Selection and assembly of crusher bearings

Both ends of the vertical shaft of the crusher are supported by bearings, which are respectively located at the lower end of the pulley and the upper end of the rotor. The lower rotor bearing is driven by the motor to run at high speed. The lower bearing bears the circumferential force, belt tension and the gravity of the entire rotor (grading impeller). The bearing is easy to be damaged, the bearing is locked, and the outer ring is deformed. Due to the assembly, sealing, lubrication and other factors of the two bearings, the lubricating grease becomes hot and liquefies, loses or leaks, causing dry friction, which quickly damages the bearings. Through in-depth analysis and research on the failure phenomenon, the cause of the failure was found, and the problem was improved to solve the problem of easy damage to the crusher bearing.

  1. Working principle and structure of flake line crusher
    The vertical impact crusher uses the kinetic energy of the high-speed movement of materials for crushing. When the crusher is working, the high-speed rotating material of the rotor enters the crushing cavity through the feeding screw and is rapidly accelerated in the rotor. The acceleration can reach hundreds of times the acceleration of gravity. Under the action of centrifugal force, it impacts on the tooth plate, so that the crushed object is crushed by the combined effects of tooth impact, friction and impact between objects.

Second, the failure phenomenon of the crusher bearing
Both ends of the vertical shaft of the crusher are supported by bearings, one near the lower end of the pulley and one near the upper end of the rotor. The lower rotor bearing is driven by the motor to run at high speed. The lower bearing bears the circumferential force, belt tension and the gravity of the entire rotor (grading impeller), and the bearing is easily damaged (bearing lock, outer ring deformation, etc.). Due to assembly, sealing, lubrication and other factors of bearing 2 and bearing 3, the lubricating grease heats up and liquefies or leaks, causing dry friction, which quickly damages the bearing.

  1. Improvement measures of the crusher bearing
  2. Selection of bearing type
    From the common sense of mechanical structure design, in addition to bearing the normal circumferential force and belt tension, the weight of the entire rotor is also borne by the bearing. Therefore, the deep groove ball bearing and only the deep groove ball bearing that can only bear radial force Thrust bearings that can withstand axial force are not suitable for use. Angular contact ball bearings that can withstand both axial force and radial force should be selected (here, the angular contact ball bearings for vertical installation can be used in pairs. The axial clearance can be pre-tightened by the gravity of the rotor and the main shaft, and a relatively high rotation accuracy can be obtained), and because the upper bearing 4 only bears radial force, deep groove ball bearings with low price, high rotation accuracy and high limit speed can be selected. .
    Bearing 1 under our rotor is a 6205 deep groove ball bearing, its radial dynamic load rating cr: 14/KN; radial static load rating cor: 7.85/KN; grease lubrication rated speed: 13000r/min; oil lubrication rating Speed: 15000r/min. It is recommended to replace with angular contact ball bearing 7205AC, its radial dynamic load rating cr: 15.3/KN; radial static load rating cor: 9.5/KN; grease lubrication rated speed: 15000r/min; oil lubrication rated speed: 19000r/min.
  3. Assembly requirements for crushed bearing
    The correct assembly of the bearing is also an important factor affecting the life of the bearing. In order to reduce or avoid abnormal heating of the bearing, some aspects should be paid attention to when designing the shaft, hole, and installing the bearing to prevent the abnormal heating of the bearing in view of the problems that are likely to occur during actual production and assembly.
    2.1 Coordination requirements
    The bearing ring and shaft should adopt interference fit, and loose transition fit or clearance fit is not allowed; the outer ring and bearing hole should not adopt interference fit, and tighter transition fit is recommended. Regardless of the ferrule or the outer ring, relative rotation between the shaft and the hole connected to it is not allowed (bearing 3 and bearing 4 have been damaged for this reason), otherwise the bearing will heat up violently, and the bearing will be damaged. If it is heavy, it will burn the shaft and damage the crusher. If the shaft and hole size is not qualified, remedial measures must be taken, for example, after the hole is processed too large, it must be welded and re-bored, and the assembly can be assembled only after the processing is qualified.
    2.2 Coaxiality requirements
    The coaxiality of the bearing hole has a direct influence on the normal operation of high-speed bearings. Practice has proved that when 7205AC angular bearings (precision grade P5) and 6205 deep groove ball bearings (precision grade P5) are used together (the distance between the two bearings is 300mm), when the coaxiality deviation is 0.06mm, the spindle Under the condition of 4200rpm, the deep groove ball bearing will be damaged by heat after only a few minutes of operation. Therefore, the higher the speed of the bearing, the smaller the deviation of the coaxiality, it is recommended to control it within 0.01. When the coaxiality is slightly out of tolerance, a bearing with a larger radial clearance can be used to compensate part of the coaxiality deviation.
  4. Grease seal
    During the production process of the pulverizer, the deep groove ball bearings were burned out at the bearings 2 and 3 many times. After repeated analysis of the cause, it was suspected that the grease used in the bearing was too thin, and the bearing with a dust cover on one side did not seal the grease. Good, cause the loss of grease and heat the bearing. It is recommended to replace grease with a high dropping point and use RD deep groove ball bearings with axial labyrinth seals on both sides.

Through the damage of each bearing of the crusher during the production process, the main reason and solution of this problem are found from theoretical analysis to specific practice. Through the research and analysis of the four aspects of bearing selection, sealing, lubrication and installation requirements, a low-cost and long-term oil sealing solution for the vertical shaft bearing of the crusher is proposed, and the main reasons and solutions for the heating of high-speed and heavy-duty bearings are pointed out. It fundamentally solves the problem of easy damage to the shredder bearing, reduces the equipment failure rate, and ensures the continuity of the silk manufacturing process.