\m 24 10 55 2 1 'Sprayer Types and Choosing a Sprayer' \m 71 30 15 3 1 'Sprayer Parts and Their Function' \m 170 74 107 4 1 'Herbicide Application Techniques' \m 171 75 20 4 2 'Broadcast Spraying' \m 232 100 9 5 2 'Band Spraying' \m 265 111 75 6 2 'Post Emergence-Directed Spraying' \m 285 118 60 6 2 'Granular Herbicide Applicators' \m 302 123 68 7 1 'Calibration of Herbicide Applicators' \m 303 123 113 7 2 'Introduction' \m 317 127 74 7 2 'Factors to Consider in Calibration' \m 358 145 66 8 2 'Typical Calibration Problems' \m 359 145 103 8 3 'General Information' \m 373 149 100 8 3 'Selecting Nozzles for a Desired Application Rate' \m 437 170 109 9 3 'Calibrating the Already Nozzled Sprayer' \m 486 188 18 10 1 'Check List Before Field Operation of Sprayers' \m 528 201 24 11 1 'Guide to Field Operation of Sprayers' \m 568 214 125 11 1 'Maintenance, Care and Cleaning of Sprayers' \t'January 1988' 'II-'page \a Richard Cromwell, Extension Agricultural Engineer \a \a APPLICATION EQUIPMENT AND CALIBRATION Richard Cromwell, Extension Agricultural Engineer \h 1 'Sprayer Types and Choosing a Sprayer' APPLICATION EQUIPMENT AND CALIBRATION SPRAYER TYPES AND CHOOSING A SPRAYER SPRAYER TYPES: Herbicides are applied with both sprayers and applicators for applying dry materials, primarily granular materials. Since the majority of the herbicides are applied by sprayers, this type of equipment will be emphasized in this equipment section of the Florida Weed Control Guide. Sprayers used in agriculture are often classified as either low pressure (up to 80 pounds per square inch of pressure) or high pressure (up to 500 psi) types. The primary difference in the two types of sprayers is the type of pump used. A low pressure sprayer is usually equipped with a roller or centrifugal pump, while the high pressure unit would have a positive displacement pump such as a piston pump. CHOOSING A SPRAYER: It would appear that the choice between a cheaper, low pressure sprayer and a more expensive, high pressure sprayer would depend largely on whether the unit is to be used for applying herbicides exclusively, which requires relatively low pressures, or whether the unit would be a multi-purpose sprayer, which could require pressures up to 500 psi. However, sprayers that are to be used for applying herbicides are normally high pressure sprayers because these more expensive sprayers are usually the only units with an agitation system capable of keeping wettable powders in a uniform suspension. Since many herbicides are formulated as wettable powders, good agitation is a primary concern when choosing a herbicide sprayer. The competively priced, low-pressure sprayer with a marginal agitation system is generally useful for low pressure spraying of liquid formulations only, and would seldom be chosen because the equipment would rule out the use of many of the better herbicides formulated as wettable powders. A high-pressure sprayer used to spray herbicides must be capable of getting down into the 20-50 psi pressure range. Manufacturers of some high-pressure sprayers have recognized that their equipment is being used for low as well as high pressure applications, and have provided their sprayers with adequate by-pass capacity so that low pressures can be reached. A high pressure sprayer can be modified so low pressure levels can be used by adding an additional by-pass line equipped with a valve to vary the amount being by-passed back to the tank. \b\v \h 1 'Sprayer Parts and Their Function' \v \v \v SPRAYER PARTS AND THEIR FUNCTION THE PUMP is the heart of the sprayer. The typical boom sprayer consists of a power take-off (PTO) driven pump which has a chain that is secured to keep the pump from turning. As the PTO turns, a partial vacuum is created in the suction line which fills with spray from the tank. The spray is forced through the pressure side of the system by the pump. Three factors to consider in selecting a pump for a sprayer are: 1. CAPACITY - The pump must have enough capacity to supply the boom output and to provide for adequate agitation when hydraulic agitation is used. The amount of flow needed for good agitation depends on the size and shape of the sprayer tank and it is difficult to give general guidelines for determining the flow needed for agitation. Pump capacities are given in gallons per minute or per hour. 2. PRESSURE - The pump must be able to operate at the pressure needed for properly applying the spray applications to be done. Pressure is measured in pounds per square inch (psi). 3. RESISTANCE TO CORROSION AND WEAR - The pump must be able to handle the chemical spray materials without excessive corrosion or wear. THE SPRAYER TANK should be of corrosion-resistant metals or fiberglass. The tank should have a large opening to allow for easy filling plus a drain to facilitate cleaning. AGITATION of spray mixtures is normally achieved by a hydraulic jet agitator or by a mechanical agitator which usually consists of paddles mounted on a rotating shaft. Generally, a mechanical agitator is the best type of agitation, but it is expensive to make. Relatively inexpensive sprayers are seldomly equipped with mechanical agitation. Jet agitators can keep pesticide materials in suspension, if they are properly designed. The line supplying the agitator must be connected into the pressure side of the spray system. The pump must have enough capacity to provide the flow to both the nozzles applying the spray and the orifices of the hydraulic agitator. Many inexpensive sprayers rely on the by-pass flow from the pressure regulator to provide agitation. This arrangement might be sufficient when using liquid and soluble powder formulations which require little or no agitation to maintain a uniform mixture, but by-pass agitation is totally inadequate for applying wettable powder formulations because they will settle out. The portion of this guide on Calibration explains how to determine a sprayer's application rate in gallons per acre in order to apply the recommended amount of pesticide to each acre. Careful calibration is of questionable value, if the spray is not uniformly mixed. Just because a sprayer is delivering a uniform rate per acre of spray mixture does not mean that the pesticide is being applied uniformly. Uniform application of pesticides can only be achieved when each volume of spray has a uniform amount of pesticide mixed with it. Achieving this uniform mixture is the function of the agitator, so its importance cannot be overemphasized. THE PRESSURE REGULATOR has two functions. One is to regulate the system pressure by allowing some of the pump output to escape back to the tank through its variable opening. The other is to relieve excess pressure when the shut-off valves are closed. \v \bTHE PRESSURE GAGE should be located where the sprayer operator can easily check the system pressure. A gage should be easy to read and the pressure range should be appropriate for the pressures being used. A gage with a maximum reading of 100 psi is adequate for sprayers equipped with most roller pumps. A sprayer that has a high pressure pump, but is often used for low pressure work, should have two gages one reading up to 100 psi and the other up to approximately 500 psi. The low pressure gage would be isolated from the system when high pressures were being used. FLOW CUT-OFF VALVE - A quick acting valve should be placed between the pressure regulator and the boom to control the flow of spray materials. One valve may be used to cut off the entire flow, or a combination of two or three valves may be used to control the flow in two or more sections of the boom. Also available is a special selector valve which will control the flow of spray to any section or combination of sections of the boom. ALL HOSES AND FITTINGS should be of quality and strength required to handle the chemicals and operating pressures. A good hose is flexible, durable, and resistant to sunlight, oil, chemicals, and the general abuse given a hose during sprayer use. STRAINERS are needed to keep foreign matter from plugging the sprayer nozzles. The primary types of strainers are the slit and the wire mesh. Probably the most widely used wire mesh strainer has a 50-mesh screen. The 50-mesh screen will screen out most trouble making particles while still allowing wettable powders to pass through. NOZZLES are available with male or female connections and may be of metal, nylon, or ceramic materials. They are designed to develop various spray patterns, rates of discharge and angle of spray. Manufacturers usually calibrate their nozzles and number them according to the angle of the spray pattern and the flow at a given pressure. All nozzle manufacturers do not use the same system for designating nozzles, but they do have performance charts which give the information needed to choose the correct nozzles. The nozzle tips of most manufacturers are of the same diameter and can be interchanged. \h 1 'Herbicide Application Techniques' \h 2 'Broadcast Spraying' HERBICIDE APPLICATION TECHNIQUES Broadcast Spraying When applying a broadcast application the full width of the sprayer swath is treated with the herbicide. Fan spray, wide angle fan spray, and boomless spray nozzles are all used to apply broadcast applications. These are discussed below. FAN SPRAY NOZZLES: Fan nozzles have various pattern angles, and the correct nozzle tip height above the surface to be treated depends on the pattern angle of the nozzle being used. The following information indicates the correct height of the boom tip for various angle fan nozzles when located on 20" spacing on the boom (a common spacing for boom nozzles): \b Pattern Angle (degrees) Nozzle Tip Height (inches) 65 21 to 23 73 20 to 22 80 17 to 19 Fan spray nozzle patterns overlap at the edges, but since the pattern width narrows down in the overlapped zone the application is uniform. The primary reason for overlapping the nozzle patterns at the edge is to avoid skips due to the boom dipping lower than the ideal height which is unavoidable when spraying in the field. The distribution of spray from tapered edge nozzles and even spray nozzles would be uniform as long as the nozzle tip was at the appropriate height. If the boom and the nozzle tips dip in height, the application rate in between the two tapered fan nozzles would diminish, but there would be an unsprayed skip between the two even spray nozzles. WIDE ANGLE FAN NOZZLES: These nozzles are designed to produce a pattern that is in the 115 to 150 degree range. Since the pattern is so wide, reasonably uniform distribution is obtained when the nozzles are spaced 40" apart and the nozzle tip is 13" above the surface to be sprayed. The coarse spray produced by this nozzle type and the low tip height would help minimize drift making this nozzle a good choice for herbicide work. BOOMLESS BROADCAST SPRAYING: A cluster of nozzles or a single special nozzle is used to cover a wide swath. These units cost less, have fewer nozzles to maintain, and are well adapted for use on rough terrain. The cluster type is often used to spray fence rows. Usually one side of the unit is closed off with blanks so it will spray in one direction when treating fence rows. Disadvantages of the boomless sprayer are (1) uniformity of distribution across the swath is not as good as with a boom, (2) spray materials penetrate the crop by gravity alone, while a boom-type sprayer forces the materials into the plant foliage, and (3) the pattern is easily distorted by wind. The best method to obtain even coverage with a boomless sprayer is to double cover the area by overlapping half of the previously sprayed swath. Since the effective swath of the sprayer is only 1/2 of its apparent swath when double covering, the spray mixture would be only 1/2 as concentrated as it would be when single coverage was applied. \h 2 'Band Spraying' Band Spraying To conserve spray materials and get effective control of weeds in row crops such as corn and soybeans, certain herbicides can be applied as a band centered on the row at planting time. The spray nozzles are usually mounted on a special bracket behind the planter press wheel. Application after the crop is planted means an extra operation, makes it difficult to center the band over the row, and introduces a chance of rain preventing treatment before the crop emerges. \bBand spraying is done with even spray nozzles in order to get uniform coverage across the full band width. Even spray nozzles tips come in at least two pattern angles, 80 and 95 degrees. The band width sprayed depends on the pattern angle and the height of the nozzle tip above the ground. The following indicates the nozzle tip heights needed to apply various band widths: ------------------------------------------------------- Approximate Height (inches) for Band Width 80 degree nozzles 95 degree nozzles ------------------------------------------------------- 8" 5 4 10" 6 5 12" 7 6 14" 8 7 ------------------------------------------------------- \h 2 'Post Emergence-Directed Spraying' Post Emergence-Directed Spraying This method of spraying is used to apply herbicides to young weeds in a crop than can withstand the herbicide on its lower, more mature portions, but not on its green tender portions. Usually special skids are used to carry the spray nozzles at a constant height above the ground to insure against getting the spray on the tender portions of the crop. Nozzles, used to apply directed sprays are sometimes mounted on cultivators in order to get a precisely applied spray without the expense of the skids. Using nozzle drops to get the nozzles down below the tender portions of the crop is not recommended. The sprayer boom bounces around under the best of field conditions, and the herbicide damage to the crop will be excessive when using this technique. \h 2 'Granular Herbicide Applicators' Granular Herbicide Applicators Granular herbicide formulations are applied broadcast across the full width of the field or in bands. The equipment for broadcasting herbicide granules is essentially the same type of spreaders used to apply granular fertilizers. The two most common designs are the centrifugal spreader and the gravity flow spreader. Equipment for applying herbicide granules in a band along the crop row is available from several manufacturers. These units usually have a separate granule hopper for each row and are mounted on the planter. \b \h 1 'Calibration of Herbicide Applicators' \h 2 'Introduction' \v \v \v CALIBRATION OF HERBICIDE APPLICATORS Introduction Herbicides are usually recommended at certain rates per acre. In order to apply a herbicide correctly the application rate, in gallons per acre or pounds per acre, of the applicator must be determined. Since most herbicides are applied as sprays, this treatment of calibration is directed specifically toward spraying. \h 2 'Factors to Consider in Calibration' Factors to Consider in Calibration The amount of liquid that a sprayer applies to a given area can be varied by changing one or more of the following: (1) pressure that forces liquid through the nozzle tip, (2) nozzle orifice (tip opening) size, (3) sprayer ground speed, and/or (4) spacing of nozzles on the boom or width of spray pattern. 1. PRESSURE - Adjusting the nozzle pressure is a good way to make small changes in sprayer output. Increasing the pressure will increase the nozzle output, but the increase is only proportional to the square root of the pressure increase (e.g. the pressure would have to be increased four times to double the output of the nozzle). Since herbicide spraying should be done in a pressure range of 20 to 50 psi, it is obvious that only minor changes in nozzle flow can be achieved by varying the pressure. Low pressures are recommended for herbicide spraying in order to reduce the drift potential of the spray. 2. NOZZLE ORIFICE - Large changes in spray output are made by changing the nozzles. Nozzles are rated as to capacity in gallons per minute at a certain pressure. Manufacturers' data sheets give the discharge of various nozzles at different pressures. This information should be used when selecting the nozzle for a sprayer to apply the desired rate at a selected tractor speed and operating pressure. After selecting the nozzles it is often necessary to make small adjustments in the pressure during calibration to get the exact gallons per acre desired. 3. SPRAYER GROUND SPEED - The speed of the tractor while spraying is generally governed by the terrain, safety or by some tillage operation that is being done at the same time as the spraying. Proper nozzles should be used to get the desired application rate for the speed best suited to the tillage operation or field conditions. 4. SPACING OF NOZZLES - The amount of spray depends on the number of nozzles per row or on the boom. The application rate in a band treated area decreases with a given nozzle as the band width increases. \b \h 2 'Typical Calibration Problems' \h 3 'General Information' \v \v \v Typical Calibration Problems General Information: There are two primary types of calibration problems encountered by an applicator of herbicides. One type of problem is where a given application rate is to be applied and the sprayer must be nozzled in order to achieve the desired rate. The other type is where the sprayer is already nozzled and its application rate must be determined. This section discusses both situations. \h 3 'Selecting Nozzles for a Desired Application Rate' Selecting Nozzles for a Desired Application Rate: The simplest method to demonstrate how problems of this type are solved is with a typical example as shown below. EXAMPLE: A grower has a boom sprayer 30 feet long that has 18 nozzles spaced on 20" centers. The grower wishes to broadcast a herbicide in a pasture at an application rate of 15 gallons per acre. Field conditions dictate a tractor speed of 6 mph. What size nozzles should be selected, if the sprayer pressure used is 30 psi? STEP 1: Write the basic equation which is applicable for any type of calibration problem. GPM Gal/acre = ------------ acres/min In this problem the Gal/acre or GPA was given as 15, so the GPM needed in order to be applying 15 GPA can be determined, if the acres per minute being treated are known. STEP 2: Determine acres per minute. 2 x Swath(ft) x Speed(mph) Acres/min = -------------------------- 1000 The swath is 30 feet and the speed is 6 mph. 2 x 30 x 6 360 Acres/min = ---------- = ---- = 0.36 1000 1000 STEP 3: Determine the GPM required to have an application rate of 15 GPA when treating 0.36 acres per minute. GPM = GPA x Acres/min = 15 x 0.36 = 5.4 \bSTEP 4: Determine the nozzle capacity needed. The capacity rating per nozzle at 30 psi is: Total GPM 5.4 GPM/nozzle at 30 psi = ----------------- = --- = 0.3 Number of nozzles 18 A nozzle would be selected from the nozzle manufacturer's catalogs that delivers close to 0.3 GPM when operating at 30 psi. After selecting the nozzle and nozzling the boom, the grower should conduct a calibration test like that outlined in the neighboring section 'Calibrating the Already Nozzled Sprayer' because many factors tend to make the flow different from what was determined mathematically. Spraying materials more viscous than water (the catalogs are based on spraying water), and having less pressure at the nozzle than shown at the gage due to friction loss tend to make the nozzle flow less than figured. Installing previously used, worn nozzles tend to make the flow greater than figured because the catalog performance data is based on new orifices. \h 3 'Calibrating the Already Nozzled Sprayer' Calibrating the Already Nozzled Sprayer - The Tank Refill Method: 1. Set two stakes, 330 feet apart, in a field that is typical of the field or fields to be sprayed. The sprayer is to be operated through one round trip between these stakes, or a distance of 660 feet. 2. Partially fill the sprayer tank with water. 3. Operate the sprayer unit to see that all of the parts are operating prop- erly and adjust the pressure regulator to achieve the desired pressure with the engine turning at the RPM to be used while spraying. Shut off the sprayer. 4. Fill the sprayer tank full or to some measurable point with water. A measuring stick or gage on the tank may be used if the water is likely to splash out of the tank as the unit moves. 5. Beginning 20 to 30 feet from the first stake, drive the tractor toward this stake at the desired speed with the sprayer cut-off valve closed. 6. Upon passing the first stake, open the cut-off valve or turn the sprayer "on" for spraying. 7. Upon passing the second stake, turn off the sprayer, and turn the unit around. Spray the course again on the return trip. Be sure to maintain uniform speed and pressure throughout the course. 8. Measure, to the nearest quart, the amount of water required to refill the tank or to restore the original level. When refilling, be sure that the sprayer is in the same location as for the first filling or is resting level in both instances to avoid possible error. \b9. Determine application rate by use of the following equation: Gallons to refill tank x 66 GPA = --------------------------- Spray Width (feet) 10. Add the recommended amount of chemical to the sprayer tank. The amount is dictated by the application rate (gal/acre) determined by calibration and the volume of spray in the tank. For example, if the chemical manufacturer or other authority recommends 2 pounds of chemicals per acre and you are applying 25 gallons of water per acre, add 2 pounds of chemicals to every 25 gallons of water to make up the spray mixture for the sprayer. \h 1 'Check List Before Field Operation of Sprayers' CHECK LIST BEFORE FIELD OPERATION OF SPRAYERS Attaching the sprayer to the tractor, making sure it is properly mounted, and visually checking all components is far too often the only preparation given a sprayer prior to calibration or field operation. A little time and effort spent at this time will insure a more effective and trouble-free spray operation. 1. Clean the supply tank, and fill it with clean water. Silt or sand particles will cause excessive wear of pump and nozzles and clogging of screens. 2. Clean suction and line strainer. 3. Remove all nozzle tips, nozzle strainers, and boom endcaps. 4. Start the sprayer, and flush the hoses and boom with plenty of clean water. 5. Inspect nozzle tips and strainers for defects and cleanliness, and make sure all tips are same type and size. Mixed nozzle tips along the boom will give uneven spray distribution. 6. Replace the nozzles and strainers, and check for proper operation and alignment. 7. Check all connections for leaks. 8. Adjust the pressure regulator to desired operating pressure. Operate sprayer with water, and check nozzle discharge for uniformity. This can be done by placing containers under each nozzle, operating sprayer for a few minutes, and then checking to see if the same amount of water is in each container. This will detect worn, defective, or incorrect nozzles. 9. Calibrate sprayer if necessary. Check calibration figures. 10. Add chemical to tank in correct ratio for desired rate of application. \b \h 1 'Guide to Field Operation of Sprayers' \v \v \v GUIDE TO FIELD OPERATION OF SPRAYERS The following information should be used as a guide for operating a sprayer in the field: 1. Check wind. Excessive wind will affect the uniformity of spray application. 2. Operate the tractor at a uniform speed. This must be the same speed and gear that were used in calibrating the sprayer. 3. Strive to keep the spray boom parallel to surface sprayed. 4. Maintain proper height of boom. The height of the nozzle above the spray surface determines the width of the spray pattern at the surface. On a boom sprayer, with nozzles spaced for complete broadcast coverage, the nozzle must be at the correct height to obtain uniform coverage across the boom width. Manufacturers' data sheets list the correct height for each type nozzle. 5. Make regular observations of the operation pressure while spraying. Maintain pressure as determined by calibration. 6. Observe nozzle patterns continuously to detect clogged nozzles or nozzle position changes that might arise. Clogged nozzles or nozzle strainers are common problems affecting spray distribution. By using only clean water, selecting and using proper nozzle strainers, and cleaning nozzles and strainers daily, this problem will be reduced to a minimum. A toothbrush is excellent for cleaning nozzles. 7. Stop the pump immediately when the liquid is gone. Pumps can be seriously damaged when operated dry. 8. Always completely flush the entire system with clean water after completing the spraying job. With some spray materials the system should be cleaned every night. \h 1 'Maintenance, Care and Cleaning of Sprayers' MAINTENANCE, CARE AND CLEANING OF SPRAYERS The owner's instruction manual, furnished by the sprayer manufacturer, is a good reference and guide to operation, care, and maintenance of a sprayer. All owners should have a manual for their sprayer, should study it thoroughly, and keep it for future reference. Sprayer pump and nozzle wear, caused by the abrasive particles in the spray material, or water and sprayer deterioration from chemical corrosive action are the most costly maintenance problems affecting sprayers. The wear can be held to a minimum by always using clean water for the spray mixture, using care in selecting less abrasive spray materials, making sure the spray \bchemicals and water have been well mixed before starting the pump, keeping the proper strainers in place at all times, and never operating the pump without liquid in the tank. Corrosion can be reduced by thoroughly cleaning the sprayer after each period of use. An ordinary field sprayer should never be used for applying liquid fertilizers because these fertilizers are very corrosive to metals other than stainless steel. Before storage at the end of the season, and after thoroughly cleaning the sprayer, run a few gallons of fuel oil through the sprayer to help prevent rust. Store nozzle tips and all strainers in a can of light machine oil. Gear and piston pumps should be filled with oil. Roller and diaphragm pumps should be flushed with rust inhibitor, and then all openings should be capped. Herbicide sprayers should be thoroughly washed and cleaned after each use. The sprayer should first be flushed with water, then cleaned with ONE of the following materials in 50 gallons of water by flushing the mixture through the sprayer: 1. 1/2 gallon of household ammonia (let stand in sprayer overnight) 2. 4 pounds trisodium phosphate cleaner 3. 2 1/2 pounds sal soda 4. 2 pounds activated charcoal (leave in sprayer and lines 10 minutes) NOTE: To remove traces of herbicides that have an oil base, such as the ester formulations of 2,4-D, rinse the sprayer with kerosene before rinsing it with water and using the cleaners. As a rule, sprayers used with chemicals to kill weeds should not be used in spraying chemicals for insects or diseases on extremely susceptible crops. The risk of damage to such crops is too great.