Randy Reed and Scott S. Klima, NIOSH, Pittsburgh Mining Research Division
Historically, longwall workers can be exposed to harmful respirable dust from multiple dust-generation sources, including intake ventilation, stageloader/crusher, shearer and shield advance. Longwall shearer operators and jacksetters have had the greatest difficulty in meeting the applicable respirable dust standard during compliance sampling by the Mine Safety and Health Administration (MSHA). Recently, MSHA passed a new dust rule that will reduce the respirable dust permissible exposure limits (PEL) from 2 mg/m3 to 1.5 mg/m3 in August 2016. In a benchmarking survey of U.S. longwall operations, NIOSH researchers observed dust clouds created by the fracturing and spalling of coal immediately upwind of the headgate drum that was migrating toward the walkway and exposing workers. In response, NIOSH has been conducting research to increase the effective zone of the directional spray system through utilization of underside shield sprays in the headgate drum area. The underside sprays on each shield can be automatically activated/deactivated by the position of the shearer along the face. The goal is to create a “traveling water curtain” to stop the migration of the dust cloud from the coal face toward the walkway by redirecting the dust toward the face where it can be captured by the directional spray system on the shearer. NIOSH has completed laboratory tests to evaluate the performance of water sprays mounted on the underside of the canopy. Five conditions for underside canopy sprays were examined: spray location, spray type, spray pressure, spray orientation, and gallery ventilation rate. This paper discusses laboratory tests to assess the performance of water sprays mounted on the underside of the canopy that when properly aligned and directed toward the face with appropriate water pressure and volume, and have the potential to be an effective tool that expands the envelope of clean air created by the shearer’s directional spray system.
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