After the unloading belt conveyor operates normally, the forward frictional force between the belt and the main drum is equal to the backward frictional force between the belt and the idler and other drums. At this time, the belt speed is equal to the linear speed of the outer surface of the drum.
When the forward friction force between the belt and the main drum is reduced to a certain value, the speed of the belt will decrease, and there will be a difference between the rotation speed of the main drum and the belt conveyor.
The slippage of the unloading belt conveyor will cause the material to be scattered and the material to be piled up in the tail chute. In severe cases, it will cause serious accidents such as belt abrasion and motor burnout, which will pose serious hidden dangers to production.
Causes of unloading belt conveyor slippage
- Water enters the surface of the belt.
Due to changes in the natural environment, on-site ground washing, equipment maintenance, etc., water, oil, ice, frost, and other lubricating attachments adhere to the non-working surface of the belt. As the belt moves to the main drum, the two The contact conditions between them will change, and the water flow will play a lubricating role, which will greatly reduce the friction coefficient. When the water flow accumulates in the main drum, the friction force on the belt is insufficient and the belt cannot support the forward movement of the belt. At this time, the belt speed will decrease and the belt will slip.
- The main drum rubber is damaged.
Roller lagging is an important part of belt conveying and transportation systems. The lagging drum can effectively improve the operation of the conveying system, protect the metal drum from being worn, and increase the surface friction between the belt and the drum, which can effectively prevent the The sliding friction between the drum and the belt reduces belt slippage. However, after the unloading belt conveyor has been running for many years, if the lagging material is aged and deformed or seriously worn, the friction coefficient between it and the belt will decrease sharply, which will cause the belt to slip.
- Insufficient belt tension
If the belt does not have enough tension, there will not be enough frictional driving force between the driving pulley and the belt, and the belt and the load cannot be pulled.
The tensioning device of the unloading belt conveyor usually includes several structures for screw tensioning, hydraulic tensioning, heavy hammer tensioning, and car tensioning. The stroke of the screw or hydraulic tensioning device is insufficient or improperly adjusted, the weight of the hammer tensioning device and the weight of the car tensioning device is not enough, and the mechanism jamming will cause insufficient tension on the unloading belt conveyor and cause slippage.
- A stacking accident occurs in the nose chute.
If after stacking occurs in the chute of the unloading belt conveyor, if the stacking protection switch fails, the material will pile up more and more at the head, and even the head and the nearby ground will be buried, thus crushing the belt. With the continuous movement of the main drum, the temperature of a section of the belt in contact with it will rise sharply, and the belt can be worn off in just a few minutes, resulting in greater economic losses and endangering personal safety.
- The load of the unloading belt conveyor is too large.
Slippage caused by excessive belt load is often caused by insufficient motor capacity. Especially after abnormal parking, there is a large amount of material in the belt. This kind of starting with a load will cause great damage to the equipment and easily cause the motor to burn out. Therefore, the operator should pay close attention to the value of the belt scale and the current of the unloading belt conveyor, control the amount of material, and avoid overload operation.
In the event of a heavy load shutdown, the driver at the post can try to start at a slow speed first, and then start by jogging twice to make full use of the inertia of the belt to overcome the slipping phenomenon. However, when this operation is invalid, multiple attempts should be avoided. Stockpiling reduces the belt conveyor load.
- The resistance increases during the operation of the belt.
The roller bearing at the end of the machine is locked or there are large pieces of material entering; the upper and lower idlers of the unloading belt conveyor are stuck; and there are foreign objects in the chute at the end of the machine that hang on the belt, which will also cause the belt conveyor to slip.
The direct reason is that the running resistance of the unloading belt conveyor is increased, which causes the friction between the main drum and the belt to relative displacement, which will cause damage to the belt equipment after long-term operation.
Preventive measures for belt slippage
- The unloading belt conveyor frequently slips, and it is difficult to handle after the event, which seriously affects the safe production. After repeated on-site surveys and long-term market research, a factory decided to use a belt conveyor slip protection switch.
The protection master-slave probe detects the main drum, redirects the pulse frequency signal generated by the magnetic block signal generation point at the drum, and alternately displays the corresponding rotation speed.
When the rotation speed is inconsistent, the relay can be controlled to close within 10s to stop the operation of the unloading belt conveyor, which effectively reduces the expansion of the accident after the unloading belt conveyor slips.
- Add a soft-start protection device to the high-power unloading belt conveyor. The soft start of the belt conveyor means that the unloading belt conveyor gradually accelerates from the static state to the rated speed.
Its advantage is that it avoids impact force when starting, which means that there is no impact force on the belt, motor, or belt frame, which greatly reduces the occurrence of belt slippage, and it can be started with a heavy load, reducing start-up currents and grid shocks.
- Ceramic lagging should be done on the main drum.The rubber plate uses ceramic particles to adhere to the surface of the rubber plate, which can effectively increase the friction between the driving roller and the belt. It can also be found through experiments that the friction coefficient of ceramic lagging is increased by 2-3 times compared to rubber lagging.
Although the price of ceramic rubber sheets is more expensive, generally 3 times the price of rubber rubber sheets, the service life of ceramic rubber sheets is longer. Generally, ordinary rubber sheets have to be replaced due to rubber wear after two years of use. Under the same working conditions, the ceramic plywood can be used for more than 10 years.
- Strengthen the coordination of production scheduling and the implementation of the equipment maintenance system to avoid belt slip accidents caused by problems in operation and equipment itself and ensure safe production.
The slipping phenomenon of the unloading belt conveyor brings great hidden dangers to safe production and operation. Therefore, management systems in all aspects should be strengthened, and the level of maintenance and inspection should be improved to ensure the reliable operation of equipment and improve production efficiency.
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