An Investigation of the Performance of the 10-mm Nylon Cyclone

Abstract

The sampling device recommended by the National Institute for Occupational Safety and Health for the determination of respirable silica is a 10-mm nylon cyclone and 37-mm cassette loaded with a PVC-type filter and operated at 1.7 lpm. The device has been subjected to a statistically rigorous determination of the sampling precision under controlled laboratory conditions using a silica-rich mine dust in a laboratory-built generation system. The statistical design used in the investigation eliminated contributions to the precision estimate from run and position effects. The precision of the device over the deposition range 826–1800 μg/sample was found to be 2.18%. In a follow-up study of air leaks in the device, five possible locations of leaks were selected. A set of sampling devices was made with air leaks of varying magnitude in the selected locations. The devices were tested using a vacuum leak testing apparatus. They were then placed in a generation system and challenged with a uniform concentration of aerosol side by side with control (leakless) cyclones. The samples were analyzed gravimetrically and the results subjected to a statistical analysis to determine which leaks had a significant effect on the sampling performance. The experiments indicated that the devices were remarkably rugged, with only the most excessive leaks affecting the amount of dust collected. Finally, a number of simple tests were developed so that significant air leaks could be detected.