Orientation Bias of the Isolated 10-mm Nylon Cyclone at Low Stream Velocity

Abstract

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 personal samplers. However, measurement of dust concentrations using this cyclone is in question because of the errors caused by cyclone orientation, wind speed, and sampling flow rate. The sampling efficiency of the 10-mm Dorr-Oliver nylon cyclone was experimentally determined in an open circuit wind tunnel for polydispersed anthracite coal particles using an aerodynamic particle sizer and the six-stage impactor. Measurements were made at a low free stream velocity (U=1.52 m/sec) for different sampler orientations and sampling flow rates. Orientation bias was found to be dependent on sampling flow rates. The bias was found to be maximum at the 0° orientation, followed by 90° and 180° orientations. A negative bias of −51% was found at a sampling flow rate of 2.0 L/min. A bias close 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 was found to give the closest agreement with the Comité European de Normalization/International Organization for Standardization/American Conference of Governmental Industrial Hygienists (1993) sampling convention.