Mining is more than dark underground tunnels of men with picks and machines extracting coal – vast opencast pits from which giant bucket excavators load tonnes of rock and ore are mines as well. So too are strip mines, where the overburden is removed and the wanted material is accessed from the surface. There is also placer mining, which is essentially sifting riverbed sands for, typically, gold or gemstones that have been washed down from their original sites by centuries or millennia of water erosion. All of these methods of extracting things we want or need from the ground come under the heading of ‘mining’, and all of them need different kinds of lifting equipment. And these days almost all of them are carried out at extremes of scale, quantity or depth that strain technological ingenuity to its limits.
Most unusual perhaps is the offshore dredging for diamonds from the ocean bed, practiced off the coast of Namibia. There are also new uses for existing or redundant mines – which again need specialised hoists of custom designs. More standard in concept, but impressively large is the Sishanling iron ore mine in China – 30 million tonnes a year is the planned extraction rate. This is a new project, which Hoist first reported on last year (April 2022). Since then, rapid progress has been made.
Siemag Tecberg is the hoisting firm involved. The installation of the rope sheaves and of all three hoists has now been completed and some of them have been put into operation: the two Koepe (or friction winding) hoisting machines – one four-rope, one six-rope – of the service shaft are already working. No-load commissioning was completed for the production shaft’s six-rope Koepe machine; rope-up started in mid-March this year. Due to slow construction progress in the area of the main shaft loading and unloading station, the commissioning of this hoist is scheduled for October 2023.
At present, Siemag Tecberg is on site with preparatory tasks for the commissioning of the main shaft. Once the ropes for the production machine have been laid, the installation and connection of the shaft switches and the connection of external equipment, such as the loading and unloading stations, will be carried out, with safety tests. Finally, commissioning of the production machine under load takes place, together with tests of the control system and final optimisation of the parameters of the drive and braking systems.
DIGGING FOR DIAMONDS
Southern Africa is, of course, another world centre of mining, and Condra, based in Johannesburg, has been a major supplier of lifting equipment since 1971. In March this year it announced a contract to manufacture a 15-ton suspension crane of an unusual configuration. It is for use underground at a Botswana diamond mine, and is one of two overhead cranes ordered. The second machine is of conventional overhead design.
The arrangement of the first suspension crane is one rarely seen: two I-beams defining its area of movement will be bolted to rock-bolt flanges anchored in the roof of a mine chamber that will have been blasted and excavated. I-beams are usually the topmost side components of a fixed gantry that has been constructed from the ground up. In this case, however, they will hang from the chamber’s ceiling. The wheeled 11m-span crane girders will then run suspended from the lower flanges of these two long-travel I-beams, with the crane’s crab mounted atop of the girders to provide the cross-travel. The whole structure of the crane becomes suspended, running along and across the roof of the chamber.
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