We gave recently performed activity of motor overhauling of a used motor which will be used to drive ID Fan. Following bearings have been installed in motor,
DE: Ball Bearing 6234 MC3 + Cylindrical Roller Bearing NU 234 MC3
NDE: Cylindrical Roller Bearing NU 234 MC3
During motor testing in decouple mode abnormal whistling sound was observed from the motor. After some greasing of bearing the sound vanishes and again after 30 to 45 minutes same sound starts again.
*Vibration values are 0.8~1.2 mm/sec even when abnormal sound is observed so vibration is remains same.
* gE value tends to go on a higher side as soon as the sound starts.
Pictures of electrical motor, abnormal sound video and thermography report has been attached for better understanding and to trace out the possible reason for this abnormal sound.