Booysendal Platinum (Pty) Ltd. (Booysendal), a subsidiary of Northam Platinum Ltd. (Northam), a South African based platinum and chrome producer, is currently expanding mining capacity at its Booysendal mining concession. Key to the success of this expansion is the cost effective, reliable, safe and environmentally low impact transport of ore over topographically challenging terrain, from mining modules in the south of the concession to the concentrator plant.
To this end, Doppelmayr Transport Technology GmbH (Doppelmayr), headquartered in Wolfurt/Austria and a subsidiary of the Doppelmayr group, the world’s leading manufacturer of ropeways, is currently constructing a RopeCon® system which will transport up to 900 t/h over 4.9 km, with an overall vertical climb of 350 m. This system is due to operate from 2019. As part of an additional expansion program, Booysendal, in October 2017, further contracted Doppelmayr to design and construct a second RopeCon®, to tie in with the first system, allowing transport of ore from mining modules in the north of the concession. This RopeCon® system will convey 400 t/h, over 2.8 km, with a vertical drop of 160 m and will operate from 2020.
Further information/Weitere Informationen: Doppelmayr Transport Technology GmbH www.doppelmayr-mts.com
Since 2005 a RopeCon® system of Doppelmayr Transport Technology GmbH, Wolfurt/Austria, has been transporting inert material along a long-stretched valley at the Tüfentobel landfill site, which will eventually be backfilled (Figure 1). The belt is being extended in several stages. It discharges the material onto a debris cone directly where it is to be used. Finally in March 2016, a novel concept was implemented which has further increased the flexibility of RopeCon®.
Relocating the discharge point of Tüfentobel RopeCon® in various stages was part of the overall project plan from the very beginning. The idea was to discharge the material at all times as close as possible to the location where it was to be used. The discharge point has been relocated several times already since the installation went into operation so as to keep transport routes as short as possible for both, the trucks supplying the material and the bulldozers spreading it from the discharge point. In March 2016 a second RopeCon® was finally installed directly into the rope span of the original system, which now discharges the material onto the new conveyor at a height of approximately 20 m. The new RopeCon® system can operate in both directions. This allows two different discharge points which can be fed alternately. The second RopeCon® system requires no support structure of its own but rather uses the track ropes of the original system. The running wheels of the second installation return onto the track ropes on a set of rails. An important advantage of the extension concept was that the original system could be kept in operation to the greatest extent possible even during the assembly work. Long shut-down periods were thus avoided.
Further information/Weitere Informationen: Doppelmayr Transport Technology GmbH www.doppelmayr-mts.com
The El Limón-Guajes gold ore pit of Minera Media Luna, S.A. de C.V. (MML), 100 % owned subsidiary of Torex Gold Resources Inc., is located approximately 180 km south-west of Mexico City in the state of Guerrero/Mexico. The ore mined at the two pits of El Limón and Guajes is processed in one central processing plant. The El Limón pit, however, is approximately 400 m higher up on a steep ridge. During the planning phase, one of the issues that had to be addressed was the transport of the material from the pit down into the valley. Along with the costs, operational safety and the impact on the environment had to be taken into account. In March 2013, MML decided to use the RopeCon® as a means of transport, a system which covers the vertical rise of approximately 400 m and the length of 1.3 km with just one tower structure before unloading the material onto a stockpile (Figure 1). Construction of the RopeCon® started in early 2014. Doppelmayr’s assembly team carried out the job in just six months – accident-free and on schedule. The RopeCon® took up operation as planned in March 2016. It now connects the pit with the processing plant.
Fig. 2. Cleats prevent the material from slipping. // Bild 2. Stollen verhindern ein Durchrutschen des Materials auf dem Gurt. Photo/Foto: Doppelmayr
RopeCon®, a product of the ropeway manufacturer Doppelmayr, essentially relies on a flat belt with corrugated side walls to transport materials of all kinds. The belt performs a haulage function and is driven by, and guided around, a drum at both ends. To account for the great vertical rise and consequently the steep incline between the El Limón pit and the valley, the belt has been fitted with cleats to prevent the material from slipping (Figure 2). Axles are mounted on the belt at regular intervals to support it. They have plastic running wheels attached to their ends. These wheels run on track ropes with fixed anchoring and guide the belt. The track ropes run over tower structures so that this conveyor system is lifted off the ground, leaving only a minimal footprint. The system features three track rope pairs in total, with the bottom pair supporting the empty belt and the pair in the middle carrying the loaded belt. An inspection vehicle travelling on the third track rope pair at the top serves to provide easy and safe access to any point along the line. Almost all moving parts are attached to the belt and therefore pass through the stations at regular intervals. Service and maintenance works can thus be performed at one central point.
The El Limón RopeCon® system generates approximately 1 MW of green energy from braking actions, which contributes to a reduction of the overall operating costs. This, and the fact that no fossil fuel (Diesel) is required to operate the system is one of the significant differences between RopeCon and trucks, the other means of transport under consideration for the transport of the ore.
Apart from the positive effects on operating costs, resulting from straight-forward maintenance and regenerative operation due to downhill transport, the avoidance of dust and noise emissions is another argument which strongly supports the use of the RopeCon®. The automatic transport system will also help to enhance operational safety and its controls can be integrated into the central control system of the mine.
Open-pit mining often relies on excavators and trucks for the extraction and subsequent removal and transport of the material. Diesel is the standard energy source used to run the machinery. This mining method has several disadvantages, i. e. high operating costs for fuel, personnel, accommodation, travelling and maintenance, a high safety risk caused by the effects of the weather or by the human factor or a heavy burden on the environment caused by CO2 and noise emissions.
Slope angles in open-pit mines can come up to 70°, which is why roads for trucks in open-pit mines are usually laid out in terraces. RopeCon® offers an alternative way of organising the transport of material in difficult terrain (Figure 1).
RopeCon® is a product of Doppelmayr Transport Technology GmbH, Wolfurt/Austria, and has been developed specifically to transport material of all kinds. The system is perfect for transporting material in and over difficult terrain: it can traverse obstacles such as rivers, buildings, gorges, or roads without any problem whatsoever and will easily overcome steep conveying sections of up to 70°.
RopeCon® transports the material on a flat belt with corrugated side walls. This belt design originates from vertical conveying, where it has been used for decades. The flat belt performs a haulage function and is driven by, and guided around, a drum at both ends. It is mounted on axles arranged at regular intervals to support it. Running wheels are fitted to both ends of the axles. These wheels run on track ropes with fixed anchoring and guide the belt. The track ropes are lifted off the ground on tower structures. Due to the rope support structure distances between the towers can be several hundred metres long, and RopeCon® will affect neither the terrain between the towers nor roads, trucks or other infrastructure.
Depending on the steepness of the terrain, the RopeCon® belt can be fitted with cleats in order to stabilise the material on the belt. These components, too, originate from vertical conveying and allow for a transport of the material over inclines of up to 90°.
RopeCon® can also be extended in line with the axis of the conveyor belt. As the open-pit mine grows and changes, the loading or discharge point can be adjusted flexibly along that axis to meet the new requirements. Additionally, under certain conditions, it is possible to discharge the material at several discharge points along the axis of the conveyor belt.
The greatest possible grain size along with the maximum conveying angle will determine the width of the flat belt, the height of the corrugated side walls, the height of the cleats and their spacing. Subject to certain conditions, RopeCon® can handle lump sizes of up to 1,000 mm. In this case, there is no need to crush the material prior to transporting it out of the pit. Conveying capacity, conveying speed, possible nominal breaking strength and required nominal breaking strength of the flat belt are the factors which determine the greatest possible vertical rise. The conveying speed is usually limited by the maximum grain size. High-strength flat belts with steel cord tension members and nominal strengths of more than 7,800 N/mm are state-of-the-art. The necessary nominal strengths are determined in accordance with the provisions of German Industrial Standard DIN 22101:2011-12. Where conveying capacities are lower and grain sizes smaller, RopeCon® can overcome differences in elevation of up to 1,200 m.
Easy maintenance characterises RopeCon®: all moving parts such as i. e. the running wheels are attached to the belt and therefore keep passing through the stations, where they can be serviced without a problem. RopeCon® can also be fitted with an inspection vehicle to facilitate inspection along the line. Consequently, only a small number of personnel is required to operate and service the system.
For the following example a mine operator must transport 5,000 t/h of ore from a loading station at the bottom of an open-pit mine to a discharge station located outside the mine (Figure 2). RopeCon® spans a terraced open-pit mine over a length of 486 m and a vertical rise of 350 m in one long stretch. It does not touch the terraces so that they can be used by the mining vehicles as before. The conveying track runs in a straight line and can be chosen independent of the geological conditions between the ground contact points. RopeCon® can be loaded and emptied just like any conventional belt conveyor, e.g., via chutes. The drive unit for the RopeCon® system in the example is positioned outside the mine. Doppelmayr has assumed a transport route of approximately 5.1 km between the loading and the discharge point if the material is to be transported on trucks. With a maximum vehicle load capacity of 363 t approximately 15 trucks will be necessary to achieve the required conveying capacity. RopeCon® will achieve the same conveying capacity at just 60 % of the costs.
Fig. 2. Example of a RopeCon® in open-pit mining. // Bild 2. Beispiel einer RopeCon® Streckenführung im Tagebau.
Further information/Weitere Informationen: Doppelmayr GmbH www.doppelmayr-mts.com
