Bearing holding, refers to the bearing due to lubrication, installation, selection and other reasons in the operation process to produce a lot of heat, these heat in a short time and can not be dissipated. This leads to a sharp rise in the temperature of the bearing, and even melts the metal of the shaft and bearing, and eventually, during the cooling process, the shaft and the inner sleeve of the bearing are fused together to hold the bearing dead. This phenomenon is more common in the overhaul of equipment, as well as production services site, the specific causes of bearing hold dead are as follows:
A, the cause of bearing fever holding dead
(1) assembly of bearing outer ring and bearing seat hole or bearing inner ring and shaft with improper.
In the assembly process, sometimes no repair grinding bore and measurement of its size, replace the new bearing for assembly, test drive found that the temperature rise is too high. When dismantling the test volume, it is found that the bearing seat hole has been deformed, making the outer ring part of the bearing extruded, resulting in the radial clearance of the bearing becoming smaller, its rolling body rotating unevenly and the wear intensifying. Bearing inner ring and shaft clearance is too large, bearing inner ring with the rolling body and shaft together with the rotation, there is friction to make the bearing hot, vibration.
2) Improper control of bearing heating temperature during assembly or uneven heating leads to bearing deformation.
In the heating operation when the commissioning bearing heater temperature is too high, it will make it produce tempering and cause hardness and precision reduction, so that the bearing temperature rises, leading to increased wear damage to the bearing. Due to uneven heating causes bearing deformation, uneven clearance, local high temperature.
3) improper adjustment of bearing clearance during assembly.
In practice, many installation sometimes only by hand to debug, clearance is too large or too small, can not meet production needs. If the axial clearance is too small, easy to cause bearing heat, accelerate pitting, and even make the rolling body stuck or glued damage; if the axial clearance is too large, the impact of the motion vice increased, the stiffness is reduced, it will lead to the operation of the sound, and even cause serious vibration or make the cage damage.
(4) oil seal problem: oil seal is used to seal the rotary shaft in the mechanical equipment with sealing components, and the cavity is basically stationary, so the oil seal is also known as rotary shaft lip seal. For the oil seal with sub-lip, its sub-lip plays a dustproof role to prevent the intrusion of impurities to prolong the life of the oil seal, but the sub-lip is often poorly lubricated, the friction is large, resulting in dry friction and damage to the oil seal, so the installation of double-lip oil seal must be filled with grease between the two lips.
5) For thermal equipment, the thermal expansion and contraction of the shaft is not considered in the installation process, and the free end bearing is squeezed during operation, generating huge heat.
6) Clearance problems
In the assembly process, if the spacer size is not carefully calibrated for assembly trial, the temperature will rise rapidly after a certain period of time. Bearing outer ring size by the end cover and bearing seat stop has been determined, the size of the spacer reduces, the inner ring size will be adjusted by the round nut, and finally pressed, the axial clearance of the bearing becomes smaller, making it hot during operation.
7) Lubrication problem
The grease in the bearing should not be too much. If the amount of grease is too large, the friction torque will increase and the temperature of the bearing will rise; if the amount of grease is too small, it will not get reliable lubrication and dry friction will occur. Generally speaking, the appropriate amount of grease is 1/3 to 1/2 of the total clearance volume in the bearing.
Equipment in the operation of the interruption of oil, the loss of lubrication, cooling bearing fever, soon damaged.
B, the processing of bearing clamping
For the bearing dead, first in the installation, lubrication, cooling and heat dissipation, to ensure that the shape and tolerance size of the inclusive parts, bearing quality in strict accordance with the instructions or maintenance program, and strive to avoid the bearing dead. Once there is a clamping accident, you must first cut off the bearing inner sleeve, then turn the shaft and use the method of coating or other methods. If the shaft is very important, it must be inspected to ensure the quality of the shaft. If necessary, the shaft must be replaced.
