Longwall shearer double row tapered roller bearing spherical roller bearing In the past few years, China’s national economy has continued to maintain a double-digit growth rate. The rapid development of the economy also puts higher demands on the supply of energy. Although “green†energy such as solar energy and wind energy is increasingly favored and valued by people, coal is still China's basic energy and important raw material, and it plays an important strategic position in energy reserve and development. According to the predictions of relevant departments, coal is still the most important energy source in China in the next few decades. Therefore, as a coal industry supporting 70% of China's national economic energy production (data source: 2008 China Coal Data Report), it has also shown an amazing growth rate. The output increased from 1.08 billion tons in 2001 to about 2008. 2.8 billion tons, an average annual increase of about 240 million tons. 1. Comparison between axial turbulence The axial turbulence of the longwall shearer during operation is mainly caused by the axial clearance of the bearing (although the clearance of the spherical roller bearing is given by the radial value, but it can be obtained by the coefficient It is converted into an axial value, and the converted axial value is much larger than the radial value.) Because the magnitude and direction of the axial force received by the shearer during the coal cutting process often changes indefinitely, it will drive When the shaft reciprocates, the larger the internal clearance of the bearing, the larger the amount of turbulence. Frequent axial turbulence can cause fatigue damage to seals prematurely until failure. When the seal fails, coal chips and other hard particles will enter the interior of the unit, causing the bearing race to flake off and also damage other components such as gears on the drive chain. Therefore, the amount of turbulence must be eliminated or strictly controlled to minimize it. The clearance of double row tapered roller bearings is precisely controlled by spacers, and the clearance after installation can be negative in order to increase the rigidity of the system during operation or to optimize bearing life and performance. Spherical roller bearings are not allowed to run under negative clearance, otherwise they will cause bearing burns. It can be seen that the double row tapered roller bearing has the irreplaceable advantage of the spherical roller bearing in this working condition. The clearance of the bearing is divided into the installation front clearance, the installation clearance and the running clearance. Usually the clearance and running clearance are less than the pre-installation clearance after installation. The size relationship between the clearance after installation and the running clearance depends on the application conditions, because although the temperature rise of the bearing during operation will further reduce the play, while the bearing raceway will have a certain amount of elasticity under the force. Deformation, which in turn increases the play, so the play is larger or smaller than the post-installation during actual operation and is determined by the operating conditions. For medium speed and stressed applications, it can be approximated that the clearance after installation is similar to the running clearance. For the sake of convenience, in the comparison of Figure 1, we will compare the amount of clearance between the two bearings after installation to determine the amount of axial turbulence caused in the application. Figure 1: Comparison of the amount of clearance between the two bearings before and after installation and the axial turbulence during operation (data unit: mm) 2. Comparison of impact load resistance In the process of coal mining, because the texture of the coal seam is not very uniform, the cutting head is often subjected to impact loads, and such loads are also a test for bearing performance. At present, the standard spherical roller bearings on the market use high carbon steel as the raw material. After through-hardening, the hardness is consistent from the inside to the outside, which is HRC58-64. Although the texture is hard, it is compared. Crisp, when encountering a relatively large impact load, it is prone to cracks, even direct fragmentation. The market is some brands. For example, a considerable part of the standard tapered roller bearings provided by Timken (especially the inch bearings) are made of low carbon steel, and the heat treatment process is case-carburizing. The bearings produced are characterized by a hard surface (HRC58-64) and a soft core (HRC30-35) that cushions the impact load and avoids impact cracks. 3. Comparison of axial load capacity Next page The blind plate is mainly used to completely isolate the production medium and prevent the production from being affected or even causing accidents due to the loose closing of the shut-off valve Blind Flange Flat Face,Blind Flange Raised Face,Jis B2220 Flange,Gost Flange Jinan Xintai Forging Co., Ltd , https://www.xtdzflange.com
The rapid growth of coal production is due in large part to the improvement of coal mining technology and the upgrading and upgrading of coal mining equipment, and the longwall coal mining machine used for underground mining is one of the typical representatives of these equipments. Compared with open-pit mining, underground coal mining is more difficult and the environment is more severe. Once it is shut down due to equipment failure, due to the small space and the inconvenient use of large-sized disassembly and maintenance tools, maintenance will be very time-consuming and laborious. The negative impact on coal production is what coal mine owners do not want to see. Therefore, in a certain sense, the performance and reliability of the longwall shearer plays a decisive role in the continuity of underground coal mining operations and the amount of coal mining. The longwall coal mining machine has a complicated structure. In addition to the basic mechanical structure, it is also equipped with hydraulic and electric power systems. The overall reliability of the shearer is a comprehensive reflection of the performance of each subsystem. The following discussion is a comparison of two typical bearing schemes for the cutting heads of longwall shearers in the domestic market. That is, the comparison between spherical roller bearings and double row tapered roller bearings. Mainly reflected in the axial yaw control, impact load capacity, axial load capacity and lubrication performance. 
From the comparison results in the above table, we can see that the running amount of the tapered roller bearing in operation is 0.085mm (the arithmetic mean of the turbulent range) is much smaller than that of the spherical roller bearing 1.05mm. Basically, it can be considered that there is no incitement. According to a coal machine manufacturer, the spherical roller bearings they used previously were relatively large, and the seals and bearings were replaced about once every two months. After the replacement of the double row tapered roller bearing, the equipment has not been damaged for more than one year. At present, some high-end manufacturers of longwall shearers in China have fully realized the advantages of tapered roller bearings in this application. They chose high-end tapered roller bearings such as Timken® in their design and manufacture.
Although spherical roller bearings and tapered roller bearings can withstand axial and radial forces at the same time, the axial force of spherical roller bearings should not be too large (usually recommended not to exceed 1/3 of the radial force) ), the tapered roller bearing can withstand the axial force can be larger than the radial force, and can even withstand the pure axial force. This is determined by the internal geometry of the bearing. When the axial load is gradually increased to a certain extent, the distribution of the radial force is changed from the first two columns of uniform distribution to one column, which makes the roller of the column relatively strong in force and friction during operation, and is easy to generate heat, especially It is for spherical roller bearings. The tapered roller bearing is a purely rolling design, and the friction and torque during operation are smaller than the aligning bearing, so that its ability to withstand axial force is much stronger than that of the spherical roller bearing.