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The working principle of a conveyor belt is based on the frictional force generated between its own rollers, idlers, and the belt, which enables the belt to move effectively and thus facilitates the transportation of materials. It is a type of friction-driven, continuous-action conveying machine. Conveyor belts are important equipment in mine production; therefore, their stable and reliable operation is essential for the proper functioning of the mine. However, in actual production processes, belt deviation is one of the most common faults. Bias occurs when the belt deviation exceeds 5% of the belt width. Belt deviation can lead to serious consequences, such as mineral spillage along the belt’s path, severe wear on the edges of the belt, and even damage to the belt due to scratching or tearing. Therefore, accurately and promptly handling such faults is of great significance for normal production. To this end, through long-term observation and research on the belts of the conveyors in the processing plant of Ordos Mining Investment Co., Ltd. in Mongolia, the causes of belt deviation were analyzed, and corresponding preventive control measures were proposed, in order to provide guidance for the proper operation of conveyors in mines and processing plants. 1. Overview of the processing plant: The processing plant of Ordos Mining Investment Co., Ltd. in Mongolia is a large-scale mine-type processing plant for power minerals, capable of processing 5 million tons of raw ore per year, with the capacity to handle an additional 10 million tons per year. The hourly processing capacity for raw ore is 947 t/h, with a daily output of 15,152 t/day. The main production system of the concentrator currently has 121 pieces of mechanical and electrical equipment as well as 28 belt conveyors. During actual operation, the belt has experienced varying degrees of deviation, which directly affects the safe operation of the conveyor belt. Mining equipment hotline: 15311826613. Dry tailings discharge: http://www.goldjigprice.cn/. Slurry pumps: http://www.ultrafinegrindingmill.cn/. Hydrocyclones: http://www.hydrocycloneprice.cn/. Linear vibrating screens: http://www.densemediumcycloneprice.cn/. Screw classifiers: http://www.grindingmillprice.cn/. Comprehensive mining processing projects: http://www.mininggrindingmill.cn/. High-efficiency thickeners: http://www.miningclassifier.com.cn/. Analysis of the reasons for belt deviation: From a physical perspective, belt deviation occurs because the driving forces on either side of the belt are not equal, which results in different directions and magnitudes of friction force, thereby causing the belt to deviate. The reasons for its deviation are as follows. (1) Poor belt quality and improper connection cause misalignment. If the belt is of poor quality or not manufactured with precision, the tension exerted during its operation causes different amounts of stretching on each side, resulting in the belt drifting off course. Or, prolonged use can cause aging and deformation as well as edge wear, which leads to the belt becoming loose and resulting in a decrease in tension. This in turn causes uneven stress distribution within the belt, leading to different tensions on either side of it and thus belt misalignment. The solution is to replace the aged and deformed belt with a new one. Furthermore, if the vulcanized joint re-made after belt damage is not centered, the different pulling forces on both sides of the conveyor belt will cause it to deviate from its path. The belt will shift to one side along its entire length, with the greatest deviation occurring at the misaligned joints; the solution is to remake the vulcanized joints of the belt that are not aligned properly. (2) Prolonged operation causes the belt to loosen or results in insufficient tension, leading to misalignment. After prolonged operation, the belt may suffer from permanent deformation or edge wear due to stretching or abrasion, which leads to a significant decrease in its tension. This results in the belt becoming loose and unevenly stressed, causing it to deviate from its path. In addition, when the belt is operating under heavy load, it may also deviate from its path, and this is also caused by insufficient belt tension. In such a situation, in order to ensure that the tension is high enough to prevent the belt from drifting, it is necessary to adjust the tensioning device. If the tensioning force of the tensioning device is insufficient, the stability of the belt is poor, making it more susceptible to interference from lateral forces; in such cases, the belt may even slip. (3) The center line of the belt is not perpendicular to the axes of the drum and idlers. When installing a belt conveyor, if the axis of the drive roller or the idler at the head or tail of the conveyor is not perpendicular to the center line of the belt, this causes the pulling force to be broken down into a lateral component and a force in the same direction as the belt’s movement. As a result, the idlers are subjected to reactive forces that cause them to shift laterally. In addition, when the frame is subjected to heavy gravitational loads, it may experience some degree of settlement overall or in certain areas, which can cause the center line of the frame to tilt or for one side to be higher than the other. This can also lead to severe belt deviation. (4) Drum and idler sticking to ore. Since ore underground is viscous, the idlers and drums will accumulate wet ore after operating for a certain period of time, causing the diameter of these components to increase locally and become thicker; this results in uneven tension on either side of the belt, thereby leading to belt misalignment. (5) Vibration during belt conveyor operation. Mechanical vibration during the operation of a conveyor belt is inevitable, and belt deviation will cause the vibration to become more severe as the conveyor’s operating speed increases. When the conveyor belt is in operation, the radial runout of the idlers is one of the main causes of belt deviation. 3 Treatment and Prevention of Belt Misalignment 3.1 Adjustment for Belt Misalignment (1) Adjust the positions of the drive drum and the idler drum. The key step in addressing belt deviation is adjusting the drive drum and the idler drum. Long-distance belt conveyors generally have 2 to 5 drums, and all drums must be installed in the correct positions to ensure the proper operation of the conveyor. They should all be perpendicular to the center line along the length of the conveyor belt; if there is an excessive deviation, it will cause the belt to deviate from its path. During adjustment, if the belt shifts to the right side of the drum, move the bearing seat on the right side forward or move the bearing seat on the left side backward accordingly. If the belt shifts to the left side of the drum, move the bearing housing on the left forward or move the bearing housing on the right backward. The adjustment method for the tail drum is the opposite of that for the head drum; see Figure 1 for the drum adjustment methods. (2) Adjust the belt tensioning device. Conveyor belts that use a weight-driven tensioning device achieve tensioning by adding weights, but too many weights should not be used, as this can cause the belt to experience excessive tension and thus shorten its service life. The redirecting drum, located above the weight tension point, must be perpendicular to both the length direction of the conveyor belt and the vertical line of gravity. If the belt deviates in the same direction both under load and under no load, it indicates that the tension on either side of the belt is different; in such cases, the screw or counterweight of the tensioning mechanism should be adjusted. If the belt shifts from side to side without a fixed direction, it indicates that the belt is loose, and the tensioning device should be adjusted. For belt conveyors that use screw threads or hydraulic tensioning devices, the tensioning force can be increased by adjusting the tensioning stroke. If the belt suffers permanent deformation and has an insufficient tension travel, a section of the belt can be cut off and re-vulcanized to create a new connection. (3) Adjust the carrying idler roller set and install self-aligning idlers or V-shaped idlers. There are various types of self-aligning idler roller sets, mainly including the intermediate shaft type and the vertical roller type. The principle is as follows: the idler rollers rotate in the horizontal plane, generating a lateral pushing force that automatically adjusts the belt. Both the mounting holes on the sides of the idler roller set are long holes, which makes adjustment very convenient; the method of adjustment is shown in Figure 2. This adjustment method is generally used for belt conveyors that operate over short distances or in both directions, as short-distance conveyors are more prone to deviation and are difficult to adjust. Long-distance belt conveyors should be avoided as much as possible, because the use of self-aligning idler sets shortens the service life of the belt; replacing them with V-shaped lower idlers can provide excellent self-aligning capabilities. (4) Adjust the installation position of the ore leakage cylinder at the ore discharge point. Deviation caused by an incorrect discharge point of the mine can be corrected by adjusting the position of the belt conveyor’s discharge point. When designing the ore flow system, efforts should be made to increase the relative height difference between the two belt conveyors at the point of ore transfer, so that by the time the ore reaches the discharge point on the lower belt, its horizontal velocity is minimized as much as possible. An adjustable baffle is installed at the outlet of the ore discharge tube; depending on the properties of the different ore types, this baffle is used to change the direction in which the ore flow moves, so that it falls straight at the center of the conveyor belt. 3.2 Preventive measures against belt deviation (1) Strengthen quality inspection and maintenance. Choose belts from reputable manufacturers with guaranteed quality. Before installing the belt conveyor, it is necessary to conduct a thorough inspection; check the quality of the belt surface, drums, idlers, cleaning and tensioning devices, etc. Any defective components must be replaced to ensure installation quality from the outset. Drums with significant machining errors on their outer surfaces must be sent back to the factory for processing. During long-term use, if it is found that the rollers on both sides are wearing unevenly, the mineral deposits adhering to their surfaces should first be removed; these rollers then need to be replaced and re-processed with a coating until their diameters are equal. Belts that are severely aged and deformed, and thus unable to function properly, must be replaced entirely. The vulcanized joint of the belt must remain flat; the centerlines of the two adjoining belts must align, and the vulcanization joint must be perpendicular to the belt’s centerline. (2) Strengthen equipment management and operator training. The mineral processing plant needs to strengthen the management of its equipment, establish a comprehensive management system for mechanical and electrical equipment, improve the training of operators, and carry out routine maintenance as well as periodic inspections on the conveyor belts. It is essential to ensure that all electrical protection mechanisms related to the conveyor belts – such as those against deviation, tearing, smoke detection, low speed operation, blockages, and pull-switch functions – are effective and reliable. 4 Conclusion: The various causes of belt deviation in the production process of the concentrator operated by Ordos Mining Investment Co., Ltd. in Mongolia were analyzed, and targeted adjustment and preventive measures for such belt deviation were proposed. It is also pointed out that, as the main equipment in the conveying systems for raw ore and processed ore, belt conveyors must function properly; to achieve this, it is necessary to take preventive measures in advance, pay attention to regular maintenance checks, strengthen equipment management systems, and increase training for personnel – all of which are essential to ensure the normal operation of the mineral processing plant.