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| Unconfined spray on longwall shearer |
Background
Water sprays have been used throughout the mining industry as a primary means of controlling respirable dust. In addition to wetting, the spray pattern of water sprays can be used to induce air movement. NIOSH researchers have should that air movement induced by unenclosed water sprays mounted on coal-mining machines can be beneficial (longwall shearer-clearer) or detrimental (dust rollback on continuous miners) to controlling machine operators’ exposures to respirable dust. While higher water spray pressures increase dust capture in enclosed spaces, they can also increase spray-induced airflow and, as a result, reduce dust capture in unenclosed spaces. NIOSH has characterized water spray droplet formation, air inducement, and dust capture efficiency for various spray nozzle types. Results indicate that hollow cone and wider spray-cone-angle nozzles generally generate smaller and slower water droplets, which induce more airflow and have lower dust capture efficiencies. A flat spray pattern and sprays with narrower discharge angles tend to generate larger and faster water droplets, which induce less airflow and have higher dust capture efficiencies. This fundamental information about sprays will be verified in the laboratory and the field and applied to improvements in current spray system designs by reducing the detrimental effects of spray nozzles that push dust over machine operators.
Potential Outcome
Completion of these studies can demonstrate the pros and cons of spray nozzle types and their operating parameters to optimize respirable dust controls. This information, when fully understood and verified, will be used to educate the mining industry about optimizing the design of machine-mounted water spray systems to improve dust capture and reduce operators’ exposures to dust. This research should be completed by late 2008, and the findings made available to the industry in early 2009.