ORIENTATION BIAS OF THE ISOLATED 10-MM NYLON CYCLONE AT LOW STREAM-VELOCITY

The current methods of dust compliance in U.S. coal mines use a 10-mm Dorr-Oliver cyclone as a particle preclassifier as both area and perso nal samplers, However, measurement of dust concentrations using this c yclone is in question because of the errors caused by cyclone orientat ion, wind speed, and sampling flow rate. The sampling efficiency of th e 10-mm Dorr-Oliver nylon cyclone was experimentally determined in an open circuit wind tunnel for polydispersed anthracite coal particles u sing an aerodynamic particle sizer and the six-stage impactor. Measure ments were made at a low free stream velocity (U = 1.52 m/sec) for dif ferent sampler orientations and sampling flow rates. Orientation bias was found to be dependent on sampling flow rates. The bias was found t o be maximum at the 0 degrees orientation, followed by 90 degrees and 180 degrees orientations. A negative bias of -51% was found at a sampl ing flow rate of 2.0 L/min. A bias dose to 4% was observed at sampling flow rates of 1.7 and 1.2 L/min. A sampling flow rate of 1.7 L/min wa s found to give the closest agreement with the Comite European de Norm alization/international Organization for Standardization/American Conf erence of Governmental industrial Hygienists (1993) sampling conventio n.