Osborn screens at leading diamond mining group Petra

Exciter Driven Screens

Osborn product manager Emile Oosthuyzen explains that the screens will be employed at Petra Diamonds' Cullinan operation, where a new tailings reclamation plant is being set up. This order comprises six Osborn IFE Screens – two 12” x 24” double deck screens and four 12” x 24” single decks – as well as one 3” x 16” Osborn Obex single deck screen.

Osborn netted this order based on its competitive pricing, as well as its long-established reputation as a supplier of robust, high quality products, Oosthuyzen says. Petra Diamonds currently has a wide range of Osborn machines in operation at Cullinan, he adds, including vibrating grizzly feeders, screens, scrubbers and crushers.

Outlining the benefits of Osborn's IFE Screens, he notes that they are designed for heavy-duty to extra-heavy-duty screening, and feature a gearbox drive that is driven via a cardan shaft from an electric motor, in order to generate more G-force for the weight of the machine.

Over the years, these tough, hard-wearing screens have made their mark at operations like Kleinkopje Colliery, Iscor Sishen, Zimbabwe’s Wankie Colliery, Empressa Minera Copper Mine in Chile and Namakwa Sands, reflecting the diverse applications of this range of screens in products ranging from coal and copper to iron ore, heavy mineral sands and diamonds.

IFE Screens use finite element analysis to provide optimum performance and structural strength. The Exciter Driven Unit is designed to handle high amplitude vibrations without decreasing life expectancy. The screen consists of a sturdy soundproof housing made of cast metal. This contains two shafts that are synchronized with gears and are mounted in heavy-duty roller bearings designed for use with vibrating equipment. Lubrication of the bearings and gears is effected by a combination of oil bath and oil mist.

Eccentric weights are attached to both ends of the shaft. While stationary, adding or removing steel or lead weights can change the unbalanced mass. This consequently alters the strength of the unbalanced exciter force and the oscillation amplitude of the vibratory equipment. Oversize bearings provide long life expectancy, low maintenance and low noise emission. The unit also offers easy access to the drive unit (which can be removed by undoing just four bolts).

IFE Exciter Driven Vibrating Screens are available in a range of sizes to meet customers' specific requirements, Oosthuyzen states.

Obex Screens

Complimenting the large, heavy-duty IFE Screens that will be employed at Cullinan as primary screens is an Osborn Obex Screen that will be utilised in the final recovery stage.

Oosthuyzen elaborates: “Driven by out of balance electric motors, the Obex screen is designed for medium to heavy duty applications, and its size and design features make it an ideal final recovery screen. It is much longer than it is wide, to achieve maximum screening efficiency when working with the lower tonnages in the final recovery stage, when the raw ore has been processed down to concentrate.”

Osborn Obex Screens are locally designed and built to meet the demands of Southern African mining and quarrying operating conditions. The extensive range has been tested and proven in ongoing programmes of intensive field research, through years of use in mines and industry throughout Southern Africa. Two vibrating motors rotate in opposite directions, synchronise and impart a vibrating force in a longitudinal direction. This lifts the material and carries it forward on each rotation, providing a constant feed rate. The amplitude can be varied by adjusting the out-of-balance weights on the vibrating motors to the required stroke.

Osborn’s screens compliment its wide range of jaw crushers, gyrasphere cone crushers, mills, feeders, scrubbers and idlers, all designed and manufactured in South Africa, as well as the exceptional machines from United States-based Astec Loudon, Toro Trencor, Roadtec, BTI and American Augers that Osborn supplies into the African market.