First new trolley assist truck system for many years

The Siemens Industrial Solutions and Services Group (I&S) has received orders from Equinox Minerals for the supply of electrical equipment and systems for the open-pit haul trucks, grinding Mills and in-pit electrical reticulation, required for the development of its new Lumwana copper mine the North Western Province of Zambia. The order volume amounts to around €40 million and the new mine is scheduled to start operating in the middle of 2008.

Included in the order is the first new open-pit trolley assist system to be ordered for many years. The last major system was that installed at Goldstrike in Nevada, USA. Zambia has had a system before, at Nchanga open pit, and Southern Africa has been the region to overwhelmingly lead in embracing the technology with other systems installed at Sishen iron ore mine in South Africa and Rössing uranium in Namibia Lumwana will be the single largest copper mine on the African continent. Equinox plans to extract in excess of 400 Mt of ore during the first 20 years of operation producing an average of 169,000 t/y of copper metal contained in concentrate for the first six years of its 37 year mine life. The mine is scheduled to begin production during the second half of 2008.

To transport ore from pit to crushing stations, Siemens will supply the equipment required for the electrification for 27 haul trucks along with the associated in-pit trolley assist system. All trucks will be equipped with the latest AC drive technology. In contrast to conventional DC systems, the AC wheel motors remove the need for both commutators and brushes. This significantly reduces the maintenance and repair costs, while increasing the availability of the units. Moreover, the drive technology employed will ensure greater safety and less wear on mechanical brakes due to the availability of an electrical retarder braking system. The trolley system to be installed along the main ramp haul routes allows trucks to draw the electricity required for the AC wheel motors in much the same way as conventional railway systems. Additional benefits derived from this system are high starting torques, and increased speeds whilst on the gradient exiting the pit, the higher speeds result in increased cycle times whilst operation on trolley realizes huge savings in diesel fuel costs.

To continuously monitor all mining operations, I&S will supply a comprehensive communication system. The main component of the communications system is a fail safe fibre optic backbone known as an OTN (Open Transport Network). The fibre optic network will be used to carry all data and communication mediums associated with the mine’s operations, additionally, the transmission and provision of high-quality video signals (CVBS or S Video) will enable real-time viewing of all mine operations and critical plant equipment such as crushers, overland conveyors, pumps, mine fleet etc. The entire mining operation can thus be monitored and controlled remotely via monitors in the communications centre.

In March 2006, Siemens I&S received an order from Equinox for the engineering, design, manufacture and supply of two mill drive systems. With the Simine Mill GD (gearless drive) gearless ring-motor drive systems, the speed of the SAG and ball Mills can be varied with the help of the transvector control principle. Mill operation can therefore be precisely adapted to changing material characteristics, such as composition, size and hardness. The GD principle completely removes the need for mechanical interfacing through such components as ring and girth gears. The ‘impactless’ design eliminates mechanical wear and tear associated with conventional systems, thereby significantly reducing the amount of work and associated costs involved in maintenance and repairs to the mills. The design concepts employed in the control systems of the GMD ensure that the mills display superior efficiency and are more energy efficient than conventional drive systems. Further benefits derived from the GMD concept are such features as ‘Soft Start and Stop’, as well as the frozen charge shaker, which allows for the controlled detachment of the grind medium that may have become compacted in the grinding shell while the mill was stationary. This feature prevents expensive damage to the mill shell, removes the need for manual cleaning and thereby reduces downtime and subsequently production losses.

With the help of the eWD electronic documentation system, a comprehensive suite of documentation and information pertinent to the specific mill installation is generated during the commissioning phase. This ensures that all the relevant information is available online to facilitate maintenance and optimization of the mills.