Abstract
The Bureau of Mines has been investigating techniques to reduce dust concentrations in mineral processing plants. This article discusses three projects that reduced the respirable dust exposures of plant workers. The first project involved designing and testing a total mill ventilation system for large surface structures. This total mill ventilation system uses clean outside air brought in at the base of the mill to sweep and clear contaminated areas, and then discharges this air out of the top of the structure, where it poses a minimal contamination hazard to employees working outside. Average respirable dust levels were reduced by 40 and 64 percent at two field sites using this technique. The second project involved a bag and belt cleaner device that uses a combination of brushes and air jets to clean the dust that collects on the outside of 50- to 100-lb. bags of product and the conveyor belt used to transport them. The system is totally enclosed and under negative pressure to contain all dust cleaned from the bags and conveyor belt. There was a 78 to 93 percent reduction in the amount of product removed from the bags with this system. The third project reduced worker exposure from secondary dust sources at processing operations through improved work practices. A number of work practices, which are often overlooked but which often have a significant influence on reducing worker respirable dust exposures, were identified.