Contact: Dr. Milt Teske, Senior Associate, Continuum Dynamics, 34 Lexington Ave., Ewing, NJ 08618  Email: milt@continuum-dynamics.com

 Summary: The release of ASAE standard S-572 enabled the nozzle industry to begin classifying nozzles based on droplet size, with emphasis on the fines which affect drift potential.   The ASAE standard identified the nozzle classifications of Very Fine, Fine, Medium, Coarse, Very Coarse, and Extremely Coarse, and enabled aerial applicators to recognize the influence of nozzle classification on the drift anticipated from the selected nozzle.  This development helped the industry and applicators in responding to the drift issues raised by the Environmental Protection Agency and concerned environmental groups.

 One of the problems with the nozzle classification scheme is the appropriate selection of nozzle type when the drop size distribution crosses classifications, for example, from Medium to Fine.  These crossings, which are fairly common for certain nozzle types and tank mixes, tend to occur as the finer droplet sizes are approached, reflecting the general characteristics of the typical drop size distribution (plotted as droplet size vs. cumulative volume fraction).  Since the prevailing literature and field studies confirm the importance of the finer droplets in contributing to drift, it is imperative that the nozzle classification scheme reflect the true nature and impact of, say, a nozzle classified by the ASAE standard as Medium when the finer portion of the drop size distribution actually crosses into Fine.  This paper will explore the issues consistent with a careful application of the ASAE nozzle standard, particularly the potential inequities in applying what was essentially a classification scheme for ground sprayer nozzles to aerial application nozzles, and the effects of nozzle type and tank mix on classification selection.  The conclusions reached by this study may lead to improvements in the standard itself.

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Note:  A copy of the manuscript for this paper is not available at this time.  Please email the author to receive a copy.  milt@continuum-dynamics.com