Specific application instructions for crop protection products are listed on the products label. You should always read and follow these label instructions. You may still need to adjust your sprayer to the specific spraying conditions you choose for volume rate, driving speed, nozzles and spray pressure.
Often volume rate and driving speed are decided first – then the nozzle choice is limited to the possibilities within the accepted pressure range (normally 20 to 70 psi for conventional nozzles). This is easily found on the HARDI calibration disc or you can calculate the required nozzle flow and find the nozzles in a nozzle table.
Example: We want to apply 15 GPA at 7 mph
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Check driving speed:
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- Drive the measured distance (with a ½ filled tank) and measure the time.
- Calculate the speed:
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Measure 300 feet. It may be useful to have some ‘permanent’ markers that are located in a convenient place (in a field or field like conditions). From the table in the tractor you find the gear to achieve the speed you want at a given rpm.
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Examples of speed calculations
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Sec/300 ft
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17
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18
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20
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23
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25
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29
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34
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41
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51
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mph |
12
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11
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10
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9
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8
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7
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6
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5
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4
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Select nozzle
Use the calibration disc or formula (nozzle spacing 20 in):
Example: By aligning 15 gpa and 7 mph on the calibration disc the line in the "window" (gpa) shows that we need a flow of 0.350 gpm.
Then a suitable combination of nozzle size and pressure can be found on the lower half of the calibration disc: ISO 04 at 32 psi (or ISO 03 at 58 psi).
 .
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Nozzle and pressure to obtain .350 gpm can also be found in the nozzle catalog
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Check liquid system
- Mount the chosen nozzles on the boom.
- Turn on the sprayer and spray at minimum 80 psi while you check the liquid system for any leakages.
- Check the agitation
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Check nozzle output
- Set the pressure.
- Adjust the pressure equalizing valves
- Measure the nozzle output for one minute.
- Repeat this process - measuring at least 2 nozzles for every boom section.
- Calculate average nozzle output