For belt conveyors, conveyor belts occupy a very important position. They are both traction components and load-bearing components, and they are expensive, accounting for about 30% to 50% of the total belt conveyor cost. Once the conveyor belt becomes thinner due to wear, it will be followed by faults such as reduced strength, shortened life, and belt deviation. This article analyzes several major forms of wear and puts forward some maintenance measures based on actual production.
1. Wear between the feeding chute and the conveyor belt
The feeding chute is in close contact with the conveyor belt. Its design and installation have a great influence on the wear of the conveyor belt, which is the main manifestation of conveyor belt wear.
Causes
a) When feeding, the material has an impact on the conveyor belt, especially when the angle between the material and the conveyor belt direction is greater than or equal to 90°, it will cause strong wear on the conveyor belt;
b) In order to prevent the material from scattering, the guide plate is in too tight contact with the conveyor belt, causing the conveyor belt to wear;
c) Long hard objects mixed in the material are stuck in the feeding port, wearing or scratching the conveyor belt.
Maintenance measures
In order to reduce the wear of the conveyor belt at the feed port, the structural design of the feed port should meet the following conditions:
a) The feed and the conveyor belt run in the same direction. During the feeding process, the material moves at almost the same speed as the conveyor belt;
b) The equivalent free fall height of the material falling on the conveyor belt is less than 1m, so that the impact force on the conveyor belt is as small as possible;
c) A bar screen is installed in the feeding chute to allow fine-grained materials to fall on the conveyor belt first and provide padding for large pieces of material;
d) The chute and guide trough are reasonably designed to allow the material to fall continuously to the center of the conveyor belt;
e) The baffle width of the guide trough becomes narrower and narrower along the running direction of the conveyor belt, and the guide trough should be extended to the speed of the material to reach the belt speed;
f) The feeding section is kept horizontal, or the slope is not greater than 8°, and the feeding section is equipped with buffer rollers or the trough rollers are arranged densely.
In addition, the chute and guide trough should be firmly fixed so that they are correctly positioned against the conveyor belt, and the bottom of the guide trough should not be too close to the conveyor belt.
2. Wear between the redirecting roller and the conveyor belt
The redirecting roller is located at the tail of the conveyor. The conveyor belt rotates with the redirecting roller, so that the lower conveyor belt becomes the upper conveyor belt to carry the material.
This wear is mainly due to the entry of debris between the redirecting roller and the conveyor belt, which sticks to the roller, causing the local radius of the redirecting roller to deform and wear. The main reasons are:
a) Due to unclean cleaning and environmental influences, the redirecting roller is easy to stick to the material. When these materials reach 3cm, the local stress of the redirecting roller increases rapidly, and the wear between the two is aggravated, causing the rubber layer of the conveyor belt to become thinner or holes to appear.
b) There is a long unsupported section between the redirecting roller and the lower roller. At this time, the shape of the conveyor belt gradually changes from a trough type to a straight line type, and the material is easy to scatter and fall on the unloaded section of the conveyor belt, entering between the conveyor belt and the roller, causing wear of the conveyor belt.
Maintenance measures
a) Install a scraper plate close to the surface of the redirecting roller. The scraper plate and the receiving plate are welded together as a whole. The receiving plate is connected to the conveyor frame by bolts, and the scraper plate and the roller have a certain inclination angle to increase the scraping capacity.
b) Install a V-shaped sweeper (connected to the frame by bolts) in front of the redirecting roller. Install a rubber strip at the contact end between the sweeper and the conveyor belt to reduce the wear on the belt. The structure is shown in the figure below:
In addition, in order to solve the problem of material leakage in the unsupported section in front of the redirecting roller, a baffle can be installed in the unsupported section to reduce material leakage.
3. Local wear caused by conveyor belt deviation
Conveyor belt deviation is a common fault of conveyor, which mainly refers to the deviation of the center line of the conveyor belt from the longitudinal center line of the conveyor when the conveyor is running
Causes
The fundamental reason for conveyor belt deviation is: the lateral force is generated when the inclined rollers on both sides of the belt conveyor contact the conveyor belt. When the lateral forces on both sides are not equal, the conveyor belt deviates, which is mainly manifested in the following points:
a) The center lines of the conveyor head and tail rollers are not parallel, which makes the tightness of the conveyor belt inconsistent on both sides, and the conveyor belt moves to the tight side;
b) The quality problems of the conveyor belt itself (such as uneven elongation, uneven bending, etc.), as well as serious wear on the edge of the belt, will make the tension on both sides of the conveyor belt inconsistent, causing deviation;
c) The joint of the conveyor belt is not straight;
d) The rollers are not installed correctly, which applies a biasing force to the conveyor belt;
e) Improper feeding of the conveyor belt causes uneven force on the conveyor belt, resulting in deviation;
f) The roller adheres to the material, causing the roller radius to change locally, causing the conveyor belt to deviate laterally.
For various forms of conveyor belt deviation, the following rules are summarized: the conveyor belt runs tight but not loose; runs high but not low; runs backward but not forward.
Maintenance measures
a) The head and tail rollers are not parallel, and the phenomenon of running tight but not loose occurs.
If the center line of the entire conveyor is offset, the center line must be recalibrated; if it is only a slight deviation, the bearing seat on the tight side can be tightened. However, this method can only adjust a small deviation. For a large deviation, the tail roller can be installed on a movable trolley (see the figure below) and the deviation can be corrected by adjusting the trolley.
b) Due to the uneven force of the conveyor belt itself due to the uneven bending of the conveyor belt or the incorrect joint, the conveyor belt should be cut straight, re-glued or nailed.
c) The axis of the roller group is not perpendicular to the center line of the conveyor belt, causing the conveyor belt to run backwards instead of forwards, that is, the conveyor belt deviates backwards (opposite to the running direction of the conveyor belt). The adjustment method is to deviate the roller on the side of the deviation by 2°~4° to the forward direction of the conveyor belt (see the figure below). Generally, several rollers need to be adjusted to correct the deviation.
4. Wear between rollers and conveyor belts
Causes
The causes of wear between rollers and conveyor belts mainly include installation errors, deformation of roller frame structure, and corrosion of rollers.
a) Improper installation of roller frame
The conveyor belt generates a certain friction force under the support of rollers to ensure its normal operation. Due to improper installation, the axis of the roller is not perpendicular to the center line of the conveyor belt, and the conveyor belt slides relative to the roller, aggravating the wear of the conveyor belt.
b) Wear caused by self-aligning roller correction
When self-aligning rollers are corrected, a certain tilt angle is generated. Due to processing quality and rust, the rotating frame cannot rotate flexibly and cannot be rotated and reset in time, which will wear the conveyor belt.
c) Roller rotation lag
Due to the quality problems of the rollers themselves (such as poor sealing, inflexible bearing rotation, etc.), the roller rotation lags behind the running speed of the conveyor belt, causing relative sliding between the rollers and the conveyor belt and wearing the conveyor belt
Maintenance measures
a) Ensure that the entire conveyor is on the same center line; secondly, the inclined rollers on both sides have the same tilt angle as the middle horizontal roller, and all the middle rollers are on the same horizontal plane, so that all rollers have good contact with the conveyor belt and ensure that each roller is evenly stressed.
b) Use self-aligning rollers as little as possible.
c) Strengthen the daily maintenance of rollers, and replace damaged rollers in time.
Conveyor belt wear is one of the more common faults, but if it is not taken seriously it will often cause more serious accidents. Therefore, taking corresponding measures to reduce conveyor belt wear and extend its service life is of great practical significance to the normal operation of the belt conveyor and reduce maintenance costs.
