1. Inner and outer rings are not in the same center of rotation, resulting in shaft deflection Shaft skew is a common phenomenon in the actual operation of the bearing, and the skew of the shaft centerline is one of the main reasons for the failure of the thrust bearing. The causes of bearing and shaft misalignment are: (1) shaft tilt; (2) rotor installation error; (3) rotor manufacturing error; (4) thermal elastic deformation of the shaft, rotor and bearing during operation. Shaft deflection causes the oil film thickness, pressure distribution and tile surface temperature of each tile to be different, which has a great impact on the oil film thickness and pressure distribution, and a small impact on the temperature distribution of the tile surface; shaft deflection causes uneven fluid dynamic pressure in the bearing, resulting in fluctuations in the oil film force on the shaft, and with the increase in the degree of deflection, the more serious the oil film force fluctuation; in the full oil lubrication state, a small change in the deflection angle will cause the minimum oil film thickness and maximum pressure change, but the maximum temperature change of the tile surface is very small. To sum up, the shaft deflection causes uneven oil film thickness in the bearing, which may lead to oil film rupture and make the bearing fail. When mounting, in order to keep concentric as much as possible, the best way is to use the whole structure of the housing and bore out the two holes for mounting the bearing at one time. If a shaft is equipped with different sizes of bearings, the bearing holes in the housing should still be bored out at one time, and then the liner can be used to install the smaller size bearings. When two bearing holes are divided in two shells, the two shells should be combined together for boring. 2. The installation is not in place, there is a deviation or not installed to the bearing position, resulting in too small bearing clearance When running, the temperature of the shaft is generally higher than the temperature of the outer ring, the axial and radial thermal expansion of the shaft will be greater than the thermal expansion of the shell, if the bearing clearance is too small, it may lead to jamming. 3. Over tight fit between rotating ring and immovable ring The selection of bearing fit type should be decided according to the type and size of the bearing, the size and direction of the load and the nature of the load. The correct choice of bearing fit should ensure the normal operation of the bearing and prevent the relative rotation of the inner ring and shaft, outer ring and housing hole during work. Generally speaking, when the direction of the working load remains unchanged, the rotating circle should be tighter than the non-moving circle with some tighter fit, because the rotating circle bears the rotating load, while the non-moving circle bears the local load. When the higher the speed, the greater the load and the stronger the vibration, then the tighter the fit should be selected. When the bearing is installed in the thin-walled shell or hollow shaft, should also use a tighter fit. But too tight fit is unfavorable, this may be due to the elastic expansion of the inner and outer ring and the contraction of the outer ring and make the internal clearance of the bearing reduced or even completely disappeared, may also be due to the irregular shape of the shaft and seat hole surface or uneven rigidity and lead to irregular deformation of the inner and outer ring of the bearing, these will damage the normal work of the bearing. Too tight fit will also make the installation and disassembly difficult, especially for heavy machinery. 4. The installation process, preload force is too large Preload is the use of the external force applied during the assembly process to give the bearing the appropriate preload. Preload force is too small will make the bearing work with clearance, resulting in support stiffness and rotation accuracy is reduced, causing vibration and noise. Too much preload will increase the friction between the rolling body and the inner and outer ring raceway, and the temperature will rise too fast during operation, reducing the transmission efficiency and bearing life. Only apply the appropriate preload can eliminate axial clearance, reduce the reverse error, improve the shaft system rotation accuracy, reduce vibration and noise. Give the bearing appropriate preload, even if the bearing after a certain period of operation, the relative position of the bearing slightly changed, pre-applied load can still make the bearing inner and outer ring position to maintain stability, so the installation of preload control is very important.  

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