The Siemens Drive Technologies Division has received an order from ThyssenKrupp Robins (Greenwood Village, Colorado, USA) to supply the gearless drive system for the overland conveyor system in the Las Bambas copper mine in Peru owned by Xstrata Copper. Las Bambas will be the second Xstrata Copper mine in Peru to use gearless drives from Siemens on its overland conveyors. The first Peruvian copper mine that is utilizing Gearless Drives is the Antapaccay Mine, which began commercial operations at the beginning of November 2012. When compared to conventional drive systems, gearless drives not only have higher efficiency, availability, and reliability, but also lower maintenance requirements. Start-up of the new conveyor system at Las Bambas is scheduled for 2014 (Fig.).
The overland conveyors at Xstrata‘s Las Bambas copper mine are being designed and supplied by ThyssenKrupp. Each of the two overland conveyors is approximately 2.5 km long and will transport ore from the mine to the processing plant. The belts will be 1830 mm wide, travel at 6.5 m/s, and are designed to transport approximately 9400 t of material per hour.
The Siemens drive systems for each of the two overland conveyors comprise two low-speed synchronous motors – each with a total power of 4400 kW – and the associated Sinamics SL150 cycloconverters. This gearless drive solution has a number of advantages over the combination of high speed motor and gearbox drives usually used on conveyor systems. The size of the motor is not limited by the size of gearbox available, thus eliminating the necessity to install multi-motor drives. The power required to drive a belt can be provided by just one drive per belt pulley. This enables the size of the electrical room to be reduced, thus saving space and weight. The elimination of a whole series of mechanical and electrical components increases the reliability and efficiency of the overall system by between three and four percent. Using gearless drives instead of standard motor reducer packages will eliminate approximately 40 bearings and eight couplings per conveyor. The maintenance requirements of the drive system are also substantially lower. Gearbox maintenance work alone can amount to up to five percent of the original annual investment cost for each year. Lubrication and gearbox cooling systems, together with their maintenance, are also obsolete for this solution.