All kinds of mechanical equipment are used in the process of coal mining, among which the belt conveyor is the key equipment to ensure the continuous mining and transportation of coal materials. The mining environment faced by the belt conveyor is becoming worse and worse, resulting in its high failure rate. It is easy to shut down or even break the belt in the mining process, which seriously affects the economy of coal enterprises. Therefore, it is necessary to improve the management level of its intrinsic safety, reduce manual intervention in belt conveyor and installation of protection devices, and study the installation method of safety protection devices of belt conveyor, So as to improve the efficient and economic operation level of belt conveyor.
1 Introduction to mine belt conveyor
Belt conveyor has the advantages of high conveying efficiency, large conveying capacity, simple structure and small maintenance. It can transport different materials at different distances. Typical problems often occur in the operation of belt conveyor, especially the roller bearing and roller shaft are prone to failure and lack of necessary protection devices. If the safety protection devices can be installed according to the national mandatory standards, the intrinsic safety level of belt conveyor will be improved.
2 Typical faults of conveyor belt
2.1. Belt deviation of conveyor belt
The working environment of belt conveyor is complex, so belt deviation often occurs in work. As the deviation of the conveyor belt may cause wear between the belt edge and the frame, it will directly affect the production of the belt. As the conveyor belt is more important and the most expensive component, its price accounts for about 25% ~ 50% of the total price. Belt deviation due to the following factors.
2.1.1 Equipment factors：
1) The frame has poor rigidity and large deformation under load, resulting in belt deviation.
2) The error of the outer column of the roll is large, resulting in deviation when the conveyor belt is running.
3) The inflexible rotation of the support roller leads to uneven stress on both sides of the conveyor belt and deviation of the conveyor belt.
4) The parallelism error is too large for the cylindrical shaft and axle, resulting in the deviation of the conveyor belt.
5) The quality of the conveyor belt itself is suspicious, and the thickness is uneven, resulting in the deviation of the impact lead conveyor belt.
6) The manufacturing quality of the conveyor belt is defective, and the side lengths on both sides of the belt are inconsistent, resulting in the operation deviation of the conveyor belt.
7) It is not parallel to the belt joint, and the connection error is too large, resulting in belt deviation.
2.1.2 Installation process factors
1) The vertical error of transmission, roll changing shaft and conveyor center line is too large, resulting in large inclination between conveyor and horizontal line, resulting in belt deviation.
2) The vertical error between roller shaft and conveyor center line is large, which will also lead to belt deviation.
3) The connection strength between the frame and the grounding is not enough, and the frame is unstable, resulting in belt deviation.
4) The position of discharge chute plate is incorrect, and the belt deviation is caused by uneven force on both sides of the conveyor belt.
2.2 Measures to prevent belt deviation
First, the deviation caused by the equipment in the manufacturing of conveyor belt, mainly through improving the design and manufacturing accuracy to prevent and reduce the occurrence of conveyor belt deviation. Second, improper installation and adjustment, resulting in deviation in daily use, mainly considering the following aspects:
The deviation of the conveyor belt on the driving wheel or rear wheel is usually eliminated by adjusting the position of the roller bearing.
1) The roller rotation axis is not perpendicular to the longitudinal center line of the conveyor, resulting in the looseness of one side of the conveyor belt and the tightness of the other side. The belt moves from the tight side to the loose side, resulting in deviation. The bearing position on the tightening deviation side should be adjusted. Make the horizontal tension of the belt equal and eliminate the deviation. When the tail roller is spirally tensioned, the reason for the deviation of the tail roller may be the unequal jacking power of the screws of the tensioning devices on both sides, resulting in imbalance.
2) The cylinder shaft is not horizontal, and the height difference of the bearings at both ends is another reason for the head or tail deviation. At this time, the roller bearings at both ends should add or subtract the shims passing through the leveling roller shaft to eliminate the deviation of the conveyor belt.
3) The adhesion material on the roller surface is equivalent to increasing the local circular diameter of the roller, which will lead to the deviation of the conveyor belt. The empty section cleaning of the conveyor belt should be strengthened to reduce the adhesion of dust on the belt surface and prevent dust from generating static electricity. Usually, the conveyor belt will produce local deviation, which will cause center deviation in serious cases. In the face of deviation, in-depth analysis shall be carried out according to the working conditions, and arbitrary decision shall not be made.
3 Safety protection measures for belt conveyor
The installation quality directly affects the service life and running resistance of the conveyor belt. The maintenance and replacement cost of belt conveyor is also an important part of operation cost. The running resistance, power consumption, roller, belt life, maintenance workload and transportation cost of the conveyor have a significant impact on the running quality of the roller. Therefore, the correct installation of protection device is an important content to ensure the stable operation of belt conveyor, which is of practical significance to the project.
3.1 Anti slip protection device
The installation and protection points of anti-slip protection device are as follows:
1) The magnet of the electromagnetic anti-skid protection device shall be installed on the side of the driven roller, and the speed sensor shall be installed on the support corresponding to the magnet.
2) Generally, the anti-skid protection device should be installed close to the belt surface of the belt conveyor in order to achieve the anti-skid effect. When installing the anti-skid protection device, the external support shall be made.
3) The external support of the sensor shall be standard parts, which does not conform to the support shape designed at will. When installing the sensor through the support, other non-safety parts shall not be used for binding and fixing.
3.2 Anti deviation protection device
The installation and protection points of anti-deviation protection device are as follows:
1) The support shall be installed in the section where the belt is prone to deviation, and shall not be bound with iron wire. When the belt deviates and the guide rod of the sensor pushed by the belt deviates from the center line by 150 mm ± 50 mm, the deviation switch shall act and send a deviation voice alarm; When it is still in the deviation state after a delay of 10 s and 5 s, the host of the protection device shall automatically cut off the power supply.
2) The automatic deviation correction device shall be installed on the belt conveyor at an interval of 50 m for the upper belt and 100 m for the lower belt.
3) The deviation protection device should be used in pairs and away from the nose One group shall be installed at 10 ~ 15m of the tail. When the slope of the belt conveyor changes, one group shall be installed at the slope changing position. One group of simple belt deviation protection can be installed at the head.
4) The deviation protection shall be fixed on the frame or longitudinal beam of the belt conveyor with a special bracket.
3.3 Anti coal stacking protection device
According to the national standards of 15.3.8 of GB 51145 and 16.5.2 of GB 51145, the installation and protection points of anti stacking coal protection device are as follows:
1) The coal stacking protection sensor at the coal bunker shall be installed below the 200 mm level of the tape under the machine head, and its plane position shall be within the range of the coal bunker mouth.
2) When the belt is directly overlapped with the coal bunker, a coal stacking sensor shall be installed at the full position of the coal bunker and 500 mm above the coal falling point of the coal chute respectively, and the sensor shall be sensitive and reliable.
3) When the two belt conveyors are transferred and overlapped, the coal stacking sensor shall be hung in front of the unloading drum, the horizontal position of the sensor contact shall be directly above the coal falling point and in the middle of the belt surface, the distance from the highest point of the belt surface on the lower belt shall not be more than 500 mm, and the hanging height shall not be higher than the lower edge of the unloading drum; The installation shall meet the requirements of sprinkler.
4) When the belt is overlapped with the coal chute, the contact of the coal stacking protection sensor can be installed on one side of the unloading drum, the hanging height shall not be higher than the lower edge of the unloading drum, and the horizontal position shall not be more than 200 mm from the outer edge of the unloading drum.
5) The coal stacking protection control line shall be vertically led down from the roadway roof, and the sensor contact shall be hung vertically and fixed reliably.
6) When two belt conveyors are inclined or vertically overlapped, the coal level sensor can be installed on one side of the unloading drum, the contact position of the sensor shall not be higher than the lower edge of the unloading drum, and the horizontal position shall not be more than 200 mm from the outer edge of the unloading drum.
3.4 Temperature monitoring device
According to the national standards in 15.3.7 and 16.5.5 of GB 51145, the installation and protection points of temperature protection monitoring device are as follows:
1) The infrared sensor is used to detect the transmission shaft of the belt conveyor drum, sense the transmission speed on the bearing seat, and match the infrared emission frequency with the speed of the transmission shaft. In the detection process, the sensor temperature is easy to rise, so it is necessary to keep a safe detection distance from the drum, which is 300 ~ 500 mm.
2) The infrared emission light speed of the sensor should face the transmission key of the transmission roller. In order to prevent abnormal temperature, the detection distance should be maintained at 300 ~ 500 mm.
3) The bearing cover of the transmission rolling Jane is generally equipped with multiple driving devices. The design optimization shall be carried out when installing the sensor. The general installation principle is to install it on the bearing cover far away from the rolling Jane.
4) The thermocouple temperature probe shall be installed at the position where the contact surface between the driving drum and the conveyor belt does not exceed 10mm. In order to prevent the thermocouple from being damaged, the thermoelectric is fixed by soft fixing
3.3.2 Gas drainage pipe shall be buried in advance
Before plugging, the 400 mm drainage pipe shall be installed at the auxiliary side of the first section of the goaf, pinched and transported to the 100m working face and waiting for recycling in a spacious section. The short-circuit drainage pipe head is extended to the goaf.
The current methods of fully mechanized top coal caving cannot reasonably solve the relevant problems. After many experiments and studies, it is finally determined that the later scheme is to introduce relevant measures, such as installing the reserved top coal and retaining research advance support, which can solve the problem of reducing gas and coal outburst in the process of mining top coal caving under poor geological conditions, meet the requirements of safe mine production, and provide relevant experience for the same industry.
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