Evaluation of mechanical prototype machines for continuous separation of respirable cotton dust fractions.

The original cotton particulates analyzer used stationary screens to separate aerodynamically the coarse and fine dust fractions from small samples of cotton. By replacing stationary with rotary screens that were continuously cleaned, larger supplies of respirable dust were obtained without interruption. A ginned and a waste cotton were used to test two methods of separation: a rotating 38-micron screen and a tandem rotating 710- or 38- micron screen and cyclone. The fine dust fractions from both systems were captured on filters and examined gravimetrically, by Coulter counter, and scanning electron microscope. The dust passing 38 micron stationary or rotary screens contained particles of 15 micron maximum diameter whereas dust from the 710-gmm rotary screen and tandem cyclone exhibited particles of 10 micron maximum diameter and lint fragments. Dust fractions with particles less than 10 micron diameter and free of lint were obtained with a 38-micron rotary screen and tandem cyclone.