Protective device of mining belt conveyor

Preface

In the process of coal mine raw coal transportation, the belt conveyor plays a very important role. However, when the transportation distance is long and the speed is fast, the belt conveyor is prone to deviation, fracture, and other problems, which directly affect the normal transportation process. In this regard, on this basis, this paper analyzes the problems during the operation of the belt conveyor and points out the relevant improvement suggestions, to improve the operation efficiency of the belt conveyor and improve the economic and social benefits of the enterprise to the greatest extent. Therefore, the improved design and analysis of the belt conveyor protection device are carried out.

  1. Type of comprehensive protection device for mining belt conveyor

Coal mine belt conveyor protection includes emergency stop, belt tearing, coal stacking, speed, temperature, and smoke. It sends fault signals to the control system, and then adopts targeted solutions, to better ensure the operation safety of staff and mechanical equipment.

(1) Emergency stop protection

The emergency stop protection of the coal mine belt conveyor includes an emergency stop lock switch and pull rope switch. The frame on one side of the belt conveyor body is equipped with an emergency stop switch, and the interval between each set is 50m or 100m. The pull rope is used to connect the emergency stop switch, and the lifting ring shall be arranged in the middle to avoid large misoperation during the pull rope. The normal contact of the emergency stop switch shall be set at the edge stop and ground terminal of the control box. When the belt conveyor maintains the normal operation mode, the emergency stop switch shall be set at the vertical position. The emergency stop switch shall be rotated by a manual rocker arm to keep the microswitch action and send out the signals of fault shutdown and emergency shutdown. In addition, the action of the emergency stop switch shall also realize automatic locking, manually press the reset key to eliminate the fault, and the belt conveyor c an be restarted only when the rocker arm of the emergency stop switch is in the vertical position.

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(2) Deviation protection

Deviation switches are mainly installed on both sides of the belt and used in pairs, with an interval of 100m to ensure the perpendicularity between the belt edge plane and the vertical drum, and set them at 1 / 4-1 / 3 of the drum. During the transportation, the staff shall set the distance between the belt edge and the vertical roll according to the actual transportation situation, which is generally the natural deviation of the belt plus 50-100mm

(3) Tear tape protection

The tear tape sensor mainly applies the pressure-sensitive principle, which has high safety and convenient installation. During transportation, when the belt is longitudinally torn, the sensor will automatically mine underground. The metal fixed support and conductive plate assembly are the common components of tear sensing. When the belt conveyor maintains the constant shackle as the fertile hole to a certain extent, it transmits high resistance to the control box. When the coal amount of belt tear reaches a certain extent, the sensor will take protective action to realize shutdown protection. The pitching Buli women’s powder sensor is installed, the support is fixed in the channel steel of the middle frame of the conveyor, and the feeding point is set 3-5 in the belt transportation direction. At the same time, the normally open contact of the strip tearing switch shall be set at the strip tearing and ground terminal of the control box. To avoid the misoperation of the sensor, the sta ff shall clean the coal falling debris of the sensor in time to ensure cleanliness.

(4) Coal stacking protection

The main body and the probe rod are the main components of the material detection sensor, in which the normally open contact is installed in the main body shell to ensure that the sensor is in a vertical state. In the process of raising coal, when the inclination angle of the sensor is too large, the normally open contact will be closed, and the switch will act to send out a fault signal. After that, the coal material drops, the normally open contact is reset, and the sensor maintains the original vertical state.

(5) Smoke sensor

In the process of belt transportation, the staff should also check the smoke in time. The voltage of smoke-free detection is 5-10v, and the voltage of smoke detection is less than or equal to 0.5V. When the smoke concentration reaches 0.1 mg/m, the response time of the sensor shall be less than or equal to 30s

(6) Speed ​​and temperature protection

In case of Overspeed or stall of the belt conveyor, the staff shall set up a special speed protection system to monitor and protect the belt. At the same time, it is also necessary to protect the temperature of the belt conveyor and install the temperature sensor , which has a simple wiring process and good protection performance. During transportation, a low level will be output when the temperature is normal, and a high level will be output when the temperature is abnormal.

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(7) Acoustooptic combined signal

The acousto-optic combined signal has the functions of communication, acousto-optic alarm, public address telephone, and so on. Generally, this device is installed on one side of the conveyor with an interval of 100m. When operating the acousto-optic combination device, the staff press the “dot” key when sending the signal, and each station sends the acousto-optic signal at the same time. When the main control system outputs a signal, all acousto-optic signal devices will send a dot signal and press the “call” button to make a call. Press and hold it while speaking, and other online users can hear a voice to ensure smooth communication.

  1. Fault analysis of mining belt conveyor

(1) Belt slip

During the operation of the belt conveyor, when the resistance is greater than the traction force of the driving system drum, the problem of slipping will occur. One is the increase in running resistance. For example, the belt is stuck on the frame due to overload during transportation, so the support is damaged due to the winding of sundries, resulting in the problem of mixed support and slipping. The second is the reduction of the tension at the separation point of the driving drum. After the conveyor works for a certain time, the belt will be elongated. Because it has the characteristics of plastic deformation, if the belt is not tensioned in time, there will be slippage. In addition, the belt conveyor tensioning failure or failure will also lead to slip problems. Third, the friction coefficient between the driving drum and the belt conveyor is reduced. When there is coal slime and coal dust at the contact part between the driving drum and the belt, the conveyor will slip on rainy a nd snowy days. Fourth, is the reduction of the wrap angle between the driving drum and the belt conveyor. If the belt conveyor does not set a reasonable wrap angle coefficient, it will cause a frequent slip.

(2) Belt deviation

Firstly, when there is a large deviation between the vertical angle of the supporting mixing axis and the centerline of the belt on the belt conveyor, it will lead to the deviation of supporting mixing. During the operation of the belt conveyor, the supporting rod on the bearing surface will be subject to traction force. Through the force analysis, the force will be generated in the direction perpendicular to the axis of the supporting rod and move along the axis, which will bring the reverse force to the supporting plate, resulting in Secondly, when the drum is made, there is a deviation, which can not ensure the consistency of the drum diameter, so that the belt is easy to deviate to the side with a larger diameter. When the belt conveyor is running, the roller will give the belt a force opposite to its running direction. The force analysis can get the force perpendicular to the surface of the roller. Under the action of component force, the belt will deviate. Finally, the belt itself has aging problems, the edge ratio is worn, and the joint part is not correct, resulting in deviation.

(3) Belt fracture analysis

First of all, the vulcanization joint of the belt conveyor is not designed according to the standard, resulting in low tensile strength. When there is a heavy load, the steel wire rope core of the vulcanization joint will be deformed under the influence of external force . When it reaches a certain degree, it will be pulled out, resulting in a belt fracture. Secondly, the core glue and surface glue of the belt conveyor does not meet the standard. When subjected to external force, the belt will break, the steel wire rope core will be exposed to the air, and its tensile strength will be reduced, resulting in fracture. Finally, the production conditions in the mine are poor, there are harmful gases or air humidity, resulting in the deterioration and aging of the belt, and the water vapor in the air will seep into the cracks, resulting in fracture due to corrosion.

In addition, during the operation of the belt conveyor, there will be problems such as nonrotation of the supporting pulley, nonrotation of the belt, and too high roller temperature, which seriously affect the normal production process and bring great economic losses to the enterprise. Therefore, coal mining enterprises should reasonably design the belt conveyor protection device based on their actual mining situation.

  1. Improvement analysis of protective device of mining belt conveyor

The belt conveyor is prone to slip, fracture and deviation during operation, and the sudden increase of transportation volume during raw coal transportation will also lead to the coal falling into the belt. If the operator does not deal with it in time, it will lead to the coal falling into the drum, resulting in deviation, fracture, and other problems. At present, the belt conveyor has been equipped with sweeper equipment, but the coal will be cleaned into the tail drum during operation, which is easy to damages the belt and can not ensure the safety of workers. In this regard, enterprises should reasonably improve the belt conveyor in combination with their situation to avoid the rebound of the belt during the return trip.

In this paper, the coal falling device, coal return induction device, and tail protection device are improved to ensure the normal operation of the belt conveyor.

(1) Improvement of coal falling protection device

During the raw coal transportation of the belt conveyor, the tail unloading point, driving station, and slope change point are very prone to coal falling. To avoid the coal block damaging the belt and entering the return belt, the staff shall reasonably set the protective net device for the belt conveyor. For the slope change point and transfer point of the belt conveyor head, the staff shall weld the steel plate in the middle of the frame to avoid coal falling into the return belt. The coal receiving hopper shall also be installed in the driving drum device to avoid falling coal entering the drum, to ensure the safe operation of the drum and belt. In addition, the role of the driving device of the belt conveyor with a large inclination angle will also drop coal. At this time, the protective net should also be installed in the conveyor with a large inclination angle.

(2) Coal return induction device

At present, most belt conveyors are equipped with coal falling protection devices, which can avoid coal falling into the return belt, but it can not be completely avoided. For this, the coal return sensing device should also be installed in combination with the operation of the belt conveyor to effectively detect the coal return. To turn over the plate, the volume of the coal return sensor device shall not be too large and shall be installed in the middle of the upper and lower belts, so as not to affect the normal operation of the belt conveyor. According to the analysis of coal mining, the lifting angle of the belt conveyor is maintained at about 10 °. Due to the fast speed of return coal, this device should be able to sensitively sense the amount of return coal without being affected by external factors. In addition, the coal return induction device shall also be connected in series with the switch output line to the control contact of the protection switch to ensure that the belt c onveyor can stop immediately and fully realize the protection function based on combining the power-off principle of rope pulling protection.

(3) Tail protection device

At present, a plow sweeper is installed at the tail of the belt conveyor. To achieve a better protection effect, the staff should also design the tail protection device in combination with the coal falling and transportation characteristics of the belt conveyor to ensure that in any case. Falling coal cannot enter the belt conveyor. When installing the tail protection device, the staff shall ensure that the device maintains a certain inclination angle with the belt, install the wear-resistant material and spring pressure device to the bottom of the cleaner and weld it with the conveyor frame to ensure efficient and continuous coal sweeping. At the same time, the protective net shall also be installed in the cleaner to ensure the rationality of the installation position and avoid large objects or supporting rods falling from the tail drum. To ensure that the sweeper does not fall into the tail roller, the staff should also reasonably set the safety rope and set a partition between the t ail drum of the belt conveyor and the protective device to fully protect the operators and enhance the practicability of the protective device on the premise of reducing the economic cost.

  1. Conclusion

During coal mine transportation, the belt conveyor is prone to fracture, deviation, and slip, which seriously affects the normal transportation process. Based on this, the staff should improve the basic structure of the belt conveyor based on cost-saving, enhance the adaptability of transportation, and comprehensively promote it on the premise of improving efficiency.

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