M. Ing. / Reliability is basically the measure of performance, it is the probability that a system or component will perform its required task without failure under certain conditions for a given period of time [1]. As systems have become more complex in recent time the need for reliability within that system has become more and more important, safety, productivity and profit are three factors that have also demanded an increased level of reliability [2]. The reliability of an industrial gear unit comes from the reliability of all the individual components within the gear unit. Bearing lives are often the limiting factor of a gear unit and more often than not the lubrication becomes contaminated through insufficient maintenance practices, operational practices and harsh environments. This then results in the premature bearing failures within the gear unit. If the gear unit’s “health” can be monitored and imminent failures are known then the unit can be taken out of service and replaced or repaired prior to failure and during scheduled maintenance periods, this will then reduce overall repair costs and drastically reduce unscheduled maintenance time and cost.