Selecting Appropriate Spray Nozzles for Backpack, ATV and Hand Gun Sprayers
SPRAY NOZZLES ARE AN IMPORTANT PART OF YOUR HERBICIDE APPLICATION PROGRAM. Nozzles meter or regulate flow of the liquid, atomize the liquid stream into droplets, and spread droplets in a specific pattern. There are many different types of nozzles available from manufacturers, and each nozzle can perform differently.
Selecting the proper spray nozzle and operating sprayer pressure within the manufacturer’s recommendation for the specific nozzle is critical to determine:
Amount of herbicide/spray solution applied to an area
Uniformity of the application
Coverage of the herbicide on plant surfaces
Potential for herbicide to drift off-target
Remember that herbicide application, coverage, droplet size, and drift potential* will vary based on sprayer pressure, spray height above the target plant, and application method. Always follow the manufacturer’s recommendations for the nozzles you purchase to achieve optimum performance. (*Drift potential is inversely related to droplet size. As droplet size decreases, drift potential increases.)
Sprayer Calibration is also critical since each herbicide applicator is unique. Click here for guidelines on calibrating backpack, hand gun, and boomless nozzle equipment.
Sprayer Pressure Facts
Increasing the pressure by four times will double the flow rate. For example if nozzle output is 0.5 gallons/minute at 30 psi (pounds per square inch) it would require about 120 psi to get an output of 1 gallon/minute.
Higher pressure decreases droplet size and increases drift potential.
Higher pressure increases orifice wear of the spray nozzle.
Pressure impacts the spray angle and coverage.
If you want to increase your application rate, use a higher output nozzle rather than increase pressure. Always operate the nozzles within pressure recommended by the manufacturer.
Nozzle Nomenclature: What Does the Number Mean?
Most manufacturers code nozzles, and with access to the manufacturer’s guide you can determine the type of nozzle, spray angle, composition, and gallon per minute output at recommended psi. Some manufacturers identify nozzles with a four- or five-digit number designation. The first numbers are the spray angle followed by the discharge rate at a rated pressure. For example, the TeeJet “11004 nozzle” has a 110-degree spray angle and applies 0.4 GPM at the rated pressure of 40 psi (Figure 1).
Additional designations are:
BR = brass material
SS = stainless steel
HS = hardened stainless steel
VP = polymer with color coding
VK = ceramic with color coding
VH = hardened stainless steel with color coding
VS = stainless steel with color coding
Backpack (or ‘can’ type hand-held) Sprayers
Hand operated sprayers are used by applicators for smaller spot applications or in hard-to-reach areas where access is limited to hiking. These sprayers can have single or multiple nozzle systems.
Unfortunately, some hand-held and backpack sprayers come equipped with cheap plastic spray tips that are not durable and may provide a poor spray pattern. Replace these tips with a higher quality tip suited for backpack spraying, such as flat fan or cone nozzles. Some applicators use several nozzles mounted on a small boom attached to a backpack sprayer.
FLAT FAN NOZZLES form a tapered spray pattern with heaviest deposition of the herbicide solution at the center of the pattern and lightest toward the outer edge (Figure 2). Benefits of the standard fan nozzle include lower application pressure, larger droplet size and minimal drift increasing applicator safety. The ideal operating pressure range for standard flat-fan nozzles is between 30 to 40 pounds per square inch (psi). The extended-range flat-fan nozzle provides uniform distribution of a flat-fan nozzle with lower operating pressures (less than 30 psi) for drift control. The off-center fan provides a uniform end-to-end application rather than tapered at the edges. Applications to weed infestations are usually made with a sweeping motion (like painting a car) while walking through an infestation. If several nozzles are mounted on a boom sprayer, they would be positioned so that the spray overlaps. Flat fan and extended range flat fan are rated as “good to very good” for post-emergence weed control with systemic herbicides (e.g. herbicides such as Milestone® herbicide and Transline® herbicide that move throughout the plant).
CONE NOZZLES: Solid cone and adjustable solid cone nozzles are common on hand-held sprayers. These nozzles adjust from solid stream to solid cone and can be used for spot treating individual plants. Application rates may vary considerably depending on nozzle adjustment and sprayer pressure with adjustable cone nozzles. Raindrop hollow cone tips are rated as “good” for post-emergence weed control with systemic herbicides.
Solid stream nozzles are used in handgun sprayers to spray a distant or specific target such as woody plant foliage. Handguns can have adjustable nozzles that apply a medium to coarse spray with high volumes of water under high pressure. Tall vegetation or woody plants that require good coverage of the herbicide solution are often treated with handgun applicators. Additional information on handguns is discussed by herbicide applicators and is available here.
Fixed booms are not practical for most wildland and natural area herbicide applications because of uneven application over rough terrain and obstacles. Boomless nozzles that are mounted on the rear of all-terrain vehicles (ATV) or utility-terrain vehicles (UTV) can be operated to provide an application pattern either left, right or both. These nozzles are particularly well suited for hard-to-reach locations when controlling weeds on wildlands and natural areas. Flat spray and extra wide flat spray patterns are typically used to provide a wide application swath. Boom Buster and Boominator nozzles are commonly used by herbicide applicators. Coverage of the spray solution with boomless nozzles may be variable because the spray pattern is not uniform and spray droplets vary in size from very small to very large. A review of some boomless nozzles is available here.
How Long Will a Nozzle Last?
All nozzles will begin to show wear after long periods of use. The operating life of nozzles will vary based on nozzle composition and the type of solution being sprayed. In general, nozzles made from ceramic, stainless steel and plastics will last longer than brass. Since the price of nozzles vary based on composition, a more expensive nozzle that lasts longer may cost less to operate over the long term. For example, if you normally use brass nozzles and replace them every two years, stainless steel nozzles will be more cost effective since they last 8 to 12 years. When you are replacing nozzles in a sprayer, you may want to consider installing nozzles made from materials that offer a longer accurate operating life especially if spraying corrosive materials such as liquid nitrogen with herbicides.
The following information compares the operating life of nozzles made from various materials compared to those made of brass.
Brass: recommended replacement every two years depending on use
Plastic (high quality): 2 to 3 times longer than brass.
Stainless steel: 4 to 6 times longer than brass
Hardened stainless steel: 10 to 15 times longer than brass
Ceramic: 20 to 50 times longer than brass
Cleaning and Replacing Nozzles
Worn nozzles spray poor patterns and have different output than new nozzles of the same type and size. Nozzle tips are considered excessively worn and should be replaced when their flow exceeds the flow of a new nozzle tip of the same size and type by 10 percent^. Be sure to recalibrate the sprayer when nozzle tips are changed.
Clean removed nozzles, screens and strainers separately with appropriate cleaning solution for the herbicide you are applying (usually 3% solution of ammonia and water for most range and wildland herbicides). For details see TechLine’s article on Cleaning and Winterizing Your Herbicide Sprayer. Use a soft-bristled brush or compressed air for cleaning. Do not use metal objects on the nozzle under any circumstances as this will change the output if the nozzle orifice is damaged. If you are removing nozzles at the end of the season, clean nozzles, strainers, caps and check valves. Store in a dry, secure location and cover or plug the nozzle bodies after removing the hardware.
^After making sure the sprayer is clean, fill approximately half full with water. Use a digital flow calibrator (e.g. http://ohiovalleyag.com/spot-sprayer-calibrator/) or place a graduated container under each nozzle. Set the sprayer pressure within the recommended pressure range and spray into the container for one minute or operate the digital flow calibrator as per instructions. Measure to see that the flow rate is within 10% of that recommended by the nozzle manufacturer. Replace or clean any nozzles as needed.
CONSULT THE LABEL. The most important source of information is the herbicide label. Not only will the label specify the application rates, plants controlled, and conditions needed to apply the herbicide, it may provide information concerning gallons per acre required to optimize control.
CONSULT A NOZZLE CATALOG. Once the nozzle discharge has been determined for the application equipment and invasive plant targets, consult a nozzle catalog for a specific nozzle number or size. It is best to select a nozzle that operates at a low pressure and gives a range of droplet size for “fine-tuning” to meet your desired application needs.
SPRAYER CALIBRATION. Once you have the appropriate nozzle be sure to calibrate your equipment to ensure application success.
Resources and References
Klein RN, Kruger GR. 2011. Nozzles -- Selection and Sizing. University of Nebraska Lincoln Extension, Institute of Agricultural and Natural Resources, publication EC141. http://extensionpublications.unl.edu/assets/pdf/ec141.pdf
TeeJet Technologies. 2013. A Users Guide to Spray Nozzles. http://www.teejet.com/media/40076/user's%20guide%20to%20spray%20nozzles_2013_lo-res-sequential.pdf
Selecting Nozzle Tips and Strainers: Montana State University: Available online at: http://www.pesticides.montana.edu/Reference/SelectingNozzles.pdf
Pesticide Management Education Program, Module 18: Cornell University http://psep.cce.cornell.edu/Tutorials/core-tutorial/module18/index.aspx
Robert “Bobby” Grisso R, Hipkins P, Askew SD, Hipkins L, McCall D. 2013?. Nozzles: Selection and Sizing. Virginia Tech, Virginia State University Extension: Publication 442-032. http://pubs.ext.vt.edu/442/442-032/442-032_pdf.pdf
Pesticides: Safe and Effective Use: Part 4. UC Davis College of Agriculture and Environ. Sci. Online at http://www.slideshare.net/ipoucd/ppt-pcidetrainingcourseucd4
Published 2016; reviewed and updated June 2019
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