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In-Depth Survey Report: A Laboratory Evaluation of a Local Exhaust Ventilation System on a Roadtec Cold Milling Machine at Roadtec, Chattanooga, Tennessee
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2013/02/01
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Description:In April 2012, National Institute for Occupational Safety and Health (NIOSH) researchers and the Silica/Milling-Machines Partnership coordinated by the National Asphalt Pavement Association (NAPA) conducted laboratory testing of a local exhaust ventilation (LEV) system on a Roadtec RX600e cold milling machine. The testing was conducted indoors at the Roadtec manufacturing facility in Chattanooga, Tennessee. All tests were conducted on a stationary milling machine with the cutter drum and conveyor belts moving, but without any reclaimed asphalt pavement (RAP) moving through the system. Smoke and tracer gas were used as surrogates for silica dust to evaluate capture efficiencies of the dust emission-control system in the cutter drum housing of the machine. Smoke was used as an initial qualitative test to visually check for leaks. Sulfur Hexafluoride [SF(6)] was used to quantitatively evaluate capture efficiency of tracer gas released in the cutter drum housing of the machine. Two independent analytical instruments were used to measure the resulting SF(6) concentrations in the LEV exhaust duct, an Innova AirTech Instruments 1412 Photoacoustic field gas-monitor and a Miran SapphIRe infrared spectrometer. Capture efficiency tests were conducted at a single flow rate on the Roadtec cold milling machine. The mean capture efficiency from the Innova AirTech Instruments 1412 Photoacoustic field gas-monitor and Miran SapphIRe data were 98% and 99%, respectively. The lower 95% confidence limits were 97% for both the Innova AirTech Instruments 1412 Photoacoustic field gas-monitor and Miran SapphIRe results. Additional testing during actual milling activities is recommended to document capture efficiency under true field conditions. The testing reported here only evaluated capture efficiency within the cutter drum housing. Other potential dust release locations on the machine such as the transition between the primary and secondary conveyor and the top of the secondary conveyor were not evaluated during this testing but could contribute to silica exposures during actual field operation.
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Pages in Document:1-14
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NIOSHTIC Number:nn:20043147
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NTIS Accession Number:PB2014-100520
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Citation:Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 282-21a, 2013 Feb;:1-14;
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Federal Fiscal Year:2013
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Peer Reviewed:False
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[PDF-518.80 KB]