The conveyor belt is the part of a belt conveyor that carries the material, and usually its most expensive single spare part. In crushing and screening plants, belts are exposed to the impact of sharp-edged rock, abrasive fines, the weather and continuous operation. A correctly selected and well-maintained belt lasts for years, while a poorly selected or neglected belt can tear, fray at the edges and cause plant downtime within a few months.
In this guide we cover in detail the structure of the conveyor belt, carcass and cover selection, determining thickness and width, splicing methods, damage types, repair and replacement steps, and what to watch for when sourcing spare parts. For general belt conveyor maintenance, see our belt conveyor guide.
Structure of a Conveyor Belt
- Carcass: The textile plies (EP: polyester-polyamide) or steel cords that carry the belt’s tensile force.
- Top cover: The rubber layer that carries the material and is exposed to wear and impact.
- Bottom cover: A thinner rubber layer in contact with the pulleys and idlers.
- Edges: Can be cut edge or moulded edge.
Belt Types
| Type | Characteristics | Use |
|---|---|---|
| EP textile carcass | Flexible, economical, easy to splice | Most crushing and screening conveyors |
| Steel cord | Very high tensile strength, low elongation | Long, high-capacity conveyors |
| Chevron | Profiled surface, prevents slippage on steep inclines | Inclined conveyors, mobile plants |
| Sidewall and cleated belts | Very steep or vertical conveying | Special applications |
| Heat/oil resistant | Special rubber compounds | Hot material, oily environments |
For details on chevron belts, see our article on chevron conveyor belts.
Cover Grade and Thickness Selection
- Abrasion grade: Grades such as DIN-Y (general), DIN-X (cut and tear resistant) and DIN-W (high abrasion resistance) are chosen according to the material. Cut resistance is the priority for large, sharp-edged rock; abrasion resistance for fine, abrasive material.
- Top cover thickness: Determined by loading frequency (which depends on belt length and speed), particle size and drop height. Short, fast belts are loaded at the same point more often, so they need a thicker cover.
- Bottom cover: Usually thinner than the top cover; protects against pulley and idler friction.
- Number of plies and strength rating: Chosen according to the conveyor’s belt tension calculation and pulley diameters; the minimum pulley diameter is related to the number of plies.
Belt Splices
| Splice type | Advantage | Disadvantage |
|---|---|---|
| Hot vulcanised | Highest strength and life | Requires a specialist team and press |
| Cold vulcanised | Practical, can be done on site | May be weaker than a hot splice |
| Mechanical fastener | Very fast, emergency repair | Wears scrapers, can leak fines |
The splice must be made square and straight to the belt axis; a crooked splice causes permanent belt mistracking.
Damage Types and Causes
| Damage | Possible cause |
|---|---|
| Longitudinal rip | Trapped sharp rock or metal, jamming under the chute |
| Edge fraying | Belt mistracking, rubbing on the structure |
| Top cover wear | Abrasive material, high drop, incorrect loading |
| Impact gouges | No impact bed/idlers at the loading point |
| Bottom cover wear | Seized idlers, dirty pulleys |
| Splice separation | Poor splicing workmanship, excessive tension, small pulley |
| Cover separation/blistering | Oil, heat or ageing |
Inspection and Maintenance
| Check | Interval | Method |
|---|---|---|
| Tracking and edge condition | Daily | Walk-around |
| Rips, cuts and splices | Weekly | Visual, with the belt stopped |
| Top cover thickness | Every 3–6 months | Thickness gauge |
| Tension and sag | Weekly | Sag measurement (2–3% of idler spacing) |
Repair Options
- Cold vulcanised patch: Fast, permanent repair for small cuts and gouges.
- Rip repair with mechanical fasteners: Temporarily closes longitudinal rips in emergencies.
- Section replacement: The badly damaged section is cut out and a new piece of belt is spliced in.
- Edge repair: Frayed edges are trimmed; the real solution is to eliminate the mistracking.
Belt Replacement Step by Step
- Preparation: The new belt roll, splicing materials, belt pulling and clamping equipment are prepared.
- Safe shutdown: The conveyor is locked out; the take-up is slackened.
- Cutting the old belt and pulling in the new one: The new belt can be attached to the old belt and pulled through.
- Splicing: A vulcanised or mechanical splice is made.
- Tensioning and tracking: Tension is set and the belt is run empty to adjust tracking.
- Initial operation: A new belt can stretch in the first days; tension is checked again.
Ways to Extend Belt Life
- Using an impact bed or impact idlers at the loading point,
- Reducing the drop height and loading material in the direction of belt travel,
- Using effective scrapers (see belt scrapers),
- Replacing seized idlers promptly (see conveyor idlers),
- Correcting mistracking immediately,
- Removing metal with a magnetic separator.
Common Mistakes
- Choosing a belt on price alone,
- A ply count unsuitable for the pulley diameter,
- “Managing” mistracking with temporary adjustments,
- Using mechanical fasteners as a permanent solution,
- Storing belt rolls without protection from sun and moisture.
Troubleshooting Table
| Symptom | Possible cause | Solution |
|---|---|---|
| Belt constantly runs to one side | Crooked splice, off-centre loading, dirty pulley | Check the splice, loading and pulleys |
| Cover wears quickly | Wrong cover grade, high drop | Change the cover grade, reduce the drop height |
| Longitudinal rip | Metal, jamming under the chute | Magnetic separator, correct the chute clearance |
| Splice opening | Poor workmanship, excessive tension | Remake the splice, adjust the tension |
An Example from the Field
At one plant, the belt under the primary crusher tore every few months. It was found that large, sharp rocks from the crusher were dropping directly onto the belt from a height of about one metre, and there was no impact bed in the loading zone. A rock box chute, an impact bed and a cut-resistant DIN-X cover belt were installed. Belt life increased several times over.
Pre-Purchase Checklist
- Have belt width, length, number of plies and strength rating been determined?
- Have top/bottom cover thicknesses and the cover grade been chosen?
- Are pulley diameters suitable for the number of plies?
- Have the splicing method and splicing materials been planned?
- Are there special requirements (chevron, heat, oil)?
Frequently Asked Questions
How long does a conveyor belt last?
It varies greatly with the material, loading conditions and maintenance; loading point design is the factor that most affects belt life.
EP belt or steel cord belt?
EP belts are sufficient for most crushing and screening plants; steel cord belts are preferred for very long, high-tension conveyors.
How are belt splices checked?
Visually every week; if separation, blistering or cracks appear at the splice edges, it should be repaired.
What should be considered when storing belts?
They should be kept in a dry, cool place out of direct sunlight, with the rolls off the ground and wound evenly.
A Sample Assessment for Belt Selection
When selecting a belt, the following questions should be answered in order:
- What is the material? Large, sharp-edged crushed rock, fine abrasive sand, or wet, sticky material?
- What are the loading conditions? Drop height, largest particle size, loading angle.
- Conveyor geometry? Length, lift, incline, pulley diameters.
- Required strength? Belt strength rating and number of plies according to the conveyor tension calculation.
- Environmental conditions? Temperature range, sun, oil, chemicals.
For example, on a short belt under a primary crusher carrying large, sharp rock, a thick cut- and tear-resistant top cover (e.g. DIN-X grade) and an impact bed are the priority. On a long stockpile belt carrying sand, a highly abrasion-resistant cover and a low-elongation carcass are more important.
Effect of Operating Conditions on Belt Life
| Condition | Effect | Recommendation |
|---|---|---|
| High drop height | Impact gouges, rips | Rock box, curved chute, impact bed |
| Mistracking | Edge fraying | Eliminate the root cause |
| Seized idlers | Bottom cover wear, cuts | Idler checks |
| Metal pieces | Longitudinal rip | Magnetic separator, metal detector |
| Sun and ozone | Cover ageing, cracks | Suitable rubber compound, covers |
Belt Life and Cost Analysis
When selecting a belt, the belt cost per tonne should be the basis rather than the price per metre. A belt with a better cover can reduce total cost through longer life and fewer shutdowns, even if its unit price is higher. Since a belt change usually requires a long shutdown and considerable labour, every measure that extends life (correct loading, good scrapers, sound idlers) translates directly into savings.
Maintenance Record Form
| Field | Record |
|---|---|
| Belt type and installation date | Carcass, cover, thickness |
| Top cover thickness | Periodic measurement |
| Damage and repairs | Date, location, method |
| Splice condition | Splice type and observation |
| Mistracking events | Cause and solution |
Stock Planning
- Keep a spare belt roll of suitable length for critical conveyors.
- Cold vulcanising repair kits and mechanical fastener sets should always be ready.
- Standardising belt widths across the plant makes stock management easier.
More Questions
When should a belt be replaced?
When the top cover has thinned close to the carcass, when the carcass is damaged, or when the number and cost of repairs exceed the economic limit.
Does a torn belt need to be replaced immediately?
Small tears can be repaired by cold vulcanising; long longitudinal rips may require a section or belt replacement.
Why does a new belt slip or mistrack in the first days?
New belts stretch and settle during the initial running period; tension and tracking should be checked frequently during this time.
Spare Parts and Service for Conveyor Belts
CSP Mühendislik manufactures belt conveyors and supplies EP, steel cord and chevron belts suited to your application as part of its belt conveyor spare parts range, and provides service support for belt replacement, splicing and tracking adjustment. Share your belt dimensions on WhatsApp and we will prepare a quote quickly.
