In brief
In an aggregate plant, availability depends on four fronts: the condition of the conveyor belts and their splices, the idlers and pulleys carrying them, the screen media and its tension, and protecting bearings from abrasive dust. A belt always steers off the last point that touches it, so tracking is corrected at the idler, not by adding tension. A seized idler stops turning and starts cutting the belt through friction, and a badly set cleaner returns carryback to the return run that eventually mistracks the whole section. Each of these points is inspected with the plant stopped and locked out, and corrected before it becomes a production stoppage.
A crushing and screening plant does not fail from one cause; it fails from accumulation. Dust enters where the seal no longer closes, the seized idler wears the belt, the mistracked belt spills material onto the return run, and that material loads the idler again. When the failure happens, the component that breaks is almost never the one that started the problem.
This article works through the four fronts in order of impact on availability, with inspection criteria that fit inside a short planned shutdown.
Conveyor belts: tracking before tension
The golden rule of belt tracking is that the belt moves towards the side it touches first, and that it is corrected at the component before the point where the deviation appears. The instinctive reaction — adding tension or shifting the tail pulley — almost always makes things worse and adds load to the pulley bearings.
- Adjust one idler at a time and give the belt time to respond: simultaneous adjustments make it impossible to know which one worked.
- Check the structure is square before touching idlers. A twisted structure brings the deviation back no matter how much you adjust.
- Check for off-centre loading at the feed point: a belt loaded to one side always tracks to that side, and no idler will correct it.
- Clean built-up material from pulleys and return idlers. A layer of adhered material changes the effective diameter and mistracks the belt permanently.
Splices: mechanical or vulcanised
The splice is the weakest point of the belt and defines its real working capacity. Choosing between mechanical fasteners and a vulcanised splice depends on the material, working tension, the presence of cleaners and the shutdown time available.
| Criterion | Mechanical splice | Vulcanised splice |
|---|---|---|
| Installation time | Short: allows a fast restart | Longer: needs a press and a cure cycle |
| Tension efficiency | Lower than the full belt | Close to the belt's own strength |
| Passing cleaners | Needs careful scraper setting | Continuous surface, no interference |
| Field repair | Simple and quick | Requires equipment and trained personnel |
Rodacaribe distributes Flexco and Fenner Dunlop for belting, fasteners and splicing accessories, and carries out vulcanising, conveyor belt repair and roller lagging as its own services. Having both options available means the decision is made on technical grounds rather than on whatever is at hand when the belt opens up.
Idlers, pulleys and cleaners
A seized idler does not merely stop contributing: it becomes a cutting tool against the belt and a source of frictional heat. Inspection is simple and needs no instruments: with the plant stopped, turn each idler by hand and look for abnormal resistance, axial play and noise; running, walk the conveyor listening and taking temperatures with an infrared thermometer.
- An idler that does not turn, or turns with resistance: replace it, do not grease it. The bearing has already lost its seal.
- An idler with a flat worn area on one side: it was seized at some point; check the belt over that section too.
- A drive pulley slipping: check the lagging before increasing tension. Worn lagging loses the friction coefficient the design assumes.
- Cleaners and scrapers: set the pressure to specification. Too much pressure wears the belt cover; too little leaves carryback that fouls the whole run.
Screening: tension, aperture and blinding
Screen efficiency depends as much on how the media is mounted as on the media itself. A poorly tensioned panel does not vibrate with the frame, loses separation capacity and breaks at the point of least support. Tension checks must be periodic and systematic, not reactive.
- Check panel tension at every planned shutdown and re-tension following the manufacturer's pattern.
- Record aperture wear: worn media passes out-of-spec material long before it breaks.
- Address blinding and pegging according to the material: moisture, particle size close to the aperture and adhered fines are the usual causes.
- Monitor the vibrating mechanism bearings on temperature and vibration: they work under continuous shock loading and are critical plant components.
Abrasive dust: the underlying enemy
In an aggregate plant, the abrasive wear ISO 15243 describes for bearings is not an exceptional case: it is the normal working condition. Silica particles enter through any failed seal and act as an abrasive between the raceways.
- Prioritise sealing: an intact seal protects more than a higher-grade bearing with a failed one.
- Relubricate at shorter intervals than in general industry: the grease purge is also a barrier against particle ingress.
- Filter hydraulic systems to a defined cleanliness target, and protect reservoirs with desiccant breathers.
- Keep instrument air dry and filtered; humid, dusty air ruins actuators and valves.
Making a planned shutdown count
- 01
Walk and list before stopping
With the plant running, record noises, temperatures, spillage and mistracking. The work list is built before the shutdown, not during it.
- 02
Secure critical spares
Idlers, splice fasteners, screen panels, seals and drive belts. A shutdown that stretches for want of a low-cost component is the worst possible outcome.
- 03
Execute by risk priority
First what can stop the plant, then what degrades efficiency, last what is cosmetic.
- 04
Close with baseline readings
Temperature and vibration at critical points once the plant is running again. That is the standard the next walk will be compared against.
Rodacaribe supplies Superior Industries equipment and solutions for mining, quarries and aggregate plants, screen media for classification, SKF bearings and seals, and Optibelt and Gates drive belts for the drives.
Frequently asked questions
- Why does the belt always run off at the same point?
- Because the cause is in that section or immediately before it: a misaligned or seized idler, an out-of-square structure, material adhered to a pulley, or off-centre loading at the feed point. Adding tension does not correct it and loads the bearings further.
- When is vulcanising preferable to a mechanical fastener?
- When working tension is high, when the material is fine or abrasive and sifts through the joint, when cleaners strike the fastener on every pass, or when maximum splice life is the goal. Mechanical fasteners remain the right choice for fast repairs and lower-tension belts.
- How often should conveyor idlers be checked?
- A listening and temperature walk is worth doing weekly in continuous plants, with manual rotation checks at every planned shutdown. A seized idler caught in time costs an idler; caught late it costs the belt.
- Can screen media life be extended?
- Yes, mainly through correct and verified tension, feed distributed across the width of the frame, and control of material moisture to reduce blinding. Most premature panel failures start with insufficient tension, not panel quality.
Related industries
Need to solve this in your plant?
Our technical team reviews your case against real operating data and proposes the component and the procedure that fit.
About this contentThese guides collect industrial maintenance good practice and widely used standard references. They do not replace the technical documentation of the equipment or component manufacturer, which always prevails.