While still waiting for a significant commitment from the coal mining industry to its new design, Sydney-based AGE Mining Services officially launched its Dp cutting system last month after more than six years of development and testing. A report on testwork at the Myuna mine near Newcastle, conducted when the mine was owned by Powercoal (it is now owned by Centennial Coal) says the AGE picks offer better wear characteristics, reduced fines and respirable dust generation, and significantly lower miner power consumption compared with conventional conical pick designs.
The tests with Joy 12CM12 and 12CM14 miners in coal and abrasive hard rock (pebble conglomerate) were carried out in two stages for 16 operating shifts. Three AGE non-rotating pick designs, two coal cutters and one rock cutter were tested against two conical rotating bit designs with 75-degree tungsten carbide tips. AGE's report said its objective was to obtain data on cutting parameters and primary coal and silica respirable dust generation. Each of the picks was tested under identical conditions and within the same coal and other rock strata.
Cutting parameters studied during the trials were pick tip geometry, product coarseness, fine dust creation and pick wear. The recorded uniaxial compressive strength of the coal was 40-45Mpa, and of the pebble conglomerate 100-110Mpa.
AGE managing director George Wawryck said his company's picks had demonstrated a 33% power consumption reduction in rock and 58% in coal. Fines and dust generation were “significantly” lower than with the conical picks.
Wawryck said wear rates were also lower with the Dp chisel picks. “The key to efficient cutting is the maintenance of the sharpness of the cutting tool,” he said. “The Dp cutting system always maintains the sharpness of the tool resulting in a chisel cutting action rather than percussive hammering.
“The conical pick is advertised as self-sharpening as it rotates in the tool holder (but) this is not the case as proven by the wear patterns on the used picks. The tip of the pick flattens and begins to cause all the problems.”
Wawryck said dust generation caused by conical picks was a significant problem for the underground coal industry in Australia and elsewhere. However, despite attempts to work around pick design with various dust suppressing agents and methods, the problem was escalating due to increasing production rates and higher-powered mining machines. Injecting large quantities of water into the equation only created headaches at the coal preparation and/or transport stages. Lower dust and fine-coal creation at the coal face was the answer, Wawryck said.
“Mine owners have not been given any alternative up until now,” he said.
The industry appears to be watching and waiting for further developments. Australia's Mining Monthly understands there is still interest on Centennial's part in exploring the potential of the AGE picks to reduce fines generation at Myuna. However, there was no agreement on further testwork in place at the end of October. A planned demonstration at BHP Billiton's Appin mine near Wollongong has been repeatedly delayed.
Thin Seam Mining, which is mining the Balgownie seam at Gibsons colliery, near Corrimal, NSW, with a Joy 14CM15 miner, is understood to be close to making a commitment to use the AGE picks. It had not commenced using the picks when AMM went to press.
Wawryck said the market for picks in Australia, covering underground coal mines, opencut coal applications and some metalliferous-mine use, was at least five million picks a year
“The international market is many times this figure,” he said.
