The Siemens Drive Technologies Division has commissioned a gearless belt conveyor system in the Antapaccay copper mine in Peru. This is the first large-scale reference for this technology outside Germany. The mine, 4200 meters above sea level, belongs to Xstrata Copper and is scheduled to produce an average of 160,000 tonnes of copper in concentrate per annum in the initial years of its more than 20-year projected mine life.
The gearless drives will help to boost the efficiency and reliability of the conveyor system in Peru and reduce maintenance requirements when compared with conventional systems. The Siemens' scope of supply includes additionally the entire switchgears and gearless drive systems for a 40ft SAG mill and two 26ft ball mills with the associated power supply.
The belt system in the Antapaccay copper mine was supplied by ThyssenKrupp and transports ore from the mine to the processing plant over a distance of around 6.5 kilometers. With a belt width of 1,370 millimeters and a conveyor speed of 6.2 meters per second, approximately 5,260 tonnes of ore can be transported in an hour. The conveyor system is the second of its kind worldwide. The first belt system with gearless drives was installed back in 1986 by Siemens and ThyssenKrupp (previously O&K) in the Prosper-Haniel pit of Deutsche Steinkohle AG.
The Siemens drive system for the belt conveyor consists of two slow speed running synchronous motors, each with a power rating of 3,800 kilowatts, and the associated cycloconverters Sinamics SL150 and convertor transformers. Compared with the combination of high-speed motor and gear units otherwise used in belt conveyor systems, this gearless drive solution offers a range of benefits. The size of the motor is not limited by the size of gearbox available, thus eliminating the necessity to install multi-motor drives. The required belt driving power can be provided with one drive per drive pulley. This means that the number of switchgear enclosure could also be scaled down, 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. Another important factor is that the maintenance requirements of the drive system have been significantly reduced. This is important as gear maintenance work alone can account for up to five percent per year of the original investment volume for the gears.
In addition, the company supplied the high-voltage and gas-insulated medium-voltage switchgear for the main distribution, as well as the low-voltage switchgear for the overall plant. The equipment enables safe and reliable power distribution under the harsh environmental conditions typical for high altitude mountainous regions – a decisive criterion for mining. The maintenance-free long-term operation of these products is also noteworthy.
Xstrata Copper, based in Brisbane, Australia, is part of Xstrata plc and operates mines and production plants in Argentina, Australia, Chile, Canada and Peru. The company is the fourth largest copper producer in the world. The Antapaccay copper mine in the south of Peru began production in the fourth quarter of 2012. Siemens was entrusted with the conveyor belt project in 2010, having already been awarded the contract to supply the electrical equipment for three grinding mills of the mine in 2008. These have also been fitted with gearless drive systems. Siemens was responsible for the configuration, manufacturing and the supply of the electrical equipment of the grinding mills. The SAG mill was fitted with a gearless drive with a power rating of 24 MW and the ball mills were also fitted with gearless drive systems, each providing 16.4 MW. Also included in the scope of supply were transformers, E-houses, the drive control, the cooling system, protection equipment and operator control systems.