Dust Control Handbook for Industrial Minerals Mining and Processing

Open screen decks slowly to allow internal exhaust system to function at the deckperiphery. Opening decks rapidly can cause a swirling effect with dust being releasedinto the work area, potentially exposing personnel.Do not slam screen decks closed. Any material, no matter how slight, has the potential ofbecoming airborne due to the shock of deck closure.Decks must be kept clear of dust. A clean deck lessens the potential of dust emissionsresulting from opening and closing decks, as well as from environmental factors such aswind.Maintain seals on screen decks where an airtight closure is desired. Decks that areproperly sealed should remain sealed when all fasteners and sealing materials are inplace.Closure and locking devices such as clamps and other fasteners must be well maintained.Fasteners are ineffective unless they are utilized.Where compatible with the process, wash down areas around screens on a periodic basis.Periodic washing removes material before it accumulates to a degree where dry cleanupmethods become necessary. Dry cleanup activities present a much higher potential forworker exposure.MAINTENANCEMaintenance of dust control systems is critical to ensure continuing worker protection [USBM1974]. Crushers and screens are subject to constant vibration when in use and this condition cancause accelerated wear on all components. Even small openings from worn seals, missingfasteners, and damaged flexible connectors can cause unwanted air infiltration, degradingcapture velocity at necessary penetrations [Goldbeck and Marti 1996]. This could potentiallyresult in worker overexposure, particularly when exposure limits are low.Operators should document baseline parameters of an effectively functioning dust controlsystem, including for example:inflow velocity at enclosure openings,static pressure in ducts,velocity pressure in ducts and at hood entry points, andwater pressure and flow in wet systems.Results of subsequent periodic checks should be compared to the baseline values. Significantdeviations from the baseline values should be explored, and corrective action implemented whennecessary.A preventive maintenance schedule should be established based on manufacturerrecommendations, observed component wear, system performance measures, and exposuresampling results.128 Crushing, Milling, and Screening