Premature discard of 45 mm ropes operating on a Blair Multi-Rope rock winder
In September 2005, Driefontein Gold Mine, located west of Johannesburg, installed four 2500 m long 45 mm diameter CASAR Duroplast ropes on the No. 2 Shaft electrically coupled Blair Multi-Rope (BMR) rock winder. This was the first time a rope with eight compacted outer strands and a plastic coated steel core was used by the mine for deep vertical shaft mine hoisting. At the end of May 2006, two of the ropes on one BMR drum had to be discarded due to broken wires in the outer strands at the drum end, detected during routine magnetic testing. These ropes, as a pair, had completed 35,000 cycles (i.e. hoisted 70,000 skips or 604,000 tonnes of rock). The two ropes on the other BMR drum showed no damage at this time. On 20 June 2006 the remaining two ropes were discarded at 38,000 cycles also due to broken wires in the outer strands at the drum end. The average standard rope life previously achieved on the same winder was circa 66,000 cycles. This paper describes the full operating history of the ropes, the lubrication used and the general maintenance practices. A detailed description of the rope failure mechanisms is given including SEM micrographs. Finally, recommendations are made as to how this situation can be avoided in the future.
Author(s): P. Greyling, R.Rontgen, G. Rebel and B. Schmitz