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MODIFICATION AND CHARACTERIZATION OF DRY MATERIAL FEEDER FOR DELIVERY OF RED AND VIOLET DYE MIXTURES
Citation:
Higuchi, M. AND W. Stienhagen. MODIFICATION AND CHARACTERIZATION OF DRY MATERIAL FEEDER FOR DELIVERY OF RED AND VIOLET DYE MIXTURES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-91/112.
Description:
Uniform delivery of dry material for stable concentrations of aerosols in inhalation exposure chambers is essential in inhalation experiments. his paper characterizes an AccuRate dry material feeder with modifications, for different helix sizes, actuation rates, nozzle types and dye mixtures. he basic design of the AccuRate dry material feeder used to deliver precise quantities of dye mixtures is inadequate for aerosol exposure research (Cheng et al., 1985). o improve delivery, a "push-pull" type solenoid was mounted to the feeder and connected to a microprocessor controlled timer for actuation. ithout the actuator, the coefficient of variability increased with smaller size helixes and reached 35, 34 and 121% for 1/2", 3/8", and 1/4" helixes, respectively. ith the actuator, the coefficient of variability was reduced to 2.5, 4.8 and 8.8% for the same helix sizes and red dye mixture. he optimum actuation rate was determined to be 90 cycles/min. he use of the stainless steel nozzle improved feed rates by presumably limiting any additional amount of electrostatic charge on dye particles. his may be demonstrated when a polyvinyl nozzle with 3/8" helix, using red dye mixture has a coefficient of variability of 10.2% compared to 2.8% for a stainless steel nozzle. ur modification, addition of actuator with rate of 90 cycles/min to the AccuRate feeder greatly decreased the amount of variability in feed rates for all helixes and dye mixtures, while increasing the dye flow rates. his modification is recommended when dry material characteristics are such that accuracy and recision of feed rates cannot be optimized.