Factors that determine the service life of screw conveyors

1. The diameter of the driving drum.

When the conveyor belt bypasses the drum, bending stress is generated, which causes the core fatigue. The smaller the diameter, the greater the bending stress. Obviously, the diameter of the roller is beneficial to increase the length of time the conveyor belt is used, but when it reaches a certain value, the bending stress is not significantly reduced, and it will also make the equipment volume. Therefore, in order to ensure that the bending stress of the conveyor belt is not too large, the small diameter of the roller should be restricted. The principle of selecting the diameter D of the driving drum is: when the multi-layer core conveyor belt adopts mechanical joints, D≥100i, mm (i is the number of canvas layers); when vulcanized joints are used, the joints are trapezoidal lap joints, which are easy to be under bending stress. Peeling, so D≥125i, mm. When the whole braided core conveyor belt uses mechanical joints, D≥K8, mm (k depends on the parameters of the core frame material; 8 is the core thickness, mm). When steel cord conveyor belt is used, D=(150～200)(t, mm (d is the diameter of the steel wire rope, mm). The diameter of the reversing drum is based on the driving drum diameter, the force percentage, and the angle of the conveyor belt to the drum. determine.

2. The idler rolls into a groove angle.

The load-bearing branch usually adopts a trough-shaped roller group composed of three rollers, and the angle between the side roller and the middle roller is called the groove angle. The heat-resistant conveyor belt is made of multi-layer rubber cotton canvas (polyester cotton cloth) or polyester canvas covered with heat-resistant or heat-resistant rubber and bonded together by high-temperature vulcanization. It is suitable for conveying hot coke, cement, slag and slag below 175℃. Hot castings, etc. Within a certain limit, the greater the groove angle, the greater the material flow (unit: cubic meters per second). However, when the grooving angle exceeds the grooving capacity of the conveyor belt itself, the conveyor belt will not be close to the middle idler when it is running under no load, which will cause strong wear on the edge of the conveyor belt and unstable operation; during heavy load operation , The conveyor belt will inevitably produce a great folding stress at the corners of the side roller and the middle roller, causing the conveyor belt to break longitudinally or the canvas layer to peel off quickly. Therefore, in the design, the roller groove angle is required to be consistent with the groove forming capacity of the selected conveyor belt, and this principle should also be observed when replacing the new conveyor belt in use. The groove angle of the idler is usually 30. When the conveyor belt has good performance in troughing, it can reach 35.

3. Excessive distance.

The conveyor belt section between the head and tail rollers of screw conveyors and a set of supporting rollers (supporting the conveyor belt and the weight of the material) is called the transition section. The rubber conveyor has the characteristics of heat-resistant belt, wear-resistant belt, burn-resistant belt, oil-resistant belt, alkali-resistant belt, alkali-resistant belt, heat-resistant belt, and cold-resistant belt. It is mainly used for the transportation of solid materials in various mining, metallurgy, steel, coal, hydropower, building materials, chemical, food and other enterprises. In the transition section, the conveyor belt changes from trough shape to parallel or from parallel to trough shape, and the edge of the conveyor belt is stretched to generate additional tensile stress. The smaller the length of the transition section, the greater the additional tensile stress, which will cause serious wear on the edges of the conveyor belt and the side rollers, which will cause the conveyor belt to fatigue prematurely and even cause the edges of the conveyor belt to break. In order to ensure that the local elongation of the edge of the conveyor belt does not exceed the use elongation of the conveyor belt, the length of the transition section should not be too small. For the fiber core conveyor belt, the transition section length is taken as 1.3 times the distance between the idlers; since the allowable elongation rate of the steel cord conveyor belt is 0.2%, the transition section length is calculated according to the formula L≥2.67cc B, where B is the bandwidth , M; d is the groove angle of the idler, rad. If the L value is much larger than the distance between the supporting rollers, several transition roller groups should be installed between the roller and a group of supporting rollers to prevent the belt from sagging and sprinkling.

4. The radius of the convex arc.

When there is a convex arc on the screw conveyor line, there is also a great tensile stress on the edge of the conveyor belt when it passes, which causes the conveyor belt and the idler (supporting the conveyor belt and the weight of the material) to be damaged prematurely, so the radius of the convex arc is not Should be too small. When using steel cord conveyor belt, the radius of the convex arc should not be less than (75～85)B.

5. Feeding device.

Whether the structure of the feeding device is reasonable or not determines the service life of the conveyor belt to a large extent. In order to reduce the wear and impact stress of the material on the conveyor belt, the technical requirement f-1 of the design and selection of the feeding device is: the speed and direction of the material fed to the conveyor belt should be approximately the same as the belt speed; minimize the drop of the material, In particular, it is necessary to prevent large pieces of material from falling directly onto the conveyor belt; inside the feeding device, the material should form a free continuous flow, and the material can be evenly loaded to the middle of the conveyor belt in the correct shape, and it is not allowed There is material accumulation and sprinkling; as far as possible, first unload the powder and fine pieces on the conveyor belt to form a cushion, and then load the blocks. A buffer roller (supporting the weight of the conveyor belt and the material) group should also be set at the loading point to reduce the impact of the material on the conveyor belt. The installation position of the feed hopper ensures that the material falls between the two buffer roller groups. It does not fall on a certain set of buffer rollers.

6. Start and brake mode of screw conveyors.

During the starting and braking process of the belt conveyor, the soft start method should be used to control the acceleration and deceleration when starting and stopping, so as to reduce the dynamic stress. The heat-resistant conveyor belt is made of multi-layer rubber cotton canvas (polyester cotton cloth) or polyester canvas covered with heat-resistant or heat-resistant rubber and bonded together by high-temperature vulcanization. It is suitable for conveying hot coke, cement, slag and slag below 175℃. Hot castings, etc. For general small and medium-sized belt conveyors, it is reasonable to use a torque-limiting fluid coupling to achieve soft start. For long-distance, large-capacity large belt conveyors, due to the large dynamic tension, a controllable soft start device should be used to extend the starting and braking time and reduce the dynamic stress. Commonly used controllable soft start devices include speed-regulating hydraulic couplings, CST controllable drive devices and frequency conversion speed devices.