1. Bearing quality

The service life of the pulley mainly depends on the performance of the bearing and the seal. If the pulley uses high-quality bearings and seals, the service life of the pulley will be greatly extended. Test results show that the friction resistance of the bearing accounts for about 1/4 to 1/8 of the total resistance of the pulley rotation. At present, the bearing model used in the pulley is 6204, 6205, 6305, 6306 and other rolling bearings. Generally, for domestic and foreign bearings, it is believed that the processing accuracy and material heat treatment of Chinese bearings are basically the same as those of developed countries, but in 1974, the imported British Dowty Company and Gallic Company used 415705 type pulley special bearing, whose service life was increased by more than 10 times compared with the life of common rolling bearings in our country, and the resistance to rotation was reduced by more than 2 times. It can be seen that our country should improve the processing accuracy and heat treatment quality of bearings, and catch up with the world-developed countries.

Bearing quality determines the operating life. At present, a certain number of production enterprises choose low-priced, low-quality bearings to assemble pulleys, and the inner and outer diameter precision, hardness and clearance of the bearings do not meet the technical specifications requirements. Therefore, it is necessary to purchase reliable products from domestic genuine bearing manufacturers, such as: Wafangdian Bearing Company, Luoyang Bearing Company.

2. Bearing cup quality

The poor machining accuracy of the inner hole of the bearing cup causes the radial movement of the bearing in the bearing cup, which is one of the reasons for the damage of the pulley.

Stamping bearing cup, 3 sets of stamping dies can complete the production of finished products. The quality of the stamping die determines the quality of the bearing cup, and ultimately determines the life of the bearing, which is related to the service life of the pulley. Therefore, the pulley production enterprises must track and evaluate and do management review to ensure that they are qualified procurement control list suppliers, and strictly inspect the bearing cups according to the inspection procedures.

3. Welding of bearing cup and pulley tube

The quality of the welding between the bearing cup and the tube is poor, causing the axial separation or the ingress of dust and water into the bearing of the pulley, causing the pulley to be damaged. Therefore, the welding of the bearing cup and the tube should be listed in the process flow chart of the pulley production process as a special process and key process, and a special process guidebook should be specially formulated for this process. The parameters such as welding voltage, welding current, gas flow rate, wire feed speed, and tube selection speed should be clearly specified in the process guidebook. The welding equipment, welding wire material, and welding operator should be verified and calibrated. In summary, the welding of the bearing cup and the tube should be controlled as a special process point.

4. Selection of lubricating grease

The improper selection of lubricating grease will cause bearing damage and then lead to pulley damage. MT821-2006 coal industry standard clearly requires the selection of 3# lithium grease, and all production enterprises must follow the implementation. Otherwise, the pulley will be damaged after running for several hours.

Here, it is emphasized that for pulleys operating in an environment of -25℃, special type of aviation lubricating grease with low temperature resistance must be selected.

5. Pulley assembly

Pulley assembly not only requires the manufacture of special process equipment, but also must be completed on the pulley press. Only in this way can the axial specified assembly pressure of the bearing, sealing component and washer be controlled. In addition, it is required that the installation personnel must be trained and passed the technical training and examination before operation. In summary, pulley assembly should be controlled as a key process point and a key process guidebook should be formulated.