Introduction
The chevron conveyor belt is the main equipment for transporting coal in a coal mine, so it is important to keep in mind, that its safety and stability are of great significance for efficient and safe production. Safety should be considered when enterprises work to improve coal transport efficiency. Otherwise, workers’ safety and protection of machines can be put at risk.
1 Protection Function
According to the actual needs of the mine site, there are many types of comprehensive protection devices for belt conveyors, but in general, various types of protection functions are relatively similar. At present, the L2 type comprehensive protection device is mainly used in mines, which has the functions of temperature protection, speed protection, belt protection, and so on.
1.1 Coal protection pile
When the coal level electrode probe contacts with coal, the coal resistance value measured is less than 1 000 Q, after 1~3 s delay, the fault protection function starts, and the belt conveyor stops running. In addition, a travel coal level probe can also be used, because there is friction after contact with coal, when the probe is offset 15, the fault protection function starts, and the belt conveyor stops running. These two types of coal pile protection are the most widely used.
1.2 Speed protection
The main principle of speed protection is to use the speed sensor to collect the speed of rolling, and to judge whether to start the protection action. The speed sensor is generally installed on the side of the drum, and the installation position of the speed sensor should be 3-6 cm away from al-Ni-Co alloy. After the sensor is powered on, the signal light will be on for several seconds, and then the signal light will be off and the sensor will start to collect the drum speed . In the conveyor operation process, if the drum speed is lower than 0.5 times the standard speed for 10s, the speed protection action makes the belt conveyor stops working, and sends out low speed alarm signal. The speed protection function has high-reliability in -field use and can prevent the conveyor belt from slipping and causing friction fire between the conveyor belt and the roller.
1.3 Off-track protection
The principle of the protection function is to judge whether the conveyor belt is running off by using the guide rod angle of the deviation sensor. Generally, when the guide rod Angle deviation is 10°~20 and lasts for more than 10s, the off- track protection action is set. Deviation sensors can be installed in the conveyor head and belt and other locations. The guide rod of the traditional deviation sensor is made of plastic material with short service life. The guide rod can be made of metal material. If the belt deviation occurs, the friction between the frame and the edge of the belt increases, and the service life of the belt is greatly shortened. When the deviation range is larger, the belt will even be torn by the supporting wheel or the frame. Therefore, according to the actual production situation of the mine site, a group of supporting and mixing devices are clamped on the frame every 10 to prevent the belt from running off. In practical application, the device has a good anti- deviation effect.
1.4 Smoke Protection
The smoke alarm should be installed in the head return wind direction of 5 m, the principle of smoke protection is that when the smoke concentration exceeds the limit value, the smoke sensor sends an alarm signal to the host, then start the smoke protection, the Conveyor stops running. But in practical application, most mines use blasting mining technology, so the smoke sensor will make a frequent alarm, affecting the normal production work. Therefore, temperature protection and smoke protection can be combined, when both of them send alarm signals , and can start the smoke protection system.
1.5 Overtemperature protection
When the ambient temperature measured by the temperature sensor is higher than 70 ° C, the overtemperature protection function operates and automatically sprinkles water to cool down. The temperature sensor can be installed near the bearing and other parts to maintain the safe operation of the belt conveyor .
1.6 Tear Protection
At present, the surface and the end face of most supporting wheels are nearly 90° rectangular in shape. When the material on the conveyor belt is heavy, the edge of supporting wheels is easy to insert into the belt, resulting in belt tearing. , a circular arc supporting mix can be used to avoid damage to the conveyor belt. At the same time, in the conveyor head of the conveyor belt at the bottom of the installation of the tear protection device, when detected material leakage, can be considered As belt tearing, the tearing protection device started, the conveyor immediately stops running. To avoid accidental shutdown due to coal leakage caused by a belt running deviation, tear protection, and deviation protection can be combined to judge whether the conveyor belt is torn.
2 Protection device use problem
- The operation of staff is not standardized. The general application time of the integrated protection device is short, and some workers do not have a strong sense of safe operation. First of all, the working time of the conveyor should not be too long , but the staff often let the conveyor for a long time uninterrupted operation, This can result in equipment temperature is higher, reaching a limit that will trigger the overtemperature protection, workers for protection devices do not know right now, there will be a lot of the wrong operation, also has the enterprise in the pursuit of efficiency, forced to restart the protection device, eventually lead to the comprehensive protection sensitivity is reduced, unable to protect the conveyor.
- Poor quality of protection device. The cost of comprehensive protection devices is generally high, and many enterprises choose poor quality and low price comprehensive protection devices to reduce costs. These protection devices have a short service life, and the protection function often fails, and the protection function is meaningless.
- Bad environment leads to frequent accidents. For mines with fewer coal reserves, it is difficult to mine, so the motor with less power can maintain the normal operation of the conveyor. However, when this belt conveyor is applied to larger mines, the conveyor is in an overload running state for a long time, and it is easy to wear and heat after long-term use, and the probability of accidents increases greatly.
3 Suggestions for Improvement
- Ensure the manufacturer of belt splicing machine and tools. First of all, an effective procurement system should be established to form an effective supervision system for procurement personnel to prevent the purchase of belt conveyors and protection devices from the shoddy phenomenon. Before purchasing, a purchasing group should be set up to investigate and understand the equipment put into use in other mines, and select suitable belt conveyors and comprehensive protection devices according to the actual production situation.
- Training staff. The use effect of the comprehensive protection device ultimately depends on the operation mode of the staff, so it is necessary to train the staff on safety awareness and operation standards and teach the principle and operation of the comprehensive protection device. At the same time, the staff should have certain maintenance skills and the ability to troubleshoot potential faults, which can improve the production efficiency of equipment and reduce the probability of safety accidents.
- Establish a supervision and assessment system. Professional supervision personnel shall be set up to check the integrated protection device regularly and repair it in time when faults are found. At the same time, the establishment of an assessment system, the operation standard, good performance of the staff to give material and spiritual rewards, often misoperation, work attitude is not correct staff punishment, to mobilize the enthusiasm of the staff, and finally put an end to the occurrence of safety accidents.
4 Conclusion
As important equipment for transporting coal in the mine, the stable and safe operation of the belt conveyor is of great significance. At present, the belt conveyor integrated protection device has a variety of protection functions, but there are still many problems in the practical application process, this paper puts forward the corresponding improvement suggestions for these problems, to reduce the probability of safety accidents. At the same time, the comprehensive protection device of the belt conveyor should be improved to further improve the production efficiency and safety of the mine.
