SIEMAG South Africa (Pty) Ltd., a subsidiary of SIEMAG Transplan GmbH, has received an order from Placer Dome Western Areas Joint Venture for the supply of the mechanical portion of a large Blair double-drum rock winder. With an overall length of 33 metres, a width of approx. 11 metres, and a total machine weight of approx. 800 metric tons, this is probably the largest winder in the world.
The new machine will operate as a production winder for the main shaft of the South Deep Gold Mine. The shaft has a depth of 3000 metres, resulting in the machine carrying a total of 4 x 3245 metres of rope. The supply of plant and machinery for shafts of this depth has been made possible by the new guideline SABS 0294, which requires special measures to be taken to allow loads to be hoisted from such depths. This includes increased attention to observing common permissible dynamic stresses on the ropes, while allowing a greater static load.
In order to minimise the stress on the ropes, a winder drum diameter of 7.1 metres was selected. Each of the two skips in the shaft is suspended from two ropes, which are wound onto separate drum compartments, each of which is 1.9 metres wide. Owing to the length of each drum, and the maximum allowable obliqueness of the ropes, the two double-rope drums have been arranged at an angle of 4.5° to one another, thus necessitating the use of a Hooke’s Joint (cardan) between the two drums. The driving power of over 12,000 kW is supplied by two directly coupled AC (three phase) motors, which are located at the free ends of the machine in an overhung configuration. Owing to the use of a Hooke’s Joint, the motor torque required is reduced as a result of the compensating torque of the second drum being utilised. This differs from an ‘electrically coupled Blair winder’, which, from a mechanical point of view, consists of two completely separate machines.
Each of the drums is fitted with a clutch, which makes it possible to position the two skips independently in the shaft, at any time and in any position.
Each of the drums has two brake disks on which a total of 32 brake callipers of the new type SIEMAG BE-200 act. These exert a force of 12,800 kN which can bring the machine safely to a halt under any normal load condition. The brake system is of the 4-channel closed loop design, where each channel acts on both drums. Thus, in clutching mode, all the channels are available. With the safety brake, the braking force is controlled in such a way that the machine comes to a standstill with a set retardation. Even in the event of an entire brake circuit failing, this design ensures that the machine is stopped in a controlled way. Gentle acceleration transitions (‘jerk limitation’) are provided which are important for limiting the dynamic stresses on the ropes.
Most of the machine is manufactured in South Africa with the design and essential components such as the main shafts, the Hooke’s Joint and in particular the entire brake system being done in Germany.
In this project, SIEMAG has, for the first time, succeeded in securing an order for a Blair winder for the South African market in the face of competition of traditional local suppliers. Constructing this exceptional machine represents a special challenge, which SIEMAG will be able to meet thanks to its experience with Blair winders previously installed in Europe and Asia. The decades of presence on the local market – now as SIEMAG South Africa (Pty) Ltd. – were of decisive importance in gaining this contract.