Closed Chemical Transfer Systems
Current pesticides are more potent than the pesticides manufactured even only 10 or 15 years ago, requiring more care when handling pesticides. The major source of water contamination by pesticides is spills that occur during mixing and transport of pesticides. Although closed chemical transfer systems are not required in the United States, they are becoming standard equipment on most of the currently manufactured sprayers because they reduce the risk of operator exposure to pesticides, and lessen the risk of contaminating the environment. Using closed transfer systems, an operator can automatically meter only the desired portion of liquid product and load it to the spray tank, and can automatically rinse empty containers and the interior of the sprayer tank.
Nozzles! Nozzles! More Nozzles!
Several recent developments have been aimed at modifying existing equipment to increase deposition efficiency of the more effective small droplets while reducing the potential for drift. In general, this has been accomplished by using new nozzles/atomizers, air-assist technology, or some kind of shield or shroud to overcome the drift-producing air currents and turbulence that occur around the nozzle during spraying. Here is a look at some of the new nozzles designed mostly for reducing the number of small, drift-prone droplets.
Low-Drift Nozzles
Almost all major agricultural nozzle manufacturers have recently introduced their version of so called Low-Drift nozzles (Figure 1). These nozzles are designed to create larger droplets at the same flow rate and operating pressure than comparable standard flat-fan (SFF) nozzles. This has been accomplished by adding a pre-orifice to the nozzle tip assembly just ahead of the conventional discharge orifice.
Liquid input
Discharge
Fig.1. Low-drift Nozzle Tip (Source: Spraying Systems Co.)
SFF tips have straight bore that carries liquid from boom to the tip. With these new low-drift nozzles, liquid enters through a small orifice and flows into a pocket machined into the nozzle body. The liquid then flows from this chamber into a short passage and out of the discharge orifice. The pre-orifice reduces liquid velocity creating larger droplets to reduce drift significantly. According to one of the manufacturers of these nozzles, their low-drift nozzle tips reduce the number of droplets smaller than 200 m by 50 to 80 percent.
Turbo TeeJet Nozzle
Spraying Systems Co. has introduced a new flat-fan nozzle (Turbo TeeJet) that can be used for the same purposes as a standard flat-fan (SFF) nozzle. The advantages of the new Turbo TeeJet nozzles are twofold: they can be operated at a wider range of pressures (30 to 60 psi with SFF vs. 15 to 90 psi with Turbo TeeJet), and they produce fewer drift-prone droplets compared to the same size of a SFF.
Liquid inlet
Discharge
Fig. 2. Turbo TeeJet Nozzle (Spraying Systems Co.)
A hybrid between SFF spray tips and clog-free flooding nozzles, Turbo TeeJet has a pre-orifice at the tip that slows liquid velocity. The resulting larger droplets are less likely to drift but still provide good coverage with a uniform spray pattern. These nozzle tips fit in standard Quick TeeJet flat-fan nozzle caps as well as threaded caps, and are available in 0.1 to 0.5 gal/min capacities.
Turbo Flood Nozzle
Turbo Flood nozzles introduced by Spraying Systems Co., combines the precision and uniformity of flat spray nozzles with the clog-resistance and wide angle pattern of flooding nozzles (Figure 3).
Fig. 3. Turbo FloodJet nozzle tip (Spraying Systems Co.)
The major design difference between the new Turbo Flood nozzles and the conventional flood nozzles are a pre-orifice at the point of liquid entrance to the nozzle, and a turbulence chamber at the exit point. This new design has resulted in more uniform droplet sizes and improvement in pattern uniformity over existing flooding nozzle designs. At common operating pressures, Turbo FloodJet nozzles produce droplets that are 30 to 50% larger than those produced by standard flooding nozzle tips.
In addition to improvement in droplet size, Turbo FloodJet tips provide a better spray pattern than conventional flood tips. This is shown below.
| Conventional Flood | Turbo FloodJet |
|---|---|
Pattern for 1 TK-4 at 25 psi
|
Pattern for 1 TF-4 at 25 psi
|
| Spray pattern for boom TK-4 30 psi, 30 inch spacing, 20 inch spray height 
|
Spray pattern for boom TF-4 30 psi, 30 inch spacing, 20 inch spray height 
|
TurboDrop Nozzle
These nozzles were originally manufactured in Germany by Agrotop Company and distributed in the US by Greanleaf Technologies (Covington, Louisiana). The TurboDrop nozzles are designed to produce larger droplets while reducing the percentage of fine droplets. As with other low-drift nozzles, TurboDrop nozzles have a pre-orifice ahead of the exit orifice to reduce the pressure exerted on the liquid at the point of discharge (Figure 4). The lower part of this nozzle represents a typical standard flat- fan nozzle set up. The top part of the nozzle contains a pressure reduction chamber with a narrow port used to draw air into this pressure chamber. The flow rate is controlled by a ceramic orifice plate located at the bottom of the first section. As the liquid passes through the orifice plate, as a result of the pressure drop created by this venturi, air is sucked into the nozzle body. In the mixing chamber, air and spray solutions are blended much like a water aspirator. As the liquid is discharged from the nozzle tip, droplets filled with air are produced. The exit nozzle does not control the output rate, but rather forms the desired pattern. Therefore, a standard flat-fan tip with a larger orifice can be used to produce larger droplets. Upon leaving the nozzle orifice, the air included in the nozzle expands, which makes the size of droplets somewhat larger and causes an increase in velocity of droplets. In addition to the large droplets, having a higher velocity on the nozzles further improves the chances the droplet will reach the target before becoming subject to drift. Another benefit mentioned by the manufacturers of this nozzle is that the large droplets shatter and splatter on contact, causing the small air-filled drops to spread out on the target for better coverage. According to its manufacturers, TurboDrop reduces the drift of small droplets considerably. (See next issue of the newsletter for droplet size data on TurboDrop nozzles).
Fig. 4. TurboDrop Nozzle (Greenleaf Technologies)
The "CP" Nozzle
The CP nozzles are designed to bring convenience to the commercial applicators who use various sizes of flood nozzles as they go from one field to another.
The atomizer consists of an orifice plate, which contains various sizes of holes (orifices), and a curved, circular deflection plate, which provides a spray pattern similar to the pattern produced by the "Flood-fan" nozzles (Figure 5).
Fig. 5. CP Nozzle
By simply dialing in the desired orifice, the applicator can choose the flow rate desired without changing the tips. These nozzles have been used by the aerial applicators for a long time. Currently the manufacturer (CP Products, Mesa, Arizona) has produced similar nozzles for ground applicators. Depending on the orifice selected, this nozzle can provide application rates ranging from 2.5 to 10 gal/min. For best results, this nozzle body should be mounted on the boom 0 to 30 degrees above the horizontal pointed opposite to the travel direction.
Classification is coming to USA!
Pesticide applicators in the United Kingdom have been using a nozzle classification scheme since 1986. This will reach farms in the United States as early as next year.
Droplet size plays a major role in creation of spray drift and efficacy of a pesticide. Several product labels already direct applicators to choose nozzles that produce certain size droplets. Unfortunately, it is not easy to look at nozzle catalogs and immediately identify a nozzle that will meet that criterion.
The British classification scheme classifies nozzles based on relative droplet sizes into five categories: very fine, fine, medium, coarse, and very coarse. The American Society of Agricultural Engineer-- working with nozzle manufacturers, regulators, and the Spray Drift Task Force-- has determined that it would be best to determine some general droplet size categories first, then specify which nozzles would fall into each category under different nozzle operating conditions.
This classification system would allow applicators more flexibility in selecting nozzle type, size, and pressure as they wish -- as long as the combination they selected produces the droplet size that falls within the specified category. While a system of nozzle classification has not yet been fully developed and is not in effect yet in the United States, it likely will be in the next several years.
Disclaimer
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Return to CAT News Homepage