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San Antonio, TX, United States

Fritz B.K.,Texas A&M University | Hoffmann W.C.,Texas A&M University | Czaczyk Z.,Texas A&M University | Bagley W.,Wilbur Ellis | And 2 more authors.
Journal of Plant Protection Research | Year: 2012

An increasing number of spray nozzle and agrochemical manufacturers are incorporating droplet size measurements into both research and development. Each laboratory invariably has their own sampling setup and procedures. This is particularly true about measurement distance from the nozzle and concurrent airflow velocities. Both have been shown to significantly impact results from laser diffraction instruments. These differences can be overcome through the use of standardized reference nozzles and relative spray classification categories. Sets of references nozzles, which defined a set of classification category thresholds, were evaluated for droplet size under three concurrent air flow velocities (0.7, 3.1 and 6.7 m/s). There were significant, though numerically small, differences in the droplet size data between identical reference nozzles. The resulting droplet size data were used to categorize a number of additional spray nozzles at multiple pressure and air flow velocities. This was done to determine if similar classifications were given across the different airspeeds. Generally, droplet size classifications agreed for all airspeeds, with the few that did not, only differing by one category. When reporting droplet size data, it is critical that data generated from a set of reference nozzles also be presented as a means of providing a relative frame of reference. Source

Fritz B.K.,U.S. Department of Agriculture | Hoffmann W.C.,U.S. Department of Agriculture | Bagley W.E.,Wilbur Ellis | Kruger G.R.,University of Nebraska - Lincoln | And 2 more authors.
Atomization and Sprays | Year: 2014

With a number of new spray testing laboratories going into operation and each gearing up to measure spray atomization from agricultural spray nozzles using laser diffraction, establishing and following a set of scientific standard procedures is crucial to long-term data generation and standardization across the industry. It has long been recognized that while offering ease of use as compared to other methods, laser diffraction measurements do not account for measurement bias effects due to differ-ential velocities between differing sized spray droplets, and in many cases significantly overestimate the fine droplet portion of the spray. Droplet sizes and velocities were measured for three agricul-tural flat fan nozzles (8002, 8008, and 6510) each at three spray pressures (138, 276, and 414 kPa) at four downstream distances (15.2, 30.5, 45.7, and 76.2 cm) across a range of concurrent air velocities (0.7-80.5 m/s). At air velocities below 6.7 m/s, large gradients in droplet velocities resulted in over-estimation of both the 10% volume diameter (Dv0:1) by more than 10% and the percent volume of the spray less than 100 m (V<100) was overestimated two-to three-fold. The optimal measurement dis-tance to reduce droplet measurement bias to less than 5% was found to be 30.5 cm with a concurrent air velocity of 6.7 m/s for measuring droplet size from ground nozzles. For aerial spray nozzles, the optimal distance was 45.7 cm. Use of these methods provides for more accurate droplet size data for use in efficacy testing and drift assessments, and significantly increases inter-lab reproducibility. © 2014 by Begell House, Inc. Source

Fritz B.K.,U.S. Department of Agriculture | Clint Hoffmann W.,U.S. Department of Agriculture | Birchfield N.B.,U.S. Environmental Protection Agency | Ellenberger J.,U.S. Environmental Protection Agency | And 4 more authors.
Journal of ASTM International | Year: 2010

The EPA's proposed test plan for the validation testing of pesticide spray drift reduction technologies (DRTs) for row and field crops, focusing on the evaluation of ground application systems using the low-speed wind tunnel measurements and dispersion modeling, was evaluated. Relative drift reduction potential for a given DRT tested in a low-speed wind tunnel is derived from airborne droplet size measurements and airborne and deposited liquid volume measurements downwind from the spray nozzle. Measurements of droplet size and deposition data were made in a low-speed wind tunnel using standard reference nozzles. A blank emulsifiable concentration spray was applied at two different wind speeds. The wind tunnel dispersion (WTDISP) model was used to evaluate the drift potentials of each spray using the droplet size and spray flux measured in the wind tunnel. The specific objectives were [1] the evaluation of model accuracy by comparison of modeled downwind deposition to that measured in the wind tunnel, [2] the evaluation of drift reduction potential of the spray nozzles relative to a reference nozzle, and [3] the determination of low-speed wind tunnel data collection requirements for model input to optimize the evaluation process. The modeled deposition data did not compare well to the measured deposition data, but this was expected as the model was not meant to be used for this purpose. The tested nozzles were rated using the International Standards Organization drift classification standard. The drift ratings generally showed trends of larger droplet producing nozzles having greater drift reduction ratings. An examination of several scenarios using reduced model input requirements, which would decrease the low-speed wind tunnel data collection time, did not show any conclusive results. They suggest that further testing and refinement of the data collection process and the WTDISP model may support wider use of this system for the assessment of DRTs. Copyright © 2010 by ASTM International. Source

Fritz B.K.,U.S. Department of Agriculture | Hoffmann W.C.,U.S. Department of Agriculture | Bagley W.E.,Wilbur Ellis | Kruger G.R.,University of Nebraska - Lincoln | And 2 more authors.
Pesticide Formulation and Delivery Systems: 33rd Volume, | Year: 2014

Droplet size is critical in maximizing pesticide efficacy and mitigating off-target movement. The correct selection and adjustment of nozzles and application equipment, as well as the use of adjuvants, can aid in this process. However, in aerial applications air shear tends to be the dominant factor influencing spray droplet size. The objective of this work was to take a step-wise approach to examine the influence of both adjuvant type and airspeed on droplet size in the presence of a formulated glyphosate product. Although the results show that the spray adjuvants tested did play a role in determining droplet size, as airspeed increased the differences between droplet sizes resulting from the use of the adjuvants tested decreased. A number of the adjuvant-nozzle-airspeed combinations tested did not necessarily increase droplet size or reduce fines, but this does not indicate that they do not have a place in aerial application. Other benefits that could not be measured as part of this study, such as retention and reduced evaporation, can also be critical to an application's success. For any pesticide application, applicators should read and follow product label instructions while being cognizant that the decisions they make, whether they are about nozzle selection or products, will affect droplet size. Copyright © 2014 by ASTM International. Source

Henry R.S.,University of Nebraska - Lincoln | Kruger G.R.,University of Nebraska - Lincoln | Fritz B.K.,U.S. Department of Agriculture | Hoffmann W.C.,U.S. Department of Agriculture | Bagley W.E.,Wilbur Ellis
Pesticide Formulation and Delivery Systems: 33rd Volume, | Year: 2014

Analysis of droplet size data using laser diffraction allows for quick and easy assessment of droplet size for agricultural spray nozzles and pesticides; however, operation and setup of the instrument and test system can potentially influence the accuracy of the data. One of the factors is the orientation of the spray plume relative to the laser beam. The common practice is to orientate the nozzle such that the nozzle orifice's long axis is 90 degrees from the laser beam. Some wind tunnels are designed in a manner such that the spray plume impinges with the walls or the design of the nozzle may necessitate a deviation from this standard practice to obtain a measurement in some situations. The objective of this research was to determine the influence spray plume orientation had on measured droplet size spectra in a low-speed wind tunnel. The orientation of the nozzle tested was 45, 60, 75, and 90 degrees in rotation relative to the laser beam. Four nozzles (AIXR11005, AI11005, TT11005, and XR11005) were evaluated using three different spray solutions. Treatments were evaluated using a laser diffraction system. The results indicate that spray plume orientation does not have an effect on droplet size data for these nozzles, regardless of spray solution. The data from these tests will aid in the standardization of laser diffraction use in low-speed wind tunnels and increase the repeatability of measurements between different spray testing laboratories. Copyright © 2014 by ASTM International. Source

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