A Belt conveyor is important electromechanical equipment in coal mining construction. It has the advantages of large transportation capacity, short transportation cycle, and easy operation. However, in actual coal mine production, due to the complex installation conditions of belt conveyors, poor installation quality of conveyors, operators’ lack of understanding of conveyor structure principle, and inadequate safety management and maintenance of conveyor, the conveyor often fails in the process of use, It is mainly reflected in the deviation of conveyor, belt breakage, jamming of transfer point, etc., which not only reduces the transportation efficiency of mining face, increases the failure rate of belt conveyor and the maintenance cost of conveyor, but also easily leads to major coal mine safety accidents, such as dust explosion accident in transportation roadway caused by friction fire of conveyor belt; Broken belt injury accident, etc. Therefore, in the production process of a coal mine, we must strengthen the safety management of the belt conveyor to ensure its safe and stable operation.

1 structural features of belt conveyor

According to the different structures, the belt conveyor is divided into roller part, non roller part, and device part Conveyor belt part. Because the conveyor belt has the characteristics of high-temperature resistance and a simple structure, it is suitable for transporting chemical materials , waste materials, and large gangues. If the maintenance personnel can carry out normal maintenance according to the requirements, the service life of the belt conveyor can reach 5 ~ 10 years without breaking the conveyor belt. The drum and drum of the worn part of the belt conveyor are made of high-strength materials, which can reduce the total weight of the equipment and prolong the service life of the equipment at the same time. The instructions for the use of a belt conveyor stipulate that the conveyor belt is required to be installed at a slope of less than 20 °, so the roadway should be maintained at a horizontal angle as far as possible during the construction of the belt roadway. The belt conveyor uses low-quality components, which can ensure that the conveyor is in a state of low energy consumption and improve the transmission efficiency of the belt conveyor.

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2 Installation principle of belt conveyor

The Belt conveyor is mainly composed of the belt, supporting wheel, an intermediate frame, roller, anti deviation device, tensioning and braking device. Among them, the belt is the most important component, because the belt is not only the bearing mechanism of the conveyor but also the traction mechanism of the conveyor.

1) When installing the belt conveyor, the construction personnel should first pass the belt through the transmission drum and the tail reversing drum to form a closed-loop annular belt and use the supporting wheel to support the upper and lower parts of the belt. The tensioning device can keep the belt with a certain tension so that a certain friction force can be generated between the belt and the roller, to drive the whole belt to run. The raw coal mined underground enters the conveyor belt at the loading point and is unloaded at the unloading point to complete the whole transportation process of raw coal from underground to the ground.

2) To increase the coal transportation volume of the belt conveyor, the upper support adopts V-shaped support, which can increase the area of ​​the raw coal flow end of the belt, to increase the coal transportation volume. The lower part of the belt is used as the return section of the conveyor belt and supported by the lower flat supporting wheel. The belt conveyor can transport the raw coal of multiple belts. Generally, the upward inclination angle shall be less than 18 °, and the downward inclination angle shall be less than 15 °.

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3 conveyor installation and maintenance requirements

3.1 installation requirements

1) Before the installation of the belt conveyor, the floating coal at the installation site shall be cleaned to ensure the flatness of the roadway floor. Before the installation of the belt conveyor, the bottom hardening construction of the panel area and fully mechanized mining face must be carried out, and the conveyor foundation base shall be installed to ensure that the conveyor is firm and reliable after installation.

2) After the belt conveyor is installed, it shall be subject to trial operation, adjustment, and maintenance. The adjustment contents mainly include conveyor deviation adjustment, conveyor tension adjustment, conveyor installation quality reinforcement, and all kinds of oil and lubricating oil supplement.

3) After the installation and before the operation of the belt conveyor, it must be ensured that all kinds of protective devices of the conveyor are complete. The protective devices mainly include smoke protection devices, coal stacking protection devices, deviation protection devices, Overspeed protection device, etc.

4) According to the transport capacity of the belt conveyor, the motor power and power supply load of the belt conveyor shall be reasonably selected. It is strictly prohibited to operate the belt conveyor under fault and overload.

3.2 maintenance contents

1) In daily maintenance, the maintenance personnel shall fasten all connecting bolts of the conveyor in the state of shutdown. In particular, the bolts at the upper bracket and side beam are easy to be loosened by vibration. At the same time, the maintenance personnel can check the bearing of the conveyor by hand or ear, and find that there is abnormal noise in the bearing Replace in time in case of vibration or cracking.

2) Replace the conveyor belt supporting roller or supporting roller frame in time if it is found damaged; Check the explosion-proof of various electromechanical equipment of the conveyor: check various protective devices of the conveyor; Check whether the tape is cracked or broken, and replace it in time if the tape is damaged.

3) Check the mechanical part of the conveyor belt, mainly including whether all kinds of oil pipes have oil leakage, whether the coal retaining leather at the loading point is lost or damaged, and whether the coal sliding device can work; Inspect the vulcanization interface of the conveyor belt through special equipment.

4 Safety management of key parts

The loading point is the retaining and buffer device after the raw coal transported by the upper belt falls on the lower conveyor belt through the coal chute. It is an important part of the belt conveyor. In actual production, the large grinding stone or hard iron on the conveyor belt will tear the conveyor belt, causing huge economic losses to the mine. Therefore, the management of loading points should be strengthened when using a belt conveyor.

1) Each production team shall strengthen the management of fully mechanized mining machine excavation to avoid large grinding stones or hard irons mixed with raw coal. The grate can be installed at the upper opening of the coal chute of the belt conveyor, and each mine can design a reasonable square opening size according to the transportation volume.

2) To reduce the impact of raw coal on the belt, a set of buffer devices can be installed under the coal chute. A 5 mm gap shall be reserved between the buffer device and the belt to reduce the impact on the belt when raw coal falls, and prevent the cracking of the inner covering glue on the surface of the belt and the fracture of the internal steel wire rope.

3) When installing the coal sliding device, the construction personnel shall ensure that there is a certain gap between the lowest end and the belt to prevent large materials from being stuck between the coal sliding device and the belt. The size of the gap can be determined according to the size of the grate.

4) Strengthen the maintenance of belt conveyor coal sliding device and coal retaining device. The maintenance contents mainly include device damage, device fixation, etc. If problems are found, they should be replaced in time; At the same time, the operators at the loading point shall be provided with detailed pre-job professional training to ensure that the loading point can be handled in time in case of failure.

5) To prevent the blocking of large materials at the unloading point, resulting in deviation, belt tearing, and other accidents of the lower horizontal conveyor, a fully enclosed device can be installed at the unloading point of the conveyor. The device mainly includes a metal shell, a buffer device, and a large material screening device.

5 Conclusion

According to the actual application effect in Xiaoyu coal mine and Wangping coal mine, after taking safety management measures, the failure rate of belt conveyors in the coal mine is reduced from 17% to less than 3%, and the maintenance cost of conveyors can be saved up to 470000 yuan in the whole year, which greatly improves the service life of conveyor, ensures the safe and stable transportation of coal mine, and achieves remarkable safety and economic benefits.