The vibrating screen is a commonly used equipment in mining machinery and equipment, and its vibration is mainly generated by the vibration exciter. However, the operating conditions of the vibration exciter are harsh, and it bears strong vibration impacts. Therefore, its bearings will inevitably experience heating, burning, and other phenomena, seriously affecting the normal operation of the vibrating screen. This article shares the reasons and solutions for the damage of the vibrating screen bearings. 

1、 Design reasons

1. Unreasonable bearing selection

The use type, extreme speed, installation fit size, clearance, self-lubricating performance and other requirements of bearings are high, and ordinary bearings are prone to damage when working under harsh conditions. If the selection of bearings is not appropriate in the early stage of design, the service life of the bearings will be shorter.

Solution: Use specialized bearings. Commonly used vibrating screen bearings generally include cylindrical roller bearings and self-aligning roller bearings. Both have significant radial load-bearing capacity, with the former having a higher limit speed and strong load-bearing capacity for both dynamic and static loads, but requiring a higher coaxiality of the bearing seat hole; The latter has good centering performance and can compensate for different shaft problems caused by bearing seat hole processing, but cannot withstand pure axial loads.

2. Unreasonable design of lubrication and sealing structure

At present, many exciter bearings in China adopt grease lubrication and labyrinth sealing structures, with a sealing gap generally between 1 and 2mm. However, in practical use, as the temperature of the exciter bearing increases, the viscosity of the lubricating grease gradually decreases, and the spindle rotates at high speed. The lubricating grease inside the labyrinth cover continuously leaks from the labyrinth cover, ultimately leading to bearing damage due to a lack of lubrication.

Due to the unreasonable design of the lubrication and sealing structure, insufficient lubrication of the bearings is the main reason for the deformation and burning of the bearings due to heating.

Solution: Use thin oil lubrication, improve lubrication channels, and improve sealing structures. Currently, many manufacturers adopt a structure that combines thin oil circulation lubrication, labyrinth seals, and other non-contact seals.

3. Improper selection of matching between bearings and bearing seat holes

The tolerance of the fit between the bearing and the bearing seat hole is a key point in design. If a larger interference fit is selected, it will force geometric deformation of the bearing raceway shape and cause abnormal vibration during operation; If a larger clearance fit is selected, it will cause the outer ring of the bearing to slide relatively in the bearing seat hole, leading to rapid temperature rise and damage to the bearing.

Solution: Choose a reasonable fit tolerance. The inner ring of the bearing and the shaft are fitted with a loose transition fit or clearance fit tolerance, while the outer ring and the bearing seat hole are fitted with a tight transition or slightly smaller interference fit tolerance.

4. The design did not consider the expansion and contraction of the shaft

The operating temperature of the vibration exciter is generally between 35 and 60 ℃, and the expansion and contraction of the shaft caused by thermal expansion and contraction cannot be ignored.

Solution: Design one end bearing as a transitional or clearance fit, so that the exciter shaft can slide relative to the inner ring during thermal expansion and contraction.

2、 Process reasons

1. The machining accuracy of the bearing seat hole is not enough, and the two bearing seat holes on the same shaft are not concentric.

Solution: Use equipment with high machining accuracy to cut the two bearing holes in one operation on a CNC boring and milling machine or machining center.

2. Uneven force is applied during bearing assembly. If uneven force is applied to the inner and outer rings of the bearing during cold assembly, it may cause a certain amount of deviation between the inner and outer rings of the bearing and the shaft or bearing hole, resulting in faster wear during operation.

Solution: Use specialized tooling to evenly compress the inner or outer rings during the bearing assembly process and assemble them in place.

3. Failure to clean the bearing during installation or unclean lubricating oil can lead to wear of the bearing raceway, increased friction of the rolling element, and increased temperature, resulting in bearing damage.

Solution: Clean the bearings before assembly. Regularly change the lubricating oil during the use of the vibration exciter. The first change of lubricating oil is after 150 hours of equipment use, and then every 1000 hours of operation.

4. Differences in the quality of grouped eccentric blocks, or significant installation angle errors of grouped eccentric blocks, can cause vibration at the center of the vibration source and cause bearing heating.

Solution: Adjust the mass and angle of the eccentric block to ensure symmetry and consistency. When installing or adjusting the excitation force, it is necessary to ensure that the angles of the eccentric blocks on the same shaft are consistent, and the angles of the eccentric blocks on parallel shafts are symmetrical.

3、 Reasons for use and maintenance

1. Due to uneven foundation or incorrect installation of the spring seat, abnormal movement of the screen body is caused, resulting in rotation or distortion of the vibrating screen, and heating and damage to the exciter bearings.

Solution: Adjust the foundation to make it level. When installing, first use a level gauge to measure whether the foundation is level. If it is uneven, it can be adjusted by adding a pad to the foundation.

2. The large error in the center of gravity of the vibrating screen causes abnormal operation of the screen body, resulting in heating and damage to the bearings.

Solution: The ideal working state of the vibrating screen is that the entire machine runs smoothly and the amplitude is consistent in all parts. Therefore, it is necessary to strictly control the production and installation accuracy of the product, ensure that the center of gravity position is not offset, and try to feed as much as possible.