How do you determine whether a bearing can be reused? Pay attention to the bearing grease seal.

发布时间：2022年01月24日 10:44

When performing regular maintenance, operational inspections, and replacement of peripheral components on equipment, the bearings that have been removed should be inspected to determine whether they can be reused or whether their current condition is better or worse than before. It is essential to carefully examine and document the condition of the removed bearings, including their external appearance. To accurately determine and investigate the remaining amount of lubricant, after taking samples, the bearings must be thoroughly cleaned. Next, inspect the raceway surfaces, rolling element surfaces, mating surfaces, and the condition of the retainer for any signs of damage or abnormalities. To decide whether a bearing can be reused, the China Lubricant Network recommends considering factors such as the extent of bearing damage, machine performance, the importance of the component, operating conditions, and inspection results.

Determining Whether a Bearing Can Be Used Again – China Lubricant Oil Network

To determine whether a bearing can be reused, one must first take into account the extent of bearing damage, as well as factors such as machine performance, operational importance, running conditions, and inspection intervals. If the inspection reveals any damage or abnormalities in the bearing, the relevant section should identify the root cause and develop appropriate countermeasures. Furthermore, according to the inspection results, if any of the following defects are found, the bearing must no longer be used and should be replaced with a new one.

a. Any one of the inner and outer rings, rolling elements, or retainer shows cracks or fragments.

b. One of the inner or outer rings, or the rolling elements, has spalling.

c. The raceway surface, retainer, and rolling elements show significant signs of galling.

d. The retainer is severely worn or the rivets are badly loose.

e. The raceway surfaces and rolling elements are rusted and scarred.

f. With noticeable dents and marks on the rolling surfaces and rolling elements.

g. There is creep on the inner ring’s inner diameter surface or the outer ring’s outer diameter surface.

h. Severely discolored due to overheating.

i. The seals and dust covers of grease-lubricated bearings are severely damaged.

Operation Check and Fault Handling

The inspection items during operation include the rolling sound of bearings, vibration, temperature, and lubrication condition, with specific details as follows:

I. Rolling Noise of Bearings

Use a sound level meter to check the magnitude and quality of the rolling noise from bearings in operation. Even if a bearing has minor damage such as slight spalling, it will emit abnormal and irregular sounds, which can be detected using a sound level meter.

II. Bearing Vibration

Bearing vibrations are highly sensitive to bearing damage—for instance, spalling, pitting, rusting, cracking, and wear—all of which can be detected through bearing vibration measurements. Therefore, by using specialized bearing vibration detectors (such as frequency analyzers), it is possible to measure the magnitude of vibrations and, through frequency analysis, pinpoint the specific nature of any abnormalities. The measured values will vary depending on factors such as the operating conditions of the bearing or the installation location of the sensor; thus, it is essential to analyze and compare the measurement data for each individual machine beforehand in order to establish clear judgment criteria.

III. Bearing Temperature

The temperature of a bearing can generally be estimated from the temperature outside the bearing housing. If oil holes are available, it is even more appropriate to directly measure the temperature of the bearing’s outer race. Typically, the bearing temperature gradually rises as operation begins and reaches a stable state after about 1 to 2 hours. The normal operating temperature of a bearing varies depending on factors such as the machine’s thermal capacity, heat dissipation rate, rotational speed, and load. If lubrication or installation conditions are improper, the bearing temperature may rise sharply, leading to abnormally high temperatures. In such cases, operation must be immediately stopped, and preventive measures taken. By using a thermal sensor, the bearing’s operating temperature can be monitored continuously, and an automatic alarm or shutdown can be triggered when the temperature exceeds the specified limit, thereby preventing accidents caused by bearing overheating.

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