A Case Study on Lifetime Assessment of Stator Windings in Large Machines that can be a Critical and Effective Tool in a Predictive Maintenance Plan

The cost of an unexpected plant shutdown due to failure of critical equipment such as a large motor in the Chemical Oil and Gas process industry could have a significant impact on earnings. Failure surveys of motors in petrochemical plants have indicated that in motors rated over 2000 kW over 60% of all failures are attributed to stator windings. Additionally, the downtime involved in repairing or rewinding a stator could be considerable. Condition assessment and life time estimation techniques of stator winding could be very beneficial to determine the anticipated rate of degradation and estimate the existing and expected reliability till the next outage. A clear plan then could be devised for administering the necessary machine maintenance. This paper explains how such an approach helped to make the right maintenance and budget decisions and to minimize the risk of unplanned shutdown a 17,433 HP (13000kW) synchronous motor. This motor, which drives a compressor that’s critical to production, has been in operation since 2003 and has no spare. By adding the routine inspection of the stator winding to condition assessment and lifetime estimation techniques that estimate the amount of life consumed and the anticipated rate of degradation, this team has increased optimal asset reliablity and machine life