Introduction
Belt conveyor has been developed for more than 160 years since its invention and has become one of the main transportation equipment in coal preparation plants. Belt conveyor is mainly composed of roller, driving parts, drum parts, head frame, cleaner and safety protection equipment, driven by the drum belt, so as to realize the transport of coal.
Belt deviation is one of the most frequent faults of belt conveyor in operation. Statistics show that the accidents caused by belt deviation faults account for about 30% of all conveyor faults. Conveyor inherent manufacturing and operation mode, in the process of its work will inevitably lead to the occurrence of belt deviation fault. There are many reasons for the formation of deviation faults. This paper will explore the causes of deviation of belt conveyor, introduce in detail various factors causing the unstable operation of belt conveyor, and put forward targeted rectification measures. It has certain economic and safety significance for daily operation of coal preparation plant.
1. Causes of belt conveyor running deviation
Belt deviation refers to the belt conveyor in the operation process, the belt center line deviates from the axis of the frame, and the offset exceeds 5% of the belt transverse width. The main factors of belt deviation can be summarized as follows: one is the deviation caused by defects in the design or manufacturing process of belt conveyor; Second, the machine installation is not standard caused by the deviation; The third is the deviation caused by the running process. Detailed introduction is as follows:
1.1 Design or manufacturing factors
1.1.1 Conveyor belt design factors
The following problems usually occur in the design of belt conveyor: First, the stiffness of the frame design is low, and the steel type selected is not appropriate, which leads to the large vibration of the machine in operation and the problem of running deviation is easy to occur; Secondly, the coal drop of the upper belt transportation is larger, and the impact caused by it is easy to make the belt run off; Again, the center of the feeding chute is offset, leading to the coal is not in the center of the belt, the belt is prone to deviation or even torsion; Finally, due to insufficient tension of the conveyor, it is easy to lead to deviation of the belt, so relevant parameters need to be recalibrated.
1.1.2 Conveyor belt manufacturing defects
In the process of manufacturing conveyor belt, the existence of process error will have a great impact on the quality of belt, serious will lead to the occurrence of deviation phenomenon.
1.1.3 Manufacturing defects of supporting roller
The process error of the supporting roller will lead to the problems such as the rotation of the part stuck or the longitudinal jump, which will exert extra friction on one side of the belt and easily lead to the deviation of the belt.
1.1.4 Cylinder manufacturing defects
Defects in the manufacturing process of the drum can lead to uneven sizes at both ends and a surface similar to a drum or conical shape.
1.2 Installation quality factors
According to the investigation of several coal preparation plants, it is found that the improper installation of conveyor has a great influence on the deviation of belt running, and this kind of deviation fault is difficult to solve. The installation quality factor of conveyor usually refers to the installation error of rack, drum and bin.
1.2.1 Rack Installation Error
When installing the frame of the conveyor, improper installation position is easy to lead to deviation of the belt. The installation position is not suitable mainly refers to the low levelness and straightness, the belt can not be lifted with the roller at the lower part of the conveyor frame, when there is lateral force, the belt is prone to deviation or even torsion. The height difference between the two sides of the frame will cause the uneven force on both sides of the belt, leading to the occurrence of deviation.
1.2.2 Roller installation error
When there is a deviation in the installation position of the roller, its axis will no longer be orthogonal to the longitudinal center line of the belt, and the belt is easy to bias to the more relaxed side.
1.2.3 Roller installation error
When there is an error in the installation position of the idler, the deviation of the axis will easily lead to the deviation of the belt. There are four main conditions of roller deviation: roller and belt longitudinal center line is not orthogonal; The roller Angle inclines, and the horizontal component of the resistance to the belt appears in the guide; Toewen frame this pressure in the position, the belt will be offset to the lower part of the bracket; Uneven pressure on both sides of the feeding groove will lead to greater friction on the side under greater pressure, causing belt deviation.
1.3 Running Problems
1.3.1 Material bonding conveyor roller or idler
When the conveyor is transporting materials, coal and other materials are easy to stick to the surface of the roller or roller. If it is not cleaned in time, the roller and roller are no longer regular cylinders, which will cause the deviation of the belt.
1.3.2 Belt stretching deformation
After long-term use, the belt of belt conveyor will cause irreversible deformation, which will lead to insufficient belt tension, resulting in belt deviation.
1.3.3 — Uneven material falling position
In the transfer of two conveyors, if the height difference between the two is large, the impact force generated by the falling of coal and other materials is easy to lead to the deviation of the lower belt, and the randomness of the distribution of the falling position will lead to uneven force on both sides of the belt, causing the deviation of the belt.
1.3.4 Vibration of mechanical parts
When the machine is working, mechanical vibration must exist. Therefore, when the conveyor is transporting materials, the idler will vibrate longitudinally, which will lead to the occurrence of the deviation of the conveyor belt.
1.3.5 Support bar Failure
After long-term use, the bearing of the idler will wear, the rotation of the idler will be stuck, and the longitudinal vibration amplitude becomes larger, resulting in friction on both sides of the belt, easy to make the belt run off.
2 Corrective measures
2.1 Guarantee the quality of belt conveyor
The design and manufacturing level of the conveyor is the premise of its good operation. The supervision department should carefully review and inspect the design and manufacturing of the conveyor. Coal preparation plant staff should carefully study the type of steel conveyor used, the height difference of the upper and lower conveyor, the design length of the guide trough and other parameters, select the conveyor in line with the requirements, and check the design of the machinery. At the same time, the manufacturing quality of the belt conveyor should be evaluated to ensure that the belt, roller and other parts meet the operation requirements.
2.2 Ensure the quality of the belt itself
If the belt is not smooth or there is a problem with the joint, it will lead to uneven force of the belt, and then cause the belt to run off. If there is a problem with the joint, the relevant technician can re-glue the belt. If there is less uneven part of the belt itself, the uneven part can be removed and the belt can be re-bonded; If there are more uneven parts, you need to replace the belt.
2.3 Ensure the quality of idlers
If the roller shaft line is not orthogonal to the belt center line, it is necessary to correct the roller support; If the roller is not in the horizontal line, it is necessary to adjust the height of the offset side support, or add gasket in the lower part of the height.
2.4 Ensure the quality of rolling simplifications
As one of the most important parts of conveyor, the quality problem of roller will lead to the occurrence of deviation fault. When installing the roller, the roller axis must be orthogonal to the belt longitudinal center line; The bearing support can be adjusted if there is deviation in driving rolling. Also ensure that the nose and belt contact part of uniform fit, problems should be able to quickly adjust, to ensure that the belt is in the middle of the rolling position.
2.5 Reasonably set the weight range of tension device
Belt tensioning device is one of the important parts of the conveyor, if the weight range of the tensioning device is not correct, it will lead to belt relaxation or excessive tension, which will lead to the transport belt running. Belt slack should increase the weight block; When the belt tension is too large, the counterweight can be appropriately reduced.
2.6 Ensure that the guide trough is properly installed
Improper installation position of the guide groove will lead to uneven distribution of coal on the belt, and uneven force on the belt will lead to deviation. By changing the whereabouts, height and direction of the coal or increasing the length of the guide trough, the coal can be evenly distributed on the belt to improve the stability of the conveyor operation.
2.7 Check the conveyor sweeper regularly
Under the influence of climate, coal is easy to bond on the roller when the humidity is high, resulting in belt deviation. Staff need to check the conveyor belt ceramic sweeper regularly to avoid coal bonding and maintain its stable working state. And regularly clean the roller or roller to reduce the occurrence of belt deviation.
3 Conclusion
As one of the important transportation tools of coal preparation system, it is of great significance to reduce the frequency of failure of belt conveyor. In order to ensure its normal operation, this paper discusses the deviation of the belt in detail, and puts forward the corrective measures to reduce the number of deviation problems, so as to ensure the stable operation of the coal preparation plant.