Analysis and treatment of abnormal noise fault of

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Analysis and treatment of abnormal noise fault of motor bearing

a high-voltage (6kV) motor YKK of feed pump, power 450KW, speed 2975r/min. Deep groove column nu3e222 bearing is used at the shaft extension end, and deep groove ball 62 is used at the non load end to gradually open the oil supply valve 22 bearing. During operation, the sound at the shaft extension end is sharp and harsh, not like electromagnetic noise, nor like the sound of bearing oil shortage and dry grinding. The noise lasts for about 2min, and then intermittently for 2min. The vibration amplitude of the bearing measured by the vibration meter (va-80a) is 0.021mm. When the sound is abnormal, the measured vibration speed value is 53.6m, and as a fixed asset/s, sometimes it even reaches 97m/s, far exceeding the standard value of 28 m/s, and the current fluctuation is large

due to the clearance fit at the shaft extension end, the axial positioning dimension of the bearing cannot be adjusted. During the maintenance, it was found that there were uneven wear marks on the inner oil cover and two deep groove columns of the bearing were damaged. Measure the positioning dimensions of bearings, end caps and inner and outer oil retaining covers. After calculation, the allowable clearance of bearings is 0.7mm. When the bearing temperature of the motor reaches 100 ℃, the expansion value of bearings is about 0.9mm, which cannot meet the requirements of normal operation of the motor. However, compared with the imported experimental machine for many times, after replacing the deep groove column bearing, the motor noise not only did not disappear, but also the abnormal sound cycle became 4min

2. Fault analysis and treatment

according to the analysis of the characteristics of the bearing: since the motor originally used Nu type deep groove column bearing, the axial movement of the motor is allowed. There are retaining edges on both sides of the inner ring of the bearing, and there is no retaining edge on the outer ring, so the two-way displacement of the shaft relative to the bearing is allowed, and the elongation caused by the thermal expansion of the shaft can be withstood. At the same time, the clearance of the bearing is larger than that of the deep groove ball bearing, but the force on the bearing is linear, which is better than that on the point of the deep groove ball bearing. The bearing motion track is not a circle but an ellipse, which is caused by the gap between the dry deep groove column (or deep groove ball) and the raceway. The different forces during operation make the Motion Track elliptical. The force of the bearing is mainly in the lower part. For deep groove column bearings, the reflection and scattering points are easy to be in a straight line. During high-speed operation, due to the clearance of the bearing, the force point changes, and the force motion trajectory becomes a parabolic curve

when the feed pump motor operates, it is mainly affected by axial force, and the driven load is stable, and the necessity of allowable radial movement of deep groove column bearing is weakened. Therefore, replace the front bearing with deep groove ball bearing, and the bearing clearance is still C3, about 0.04mm, which can meet the operation requirements. At the same time, considering the expansion of the bearing, add a gasket with a thickness of about 0.8mm at the small cover of the oil retaining ring to overcome the channeling caused by the temperature rise of the feed pump and the bearing

the micro surface of the bearing rolling element and raceway is rough and uneven, and a certain impact will occur in the movement, but the pulse generated by this impact is high-frequency, so the parameter value of high-frequency interference measured by vibration meter is larger than the standard. The contact between the deep groove ball bearing and the raceway is more, and the high-frequency impact is large. The contact between the deep groove ball bearing and the raceway is the point, and the high-frequency impact is relatively small. Therefore, the motor in this example can use the deep groove ball bearing to replace the deep groove column bearing to solve the abnormal sound of the equipment

after replacing deep groove column bearing with deep groove ball bearing, the abnormal sound of bearing disappears. The noise did not appear again after running for a period of time. The vibration amplitude of the measured motor was 0.013mm, and the acceleration value was 2.8m/s2. The load performance was stable, and the current did not fluctuate greatly

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