The function of pre-cutters in thick seam mining, where slabbing of the coal is a problem, is to cut a centre slot in the coal seam to the depth of the pre-cutter, normally about 300 mm. On the next cut run along the face by the coal shearer the slabs of coal are now cut through the middle and cannot bridge across the AFC, or fall across into the walkway of the roof supports. The slabs are also less likely to jam across the tunnel of the shearer mainframe causing a blockage to the flow of the coal along the AFC. Pre-cuttershave been used with varying success in both Australia and the USA. A major concern with the use of pre-cutters is that they put an increased load onto the shearer's ranging arm and mainframe. |
