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To judge 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. Inspect the bearings that have been dismantled during the regular maintenance, operation inspection and replacement of peripheral parts of the equipment, so as to judge whether it can be used again or whether the use is better or worse.
First, carefully investigate and record the removed bearings and their appearance. In order to clarify and investigate the remaining amount of lubricant, after sampling, the bearings should be well cleaned.
Next, check the raceway surface, the condition of the rolling surface and the mating surface, and the wear state of the cage for damage and abnormality.
As a result of the inspection, if the bearing is found to be damaged or abnormal, find out the cause and formulate countermeasures in the content of the damage section. In addition, according to the inspection results, if there are the following defects, the bearing can no longer be used, and a new bearing needs to be replaced.
a. Any one of the inner and outer rings, rolling elements and cages has cracks and fragments.
b. Any one of the inner and outer rings and rolling elements is peeled off.
c. The raceway surface, rib, and rolling elements are significantly damaged.
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 scratches 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 seal ring and dust cover of the grease-sealed bearing are severely damaged.
Inspection and troubleshooting during operation
The inspection items during operation include rolling sound, vibration, temperature, and lubrication status of the bearing. The details are as follows:
Rolling sound of a bearing
A sound detector is used to check the size and sound quality of the rolling sound of the running bearing. Even if the bearing has slight peeling and other damage, it will emit abnormal sound and irregular sound, which can be distinguished by the sound detector.
Vibration of two bearings
Bearing vibration is very sensitive to bearing damage, such as spalling, indentation, corrosion, cracks, wear, etc., will be reflected in the bearing vibration measurement. Therefore, by using a special bearing vibration measuring instrument (frequency analyzer, etc.), the vibration can be measured. The size of the abnormality cannot be inferred from the frequency score. The measured values vary depending on the operating conditions of the bearing or the installation position of the sensor, so it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment standard.
The temperature of the three bearings
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 by using the oil hole, it is more appropriate. Usually, the temperature of the bearing slowly rises as the operation starts 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 parts are suitable, the bearing temperature will rise sharply, and abnormally high temperature will occur. At this time, the operation must be stopped and necessary preventive measures should be taken. The use of thermal sensors can monitor the working temperature of the bearing at any time, and automatically alarm the user or stop when the temperature exceeds the specified value to prevent the occurrence of burning shaft accidents.
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