A new Technology for Steep Incline High Capacity Open Pit Conveying
A new conveyor design is set to help reduce conventional heavy-duty truck traffic and the resulting high operating costs in open pit mines. This article presents the design and the initial findings of the feasibility study on the Chevron-Megapipe conveyor for a 350 m-deep open pit mine and a mass flow of 5000 t/h.
Andrey Minkin, Peter Börsting, Norbert Becker
(ed. WoMaMarcel - 04/7/2016)
When the belt was being developed, the advantages of Megapipe technology were combined with those of ribbed belts (chevron cleat belts) and of high-strength belts (St10 000 technology). High-strength ribbed pipe belts with an outer diameter of up to 900 mm and nominal strengths of up to 9500 N/mm facilitate the totally enclosed, curve-friendly transportation of large mass flows of up to 9500 m3/h and grain sizes of up to 350 mm across overall slope angles of 30° to 45° and open pit mine depths of several hundred meters after primary crushing.
The Chevron-Megapipe conveyor occupies a niche position between flat or slightly inclined conveyance methods with angles of inclination of 0° to 30° and steep-angle conveyance methods for transporting material at angles of inclination of 45° to 90°. Due to its compact design, environmental friendliness, and high industrial safety thanks to the totally enclosed material conveyance in the pipe belt, a Chevron-Megapipe conveyor can be used both for open pit mining (Fig 3a) as well as for underground operations.
A further alternative conveyance method, that is also suitable for the angle of inclination of 30° to 45°, is a sandwich belt conveyor [2,3]. In this, the conveyor cross-section is formed by two conveyor belts lying on top of each other (Fig. 3b).
However, when used for deep mines and rough-grained material, this conveyance method has the following decisive cost and system disadvantages compared to a Chevron-Megapipe conveyor:
The conveyor system consists of two fully-fledged belt conveyors with belts lying on top of one another with all the usual components; the cover belt must be motor-driven in addition to the bottom belt in the case of deeper mines.
The structure of a pressing roller station of sandwich conveyors is often very complex. A small distance between the pressing roller stations is generally selected in order to achieve an even pressing effect onto the material conveyed with sandwich belts.
Using sandwich belt conveyors for coarse mining bulk solids is problematic. The material conveyed must in this case be crushed in advance in two crushing stages in open pit mining. By contrast, when a Chevron-Megapipe conveyor is used, one single upstream primary crushing stage is necessary.
Fig. 4 provides an overview of the ratio of depths and overall slope angles for typical open pit mines based on practical experience, dated August 2003 . Nowadays, modern mines exceed the depth limit of 1000 m, and achieve slope angles of up to 75°. This means that the conveyor belts must have high nominal breaking strengths when belt conveyor systems are used. The diagram shows that most of the world’s mines have embankments with angles between 30° and 50° and are between 100 m and 400 m in depth.