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MEI Online: Plant Operation News: Africa: December 8th 2005


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:: DRA Oversees R1.6 Billion Two Rivers Project

Dowding, Reynard & Associates (DRA) has been appointed as the Managing Contractor for the Two Rivers Project on the Eastern Platinum Limb, near Lydenburg. DRA is directly responsible for the 225 000 tonnes per month concentrator and all related surface infrastructure. Their responsibility includes the engineering, procurement and management of all underground services and infrastructure. DRA has also been appointed to undertake the Managing Contractors role to integrate the capital works through underground and surface scope.

The project is a joint venture between African Rainbow Minerals and Impala Platinum, who will invest R1.6 billion in a 220 000ozpa platinum-group metals mine and is the largest project ever undertaken by DRA.

Says DRA's Wray Carvelas, "DRA has been involved with the development of the Two Rivers mine, a greenfields project, for the last three years - since its pre-feasibility and feasibility studies. The scope of the project, which received full project release in June 2005, is quite extensive and has a challenging 15 month execution programme. Carvelas adds that DRA maintains direct responsibility for the design, installation and commissioning of the mine's 2-stage milling-flotation platinum-group metals concentrator with a design throughput of 225 000 tonnes per month. The process design allows for intermediate concentrate thickening to enhance the secondary flotation circuit, resulting in increased recovery rates."

Ancillary systems included in the project include the plant's crushed ore silos, primary and secondary milling and flotation, reagent handling systems, intermediate and final concentrate thickening, filtration and load out. All associated concentrator infrastructure such as compressors, conveyors, pump and ventilation systems, access control, security, stores, weighbridge, offices and change house also fall under DRAs scope of work.

In addition, DRA Technical Services has assisted in the design of a chairlift system for the transport of personnel into and from the mine. The dual drive system will stretch for 1,5 kilometres and can shift 600 personnel per hour at speeds up to 1,5 metres per second. The chairlift system proved to be a far more economical solution than a conventional winder system for the mine which features ore reefs dipping from the surface at between 10 and 12.

DRA is responsible for the installation of the mine's surface infrastructure including power such as substations and transformer bays, power factor correction, earthing and lighting, fire protection and detection systems as well as a system power study which was required to determine fault levels. The electrical work has been designed according to SA Bureau of Standards and IEC specifications.

The instrumentation and control system, in this case a PLC/SCADA type system, allows for the provision of interfacing with high level software such as Manufacturing Execution Systems, Plant Maintenance Systems and Enterprise Resource Management Systems in the future. A fibre optic network will be used to link the network process area, portal and concentrator while telephones and a radio/leaky feeder arrangement will provide voice communications throughout the mine.

DRA is also responsible for the construction of the mine's tailings dam and for the upgrading of the Nyoni Dam wall which was in poor repair and incapable of handling the water capacity needed for the mine's requirements.

Says Carvelas, "The mine, which will be fully mechanised, has importantly gained a considerable advantage through an extensive trial mining period in order to satisfy itself of the viability of the project. The trial mining has removed considerable risk from the project, with 300 000 tonnes of reef already stockpiled on surface, and this is expected to grow to one million tonnes when commissioning of the plant commences in August 2006. "DRA has maintained a close working relationship with Two Rivers since its inception and has been an integral part of its development," adds Carvelas. "At its peak the project will employ approximately 2300 personnel including construction and mining contractors. Commitments on the project total R790 million and of significance is the BEE spend achieved on the project of 36%." The project progress to date is positive with overall progress reported to be ahead of schedule at 44% compared to a plan of 42%.




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