Bearing locking refers to the phenomenon where a large amount of heat is generated during the operation of a bearing due to lubrication, installation, selection, and other reasons. This heat cannot be dissipated in a short period of time, resulting in a sharp increase in bearing temperature and even melting of the metal between the shaft and the bearing. Eventually, during the cooling process, the shaft and the inner sleeve of the bearing are fused together to lock the bearing. This phenomenon is quite common in equipment maintenance and production service sites. The specific reasons for bearing lock up are as follows:

1、 The reason for bearing overheating and locking
1) Improper fit between the outer ring of the bearing and the bearing seat hole or the inner ring of the bearing and the shaft during assembly.
During the assembly process, sometimes the inner holes were not polished and their dimensions were not measured. New bearings were replaced for assembly, and after testing, it was found that the temperature rise was too high. During disassembly and measurement, it was found that the bearing seat hole had deformed, causing the outer ring of the bearing to be compressed, resulting in a decrease in the radial clearance of the bearing, uneven rotation of its rolling elements, and increased wear. The clearance between the inner ring of the bearing and the shaft is too large, and the inner ring of the bearing rotates together with the rolling elements and the shaft, causing friction and heating and vibration of the bearing.
2) Improper temperature control or uneven heating during assembly can cause deformation of the bearing.
If the temperature of the bearing heater is too high during heating operation, it will cause tempering and reduce hardness and accuracy, resulting in an increase in bearing temperature and exacerbating wear and damage to the bearing. Due to uneven heating, the bearing undergoes deformation, resulting in uneven clearance and localized high temperatures.
3) Improper adjustment of bearing clearance during assembly.
In practical work, many installations sometimes rely solely on hand feel for debugging, with gaps that are too large or too small to meet production needs. If the axial clearance is too small, it can easily cause the bearing to heat up, accelerate pitting corrosion, and even cause the rolling elements to get stuck or glued together; If the axial clearance is too large, the impact force of the moving pair increases and the stiffness decreases, it will cause abnormal noise during operation, and even cause serious vibration or damage to the retaining frame.
4) Oil seal problem: Oil seal is a sealing element used to seal the rotating shaft in mechanical equipment, and the cavity is basically stationary, so oil seal is also called rotating shaft lip seal ring. For oil seals with a secondary lip, the secondary lip plays a role in dust prevention, preventing impurities from entering and extending the life of the oil seal. However, the secondary lip is often poorly lubricated and has high friction, causing dry friction and damage to the oil seal. Therefore, when installing a dual lip oil seal, it is necessary to fill the space between the two lips with lubricating grease.
5) For thermal equipment, the installation process did not consider the thermal expansion and contraction of the shaft, and the free end shaft was subjected to compression during operation, generating enormous heat.
6) Gap issue
During the assembly process, if the size of the spacer sleeve is not carefully calibrated and the assembly test is not carried out, the temperature will quickly rise after a certain period of time. The outer ring size of the bearing is determined by the end cap and the bearing seat stopper, and the spacer size is reduced. The inner ring size will be adjusted by a round nut and finally tightened, reducing the axial clearance of the bearing and causing it to generate heat during operation.
7) Lubrication issues
The lubricating grease in the bearing should not be too much. Adding too much grease will increase the friction torque and raise the bearing temperature; If the amount of grease added is too small, reliable lubrication cannot be obtained and dry friction occurs. Generally speaking, the appropriate amount of grease to be added is 1/3 to 1/2 of the total clearance volume inside the bearing. Therefore, it is necessary to regularly inject an appropriate amount of lubricating grease according to the usage requirements.
The equipment experiences oil interruption during operation, causing the bearings to lose lubrication and cooling, resulting in overheating and rapid damage.
2、 Handling of bearing locking
For the locking of bearings, strict control should be carried out in installation, lubrication, cooling and heat dissipation, ensuring the shape and tolerance dimensions of the containment parts, and bearing quality. The instructions or maintenance plan should be strictly followed to avoid bearing locking. Once a lock up accident occurs, the inner sleeve of the bearing must be cut off first, and then the axle must be treated with coating or other methods. Restore the dimensions and tolerances of the shaft, and then reinstall it as required. If the shaft is very important, it must be inspected to ensure its quality. If necessary, the shaft must be replaced.

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