is much debate about the "best" lubrication configuration, given a choice between re-greasable, sealed, or oil-misted bearings. Within their own rights, all three methods have their advantages. Selection of the proper configuration is dependent upon many factors, such as motor size/type (i.e. bearing size/type), plant maintenance practice, bearing replacement availability/cost, duty cycle, environmental conditions, and downtime cost. This paper discusses the relationship between these factors and lubrication configuration, and presents an analysis of the subsequent impact on bearing life and system cost.