Slipping is one of the common faults of belt conveyor. Once slipping occurs, it is easy to cause abnormal phenomena such as material scattering, feed pipe blockage, belt abrasion, belt breakage and so on, which affect the normal operation of belt conveyor
. This article analyzes the 9 major causes of slipping for everyone, and attaches solutions.
Influence of Belt Slipping on Belt Conveyor
When the belt is running normally, its speed should be the same as the linear speed of the surface rotation of the driving roller, and the belt speed should not be lower than 95% of the linear speed of the surface of the driving roller. However, in actual operation, due to various reasons, the rotating speed of the belt and the driving roller is out-sync, or the driving roller rotates but the belt fails, which is called slipping.
The belt slipping will cause the material to flow back and scatter. In serious cases, it may cause intensified belt abrasion, burning of motor and even breakage of belt, which will affect the safe and stable operation of the belt conveyor.
Causes of Belt Conveyor Slipping and Preventive Measures
1. The belt tension is insufficient. If the belt does not have sufficient tension, there will not be enough friction driving force between the driving wheel and the belt, and the belt and the load cannot be pulled to move. The tensioning device of belt conveyor usually includes several structures such as spiral tensioning, hydraulic tensioning, heavy hammer tensioning and truck tensioning. Insufficient distance or improper adjustment of the spiral or hydraulic tensioning device, insufficient weight of the counterweight of the heavy hammer tensioning device and the truck tensioning device, and jamming of the mechanism will all result in insufficient tensioning force of the belt conveyor, causing slipping.
1) Belt conveyors with spiral or hydraulic tensioning structures can increase the tensioning force by adjusting the tensioning distance, but sometimes the tensioning stroke is not enough and the belt is permanently deformed. In this case, the belt can be cut off for vulcanization.
2) Belt conveyors with heavy hammer tensioning and truck tensioning structures can be treated by increasing the weight of counterweight or eliminating jamming of mechanism. It should be noted that when increasing the configuration of the tensioning device, it is enough to add it to the belt without slipping, and it is not advisable to add too much, so as not to make the belt bear unnecessary excessive tensioning force and reduce its service life.
2. Severe abrasion of the rubber coated on the driving roller. The driving roller of belt conveyor is coated with rubber or cast with rubber, and herringbone or diamond grooves will be added to the rubber surface to improve friction coefficient and friction force. After the belt runs for a long time, the rubber surface of the driving roller and its grooves will be seriously worn, resulting in a decrease in the friction coefficient and friction on the surface of the driving roller, causing the belt to slipping. Solution: In case of such a situation, re-coating or replacing the roller should be adopted. During routine inspection, attention should be paid to the coating inspection of the driving roller to prevent it from being found out behind time after excessive abrasion and tear, thus causing belt slipping and affecting normal operation.
3. There are water, oil, ice and frost on the non-working surface of the belt. Due to natural environment changes, on-site ground flushing, equipment maintenance and other reasons, water, oil, ice, frost and other attachments with certain lubricating effects are adhered to the non-working surface of the belt. During the operation of the belt conveyor, they will accumulate on the surface of the driving roller, resulting in obvious reduction of friction between the roller and the belt, causing slipping. Solution: After this happens, first determine the source of the attachment and cut off the source. If it is really impossible to cut off the source, sprinkle some rosin powder on the drum, but be careful not to add it by hand and blow it with blowing equipment to avoid personal accidents.
4. Belt conveyor overload. Due to improper operation or heavy load downtime, belt conveyor overloads severely in the operation. Or the belt conveyor starts with load, causing overload operation, causing belt slipping.
1) During operation, belt conveyor current and electronic belt weigher shall be monitored to control material quantity and avoid overload operation.
2) Try to avoid shutdown under heavy load, so as not to exceed its rated load when the belt conveyor is started under heavy load. After the belt conveyor stops due to other faults under heavy load, the starting load can be reduced by manual cleaning.
5. If feeding pipe jam in the head and belt conveyor is not found in time, a large number of materials will accumulate on the head and non-working face, press the belt, causing slipping. Solution: In order to prevent this kind of situation from happening, the attendant should pay attention to the change of materials on the belt during the operation of the belt conveyor, give more frequent inspection of the head feeding pipe when it becomes sticky, and clean up the sticky materials in time to avoid the occurrence of blocking. Even if it cannot be avoided, the blocking amount should be controlled as far as possible.
6. The conveyor belt is partially jammed. When a certain part of the conveyor belt is strongly blocked, the belt will slip. This kind of situation usually occurs at the head, tail and tensioning device of belt conveyor, for example, the head and tail of belt conveyor are jammed with foreign matters, the tail redirection roller does not rotate, etc.
Solution: During operation, the monitoring of belt conveyor current should be strengthened. In case of abnormal current changes, the machine should be stopped immediately for inspection, and the machine can be started again only after finding out the reasons and removing the obstacles.
7. Slipping Speed Measuring Device. Faulty belt conveyor is generally equipped with a slipping speed measuring device. When slipping occurs, it will send out a fault signal and stop the operation of the belt conveyor. The skid speed measuring device mainly consists of a speed measuring wheel and a control box, wherein the speed measuring wheel is directly contacted with a belt and is driven to rotate by the belt. When there is sticky material on the speed measuring wheel or there is poor contact with the belt, the device will mistakenly send a slipping signal to stop the belt conveyor. This kind of situation is more frequent in actual operation, and the electrical circuit faults in the control box will occasionally send slipping signals by mistake.
Solution: When the belt conveyor stops due to slipping fault, it should first be checked on site to determine whether the belt conveyor has actually slipped. If the speed measuring device mistakenly sends a slipping signal, it should be checked and processed. The general method of treatment is to remove the sticky material on the speed measuring wheel, adjust its position and eliminate the electrical circuit fault.
8. When starting the belt conveyor, the brake cannot be turned on. When starting the belt conveyor, it will sometimes slip and stop because the brake cannot be turned on. The belt conveyor driving device cannot rotate under the control of the brake when the motor circuit has been switched on. On - site inspection will show that the motor is buzzing, while the belt and its driving device are not operating.
9. The wrap angle between the driving wheel and the belt or the friction coefficient is too small. Usually, the wrap angle between the driving wheel and the belt should not be less than 120 degrees. If it is too small, the belt conveyor will slip easily.
Solution: If the wrap angle between the driving wheel and the belt is small and the position of the tension wheel cannot be effectively increased by adjusting, the design may need to be modified. Therefore, these factors should be carefully considered during the preliminary design to ensure the design quality of the belt conveyor. If problems are found only during assembly and debugging, it will be very passive to revise the design. In addition, if the friction coefficient between the driving wheel and the belt is too small, the belt will slip. Solution: Carefully observe whether the surface of the driving wheel of the conveyor is too smooth, otherwise, use knurled structure or inlay a layer of rubber before testing. Slipping is one of the common faults of belt conveyor. If the belt conveyor can be operated in a standard way, checked carefully and maintained carefully, the occurrence of slipping can be lowered to a great extent. Even after the fault occurs, we can make accurate judgment and treatment through the above methods, thus ensuring the safe and stable operation of the belt conveyor system