Using a conveyor to transport aggregate can save money and time, improve safety, and reduce environmental impact. However, the conveyor must be matched to the application and aggregate type. Here’s an overview of the four main types of aggregate conveyors, when to use them, and some advice on selection.
Understand the material
“Aggregate” is a large class of particulate materials with varying characteristics. Particle size, density, and repose angle can vary widely. Aggregate conveyors are typically used in mining and quarrying applications as well as at storage locations and for loading and unloading. They are sized for the required tons per hour and to fit the space available.
For long life, high reliability, and low running costs, the conveyor should suit the type of aggregate being moved. Aggregate covers materials ranging from sand to crushed concrete, with various grades of gravel, ballast, and rock in between.
These materials vary in density, repose angle, and sharpness or angularity. Some may be moved wet while most are usually dry. Troughing is essential to minimize spills, but the height depends on the repose angle. One thing aggregates have in their favor is they are rarely sticky or gummy.
Conveyor belt material needs to suit aggregate
The choice of conveyor belt material may be influenced by aggregate characteristics, especially sharpness, along with tonnage and tons per hour being moved. Textile belts are common but higher tonnages typically need a steel cord belt.
Impact resistance should be a consideration where bulk material is dropped onto the belt at a loading chute or hopper. Belt covers may be rubber or another polymer that resists tearing and wear.
Bulk aggregates may have a wide range of particle sizes. The vibration experienced when moving them by truck often leads to segregation, which can cause problems in the end use. Using conveyors prevents this.
Type of transport operation
In mines and quarries, it’s common to move aggregate hundreds of yards or even miles. This is where a conveyor saves money in comparison with a fleet of trucks. Conversely, conveyor runs are shorter once the rock reaches the crusher, and may go through several changes of direction or elevation.
After crushing and grading or screening, aggregate is often stored in piles before loading onto a barge or into railcars. On reaching its destination, the aggregate is then unloaded and stored again before being transferred to packaging or distribution.
Types of aggregate conveyors
The conveyors used for transporting aggregate may fall into these categories:
- Overland
- Stacking
- Transfer
- Loading and unloading
Some of these are available in several different formats to suit the specific application. Here’s more detail:
Overland
These very long conveyors move rock, gravel, or another aggregate from where it’s extracted to the crusher and grading. An overland conveyor can be up to 84” wide and move up to 6,000 tons per hour. They follow the terrain, crossing rivers, and roads as needed, which is one way in which they’re safer than trucks.
Stacking
This type of aggregate conveyor is relatively short – typically 50′ to 150’ – and is designed to lift material and let it waterfall off the end. This is done to form a storage pile as might be needed after crushing or grading.
Stacking conveyors are often radial in design, meaning they can pivot or rotate. This allows the creation of a larger aggregate pile. They may also be telescopic so aggregate can be deposited in an even larger pile, or they can be portable. Capacity is usually under 1,000 tons per hour.
Transfer
While overland conveyors can follow the terrain, changing direction needs a very large radius. Where there’s insufficient space, as is the case at loading or unloading stages, the solution for direction changes is a transfer conveyor. These are also used to accommodate rapid elevation changes. They are more easily transferred from one project to another.
Loading and unloading
Loading and unloading conveyors are typically short and inclined. Their main applications are raising aggregate so it can waterfall into railcars or barges, or taking it from the underside of railcars and raising it to fill trucks or to move it into storage.
Conveyors serving railcars are typically narrow (18″ to 30”) and may be telescopic. Portable designs are also available. Barge-loading conveyors usually handle higher rates than are needed for railcars and so tend to be wider. Telescopic and portable designs are less common.
Designing conveyor systems for aggregates
The belt and motor/drive system must be sized for the load on a fully-laden belt. Consideration should also be given to the type of takeup device and motor coupling used.
Aggregate transport operations are inherently dusty, and this can damage bearings like those used on idler rollers. Accordingly, the conveyor system should be designed with protection against dust ingress in mind.
When designing radial stacking or loading/unloading conveyors, maximum rotation speed should be governed by conveyor size and peak load. A rotation speed that’s too high could result in unstable operation.
Choose West River conveyors for your aggregate conveyor needs
When compared to trucks, aggregate conveyors can lower costs, require fewer drivers, improve safety, and address environmental concerns like dust and noise.
West River Conveyors has experience with all types of aggregate conveyors and we engineer solutions for every kind of open-air and underground material transport application. Our materials expertise runs from coal mining to rock and ore extraction and includes challenging materials like salt, trona, and fly ash.
We are based in the mining region of Virginia but serve customers from coast to coast and overseas.