The Bugwood Network

Forest Pest Control

Douce, G.K., Moorhead, D.J., and Bargeron, C.T., Forest Pest Control, The University of Georgia, College of Agricultural and Environmental Sciences, Special Bulletin 16, Revised January 2002.

Appendix

Sprayer Calibration

Calibration determines the amount of material applied per acre within the area to be covered. By knowing the amount of material applied per acre, the rate of pesticide can be dispersed according to label directions. Calibrate with clean water when applying toxic pesticides that will be mixed with large volumes of water. When applying liquid materials, check uniformity of nozzle output across the boom or band. Collect spray from each nozzle for a known time period. Each nozzle should be within 10 percent of the average output. Replace worn or malfunctioning nozzles as necessary. When applying materials that are appreciably different from water in weight or flow characteristics (such as fertilizer solutions, etc.), calibrate with the material to be applied. Exercise extreme care and use protective equipment when active ingredients are involved.

Boom Sprayer Calibration
The procedure below is based on spraying 1/128 of an acre and collecting the spray that would be released during the time it takes to spray the area. There are 128 ounces of liquid in 1 gallon, so in this equation, ounces of liquid caught are equal to the application rate in gallons per acre.

    Step 1. Determine appropriate calibration distance from Table A1. Spacing of outlets or nozzles must be determined. Find this spacing in left column of the table and read the corresponding calibration distance. Example: for a 19" spacing, the distance would be 214.9 feet.

    Table A1. Boom Sprayer Calibration distances with corresponding widths.

    Outlet Spacing (inches)** Calibration Distance (feet)
    48 85.1
    46 88.8
    44 92.8
    42 97.2
    40 102.1
    38 107.5
    36 113.4
    32 127.6
    30 136.1
    24 170.2
    20 204.2
    19 214.9
    18 226.9
    14 291.7
    12 340.3
    10 408.4
    8 510.5

    ** To determine distance for spacing, divide the spacing expressed in feet into 340.3. Example: For a 13" band, the calibration distance would be 340 divided by 13/12=314.1.

    Step 2. Measure and mark calibration distance in a typical terrain to be sprayed.

    Step 3. Traveling at the desired operating speed, determine the number of seconds it takes to travel calibration distance. Be sure machinery is traveling at full operating speed for the full length of the calibration distance. Mark or note engine revolutions per minute (RPM) and gear. Machine must be operated at same speed for calibration.

    Step 4. With sprayer sitting still and operating at same throttle setting or engine RPM as used in Step 3, adjust pressure to the desired setting. Machine must be operated at same pressure used for calibration.

    Step 5. Collect spray from one nozzle or outlet for the number of seconds required to travel the calibration distance.

    Step 6. Measure the amount of liquid collected in fluid ounces. The number of ounces collected is the gallons per acre rate. For example, if you collect 18 ounces, the sprayer will apply 18 gallons per acre. Adjust applicator speed, pressure, nozzle size, etc. to obtain recommended rate. If speed is adjusted, start at Step 3 and recalibrate. If pressure or nozzles are changed, start at Step 4 and recalibrate.

    Step 7. To determine amount of pesticide to put into a sprayer, divide the total number of gallons of mixture to be made (tank capacity for a full tank) by the gallons per acre rate from Step 6 and use recommended amount of pesticide for this number of acres.

Calibration Method for Boomless Broadcast and Band Sprayers
Most broadcast applications are made with a boom arrangement where the nozzle tips are spaced evenly along the boom. However, in some situations this may be impossible or undesirable, so a cluster nozzle, or a single nozzle with a wide spray pattern, may be used.

The following instructions outline a simple method to calibrate a boomless broadcast or band sprayer.

    Step 1. Determine spray width. This is usually given in the manufacturers’ literature for a specific nozzle. If you are unable to find this in the catalogs, use 80 to 85 percent of the wetted spray width.

    Step 2. Using the spray width in Step 1, determine the calibration distance from the table below.

    Table A2. Boom Broadcast or Band Sprayer Calibration distances with corresponging widths.

    Swath Width (feet)** Calibration Distance (feet)
    40 85.1
    38 89.5
    36 94.5
    32 106.3
    30 113.4
    28 121.5
    26 130.9
    24 141.8
    20 170.2
    18 189.0
    16 212.7
    12 283.6
    10 340.3
    8 425.0

    ** To determine distance for swath width not listed, divide the swath width expressed in feet into 340.3 and multiply by 10. Example: For 13 feet swath, the calibration distance would be 340.3 divided by 13 multiplied by 10=261.8.

    Step 3. Measure and mark calibration distance on typical terrain to be sprayed.

    Step 4. With all attachments in operation and traveling at the desired operating speed, determine the number of seconds it takes to travel the calibration distance. Be sure machinery is traveling at full operating speed for the full length of the calibration distance. Mark or note engine RPM and gear. Machine must be operated at same speed during use as was used during calibration.

    Step 5. With sprayer sitting still and operating at same throttle setting or engine RPM as used in Step 4, adjust pressure to the desired setting. Machine must be operated at same pressure used for calibration.

    Step 6. Collect spray from all nozzles or outlets for the number of seconds required to travel the calibration distance.

    Step 7. Measure the amount of liquid collected in fluid ounces.

    Step 8. Divide the total number of fluid ounces by 10 to obtain gallons per acre applied. For example, if you collect 180 ounces, the sprayer will apply 18 gallons per acre. Adjust applicator speed, pressure, nozzle size, etc. to obtain recommended rate. If speed is adjusted, start at Step 4 and recalibrate. If pressure or nozzles are changed, start at Step 5 and recalibrate.

    Step 9. To determine amount of pesticide to put into a sprayer or applicator tank, divide the total number of gallons of mixture to be made (tank capacity for a full tank) by the gallons per acre rate from Step 8 and use recommended amount of pesticide for this number of acres.

Hand Sprayer Calibration
Hand sprayers should be calibrated before applying any materials. The method described is easy, quick and accurate if measurements are made carefully. The procedure is for knapsack (backpack) sprayers but will also work with most hand sprayers.

    Step 1. On an area that best represents the average topography for the area to be sprayed, measure and mark off the calibration distance that coincides with your band width indicated in Table A3.

    Table A3. Hand Sprayer Calibration distances with corresponding band widths.

    Band Width (inches)** Calibration Distance (feet)
    48 85.1
    46 88.8
    44 92.8
    42 97.2
    40 102.1
    38 107.5
    36 113.4
    32 127.6
    30 136.1
    24 170.2
    20 204.2
    19 214.9
    18 226.9
    14 291.7
    12 340.3
    10 408.4
    8 510.5

    ** To determine distance for spacing, divide the spacing expressed in feet into 340.3. Example: For a 13" band the calibration distance would be 340 divided by 13/12=314.1.

    Step 2. Fill the sprayer with water only and record the number of seconds required to walk the calibration distance at a comfortable, steady speed while spraying and pumping to maintain a uniform pressure.

    Step 3. While pumping to maintain the selected application pressure, collect spray from all nozzles used on one band width for the number of seconds required to travel the calibration distance.

    Step 4. Measure the amount of liquid collected. The number of ounces collected is equal to the gallons of water applied per acre for that boom, speed and pressure. For example, if you collect 20 ounces, the sprayer will apply 20 gallons per acre.

    Step 5. To determine the amount of chemical to add to the spray tank, divide the capacity of the tank by the number of gallons of water per acre (GPA) to determine the fraction of an acre that can be covered with a tankful of spray.

    Step 6. Multiply the application rate of the product per acre times the fraction of the acre covered per tank, and add that amount of chemical to the sprayer tank.

Uniform Application Check
Hand sprayers require skilled operators to achieve a uniform application. A simple and quick test of uniformity is to spray an area on a paved surface with water in your normal spraying manner on a warm day. In a few minutes,the drying pattern will indicate your distribution. Fast-drying areas indicate low application rates while slow-drying areas received high amounts of spray. Uniform drying without streaks indicates uniform application. Practice until uniform distribution is obtained.

Granular Herbicide Calibration
The following procedure will give the pounds (total weight) of material applied per acre broadcast. This calibration procedure is based on 1/16 of an acre, which is equal to 16 ounces in a pound of material. A weight scale incremented in ounces is required for this procedure. Check uniformity of outlets across the swath. Collect from each for a known time period. Each outlet should be within 5 percent of the average output. Exercise extreme care and use protective equipment when an active ingredient is involved.

    Step 1. Determine appropriate calibration distance from Table A4.

    Table A4. Granular Herbicide calibration distances with corresponding widths.

    Swath Width (feet)** Calibration Distance (feet)
    80 34.0
    70 38.9
    60 45.3
    50 54.4
    40 68.1
    30 90.7
    25 108.9
    20 136.1
    15 181.5
    10 272.2
    8 340.3
    6 453.7
    4 680.6
    2 1361.2

    **To determine distance for swath width not listed, divide the swath width expressed in feet into 2722.5. Example: For 13 feet swath, the calibration distance would be 2722.5 divided by 13=209.4 feet.

    Step 2. Measure and mark calibration distance in typical terrain to be applied.

    Step 3. With all attachments in operation and traveling at the desired operating speed, determine the number of seconds it takes to travel the calibration distance. Be sure machinery is traveling at full operating speed for the full length of the calibration distance. Mark or note engine rpm. Machine must be operated at same speed used for calibration.

    Step 4. With applicator sitting still and operating at same speed as used in Step 3, adjust gate openings to desired setting.

    Step 5. Collect from all outlets for the number of seconds indicated in Step 3.

    Step 6. Weigh the amount of material collected in ounces. The number of ounces collected is the pounds per acre rate. For example, if you collect 18 ounces, the applicator will apply 18 pounds per acre. Adjust applicator speed, gate opening, etc. to obtain recommended rate.

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Last updated on Thursday, May 02, 2002 at 01:09 PM
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