When your operation is working at full speed, trying to move product or fulfill orders, the last thing you need to worry about is your belt mistracking. Unfortunately, sometimes even the slightest movement or change in the conveyor can throw your belt off track. Misalignment of rollers or pulleys, an incorrect splice, and material build-up are just a few things that can get your belt off track. Sometimes a slight bump by heavy machinery or even the weather – high winds, frost, and even sunshine – can interrupt your belt’s path.
If caught early and fixed, a mistracked belt does little damage to the conveyor. However, if missed or left unfixed, other types of damage can occur. If a belt is constantly hitting a structure, it can not only damage the structure, but it could shave layers off the belt until there is little left. The width of the belt could also be affected, which reduces the amount of material it can carry.
If a belt mistracks enough, it will spill material off of the topside onto the area around it, which could result in safety violations. In rare cases, friction heating begins and the belt becomes a source of ignition, causing even more safety problems.
Here’s a comprehensive list of six potential problems caused by belt mistracking.
Many areas around the world have implemented safety regulations to address these problems. In the U.S., for example, MSHA enacted code 30CFR 75.1731, specifically citing that “conveyor belts must be properly aligned to prevent the moving belt from rubbing against the structure or components.” Failure to comply with these regulations may lead to fines and/or work stoppages.
A total overhaul of the conveyor isn’t often in the budget for most operations. Instead, some turn to temporary fixes – like attaching side rollers to the conveyor – that could actually make the problem worse. A roller on the edge of the belt is not always effective because belts prefer to pull, not push, so you are working against the belt. Another way to adjust the belt is to use friction – skewing the roller in comparison to the direction of the belt. The third way is to affect the tension profile. Belts naturally want to “walk away” from a higher tension. If tension is increased on one side, it will walk the other way.
Field testing has proven that a combination of friction and tension is the best way to put a belt back on track when the structure cannot be properly aligned. Many equipment manufacturers offer a steel return roller with an edge roller next to it that causes the roller to pivot or skew relative to the travel of the belt. The friction of the roller on the belt steers it back. The problem with this method is that the edge of the belt strikes the roller with heavy force without much effect, exerting heavy pressure to the belt edge. This situation can generate high force into the roller that can damage the belt.
Other manufacturers offer products commonly referred to as “wobblers,” which use a single center bearing inside of a lagged roller/tube to steer the belt. The problem with this design is that in order to create steering forces, the roller must tilt downward on the mistracked side. This is counterproductive since decreasing the tension will quickly invite the belt to mistrack even further. Only in the lightest tension applications, where steering force has more impact than tension, does this method have a chance to work well.
To avoid exerting heavy pressure or making a tracking issue even worse, choose a tracker with a “pivot and tilt” design that provides friction and changes the tension profile of the belt. When both the pivoting and tilting mechanisms work together, they are more than three times as effective at restoring belts back to the center of the conveyor.
The next time you’re struggling with a belt that is mistracking to one or both sides, consider a tracker that “pivots and tilts.” You’ll have an effective solution up your sleeve that you can get to work implementing before it causes too much damage, or downtime.
If you’re interested in learning more about the potential problems caused by a mistracking belt, here’s another blog post I wrote.
Fales manages the belt conveyor product (BCP) line, providing product development and engineering with guidance on market requirements for both new product concepts and existing products. He also leads the development of technical and promotional literature supporting BCP line. Fales graduated from Grand Valley State University with a bachelor’s degree in Marketing and is currently working toward his master’s degree in business administration from Western Michigan University.
Conveyor belts are frequently blamed for belt tracking problems and in most cases this is unjustified. The failure cause is usually to be found in the installation itself and may be the result of poorly adjusted pulleys and rollers, incorrect application of belt tracking measures or faulty design. It is therefore essential to be fully aware of the basic characteristics of the different belt tracking measures and for these to be employed correctly.
A distinction needs to be made between basic and additional measures for belt tracking. The former are appropriate for maintaining a correctly aligned belt in its central position as long as no great external influences are exerted on the belt, such as transverse forces. The latter are necessary when the basic measures alone are either insufficient or inappropriate to control belt tracking sufficiently.
Regardless which measures are taken, the following conditions are essential for problem-free belt tracking:
What happens if a conveyor has no tracking measure at all?
Where a belt runs over cylindrical pulleys that are at right angles to its directional path, then the forces acting upon it will be parallel to the running direction of the belt. No tracking forces are exerted on the belt.
In fact, the belt is running in a state of unstable equilibrium and would run off immediately if subjected to the slightest external factors such as off-center loading of product, dirt between belt and pulley, belt distortion or lateral feeding or diverting of goods.
The same scenario applies if one or both of the two pulleys are not positioned accurately at right angles to the belt running axis. The belt will inevitably run off towards the less-tensioned side.
The belt tracks to the side with the least tension.