1. Improper clearance adjustment during assembly:

The clearance of needle roller bearings is divided into radial clearance and axial clearance. Its function is to ensure the normal operation and lubrication of the rolling elements and to compensate for thermal elongation. For bearings with adjustable clearance, because there is a proportional relationship between the axial clearance and the radial clearance, the required radial clearance can be obtained as long as the axial clearance is adjusted during installation, and cutting them is generally Used in pairs (that is, installed at both ends or one end of the shaft), therefore, only the axial clearance of one bearing needs to be adjusted. Generally, gaskets are used to adjust the axial clearance, and some can also be adjusted by screws or thrusters. For needle roller bearings whose clearance cannot be adjusted, because the radial clearance has been determined according to the standard during manufacture, it cannot be adjusted. After such bearings are installed on the shaft diameter or in the bearing seat hole, the actual radial clearance is called In order to assemble the radial clearance, the size of the assembly radial clearance should be just enough to form the necessary working radial clearance during operation to ensure the flexible rotation of the bearing. When this type of bearing is working, the relative displacement of the inner race occurs due to the heat elongation of the shaft when the temperature rises, so that the radial clearance of the bearing is reduced, and even the rolling elements are stuck between the inner and outer races. If an axial gap is left between one of the double-supported needle roller bearings (the other bearing is fixed on the shaft and in the bearing seat) and the side cover, the above phenomenon can be avoided. It can be seen from the above that regardless of the needle roller bearings with adjustable clearance or non-adjustable clearance, they must adjust the axial clearance during assembly (but some bearings with non-adjustable clearance do not need to leave axial clearance), so as to compensate for the temperature rise of the shaft. When the thermal elongation, so as to ensure the normal operation of the rolling element. If the axial clearance is too small, it will cause the bearing to rotate difficultly, generate heat, and even cause the rolling elements to be stuck or damaged; if the axial clearance is too large, it will cause abnormal noise during operation, and even cause severe vibration or damage the cage .

1. Improper coupling alignment:

The input shaft of most operating equipment is connected to the power shaft through a coupling, so the coupling must be aligned during assembly so that the driving shaft and the driven shaft are on the same axis. (3) Poor lubrication. The lubricating oil (or grease) used in needle roller bearings has a certain working temperature. When the temperature is too high, it will deteriorate, thus losing its lubrication effect and causing the bearing to burn out due to high temperature. In addition, poor quality of lubricating oil (or grease) itself or untimely refueling (grease) during operation will also cause the temperature of the bearing to rise or produce abnormal noise. (4) The rotor is unbalanced. Generally speaking, the rotor of the operating equipment must be dynamically and statically balanced before assembly, so there will be no problems with the bearings. However, some rotors are corroded by the medium or worn by solid impurities during operation, or the shaft is bent, which will cause unbalanced centrifugal force, which will cause the bearing to heat up, vibrate, and the raceway will be severely worn until it is destroyed. (5) The inspection and replacement is not timely. During the operation of the bearing, check it regularly according to the regulations. If there is heat, abnormal sound, vibration, etc., stop the car in time to find the cause and eliminate the fault. When it is reduced to HRC<60, or there is too much noise and cannot be adjusted, it should be replaced in time. If the inspection and replacement are not timely, it will cause serious damage to the bearing and even the rotor, thereby affecting normal production. In addition, the vibration caused by improper disassembly of the bearing and loosening of the anchor bolts of the equipment will also cause indentations on the bearing raceway and rolling elements, and cracks on the inner and outer races of the bearing. Methods to eliminate needle roller bearing failures: (1) When replacing bearings, carefully check the new bearings, and at the same time carefully check the shaft diameter, bearing seat hole and rotor; (2) When assembling and disassembling bearings, strictly implement the maintenance process and operate carefully to avoid bearing damage caused by improper assembly and disassembly; (3) Refuel and change oil on time to ensure that the working condition of the bearing is always in good condition; (4) Carefully check during operation to find hidden troubles and eliminate them in time.