Fault analysis and treatment of abnormal bearing noise of water pump motor

1. Fault analysis

Since the motor originally used Nu bearing, it is allowed to have certain axial displacement. There are ribs on both sides of the outer ring of the bearing, and there is no flange on the inner ring. Therefore, the two-way displacement of the shaft relative to the outer ring of the bearing is allowed, and the extension caused by the thermal expansion of the shaft can be borne. At the same time, the clearance of the bearing is larger than that of the deep groove ball bearing, but the bearing force is linear, which is better than that of the deep groove ball bearing. The motion track of the bearing is not a circle but an ellipse. The bearing force is mainly in the lower part. For the deep groove column bearing, the force point is a straight line. In high-speed operation, due to the bearing clearance and the change of the force point, the force trajectory becomes a parabolic curve.

2. Treatment method

During the operation of the motor of the feed pump, it is mainly affected by the axial force, and the dragging load is stable, and the necessity of the allowable radial movement of the deep groove column bearing is weakened. Therefore, the front bearing is replaced by the deep groove ball bearing, and the clearance of the bearing is still C3, about 0.04mm, which can meet the operation requirements. At the same time, considering the expansion of the bearing, a piece of 0.8mm thick gasket is added at the small cover of the oil retaining ring to overcome the axial displacement caused by the temperature rise of the feed pump and the bearing.

The micro surface curve of bearing rolling body and raceway is rough and uneven, and 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 greater, while the contact between the deep groove ball bearing and the raceway is a point, and the high-frequency impact is relatively small, so the motor in this example can use the deep groove ball bearing instead of the column bearing to solve the abnormal noise of the equipment.

After replacing the deep groove column bearing with the deep groove ball bearing, the abnormal noise of the bearing disappears. After a period of operation, the noise did not reappear, the vibration amplitude of the motor met the requirements, the load performance was stable, and the current did not fluctuate greatly.