The Bureau of Mines recently developed a water spray system that reduces dust levels at the continuous miner operator position, particularly in mines where respirable dust standards are more stringent because of silica in the coal. The purpose is to reduce dust rollback caused by the dense dust at the cutter head spreading back over the operator's cab. This article describes the three factors that promote dust rollback and the features in the new design of the spray system that improve the dust conditions. The design features include (1) a moderate spray pressure of 100 psi at the nozzles, (2) arrangement of top and side sprays for low reach, and (3) use of underboom sprays for increasing the dust knockdown efficiency. The degree of improvement effected by the new system depends on the degree of present exposure of the operator. In recent trials, the new system reduced dust levels by 40 pct.
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