Belt Conveying in Mining and Mineral Plants

A mineral plant has to lift material, and a plain troughed belt can only climb so far before the load starts rolling back. For most free flowing ores that limit is in the high teens of degrees, and it depends on the material: lump size, moisture, friction angle and whether the surface is wet.

When the required lift divided by that angle gives a run longer than the site has, the design changes principle rather than dimension. That decision is better made early, because a conveyor route is structure, and structure is the expensive part.

The loading point is the second concentration of problems. Every tonne that enters the belt arrives with impact energy, and that energy goes into the belt cover, the idlers and the structure. A chute that delivers material at the wrong speed or the wrong direction also pushes the belt off line, which produces the spillage that plants then treat as a housekeeping issue.

And dust is a health matter. Where crystalline silica is present, the respirable fraction at transfer points is an exposure question with limits attached, not a cleanliness preference.

An incline limit established for the actual material in its actual condition, including wet, so the route is designed on something measured.

A loading point that places material on the belt at belt speed and in the direction of travel, with impact absorbed by beds rather than by idlers.

Wear items treated as scheduled consumables with a measured life, and respirable dust controlled where silica is present.

In a pet food plant the joint decides: a mechanical splice absorbs fat that no cleaning regime removes, and the claim on the bag depends on it.

The incline question is settled first. Material tests give the surcharge and friction angles for the ore wet and dry, and that sets the plain belt limit. Where the limit cannot be met, a high angle sandwich conveyor holds the material between two belts and climbs far more steeply while keeping the gentle handling of belt conveying; a bucket elevator or a steep cleated belt are the other routes, each with their own trade.

The loading point is then engineered rather than fabricated. A chute that accelerates material to belt speed in the direction of travel, skirts of the right length and clearance, impact beds under the loading zone, and a central load so the belt does not wander. Most chronic belt problems in mineral plants are loading problems wearing a different name.

Wear protection follows the mechanism: liners in chutes where material strikes, a belt cover grade matched to the lump size and impact, and idler selection for the load rather than the catalogue.

Dust control is designed at transfer points with enclosure and extraction where silica is present, and the capture velocity at the opening is the criterion rather than the fan size.

• Incline limit established from material tests, wet and dry, before the route is fixed.
• High angle sandwich conveying considered where the plain belt limit cannot be met.
• Loading chute designed to deliver at belt speed, centrally, in the direction of travel.
• Impact beds under the loading zone rather than idlers taking the energy.
• Belt cover grade, liners and idlers specified for lump size and impact energy.
• Transfer points enclosed and extracted where crystalline silica is present.

• Material friction angle and lump size, measured wet and dry, which set the achievable incline.
• Height to be gained and the horizontal space available, which together decide the conveying principle.
• Tonnage and the resulting impact energy at the loading point.
• Respirable dust control where crystalline silica is present, with exposure limits applying.
• Replacement strategy for belts, liners and idlers, including access.
• Moisture and build up, which affect both the incline and the cleaning of the belt.