DYNA Engineering’s General Manager, Thomas Greaves, explains how mistracking belts can be corrected and improve productivity by reducing unscheduled stoppages and maintenance costs.
Belt mistracking occurs when the conveyor belt is no longer aligned in its original or recommended position on the conveyor structure. This causes the edge of the conveyor belt to rub against surrounding components and structure and become damaged.
Mistracking can be caused by a broad range of factors. It is one of the most common reasons for time-wasting and costly conveyor stoppages. Some simple checks can be performed to assist in identifying the reason for conveyor belt mistracking:
1. Is the belt in poor or worn condition?
If the belt is badly worn or stretched, or shows signs of cracking or wear through the rubber cover, tracking can be problematic because the belt may no longer be straight.
2. Is the belt ripped, torn or damaged?
If the belt has rips, holes or any sort of structural damage to the belt carcass, the belt may no longer be straight. This can also cause the belt to catch on idlers or other parts of the conveyor causing the belt to run off centre.
3. Is the belt splice in poor condition?
Inspect the splice and make sure it is in good condition, has no flaps, loose items or abrupt edges that may become caught on idlers or other components.
4. Is the conveyor pulley lagging worn or material building-up on the pulleys?
If the pulley lagging is worn or material has built up around the lagging, this can alter the effective diameter across the pulley. This will likely lead to the belt wondering off centre, increased instability and may result in the belt running off the edge of the pulley.
5. Has material built-up on the idlers?
Material build-up around the idlers may result in the belt being steered off centre, running to one side and contacting other components along the conveyor.
6. Are all the idlers rotating smoothly?
If idlers cease running or become jammed, the stationary roller may act as a brake on that part of the belt. This can cause the belt to run off to one side.
The traditional pivot belt tracking frame
A pivot belt is probably the most common method of assisting to correct belt tracking. A pivot belt tracking frame uses the standard conveyor rollers with the addition of a horizontal centre pivot and side guide rollers. When the belt wanders to one side, the edge of the belt will come into contact with one of the side guide rollers causing the frame to pivot. The pivoting motion steers the belt back towards the middle of the conveyor.
However, unfortunately, the gap between the belt and side guide rollers can create a delay in the response to the movement of the belt. This may result in an overcorrection and the conveyor belt will continue to wander from one guide roller to the other.
In extreme cases, when a severe mistracking event occurs, the pivoting frame can move to a point where the pivot reaches its limit and the conveyor belt can be forced up and over the side guide roller. This will cause damage to the conveyor belt and surrounding equipment.
Another common problem is the edges of the conveyor belt can be worn prematurely or damaged when coming into contact with the traditional tracking rollers. If the centre pivot becomes worn or seized, the conveyor belt will not track properly and consistently rub and wear against the side guide rollers.
Tracking rollers
Tracking rollers (sometimes called trainers) are an alternative to the pivot belt tracking frame, designed to minimise belt mistracking. Usually fitted on the return run of the conveyor belt, tracking rollers assist in keeping the belt aligned and centred on the conveyor system. It is also possible for tracking rollers to be fitted on the carry side of the conveyor belt.
DYNA-TRAC tracking rollers are a relatively low cost and low maintenance solution to belt mistracking. Easily installed on most conveyor systems, they are self-aligning and self-adjusting. The self-adjusting mechanism uses natural belt forces provided by gravity, friction and balance to keep the belt aligned and centred while in motion.
The design effectively steers the belt towards the centre of the conveyor without the need for side rollers or pivot frames. By using conveyor belt forces to adjust the tracking, the tracking roller is constantly adjusting any small changes in the belt alignment. This eliminates any delay response, which is typical of the traditional tracking rollers. The intuitive steering mechanism streamlines the correct steering response based on the force applied and helps prevent overcorrection.
All DYNA-TRAC tracking rollers are supplied with diamond grooved rubber lagging to improve grip on the belt. This improves the steering performance in a variety of conditions including dry, wet and muddy. Diamond grooved rubber lagging enables more positive and reliable tracking than the traditional plain steel rollers.
Another important feature is the belt edges no longer come in contact with side guide rollers. The side rollers are now redundant and have been removed. This eliminates any potential damage and wear to the conveyor belt.