Mining Publication: Technology News 487 - Sweeping Compound Application Reduces Dust From Soiled Floors Within Enclosed Operator Cabs

• Cabs
• Respirable dust

Enclosed operator cabs are widely used on mobile excavation equipment in the mining and construction industries. They protect the operator from bad weather, noise, and airborne dusts. The inside cab environment usually must be kept at very low dust concentrations because of quartz dust generated from the excavation of silica-bearing rock. For cabs to be effective in controlling airborne respirable dust, they must have an efficient air filtration system, while providing a positive pressurization of the cab interior. Ideally, the recirculated and exterior makeup air filtration should provide at least 99% capture efficiency for dust particles as small as 0.3microm aerodynamic diameters. Many of these enclosed cabs use heating units mounted or directed along the floor, which can cause dust entrainment problems. Prior studies by the National Institute for Occupational Safety and Health (NIOSH) of enclosed cabs have shown that these floor heaters can generate notable amounts of dust within the cab enclosure. Multiple-shift dust levels measured inside a drill cab increased on average 0.04mg/m3 during the summer months to 0.68mg/m3 during the winter months. Additional dust level measurements, made with optical particle counters during a nondrilling time period, verified that dust levels inside the cab increased from 0.03 to 0.26mg/m3 when the floor heater/fan was turned on. Dust levels within the cab also became greater than the ambient air dust levels outside of the cab when the floor heater was turned on during the nondrilling time period. This shows that the floor heater was a notable dust source problem. Cab floors are commonly soiled from operators tracking dirt inside the cab upon entering from the mine or construction site. Interior cab dust levels can be increased by (1) airflow disturbance of the soiled floor or (2) operator disturbance of the soiled floor.