About 20 pct of U.S. underground coal production comes from longwall mining, and indications are that the number of longwall operations will increase significantly over the next 10 yr. For this reason the Bureau of Mines has undertaken an extensive laboratory and underground evaluation of the benefits to be derived from the application of water-jet-assisted cutting on longwall shearers. Possible benefits from water-jet-assisted cutting are improved cutting, reduced respirable dust, reduced product fines, improved bit life, and reduced frictional sparking. Full-scale laboratory tests were run at the Pittsburgh Research Center of the Bureau of Mines, where a simulated coal block was cut with a water-jet- assisted shearer. An underground evaluation of a water-jet-assisted shearer was conducted at the Auguste Victoria coal mine in Marl, West Germany, under a Bureau of Mines contract with Eickhoff Corp. Results obtained in the laboratory testing were similar to those obtained during underground testing. Both test programs showed that use of high-pressure water did little to reduce the shearer motor energy required to maintain a given cutting rate. However, several other major benefits were achieved with the use of water-jet- assisted cutting. At a pressure of 1,800 psi (12 mpa), respirable dust was reduced about 80 pct compared to the conventional water spray system operating at 340 psi (2.3 Mpa). Operating at the higher pressures required for water-jet assist also resulted in an increase in the average size of coal cut, which translates into a decrease in product fines.
8th Int'l Conf. on Coal Research (Tokyo, 10/16-20/88); Int'l Com. on Coal Res., 1988, Pp 92-107