Power generation in today’s highly competitive environment has created an imperative need for a shift from conventional preventive maintenance techniques to the condition based maintenance of the rotating machines in a power plant. Condition monitoring of bearings plays an important role in the reliable operation of machinery. The integrated approach in monitoring of bearings using sonic, ultrasonic vibrations and temperature measurements helps in arriving at correct decisions about maintenance requirements of the machinery.

This study focuses on application of sonic and ultrasonic measurements on a variety of power plant bearings. Ultrasonic acceleration measurements has been used for the first time in NTPC to assess condition of very slow speed equipment bearings. Effect of lubrication on the sonic and ultrasonic signals from the bearing has been explored through laboratory experiments.

Techniques for determining lubrication schedule will be the potential strategies for bearing life extension. Results indicate that the ultrasonic technique has a great potential for detecting incipient faults in bearings, much earlier than the presently used technique of vibration monitoring. Results from a laboratory study of motor indicates that this technique also has the potential for determining condition based lubrication schedules, instead of Preventive Maintenance based.

Keywords:-Sonic, ultrasonic, Slow speed bearings, Time wave, wave Shape.