How to decide whether the bearing can be used?
To decide whether the bearing can be used again, it should be decided after considering the degree of bearing damage, machine performance, importance, operating conditions, inspection cycle, etc.
Check the disassembled bearings during the regular maintenance of the equipment, the operation inspection and the replacement of peripheral parts.
By doing so, we are able to judge whether it can be used again or whether the use is good or bad.
Conditions in which the bearing cannot be used any longer
As a result of the inspection, if there are any of the following defects, the bearing can no longer be used and needs to be replaced with a new one.
a. There are cracks and debris in any of the inner and outer rings, rolling elements, and cages.
b. Any one of the inner and outer rings and rolling elements is peeled off.
c. The raceway surface, ribs, and rolling elements are obviously stuck.
d. The cage is severely worn or the rivets are loose.
e. The raceway surface and rolling elements are rusted and scratched.
f. There are obvious indentations and marks on the rolling surface and rolling elements.
g. There is creep on the inner diameter surface of the inner ring or the outer diameter of the outer ring.
h. Severe discoloration due to overheating.
i. The sealing ring and dust cover of the grease-sealed bearing are severely damaged.
How to check bearings in operation?
During operation, whether the bearing is normal or not can be judged by the following aspects
Noise of bearings
Use a sound detector to check the noise level and sound quality of the rolling sound of the running bearing.
Even if the bearing is slightly damaged by peeling off, it will emit abnormal and irregular sounds, which can be distinguished by the sound detector.
Vibration of the bearing
Bearing vibration is very sensitive to bearing damage, such as spalling, indentation, rust, cracks, wear, etc., which will be reflected in bearing vibration measurement.
Therefore, the degree of the vibration can be measured by using a special bearing vibration measuring device (frequency analyzer, etc.), and the specific situation of the abnormality can’t be deduced through the frequency division. The measured value differs depending on the service conditions of the bearing or the installation position of the sensor, etc.
Therefore, it’s necessary to analyze and compare the measured value of each machine in advance to determine the judgment standard.
The temperature of the bearing can generally be inferred from the temperature outside the bearing chamber. If the temperature of the outer ring of the bearing can be directly measured through the oil hole, it will be more appropriate. Usually, the temperature of the bearing rises slowly with the start of operation, and reaches a steady 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 are not suitable, the temperature of the bearing will rise sharply and abnormally high temperature will appear.
At this time, the operation must be stopped and necessary preventive measures must be taken.
We can use thermal sensor to monitor the working temperature of the bearing at any time.
And when the temperature exceeds the specified value, it can automatically alarm the user or stop to prevent the combustion shaft accident.
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