Sandvik's Rock Cutting Technology Advances to Meet Industry Demands
In mid-June, Sandvik Mining and Construction (SMC) hosted the latest in its series of rock-cutting symposia at its center for continuous-miner production at Zeltweg, Austria. Six years have passed since the previous such meeting, so the 140-strong attendance, drawn from Sandvik's staff and customer base, had the opportunity to hear what the company has achieved in that time, as well as to visit the machine assembly plant. Coincidentally, the Zeltweg factory, which Sandvik acquired when it gained ownership of Voest-Alpine's mining-machinery business in 1997, celebrated its 160th anniversary the same week, the plant having originally been established to service the Austrian railway network.
One of the Sandvik group's three operating divisions, SMC was the largest contributor to the company's turnover last year. SMC President Lars Josefsson pointed out the division has grown four-fold in size over the past 10 years, and recovered financially following a sharp drop in business during 2009. More than half of its business now comes from the southern hemisphere, he added, noting that "the fundamental drivers of our industry continue to be strong."
"Deeper deposits will mean that demand for equipment will be different in the future and the company is seeing a trend from drill-and-blast towards more continuous mining processes," said Josefsson. SMC is investing in exploring what can be achieved with rock cutting for continuous mining and recently formed a joint venture with China's Shandong Energy Machinery in relation to this, he said.
In the keynote address to the meeting, Professor Karl Rose, formerly with Royal Dutch-Shell and now at Graz University and a senior fellow of the World Energy Council, gave a thought-provoking overview of global energy trends and materials. Among his key points for mining, Rose said world coal demand is expected to increase by 53% by 2030, with by far the largest proportion of this rise coming from Asia. "Coal has been the fastest-growing energy carrier of the last decade," he said, pointing out the world is faced with the need for both improving energy efficiency and conserving energy; targets that equipment manufacturers and users alike will have to adopt.
Making better use of energy will require the development of much 'smarter' technologies, he said, with commodities such as rare earths coming into greater demand from a range of applications. Other commodities could also become critical in terms of their supply, however, with Rose citing copper as being one of these.
Sandvik's Bruno Reumüller reviewed the various machines the company introduced since the last rock cutting symposium in 2005. Among these are the MC250, MC350 and MC470 continuous miners, the latter having being designed for high-production coal mining in South Africa. Sandvik aims to provide complete packages for continuous mining operations, including miners, shuttle cars and continuous haulage systems, he said.
New developments have included a measurement device that provides data on the forces acting on picks during coal cutting. In addition, the system has potential applications in machine automation and in the next generation of control systems, Reumüller said.
The MB610 is a new, lower-seam addition to Sandvik's bolter-miner range, with two variants available: one for the U.S. market and one for other parts of the world, such as Australia. The company has been developing mechanized bolting systems for its bolter-miners, aimed at reducing operators' exposure to hazards, with drills that can also be used for dewatering or degassing ahead of development.
For potash mining, Sandvik has brought out its MF320 and MF420 borer miners, destined for Uralkali and a Canadian potash operation respectively, while for hard-rock mining, the company is investing in research into materials that can extend the range of rock that can be cut economically beyond 200 MPa—twice the current limit.
From the Face
The symposium also heard a number of presentations from industry, covering various aspects of continuous rock cutting. From Newcrest Mining, Steven Powell provided insight into the challenges facing the company and its partner, Harmony Gold Mining, in the Wafi-Golpu copper-gold project in Papua New Guinea. Current planning includes the development of twin, 4-km-long declines to service an underground block- or panel-caving operation.
However, rock conditions range from fair to very poor, and substantial water ingress is expected, with the companies evaluating the use of roadheaders for development. Less than 2 km of the drives will be in rock with a UCS of more than 50 MPa, while over 20% of the length the rock is so soft they are looking at using an ITC Schaeff 'Superloader' for these sections.
Also from the Pacific Rim, Roland Berndt described the work Nautilus Minerals is undertaking to get its first deep-water 'mine' into operation. Working at a depth of up to 1,800 m in the Bismark Sea off the coast of Papua New Guinea, the production of 20- to 60- MPa copper-rich ore from seabed massive sulphide deposits will involve the use of three separate mining machines: a development unit, a continuous miner and a suction unit to collect cut ore and pump it to surface. Both cutting machines, now under development by U.K.-based SMD, use Sandvik cutting tools, with the first sea trials now scheduled for mid-2013.
From Poland, Wojciech Chojnacki from the mining contractor, PeBeKa, reviewed improvements being made to haulage development at the copper producer, KGHM, through a change from drill-and-blast to continuous mining using roadheaders. PeBeKa has been using a Sandvik MH620 machine, fitted with twin roofbolters, for its evaluation, with a major challenge being development through dolomite rocks that run at over 130 MPa.
The introduction of continuous miners at Südwestdeutche Salzwerke's Heilbronn salt mine in Germany has helped the company increase its production from around 3 million mt/y 10 years ago to 4.5 million mt/y now. So said Dr. Gerd Bohnenberger, Sudwestsalz's director of mining, who described the introduction of Sandvik MB770 (formerly ABM 30- CM) machines there. With the operations at a depth of around 200 m, mining in a new area presented constraints in terms of blasting noise and vibration to communities above, so the first machine was introduced in 2006.
Since then, the company has added a further two continuous miners, with a fourth on order for delivery later this year, while retaining a small drill-and-blast capability to give it short-term flexibility. Overall long-term costs for the continuous miners have proved to be around 87% of drill-and-blast, Bohenberger reported, with a target output of more than 1 million mt/y for each machine.
Peter Achilles of the Germany hard-coal producer, RAG, described the development of the iTSM roadheader-optimization automation package in conjunction with SMC. By optimizing the way in which the roadheader cuts a face, RAG has been able to increase its average daily advance per machine from 7 m to 10 m, while improving the heading profile. It has three iTSM MR620 units at work at its Prosper Haniel mine, with SMC now having the rights to the technology for other applications.
China's Shendong Energy Group currently has 26 SMC bolter-miners in operation, according to Gao Zhengliang, with the first machines having been commissioned in 2005. Both MB670 and AMB 20 machines are in use, he said, offering advantages of high advance rates and heading profile quality, with low labor requirements.
David Hickson, SMC's regional product line manager for mechanical cutting, described the achievements made with the new MC470 continuous miner at Xstrata Coal's South Witbank mine in South Africa. Whereas previous practice was to cut the seam in stages because of a sandstone parting near the roof, the new machine is powerful enough to cut the face in one pass, he said. Despite the band, which ranges in strength from 80 to 180 MPa, the unit has achieved outputs of up to 1,700 t/h, filling a 20-mt shuttle car in less than 30 seconds.
A New Focus
While much of the agenda focused on coal and soft-rock mining, SMC remains committed to the hard-rock sector. Having developed and trialed thin-reef cutting technology successfully a number of years ago, the company is now re-instituting a stand-alone hard-rock cutting group.
Christian Halbmayr, SMC's vice president for underground mining equipment, said there is still a lot of work to be done in relation to this, especially in terms of developing new materials for picks and in optimizing cutting-disc concepts. "The principle is proven," he said, pointing out that the platinum and gold industries in particular are once again eager to see continuous mining in preference to drill-and-blast.
"Drill-and-blast will work anywhere, but at the moment, rock cutting technology is limited by the materials available. The difference between 150 MPa and 250 MPa rock does not have much effect on drill-and-blast, but it is a major challenge for continuous cutting," he said.
As much as anything, it is the variability in hard-rock conditions that presents the problems, he added, suggesting that the adoption of rock-cutting technology will need a comprehensive redesign of the mining layouts now in use. The analogy here is the difference between advance and retreat mining in longwall coal production, with retreat mining having clear advantages. "There is a huge potential market in South Africa for continuous hard-rock mining "and it will no longer be a niche technology once this market has been developed," Halbmayr said.