The last six years saw a close cooperation between the rope manufacturer CASAR, the distributor Nobles and the Telfer gold mine, based in the Pilbara region in the state of Western Australia. The Telfer mine is wholly owned by Newcrest Mining Ltd. Gold and copper are extracted, above ground as well as underground (Figure 1). The copper and gold deposits were discovered in 1972, and mining began in 1977. In 2008 it was decided to increase the extraction capacities to over 6 mt/a. This provided the basis for initial talks between Telfer and CASAR, as Telfer were not happy with the service life of the original ropes of a South African manufacturer on the floor hoisting machine and now the extraction capacities were due to increase too. The hoisting machine is a ground mounted friction winder which transports a payload of 34.5 t at a speed of 16.25 m/s from a depth of 1,132 m to the top.
The service life of the original ropes was maximally 95,000 cycles, corresponding to almost a year. The costs incurred by downtimes and the rope replacement after 95,000 cycles were immense and had to be drastically reduced to make extraction cost-effective. That is why they CASAR asked to help. After a profound study of the site and application, CASAR decided to deploy CASAR Starplast construction. This is a rotation-free rope construction made of compacted strands. A rope set consists of four hoist ropes, each with a length of 1,360 m and a rope diameter of 45 mm (Figure 2).
Fig. 2. CASAR Starplast hoisting rope. // Bild 2. CASAR Starplast-Förderseil. Quelle/Source: CASAR
CASAR succeeded to continuously increase the lifetime up to 210,000 cycles reached with the third version of CASAR Starplast. The result was overwhelming as the lifetime was more than double the previous figure. Furthermore, the ropes were in perfect condition even after these 210,000 cycles and only had to be discarded as a result of mechanical damage due to rockfall, not because of wear and tear.
In addition, it was possible to virtually exclude undesired effects such as rope elongation and rope slipping on the drum, and wear on the inlays of the rope discs was reduced to less than a quarter of the previous value. In particular the reduction of the elongation effect is really valued by Telfer as the usually necessary shortening of the ropes after occurrence of the setting effect is no longer necessary. At present the value of elongation for the fourth version of CASAR Starplast is less than 800 mm.
CASAR, Nobles and Telfer are confident that they are able to use the knowledge gained to further increase the service life to over 300,000 cycles. In this case the ropes would not have to be replaced for at least three years. This alone would represent major cost savings for the mine and also save a lot of time which could be used for other maintenance and repair work. It is estimated that at least ten working days that would normally be needed to replace the rope could already be saved during the service life of the rope currently being used.
What Telfer particularly values in CASAR is that the efforts started in 2008 aimed at increasing the service life were back up throughout with advice and support. Not only were system measurements and destruction-free rope examinations carried out on site, but there were also intensive examinations of discarded rope pieces at CASAR, always focused on improving the product.
Overall, the package of customised products coupled with outstanding expertise and technical support on-site has justified the higher purchase price of CASAR ropes for Telfer. As a result, Telfer have therefore purchased their hoist ropes exclusively from CASAR in Germany since 2009.
Further information/Weitere Informationen:
CASAR Drahtseilwerk Saar GmbH
www.WireCoWorldGroup.com
