Overcoming a Mines Embankment

IPCC-system with new Belt Conveying Concept for steep Opencast Minewalls

Overcoming a Mines Embankment

In order to allow for a continuous high capacity conveying system out of steep walled open pit mines Thyssenkrupp together with Contitech and Siemens developped the Chevron Megapipe conveyor with an up to 900 mm outer diameter. The pipe belt features highest tensile strength as well as a ribbed carrying side to hinder the transported bulk material from rolling back.
(ed. wgeisler - 30/11/2017)
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Chevron Megapipe conveyors are an alternative to conventional truck-transportation of bulk solid materials in deep open cast mines.

In 2013, Thyssenkrupp, Siemens and Conti­tech established a consortium for developing and marketing an innovative steep conveying concept for opencast mining operations. In the conveying concept, a high-performance conveyor belt takes primary crushed ore or rock overburden from an upstream primary crusher at the base of the opencast mine and conveys the material up the steep embankment of the opencast mine and directly out of the mine.

The “MegaPipe” has been subjected to interim testing at the Thyssenkrupp Industrial Solutions research center in Germany with respect to critical conveying angles and wear resistance when coarse and sharp-edged conveying material is used. The Megapipe is fitted with wear-resistant and impact-resistant chevron profiles to enable the efficient conveying of ores and rock overburden over embankments with angles of elevation of up to around 45°. Commercially available deep trough belts with appropriate profiles are also suitable for angles of elevation of up to 30°. The two new system designs can help to significantly reduce conventional heavy-duty motor traffic (trucks or rail) and the resulting high operating costs in surface mines.

Profiled Belts for steep Conveying

The Chevron-Megapipe conveyor (Fig. 1) is a continuously conveying pipe belt conveyor equipped with a pipe belt with the ribbed carrying side (top) cover for an outer diameter of Do = 780 to 900 mm. The pipe belt [1] combines the three most important technical innovations in conveyor belt technology from the last five years: high-strength steel cord belts with a very high dynamic splice efficiency based on the ST 10 000 technology, the corresponding transverse rigidity to hold the Megapipe in a pipe shape, and the solid impact- and wear-resistant chevron cleat-ribbed tread profiles for steep conveying in opencast mines. The conveyor only requires a pre-crushing stage in a primary crusher to prepare the ore or rock overburden and it enables enclosed transportation, with vertical and horizontal curves, of large mass flows of up to 6000 m3/h at a maximum conveying speed of approx. 4 m/s (787 ft/min), and a maximum grain size of up to 350 mm, over embankments with angles of elevation of up to 45° and opencast mine depths of up to 700 m. At a realistic annual plant operational availability of 8322 hours, this results in an annual conveying capacity of approximately 50 million m3

Fig. 1: The steep conveyor is a combination of three belt structure technologies

The conveying and functional principle of the chevron-pipe conveyor and the initial findings of a feasibility study for a 350 m deep surface mine with a conveying capacity of 5000 metric t/h were described previously in detail in [2]. 

For angles of elevation of up to 30° and non-cohesive/coarse bulk material, a profiled deep-trough belt can also be used as a steep conveyor. The conveyor system is then fitted with a deep trough belt with solid impact- and wear-resistant chevron cleat ribs. The conveyor belt combines the benefits of high-strength steel cord belts, transverse reinforcement based on Barrier technology, and the solid chevron cleat ribs (Fig. 2).

Fig. 2: Profiled deep trough belt for steep conveying: combination of high-strength
   steel cord belts, steel transverse “Barrier”-reinforcement, and impact-
impact- and wear-resistant chevron cleat ribs                                   

The Barrier steel transverse reinforcement is in the carrying-side cover plate of the belt, and ensures up to three times the impact strength compared to a conventional conveyor belt [3]. The deep trough belt can be produced in widths up to 3200 mm and a maximum nominal strength of 10 000 N/mm. At a slope angle of 30° and a maximum conveying speed of approx. 2.1 m/s (413 ft/min), this belt system can achieve volume flows of up to 12 000 m3 per hour or an annual conveying capacity of about 100 million m3 per year (based on 8322 working-hours/year). 

Experimental Determination of the Elevation Angle

The aim of the investigation was to determine in experiments the maximum slope angle for conveyor belts with and without 50-mm-high chevron cleat ribs, and to verify these results against theoretical findings determined previously from coupled DEM-FEM simulations [2]. The maximum feasible angle of elevation for this kind of belt system is the angle at which a relative movement against the direction of conveyance starts for large, irregularly-shaped chunks of material.

For this purpose, Thyssenkrupp set up a new test rig with control and measuring technology in its research center in Bec­kum, Germany (Fig. 3). The bulk material used in the trials was primary crushed diabase (uniform grain size distribution with dGmax ≤ 250 mm). The approximately 10 m long test rig is used to determine the critical slope angle for smooth and profiled, large diameter pipe belts or for deep trough belts, as well as to investigate the behavior of bulk material inside these conveyor belt designs.

Fig. 3: Test rig (above) and test execution (below) at the Thyssenkrupp            
research center                                                                            

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