Belt conveyors have the remarkable characteristics of strong conveying capacity, long conveying distance, simple structure and easy maintenance, and are easy to implement programmed control and automated operation. They are widely used in mining production. The conveyor belt is both the traction mechanism and the load-bearing structure of the belt conveyor. It runs through the entire length of the conveyor, with large usage and high cost. Once the belt tear occurs, the belt worth hundreds of thousands or even millions of yuan will be completely destroyed in just a few minutes, causing huge direct and indirect economic losses. Therefore, it is very important to understand the reasons for belt conveyor belt tearing and prevention.

01 Reasons for belt conveyor belt tearing

Belt tearing is a very harmful form of damage, which is accidental. The most common belt tearing is caused by sharp debris in the material stuck in the discharge port or the gap between the rollers during normal transportation of the belt conveyor. The belt tearing is mainly longitudinal tearing, and its main reasons are as follows:

1.1  Scratching by foreign objects Scratching by foreign objects is the main cause of belt tearing, which can be divided into three situations. First, sharp foreign objects directly pierce the belt and get stuck between the sealing box and the roller, causing tearing; second, foreign objects get stuck at the lower part of the feeding port, and cannot touch the belt when feeding, but the belt's center of gravity moves up when the belt is unloaded, thus scratching the belt; third, foreign objects get stuck in the gap between the rollers, and cannot touch the belt when the belt is unloaded, but the belt's center of gravity moves down during normal feeding, thus scratching the belt.

1.2  Belt deviation When the belt deviates seriously, it may fold on one side, and the belt may be scratched by the roller bracket or other objects, or even torn. Belt tearing caused by belt deviation generally only tears the belt edge, and will not appear on the inside of the belt.

1.3  Material jamming Large pieces of material are stuck at the feeding port, and a large amount of material is accumulated, resulting in abnormal operation. Large pieces of material scratch the belt. If it is not removed in time, it will cause belt tearing. For the steel industry, large pieces of material have been removed before loading, and such situations rarely occur.

1.4 Core tearing (such tearing only occurs in steel cord belts) Steel cord belts will have varying degrees of wear due to long-term use. In severe cases, the steel wire rope will be exposed or even broken. When the broken steel wire rope reaches a certain length, it may be entangled at any part of the belt conveyor, causing the belt to tear.

1.5 Improper installation of auxiliary equipment In addition to the threat of the material itself, the falling of objects on the conveyor belt itself during transportation is also a major cause of tearing. For example, the falling of vibrator linings, crusher hammers, and drop port adjustment stops may cause the conveyor belt to tear.

1.6 Blockage causes tearing The transfer chute is small, which easily hinders the passage of materials and impurities, causing the conveyor belt to tear.

1.7 The falling of the middle roller causes tearing The conveyor belt is directly pressed on the bracket supporting the middle roller. The heavy load makes the conveyor belt press the bracket tightly, and the bracket cuts through the conveyor belt like a knife, causing tearing.

1.8 Tearing at the head of the machine. The material is wedged into the connecting beam between the roller and the two sides of the head of the machine due to the full warehouse of the head. The belt is torn; or the scraper of the head of the machine is caught by sharp foreign objects such as metal wire, which causes the belt to tear.

1.9 Tearing caused by failure of conveyor components. For example, if the end cover of the roller is not welded well, the rotating end cover cuts the conveyor belt like a rotating blade. When the wire rope in the conveyor belt breaks, the broken wire rope head will be exposed outside the cover rubber from the joint, sticking point or the place where the conveyor belt is more worn. When the exposed wire rope reaches a certain length, it may be twisted into the roller, roller, etc. As the conveyor belt runs, the wire rope is pulled out of the conveyor belt cover rubber, causing core tearing.

If the belt cannot be replaced immediately after tearing, it can be used temporarily for a short time after drilling holes on both sides of the tear with an electric drill and fixing them with wire. If the tear length is small, it can be repaired. If the tear is long, it is recommended to replace the belt. Repaired belts affect the use of scrapers and sweepers, easily cause dust, and need to be inspected during use. If the repaired parts are debonded or warped, they need to be repaired again.

02 Prevention of belt tearing

2.1 Actively prevent tearing from the source, strengthen the control of material quality, and add impurity removal equipment for impurity removal. Set up a large block removal device in front of the primary belt to reduce the large block materials entering the entire conveying system.

2.2 Increase the passing capacity of the chute. Under the premise that the chute width is determined by the belt width, expand the chute outlet upward to increase its passing capacity as much as possible to avoid getting stuck with debris or large blocks of materials.

2.3 Strengthen equipment management and improve belt inspection and inspection efforts, especially the management of other ancillary equipment of belt conveyors, such as the inspection of transfer funnels, sweepers and other facilities, to prevent sharp objects such as liner plates from falling off.

2.4 Improve the conveyor structure by reducing the drop point height, adding buffer grilles, and fine materials falling before large blocks of materials, etc., to reduce impact, reduce material speed, and reduce the possibility of impurities inserting into the belt.

2.5 Improve the structure of the belt itself. For example, improve the air tightness of the belt, prevent water from entering the core layer and rusting of the wire rope, and require manufacturers to strengthen quality control and improve quality.

2.6 Add a tear detection device. When the belt is torn, detect it as soon as possible in the shortest time, issue an alarm and shut down, minimize the tear length and reduce losses.

2.7 Use tear-resistant belts. The tear-resistant belt uses wire rope as the longitudinal skeleton material and adds a transverse reinforcement to the belt body as an anti-tear layer, but the cost of this tear-resistant belt is about 20% higher than that of ordinary belts.

2.8 Use a tear-detectable belt. Add a sensor with a closed coil to the belt. The detector is installed at the tear-prone part of the belt conveyor, and the detector is connected to the controller. If the belt is torn, the closed coil of the sensor is cut off. When it passes through the detector, the detector stops sending a pulse signal. The controller cannot receive the pulse signal, and immediately alarms and shuts down. At present, this kind of belt cannot be produced domestically and the cost is high.

Although there are no obvious signs of belt tearing, we can minimize the probability of belt tearing accidents or even completely prevent them by reducing the entry of large pieces of material and sharp objects into the conveying system from the source, improving the quality and sense of responsibility of operators, strengthening equipment inspection and maintenance, promptly correcting deviations and eliminating hidden dangers of belt tearing, and using advanced anti-tear monitoring and control systems.