Vibrating screen is a common equipment in mining machinery and equipment, its vibration is mainly generated by the exciter to achieve, and the use of the exciter working conditions are harsh, and with strong vibration impact, so its bearings will inevitably heat up, burn and other phenomena, seriously affect the normal operation of the vibrating screen.
Our engineering team from JXSC Mining Machinery has analyzed by practical experience for more than 10 years, and have concluded that factors that leading to bearing damage mainly have 3 main points, the design of vibrating screen, the processing, and the use and maintenance of vibrating screens.
First, the design reasons that cause the problems.
1, bearing selection is not reasonable
Bearing type of use, limit speed, installation with size, clearance, self-lubricating properties and other requirements are high, ordinary bearings work in harsh conditions prone to damage. If the bearing is not selected properly at the early stage of design, the service life of the bearing will be shorter.
Solution: use special bearings. Commonly used vibrating screen bearings generally have cylindrical roller bearings and spherical roller bearings. Both have a large radial bearing capacity, the former bearing limit speed is also higher, the static and dynamic load carrying capacity, but the coaxiality of the bearing seat hole requirements are high; the latter alignment performance is good, can compensate for different shaft problems caused by the bearing seat hole processing, but can not bear pure axial load.
2, lubrication seal structure design is not reasonable
At present, many domestic shaker bearings using grease lubrication, labyrinth seal structure, sealing gap is generally 1 ~ 2mm. But in actual use, with the shaker bearing temperature rises, grease viscosity gradually reduced, spindle high-speed rotation, labyrinth cover grease from the labyrinth cover constantly leak, eventually leading to bearing damage due to the lack of lubrication.
Due to the unreasonable design of the lubrication seal structure, the bearing lubrication is not sufficient, which is the main reason for the deformation and burnout of the bearing due to heat.
Solution: Use thin oil lubrication, improve the lubrication channel, improve the sealing structure. Many manufacturers currently use thin oil circulation lubrication, labyrinth seal and other non-contact seal combination structure.
3, bearing and bearing seat hole with improper selection
Bearing and bearing seat hole with tolerance is the focus of the design. If you choose a large interference fit, it will force the bearing raceway shape geometric deformation, abnormal vibration during operation; if you choose a large clearance fit, it will make the bearing outer ring in the bearing housing hole relative sliding, resulting in bearing sharp temperature rise and damage.
Solution: Choose a reasonable fit tolerance. The inner ring of the bearing and the shaft with a loose transition fit or clearance fit tolerance, the outer ring and the bearing seat hole with a tighter transition or a slightly smaller interference fit tolerance.
4, the design does not take into account the expansion and contraction of the shaft
Shaker operating temperature is generally 35-60 ℃, due to thermal expansion and contraction caused by the expansion and contraction of the shaft can not be ignored.
Solution: One end of the bearing design into the transition or clearance fit, in order to make the shaker shaft in the thermal expansion and contraction can be relative to the inner ring for sliding.
Second, the process reasons
1, the bearing seat hole processing accuracy is not enough,
the same shaft two bearing seat hole different heart.
Solution: the use of higher processing precision equipment, in the CNC boring and milling machine or machining center, two bearing holes in one cutting completed.
2, bearing assembly force is uneven,
such as in the cold assembly process, uneven force on the inner and outer ring of the bearing, resulting in the inner and outer ring of the bearing relative to the shaft or bearing hole to produce a certain amount of deflection, the operation process will wear faster.
Solution: Use special tooling, so that the bearing assembly process of the inner ring or outer ring uniform pressure, assembly in place.
3, bearing installation is not clean, or lubricating oil is not clean
This will result in bearing raceway wear, rolling body friction increases, the temperature rises, resulting in bearing damage.
Solution: Clean the bearings before assembly. Shaker use in the regular replacement of lubricating oil, the first change of lubricating oil in the equipment after the use of 150h, after each run 1000h replacement.
4, the quality of eccentric block is different
into a group of eccentric block quality differences, or into a group of eccentric block installation angle error is large, causing the vibration source center flutter, resulting in bearing heating.
Solution: Adjust the quality and angle of the eccentric block to make it symmetrical and consistent. When installing or adjusting the excitation force, make the eccentric block angle on the same axis consistent, and the eccentric block angle on the parallel axis symmetrical.
Third, the use and maintenance reasons
1, due to uneven foundation or incorrect installation of the spring seat, causing abnormal movement of the screen body, resulting in rotation or distortion of the vibrating screen, the exciter bearing heat damage.
Solution: adjust the foundation to make it level. When installing, first use the level meter to measure whether the foundation is level, such as uneven can be adjusted by adding a pad on the foundation.
2, vibrating screen center of gravity error, causing abnormal operation of the screen body, so that the bearing is damaged by heat.
Solution: The ideal working condition of the vibrating screen is the smooth operation of the whole machine, the amplitude is the same everywhere, so we should strictly control the production and installation accuracy of the product to ensure that the center of gravity position does not shift, while trying to feed all.
3, the exciter fixed bolts loose, or not add anti-loose spring washers, causing the vibration source center chatter, resulting in bearing heat damage.
Solution: The first use of the exciter, running 2h and 50h to re-check the fastening bolts, found loose immediately tighten.
4, improper selection of lubricant, fill too much or too little, will cause bearing heating.
Solution: Under normal circumstances, lubricating oil should be filled with 2/3 of the lubrication cavity as appropriate, too much easy to heat up, and must use exhaust bolts exhaust. Generally in the case of no oil leakage, the shaker 80-100h refill a lubricant, a refill of no more than 1kg, and timely discharge of waste oil.
Conclusion
Exciter is the power source of the vibrating screen, improve the design and processing quality, correct use and careful maintenance is to ensure that the preconditions for good operation of the exciter bearings.