How to determine whether bearings can be reused

Bearing is an important component in contemporary mechanical equipment. Its main function is to support the mechanical rotating body, reduce its friction coefficient during movement, and ensure its rotational accuracy.
Bearings play such an important role in mechanical equipment, so the number of bearings used is also very large. How to better play the role of bearings requires correct and reasonable use. During the use of bearings, when conducting regular maintenance, operational checks, and replacing peripheral parts of the equipment, some bearings will be dismantled. Whether these dismantled bearings can be reused requires inspection, investigation, and recording of the bearing appearance. At the same time, in order to clarify and investigate the remaining amount of lubricant, it is necessary to clean the bearings well after sampling.
1、 Inspection of dismantled bearings
Firstly, check the condition of the raceway surface, rolling surface, and mating surface, as well as the wear status of the cage, for any damage or abnormalities.
Furthermore, considering the degree of bearing damage, machine performance, importance, operating conditions, inspection cycle, etc., we can decide whether the bearing can be reused or replaced. If any damage or abnormalities are found in the bearings, identify the cause and develop countermeasures. If there are any of the following defects, the bearing cannot be reused and can be directly scrapped.
1. Any one of the inner and outer rings, rolling elements, or cages has cracks or fragments.
2. Any one of the inner and outer rings or rolling elements has detachment.
3. The raceway surface, edge guards, and rolling elements are significantly damaged.
4. The cage is severely worn or the rivets are loose.
5. Rust and scratches on the raceway surface and rolling body.
6. There are significant indentations and scratches on the rolling surface and rolling body.
7. There is creep on the inner diameter surface of the inner ring or the outer diameter of the outer ring.
8. Overheating can cause severe discoloration.
9. The sealing ring and dust cover of the grease sealed bearing are severely damaged.
2、 Judgment of bearings in operation
How to determine if there is a problem with a running bearing? It can be determined by checking the rolling sound, vibration, temperature, lubrication status, etc. of the bearing.
（1） Rolling sound of bearings
Use a sound detector to check the size and sound quality of the rolling sound of the running bearing. Even if there is slight peeling or other damage to the bearing, abnormal and irregular sounds will be emitted, which can be distinguished using a sound detector.
（2） Vibration of bearings
Bearing vibration is very sensitive to bearing damage, such as peeling, indentation, rust, cracks, wear, etc., which can be reflected in bearing vibration measurement. Therefore, by using a special bearing vibration measuring device (frequency analyzer, etc.), the magnitude of vibration can be measured, and the specific abnormal situation can be inferred through frequency. The measured values vary depending on the usage conditions of the bearings or the installation position of the sensors, so it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment criteria.
（3） Temperature of bearings
Usually, the temperature of the bearing gradually increases with operation and reaches a stable state after 1-2 hours. The normal temperature of the bearing varies with the Heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are suitable, the bearing temperature will suddenly rise and abnormal high temperatures will occur. At this time, the operation must be stopped and necessary preventive measures must be taken. The use of a thermal sensor can monitor the working temperature of the bearing at any time, and achieve automatic alarm or stop when the temperature exceeds the specified value, to prevent shaft accidents from occurring.
（4） Lubrication status of bearings
Lubrication is of great significance for rolling bearings. Lubricants in bearings not only reduce friction resistance, but also play a role in heat dissipation, reducing contact stress, absorbing vibration, and preventing corrosion. They are also essential conditions for stable operation of rolling bearings.