Water pump motor bearing sound fault phenomenon

A feed pump, form a complete set of motor for three-phase high voltage ( 6 kv) Asynchronous motor, model YKK400 - 2, power 450 kw, the speed of 2975 r/min. Using NU3E222 type column bearing shaft extension end, the load side with 6222 type deep groove ball bearings. Running, the shaft extension end shrill voice, don't like electromagnetic noise, also don't like the sound of dry grinding bearing short of oil. Noise lasts about 2 min, and intermittent 2 min. With vibration measurement of bearing vibration, abnormal sound, the measured vibration velocity value of 53. 6 mm/s, sometimes even up to 97 mm/s, far more than standard 2. 8 mm/s, and the current volatile. Because of using the shaft extension end bearing clearance fit can't adjust size of bearing axial positioning. In the process of inspection, found in the bearing bore uneven abrasion marks, has two deep groove column bearing damage. Measurement bearing, end cover and inside and outside of the bearing cover location dimension, and through calculation, the bearing to allow clearance to 0. 7 mm, when the motor bearing temperature reaches 100 ℃, the expansion of the bearing value is about 0. 9 mm, can't meet the requirements of normal operation of motor. After repeatedly replacement column deep groove bearings, motor noise did not disappear, and the sound cycle into 4 min.