Conveyor belt tracking and maintenance: the tracking rule, finding the cause of mistracking, training a belt, and the inspections that keep conveyors running
Why a conveyor belt runs to one side and how to fix it: the rule that a belt moves toward the end of the idler it meets first, the causes of mistracking and how to tell them apart, how to train a belt, training idlers and other devices, and the inspections of idlers, pulleys, belt, splices, cleaners and take-up that keep conveyors running. With a drawing of the tracking rule.
Key takeaways
- A conveyor belt moves toward the end of the idler or pulley it touches first. Every tracking adjustment, and most tracking faults, follow from that one rule.
- Find the cause before steering the belt. Off-centre loading, structure or pulleys out of square, build-up and bad splices cause most mistracking, and idlers adjusted to mask them wear the belt and move the problem.
- When the belt runs to one side, advance the end of the idler on that side in the direction of travel, a little at a time, upstream of where the belt runs off.
- Training idlers, crowned pulleys and drift switches help, but they correct or protect against a symptom. The cause is usually at the transfer or in the structure.
- Most conveyor maintenance is inspection: idlers, lagging, belt cover, splices, cleaners, skirts and take-up travel, checked on a route and recorded so the trends show.
A belt on an overland conveyor keeps running off at the same transfer, and each shift adjusts the idlers nearest the problem. After a month the belt edge is frayed along its length, a third of the idlers in that section are skewed in different directions, and the belt now wanders even when empty. The cause was a liner in the transfer chute that had worn through, dropping the load off centre. Each adjustment steered around a problem in the chute and added a new one in the idlers.
This guide covers belt conveyor tracking and the maintenance that keeps conveyors running: the rule that decides where a belt goes, the causes of mistracking and how to tell them apart, how to train a belt, the devices that help, and the inspections that find failing components early. It sits beside the guides to fixed plant maintenance and transfer chute design. The references named are the usual sources, and the conveyor designer's and belt supplier's instructions come first.
The tracking rule
A belt moves toward the end of the idler or pulley it contacts first. If an idler is skewed so that one end sits further along in the direction of travel, the belt meets the other end first and moves toward it. The same applies to a pulley that is out of square. It is why a single skewed idler can move a belt, and why many small skews in different directions make a belt wander.
The rule also gives the adjustment. When the belt runs to one side, advance the end of the idler on that side, moving it a little in the direction of belt travel. The belt then meets the other end first and moves back toward the centre. The change shows downstream of the idler, so the adjustment is made upstream of where the belt runs off.
Belt runs to the right: advance the right hand end of the idler in the direction of travel. Small moves, several idlers, upstream of the problem.
Find the cause first
Idlers can steer a belt around almost any problem, which is why they are adjusted too often. A belt steered around off-centre loading runs true when loaded and off when empty, and the skewed idlers wear the belt cover all the time. The first questions are whether the belt runs off loaded, empty or both, whether it happens at one place or along the length, and whether it changes with the load. The answers point to the cause.
| Cause | What you see | Fix |
|---|---|---|
| Off-centre loading | The belt runs true empty and drifts when loaded, and the drift changes with the load | Fix the transfer chute so material lands centred and moving in the direction of the belt |
| Structure or idlers out of square | The belt runs off at the same place every time, loaded or empty | Check the stringers are straight and level and the idler frames square to the centreline |
| Pulleys out of square or level | Drift starting at a pulley, often the tail or a snub | Square the pulley to the centreline, then check it is level across its face |
| Material build-up on pulleys and idlers | Wandering that comes and goes, worse in wet or sticky material | Clean the build-up, then fix the belt cleaning that let carryback reach the return run |
| Splice not square | The belt shifts sideways each time the splice passes, then returns | Remake the splice square to the belt edge |
| Cambered or uneven belt | A new belt that runs to one side along parts of its length whatever is adjusted | Run it loaded for a period, and refer it to the supplier if it does not settle |
| Seized or damaged idlers | Drift near the seized roll, flats worn on the roll, noise and heat | Replace the idler. A seized roll also wears the belt cover |
| Wind or side loads | Drift on exposed sections in high wind | Wind guards or covers on exposed lengths |
Training a belt
Training a belt is done in a set order so each adjustment is not undone by the next. The structure and pulleys come first, because no amount of idler adjustment fixes a pulley out of square. Then the belt is trained empty, then loaded. Tracking adjustments are made with the conveyor isolated, with the result checked running from a safe position with guards in place, under the site's isolation rules and AS/NZS 4024.3610.
- Confirm the head, tail, bend and snub pulleys are square to the centreline and level.
- Check the structure is straight and the idler frames are square, and clean any build-up.
- Run the belt empty and note where it runs off. Train the return run from the head toward the tail, then the carrying run from the tail toward the head, so each pass follows the direction of travel.
- Make small adjustments to several idlers upstream of each run off point rather than a large one to a single idler.
- Let the belt run several revolutions between adjustments, because it takes time to settle.
- Run it loaded. If it now runs off where it ran true empty, look at the loading before touching the idlers.
- Record which idlers were adjusted, so the next person knows what has been changed.
Devices that help a belt track
Several devices help a belt stay centred, and one protects it when it does not. They are useful on long conveyors, reversing conveyors and those with varying loads, but each corrects or protects against a symptom. A conveyor that needs many training idlers to run straight usually has a cause that has not been found.
| Device | What it does | Its limits |
|---|---|---|
| Training idler | A troughing or return idler on a pivot that swings to steer the belt back when it moves off centre | Corrects small drift. It treats the symptom, so the cause still needs fixing |
| Forward tilt of the wing rolls | The wing rolls of troughing idlers tilted slightly forward in the direction of travel | Helps the belt centre itself. Only works in one direction of travel and adds wear |
| Crowned pulley | A pulley face slightly larger in diameter at the centre | Helps a flat belt centre. Less effective on troughed and steel cord belts |
| Belt drift switch | A switch that trips the conveyor when the belt edge moves too far | Protects the belt and structure. It does not correct anything |
What to inspect, and what it finds
Conveyors fail in predictable ways, and most failures give warning: a noisy idler before it seizes, lagging that lifts before it detaches, carryback before build-up. A route that walks each conveyor on a set interval, combined with operator rounds and condition monitoring on the drives, finds them. Recording what was found against each tagged component turns the inspections into trends, so idler replacement can be planned by section rather than one at a time after failure.
| Component | What fails | The check |
|---|---|---|
| Idlers | Seized or noisy bearings, worn shells, broken frames | Walk the conveyor listening and looking, thermography for hot rolls, replace in sets where wear is general |
| Pulleys and lagging | Worn or detached lagging, bearing failure, shell cracking | Lagging inspection at shutdowns, bearing condition monitoring on drive and bend pulleys |
| Belt | Cover wear, edge damage, rips and holes | Cover thickness measured at fixed points, edge and rip inspection, rip detection on critical belts |
| Splices | Separation, cracking, mechanical fasteners pulling out | Splice inspection on a schedule, length change between splices tracked |
| Belt cleaners | Worn or misadjusted blades, carryback | Blade tension and wear checked each week, carryback measured under the return run |
| Skirts and transfer | Spillage, worn skirts and liners, blocked chutes | Skirt clearance and liner wear checked, spillage watched as a symptom |
| Take-up | Running out of travel as the belt stretches | Take-up position recorded, a splice planned before travel runs out |
| Drive | Gearbox oil and bearing faults, coupling wear, motor faults | Oil analysis, vibration on the drive train, coupling inspection |
| Guards and pull wires | Guards removed and not refitted, pull wires slack or not tested | Guards in place before restart, pull wire and stop switches tested on a schedule |
Where tracking and conveyor maintenance go wrong
- Idlers skewed to steer around off-centre loading instead of fixing the chute.
- Every shift adjusting the same idlers, with no record of what was moved.
- Training idlers seized on their pivots, so they no longer train anything.
- Belt cleaners left worn, so carryback builds up on the return idlers and pulleys and starts the wandering.
- Idlers replaced one at a time after they seize, rather than by section when the wear is general.
- Take-up travel ignored until it runs out and the belt slips on the drive.
- Guards left off after an adjustment, or pull wires never tested.
Common questions
What is conveyor belt tracking?
Belt tracking is keeping a conveyor belt running centred on its idlers and pulleys along its whole length, loaded and empty. A belt that mistracks runs toward one side, where its edge rubs on the structure, it spills material and it wears. Tracking is set by getting the structure, pulleys and idlers square, the load centred and the belt clean, then making small adjustments to idlers where needed.
How do you track a conveyor belt?
First find the cause: check whether the belt runs off loaded or empty, at one place or along the length, and whether the drift changes with the load. Fix the cause at the source, such as the transfer chute, an out of square pulley or build-up. Then make small adjustments to the idlers just upstream of where the belt runs off, advancing the end of the idler on the side the belt is running toward in the direction of travel. Adjust with the conveyor isolated and check it running from a safe position.
Why does a conveyor belt run to one side?
Because something makes the belt contact one end of an idler or pulley before the other, or loads one side more than the other. Common causes are material landing off centre from the transfer chute, idler frames or pulleys not square to the conveyor centreline, build-up of material on pulleys and return idlers, a splice that is not square, seized idlers, and wind on exposed sections. If the drift changes with the load, the cause is almost always the loading.
What is a training idler?
A training idler, or self-aligning idler, is an idler set mounted on a central pivot. When the belt moves off centre it pushes the idler round, which skews the rolls and steers the belt back. Training idlers correct small, varying drift. They are not a fix for a structure out of square or for off-centre loading, and a training idler that is seized on its pivot does nothing.
How often should conveyor idlers be checked?
Idlers are usually checked on a regular walk of the conveyor by operators or maintainers, listening for noisy bearings, looking for seized or damaged rolls and feeling or measuring for heat. The interval depends on the conveyor's criticality, duty and environment, and is set in the maintenance plan. Thermography or acoustic surveys on critical conveyors find failing idlers before they seize.
Key terms
Plain-language definitions from our glossary for the concepts this article leans on.
Standards and further reading
Related case studies and tools
- Conveyor Capacity Calculator (tool)
- Transfer chute redesign guided by DEM modelling (case study)
Related reading
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