Deviation Mechanism and Prevention of Belt Conveyor

1.Transport status and deviation mechanism of belt conveyor

1.Transportation status of roadway belt conveyor

Until now, Lane 5201 has been excavated for 450 meters. since four normal faults have been exposed in the early excavation process of lane 5201, with an average drop of 0.7 meters and an average inclination of 52 °, the amount of gangue in the coal seam of the roadway affected by the fault has increased, and it is mainly sandy mudstone. Affected by the installation technical level of gangue and belt conveyor in the roadway and the management and maintenance of belt conveyor, a total of 7 electromechanical accidents have occurred to the belt conveyor in the early excavation stage, including 3 belt breaks One motor was burnt out and three h-frames were inverted, resulting in economic losses of 305000 yuan. Through on-site observation, it is found that the main reason for the belt conveyor accident is the belt deviation , which causes uneven stress on the belt in the running direction, resulting in belt breakage. At the same time, when the belt deviation occurs, the friction between the belt and the supporting rod and roller is serious, and the running load of the conveyor increases, resulting in serious wear of the belt and burning of the motor.

2. Belt conveyor deviation mechanism

2.1 Unqualified installation quality

The 5201 Lane belt conveyor is installed by the personnel of the machine excavation team. Due to the lack of professional technical training, the randomness of the installation of the conveyor and the absence of the conveyor center line on site before installation, the conveyor head is not firmly installed during the installation of the belt conveyor, and the axis of the conveyor unloading drum is not parallel to the tail drum, resulting in uneven lateral stress of the conveyor belt during the operation of the belt conveyor.

2.2 The quality of idler is unqualified

The excavation volume of lane 5201 is 7.5 M / d. before excavation of each shift, the tail extension length of the belt conveyor is 9.0 M. during the tail extension process, three groups of h-frames and upper and lower supporting mixers need to be installed, while the supporting mixers used in lane 5201 are used for recovery and repair of the excavated roadway. The supporting mixers are seriously damaged, the quality is unqualified, and the curved diameter of the surface of the supporting rods is inconsistent, resulting in inconsistent radial friction between the supporting rods and the conveyor belt when the conveyor transports materials, This causes the conveyor belt to deviate towards the side with high friction.

2.3 Improper belt tension

The tension of 5201 Lane belt conveyor is adjusted by the operator after each tail extension. The traditional manual adjustment method not only has high risk coefficient of labor intensity, but also has low adjustment accuracy; If the tension is insufficient, when the belt conveyor transports coal gangue, the conveyor belt is uneven under the action of coal gangue gravity and deviates; When the tension is too large, it is easy to break the belt under the work of materials.

2.4 Unqualified conveyor belt joint

5201 Lane belt conveyor needs to add a belt at the end of each extension, and the mechanical connection is adopted between the belt and the belt. During the docking process of the belt, due to the operator’s lax docking of the conveyor belts on both sides, there is dislocation after the connection of the conveyor belt. During the operation of the conveyor, the unqualified conveyor belt joint generates lateral stress under the action of supporting and mixing friction, and the conveyor belt deviates towards the stress side, accompanied by belt tearing.

2.5 Uneven unloading

Uneven unloading is the main cause of belt conveyor deviation. When two adjacent conveyors are overlapped and there is a height difference at the overlapping point, the materials of the upper conveyor produce an impact force on the lower horizontal conveyor belt during unloading. There is a component of the impact force in the horizontal and vertical directions. If the horizontal component points to both sides of the conveyor belt, the conveyor belt deviation occurs.

3 Preventive measures for belt conveyor deviation

In order to improve the operation stability of belt conveyor and control the deviation of belt conveyor, the machine excavation team decided to take several preventive measures for ssj-800 belt conveyor in lane 5201.

3.1 Improve the installation process of conveyor

In order to ensure that the conveyor is straight and stable after installation, the floating coal on the conveyor installation bottom plate shall be cleaned and the soft bottom plate shall be hardened before the installation of belt conveyor; During the installation of the conveyor, the head shall be constructed, and the head shall be fixed with four ground anchors to ensure that the head is firm and reliable after installation; During the installation of the conveyor, the line must be provided by the geological survey department on site to ensure that the head unloading drum is parallel to the tail drum and perpendicular to the center line of the conveyor belt after the installation of the conveyor.

3.2 Strengthen the maintenance of conveyor

After the installation of the belt conveyor, the vulnerable parts of the belt conveyor must be inspected regularly, especially the conveyor supporting rod. It is strictly prohibited to use the damaged, deformed and broken supporting rod, and replace it regularly; The maintenance personnel shall check the lubrication and wear of the connecting part between the conveyor motor and the reducer every shift, and replace the connecting bearing in time if it is found to be deformed; Check the conveyor head regularly and check the connecting parts of the fuselage and tail to ensure the stable operation of the conveyor.

3.3 Installation of automatic tensioning device

In order to solve the technical problems of unreasonable tensioning mode, high labor intensity and low safety factor of traditional conveyor, it is decided to install a set of automatic hydraulic tensioning device for 5201 Lane belt conveyor. The device is mainly composed of interlocking switch, PIC controller, laser scanner, gravity induction device, various traveling vehicles and other parts. The automatic tensioning device realizes the automatic adjustment of the tensioning of the conveyor belt according to the weight of the transported materials. It has the advantages of high automation level, good tensioning adjustment accuracy effect and high safety factor.

3.4 Optimize the docking process of conveyor belt

Before the butt joint of the conveyor belt, the butt joint conveyor belt shall be cut flat, and the butt joint plane shall be perpendicular to the center line of the conveyor belt. In order to avoid uneven butt joint during traditional mechanical butt joint, bulge at the interface after butt joint and increase the wear of conveyor belt, it is decided to adopt the method of thermal vulcanization for butt joint of conveyor belt interface, so as to effectively improve the butt joint level of interface.

3.5 Reduce the impact force of coal flow

In order to solve the problem of impact deviation during coal flow unloading at the butt joint of two adjacent conveyors, it is decided to install coal flow buffer device at the head. The device is mainly composed of metal shell and flexible coal receiving platform, as shown in Figure 2. When the coal flow enters the buffer device, it collides with the flexible coal receiving platform to reduce the coal flow speed and ensure that the coal flow enters the lower horizontal conveyor smoothly.

4 Conclusion

In May 2020, the mechanical excavation team of Dadougou Mine took anti deviation measures for the belt conveyor of lane 5201. As of September 2020, according to the actual application results in four months, after the belt conveyor took anti deviation measures, there were three belt breaking accidents in the later mining process of lane 5201, of which one was caused by the deviation of the conveyor. Compared with the previous mining, the deviation accident rate of the conveyor has been reduced by 87%. It is estimated that the maintenance cost of the conveyor can be reduced by 278000 yuan in the whole year, which effectively ensures the safe and efficient excavation of the machine driven roadway and has achieved remarkable application results.

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