In recent years, with the rapid development of the coal mining industry, the production and construction planning of coal mines have been continuously expanding, and the level of mechanization has been improving year by year. This requires corresponding progress in the installation, protection, and repair of mechanical equipment to meet the needs of the coal industry. Compared with rolling bearings, sliding bearings have the advantages of smaller radial scale, larger load-bearing capacity, longer service life, and lower oscillation and noise. However, the difficulty of installation and repair, the disorderly protection conditions, and the low level of technical skills of skilled workers have become limiting factors for improving the economic and reliable operation of mines.

1、 Working principle of liquid conflict sliding bearings
Liquid conflict sliding bearings are a type of bearing with excellent smoothness and functionality. When the shaft neck speed reaches a certain linear velocity during operation, a smooth oil film separates the shaft neck and the bearing, preventing the two sliding surfaces from touching each other directly. The sliding conflict becomes a liquid conflict between the smooth oil layers, reducing the conflict coefficient and increasing the bearing's load-bearing capacity, thus extending its service life.
1. Principle of Liquid Conflict Formation
There are three processes involved in the principle of fluid conflict between the journal and the bearing:
(1) When the shaft is stopped, it is in the lowest position due to its own weight (as shown in the figure below), and conflicts cannot occur because the shaft neck has not yet rotated.
(2) When starting (as shown in the figure below), the journal begins to rotate and moves upward along the inner wall of the bearing, resulting in a boundary conflict at point B.
(3) When reaching a certain speed (as shown in the figure below), the journal and the outer surface of the bearing are completely separated by an oil film, which constitutes a liquid conflict.

2. The conditions that constitute a liquid conflict:
(1) There should be a certain wedge-shaped gap between the journal and the bearing after cooperation.
(2) The journal should maintain a certain linear velocity to establish a satisfactory oil wedge pressure.
(3) The journal and bearings should have accurate shapes and high surface roughness.
(4) Smooth oil of appropriate viscosity, with continuous and sufficient supply of oil.
2、 Structure and Information of Sliding Bearings
Split sliding bearings are generally used for improving the directional cardiac pressure in mines. The bearing shell is commonly a flanged bearing shell with two flanges at both ends, divided into upper and lower bearing shells. The main bearing area is the lower bearing shell, which is combined into one set of bearings. Two sets of bearings are commonly used to support the main shaft of mining hoist. Bearing materials generally use bearing alloys (Babbitt metal, commonly known as Wujin), with commonly used ones being tin based Babbitt metal and lead based Babbitt metal. Tin based bearing alloys can be used for high-speed and heavy-duty applications. Lead based bearing alloys have slightly inferior functionality and are generally only suitable for medium speed and medium load applications. Two types of bearing alloys have advantages such as high wear reduction, oil adsorption, plasticity, and low conflict coefficient.
3、 Viewing and Protection of Sliding Bearings
1. External viewing
(1) External inspection includes checking for smoothness, temperature changes, startup interruptions, and oscillations, movements, and sounds during operation, which can mostly determine the condition of bearings. But under certain conditions, it is difficult to detect situations where the gap is too small.
(2) Online temperature monitoring: Improve the sliding bearings of the main shaft of the machine. The speed is slow, the load capacity is large, the repair distance cycle is long, and internal problems are not easy to be detected. Therefore, targeted monitoring of the bearing is necessary. Generally, bearing temperature sensors are used, which can actively alarm when overheating occurs, and timely detect bearing problems and handle them to prevent severe bearing burning incidents.
(3) Oil sample monitoring: Whether the operation of the sliding bearing is normal can also be detected from the smooth oil. Usually, investigate the oil return situation and whether there is any alloy detachment in the oil. Usually, oil samples are taken at the oil return port and investigated under sunlight to see if there is any shining or severe phenomenon, and to detect the wear of the bearing shell. In addition, oil samples should be taken regularly for laboratory analysis. With the help of iron spectrum analysis skills, the operation status of sliding bearings can be grasped regularly, and the adopted repair methods and repair time can be determined to scientifically protect mechanical equipment.
2. Crash View
After external inspection, it has been discovered that there are signs of problems. To accurately grasp the wear and tear of the bearing and the size of the gap, a collapse inspection should be conducted to understand its detailed shortcomings, in order to determine whether replacement of the bearing is needed. If not, useful methods should be adopted during the collapse inspection to eliminate existing shortcomings and improve the current situation.
Detection and processing content:
(1) The orientation and size of the touch area of the bearing and shaft neck, the wear condition, the wear condition of the bearing end, whether there are gaps at the connection between the bearing and the lining at the edge, and whether there is a hoarse sound of separation when lightly tapping the lining all over the ground.
(2) Measure the top clearance, side clearance, and axial clearance of the bearing shell and keep records.
3. Common drawbacks and solutions of sliding bearings
(1) There are two situations where the tile lining is worn and the top clearance increases:
① When there is a removable pad, reduce the thickness of the tile pad and adjust the gap. The normal wear and tear of the tile lining, along with the increase in gaps, may also present two phenomena: one is an increase in the contact angle between the tile lining and the shaft neck; The second is that the contact area has excellent wear and tear between the lining surface and the shaft neck, with a smooth and shiny appearance, which makes it difficult for smooth oil to enter the contact area. So it is necessary to scrape the bearing shell to achieve a uniform distribution of grinding points on the inner and outer surfaces of the touch area, and then remove the pad.
② When there is no pad that can be removed or there is a significant change in the orientation of the shaft beyond the allowable limit, immediate preparation for replacing the tile lining is necessary, but repairs to the touch area should also be carried out.
(2) When the tile lining is severely bitten and glued to the shaft neck, the operation should be immediately stopped, the shaft neck should be treated, and the tile lining should be replaced.
(3) When the bearing alloy layer is separated from the bearing shell or shows impurities, pores, cracks, detachment, severe pitting or scars, the bearing liner should be replaced. Those who meet the requirements of the flawless specifications can agree to welding repair and correction.
4、 Conclusion
The coal mine hoist is the main equipment for improving mine safety, and the sliding bearing is the main component of the hoist and the key and difficult point of mechanical repair. Its operation directly affects the normal production of the entire mine system. Therefore, it is necessary to understand the operating principle of the sliding bearing and grasp the repair technology of the sliding bearing to ensure the safe and efficient operation of the mine hoist.


Article compilation: Foshan assembly line http://www.zs-chsb.com/list_145.html