In-Depth Survey Report: A Laboratory Evaluation of a Local Exhaust Ventilation System on a Caterpillar Cold Milling Machine at Caterpillar, Minnesota.

摘要

In August 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 Caterpillar PM200 cold milling machine. The testing was conducted indoors at a Caterpillar facility in Minnesota. 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 (SF6) was used to quantitatively evaluate the capture efficiency of tracer gas released in the cutter drum housing of the machine. A Miran SapphIRe infrared spectrometer was used to measure the resulting SF6 concentrations in the LEV exhaust duct. Capture efficiency tests were conducted at four flow rates of 1,675 actual cubic feet per minute (acfm), 1,450 acfm, 1,250 acfm, and 980 acfm with mean capture efficiency results of 98.1%, 97.5%, 94.7%, and 88.6%, respectively. Additional testing during actual milling activities is recommended to document capture efficiency under true field conditions.