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Above: Check or confirm that a conveyor is square by measuring the diagonals of each conveyor section. If the diagonals don't match measurements, your frame is not square.

Below: A belt must be cut squarely, or at a consistent angle, and laced properly in order to track perfectly. If either of these are off, the belt will track off each time the lace comes around the end of the conveyor.

Belt tracking is a pain point for you, for your maintenance team, and for your customers. Incorrect tracking can cost you time, money and a lot of frustration, but there are a few fairly simple ways to diagnose and correct the tracking in your belt. To troubleshoot a belt that isn’t tracking properly on your conveyor, use the following steps to fix the problem.

 

Belt issues

Continually tracking off

A belt must be cut squarely, or at a consistent angle if cut on a bias, and laced properly in order to track perfectly. If either of these are off, the belt will track off each time the lace comes around the end of the conveyor. If this is the case, you can recut the ends and relace the belt as a solution.  Sometimes belts are intentionally cut and laced on a bias angle in order to quiet the belt as it flows through the conveyor.  In these applications make sure to cut each end at the exact same angle prior to installing new lacing.  Make sure to install the correct lacing size and type for the belt and the application.

Tracking over and back

If your belt is tracking over and back with each revolution and it doesn’t appear to be at the lace then the belt may have been slit to width from the manufacturer with a bow, or camber, in it. Unfortunately, if this is the case the belt will need to be completely replaced.

Visible signs of damage

Over time, a belt tracking improperly may result in the belt becoming severely damaged in structure. Again, if this is the case, the belt will most likely need to be replaced in order to achieve proper tracking. If this has occurred, the belt will show visible signs of damage, such as rips, tears, fraying edges, or discoloration on one side where it may be been folded or stretched beyond allowable limits.

 

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Conveyor issues

If you’ve checked the belt for these issues and you’re still having issues troubleshooting the problem, the issue may be with your conveyor. Conveyor issues can include any of the following.

Frame squaring

If your conveyor is a belt over roller or belt-driven live roller conveyor, the issue may be that your frame is out of square. When this happens, the rollers under or over the belt will not be perfectly perpendicular to belt travel.  This will cause the rollers to steer the belt to one side as it travels through or over the rollers.

You can check or confirm this by measuring the diagonals of each conveyor section—if the diagonals don’t match measurements, your frame is not square. You can also check using a framing square to measure for a perfect 90-degree angle between the frame and rollers.  The sections may not have been installed squarely or may have suffered from damage caused by force placed on the conveyor by something such as a lift truck.   

False crowns

End pulleys and take up pulleys typically utilize a crown in the center to assist with belt tracking.  The crown is simply a larger diameter in the center of the pulley which tapers off to a slightly smaller diameter near the ends of the pulley. The crown generates forces in each side of the belt toward the center to keep the belt tracking in the center. However, if shipping labels, cardboard, strapping or other debris have wrapped around the pulley or stuck to the pulley, this can produce a false crown and cause the forces in the belt to be uneven from each side and track the belt off to one side. To fix this, the pulley must be cleaned to reestablish the original intent and purpose of the factory crown.

Return roller adjustments

Return rollers are generally used on the underside of the conveyor to support the belt as it returns.  Return rollers are normally adjustable in squareness to frame.  Adjust these as needed to be square with the frame, consulting your maintenance manual for further instruction.

Snub roller adjustments

Conveyors utilize rollers on the underside of the unit near the pulleys where the belt needs to change angles of flow to feed the belt to the pulley which is typically larger in diameter.  These are referred to as snub rollers or snub idlers. These have a lot of control over the belt. These rollers should be adjusted to be square with the frame, therefore perpendicular to belt travel. At this time, also adjust the pulleys to be square with the frame. Once you’re sure everything is square, the snub roller on the infeed end of the belt conveyor or on the discharge end of a belt-driven live roller conveyor may be adjusted.  Adjust to steer the belt to the center; the forces created by the crown should hold the belt in a center once the belt is steered to the center tracking position.

Belt tension is important for proper tracking.  The belt must be sufficiently tight to conform to the crown in the pulley. This tension varies with belt type and severity of crown; if you’re not sure, consult your manufacturer for proper tension measurements.

 

Conveyor belt tracking is important for the smooth running of your operation and long useful life of the conveyor belts in your operation; using these troubleshooting steps, you’ll be able to maintain your belt and save a lot of headaches down the line.


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BonhamBoyce2About the author: Boyce Bonham is the Chief Engineer at Hytrol, where he has over 30 years of service. You may email Boyce at bbonham@hytrol.com.