Causes of damage to vibrating screen bearings
Writer： admin Time：2020-10-22 15:58 Browse：℃
Vibrating screen is a common equipment in mining machinery and equipment. Its vibration is mainly realized by a vibration exciter. However, the working conditions of the vibration exciter are harsh and bear strong vibration and impact, so the bearings will inevitably generate heat , Burnout and other phenomena, seriously affecting the normal operation of the vibrating screen. Among them, the bearing plays a very important role in the vibrating screen. It is connected to the various parts of the vibrating screen, and the friction force will be very large. It is inevitable that various failures will occur. The damage of the bearing will seriously affect the working efficiency of the vibrating screen. According to the analysis of the practical experience of the polyurethane screen manufacturers, the main bearing damages are as follows:
1. Design reasons
1. Unreasonable bearing selection
The use type, limit speed, installation size, clearance, self-lubricating performance and other requirements of the bearing are relatively high, and ordinary bearings are easy to be damaged under severe working conditions. If the bearing is improperly selected in the early design stage, the service life of the bearing will be shorter.
Solution:
use special bearings. Commonly used vibrating screen bearings generally include cylindrical roller bearings and spherical roller bearings. Both have large radial bearing capacity. The former bears higher limit speed and has strong bearing capacity for dynamic and static loads, but has higher requirements for the coaxiality of the bearing housing hole; the latter has good alignment performance and can compensate Different shaft problems caused by the processing of the bearing seat hole, but can not bear pure axial load.
2. The design of the lubricating seal structure is unreasonable
At present, many domestic vibration exciter bearings adopt grease lubrication and labyrinth seal structure, and the sealing gap is generally 1~2mm. However, in actual use, as the temperature of the exciter bearing increases, the viscosity of the grease gradually decreases, the spindle rotates at high speed, and the grease in the labyrinth cover continues to leak from the labyrinth cover, which eventually causes the bearing to be damaged due to lack of lubrication.
Due to the unreasonable design of the lubrication seal structure, the bearing is not sufficiently lubricated, which is the main reason for the bearing deformation and burning due to heating.
Solution:
Using thin oil lubrication method to improve the lubrication channel and improve the sealing structure. At present, many manufacturers use thin oil circulation lubrication, a combination of labyrinth seal and other non-contact seals.
3. Improper selection of matching between bearing and bearing seat hole
The matching tolerance of the bearing and the housing bore is the key point in the design. If a large interference fit is selected, the shape of the bearing raceway will be forced to produce geometric deformation and abnormal vibration during operation; if a large clearance fit is selected, the outer ring of the bearing will relatively slide in the bearing housing hole, causing the bearing to rapidly heat up and be damaged .
Solution:
Choose a reasonable fit tolerance. The inner ring and the shaft of the bearing adopt a loose transition fit or clearance fit tolerance, and the outer ring and the bearing seat hole adopt a tighter transition or a slightly smaller interference fit tolerance.
4. The amount of expansion and contraction of the shaft is not considered in the design
The operating temperature of the exciter is generally 35-60℃, and the expansion and contraction of the shaft caused by thermal expansion and contraction cannot be ignored.
Solution:
One end bearing is designed as a transition or clearance fit, so that the shaft of the exciter can slide relative to the inner ring when it expands and contracts.
2. Process reasons
1. The machining accuracy of the bearing seat hole is not enough, and the two bearing seat holes of the same shaft are not concentric.
Solution:
Using high-precision equipment, in a CNC boring and milling machine or machining center, two bearing holes are cut at one time.
2. Uneven force during bearing assembly. For example, in the cold assembly process, uneven force is applied to the inner and outer rings of the bearing, resulting in a certain amount of deflection between the inner and outer rings of the bearing relative to the shaft or bearing hole, which will wear faster during operation.
Solution:
Special tooling is used to make the inner ring or outer ring evenly compressed during the assembly process of the bearing and assembled in place.
3. The bearing is not cleaned during installation, or the lubricating oil is not clean, causing the bearing raceway to wear, the friction of the rolling elements increases, the temperature rises, and the bearing is damaged.
Solution:
Wash the bearing before assembly. The lubricating oil is changed regularly during the use of the exciter. The first lubricating oil is changed after the equipment is used for 150 hours, and then every 1000 hours of operation.
4. The quality difference of the group eccentric blocks, or the large installation angle error of the group eccentric blocks, causes the vibration source center to vibrate, causing the bearing to heat up.
Solution:
Adjust the mass and angle of the eccentric block to make it symmetrical. When installing or adjusting the excitation force, the angles of the eccentric blocks on the same axis should be consistent, and the angles of the eccentric blocks on the parallel axis should be symmetrical.
3. Reasons for use and maintenance
1. Due to the uneven foundation or incorrect installation of the spring seat, abnormal movement of the screen body is caused, causing the vibrating screen to rotate or twist, and the vibration exciter bearing is heated and damaged.
Solution:
Adjust the foundation to make it level. When installing, first use a level to measure the level of the foundation. If it is uneven, you can adjust it by adding a pad to the foundation.
2. The large error of the center of gravity of the vibrating screen causes abnormal operation of the screen body, and heat damage to the bearing.
Solution:
The ideal working condition of the vibrating screen is that the whole machine runs smoothly and the amplitude is the same everywhere. Therefore, the production and installation accuracy of the product must be strictly controlled to ensure that the center of gravity position does not deviate, and at the same time, feed materials as much as possible.
3. The fixing bolts of the vibration exciter are loose, or the anti-loosening spring washer is not added, which causes the vibration source center to vibrate, which causes the bearing to be heated and damaged.
Solution:
The vibration exciter is used for the first time. After running for 2h and 50h, re-check the tightening bolts. If it is loose, tighten it immediately.
4. Improper selection of lubricating oil, too much or too little filling, will cause bearing heating.
Solution:
Under normal circumstances, the lubricating oil should be filled with 2/3 of the lubricating cavity. If it is too much, it is easy to heat up, and the exhaust bolt must be used for exhaust. Generally, if there is no oil leakage, the exciter should be filled with lubricating oil once at 80-100h, and the filling should not exceed 1kg, and the waste oil should be discharged in time.
The vibrator is the source of power for the vibrating screen. Improving the design and processing quality, correct use and careful maintenance are the prerequisites for ensuring the good operation of the vibrator bearing.
Common causes of vibration screen bearing lock
1. Poor lubrication
The oil is not filled in time or the oil pipe is blocked or the lubricating oil has deteriorated, causing the bearing to lock up.
2. Incorrect bearing selection
Incorrect installation size or model of the bearing will cause normal operation and cause the bearing to lock up.
3. Bearing wear and clearance reduction
Due to the operation under high temperature, high speed and heavy load, the wear of the bearing and the temperature increase of the inner ring of the bearing, the increase of thermal expansion will reduce the radial working clearance of the bearing and cause the bearing to lock.
