Case 1: A certain production factory, motor bearing model: NU319/C3

The on-site motor was placed on a thick rubber pad and started up with significant vibration. It is speculated that the abnormal noise originated from the large vibration. There was no fixed test bench on site. It is recommended to move the motor to the ground, and the vibration disappeared. The site ran for 40 minutes, and the customer reported that it was normal.

Case 2: A certain motor factory, motor bearing model: 6226/C3

The double line frequency can be seen in the envelope spectrum of the on-site motor acceleration. The equipment had uneven air gaps. After the motor manufacturer corrected the centering dimensions of the end covers on both sides and adjusted the air gap gap, the motor noise disappeared.

Case 3: A certain motor factory, motor bearing model: 6208/C3 (iron cover)

On-site confirmation revealed that the 6208/C3 (iron cover) was produced in 2021. By comparing the 2021 bearing with the latest 25 bearing, it was found that the grease from 2021 had dried up to some extent when the iron cover was opened. The abnormal noise on site indicated that the 2021 bearing was manufactured, while the 25 bearing had no issues and the problem was resolved.

Case 4: A certain motor factory, motor bearing model: 6306/C3 (iron cover)

An abnormal noise was detected when the motor bearing was tested for a few minutes after startup. Continue running for 15 to 30 minutes and the abnormal noise disappears. It is speculated that the grease has not been fully running-in. After full running-in, the abnormal noise disappears.

Case 5: A production factory, motor bearing model: 6312/C3 (iron cover)

There was a relatively loud noise during the on-site fixed test bench test, but the sound remained unchanged when grease was added. A 25um paper gasket is placed at the drive end, reducing the sound. If the bearing clearance is too large, increasing the axial preload of the bearing can appropriately reduce the noise level of the bearing.

Case 6: A production factory, motor bearing model: NJ 2318/C4

When testing the motor of the factory vibrating screen after maintenance, the engineer in the maintenance workshop believed that the sound of the bearing was abnormal. After testing, the sound disappeared after adding grease, but it reappeared in a short time. The test was extended for two hours, but neither the vibration nor the temperature changed. And make a judgment in combination with a stethoscope. This sound is the inherent noise of the bearing and cannot be resolved without optimizing any components.

Considering the situation of the vibration motor, it is necessary to optimize the C4 clearance. However, there is no limit to the decibel value of the sound on site. Finally, it was decided to put the motor into use. It has been running for one year and there are no abnormalities with the motor at all.

Case 7: A production factory, motor bearing model: NU 234/C3

When inspecting the equipment, the inspection engineer uses a stethoscope to listen to the sound of the bearings. Once an abnormality is detected, the sound is recorded using the recording function. After returning to the office, I played it back on the computer and confirmed that there were regular abnormal sounds.

Go to the site again and conduct vibration spectrum inspection and analysis to further confirm the fault spectrum of the outer ring. Immediately arrange for the motor to be shut down for maintenance. After disassembly, confirm the fault of the outer ring of the bearing.