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Section 5
12. The next step is to calculate the effective spray width.
To calculate the effective spray width, take the number
of nozzles you are going to be using (3 nozzles on
the center boom and 1 on each end boom, 5 total)
and multiply it by 20.
13. The next step is to determine the output of the nozzles
on the sprayer. (Make sure the spray pressure is
set correctly, refer to the spray guide chart for the
recommended base pressure settings). To calculate
nozzle output, gather liquid (fl oz) from each nozzle
for the average amount of time it took to drive
the test course (number determined in step 10).
Measure (fl oz) each nozzle three times. Take these
measurements and calculate the average for each
nozzle (add the three test results for each individual
nozzle together and divide by 3 to get its average, do
this for each nozzle).
14. To check for nozzle wear, take all of the nozzle
averages and add them together, then divide by the
number of nozzles. This will give you the average
across the boom. If any one nozzle average is more
than 5% +/- from the boom average it will need to be
replaced or cleaned. (if the nozzle is less than the
average, it likely needs to be cleaned. If it is more
than the average, it likely is worn and needs to be
replaced.)
15. To calculate the amount (fl oz) that should be gathered
during the test period according to the desired GPA,
speed, and effective spray width being used. Use
the formula in Figure 5-5 to determine the amount
that should be coming out each nozzle during the
test period in fl oz. If the amount determined in step
13 is more than 5% +/- off of the amount determined
using the formula in Figure 5-5, the pressure, speed,
or nozzles may need to be adjusted or changed to
reach the desired results.
Desired GPA x Speed (mph) x 20
Gal/min per nozzle x Average Course Time(sec) x 128
5940
60
=
=
Gal/min per nozzle
Nozzle Output During T
Figure 5-5. Required Fl Oz To Be Gathered
- NOTE -
If all measured nozzles produce the correct
amount according to the formula in Figure 5-5,
the sprayer should be properly calibrated (within
5% +/-) for the desired GPA you were aiming for.
Skip the remaining steps.
16. Once you have the average flow (fl oz) for each nozzle,
add all the nozzle average (fl oz) results together. It will
then need to be converted to gallons (fl oz divided by
128). A flow rate in gallons per minute will then need
to be calculated. Follow the formula in Figure 5-6
Flow Rate of All Nozzles (gallons) x 60
Average Course Time (secs)
=Flow Rate (gal/min)
Figure 5-6. Gallons Per Minute Formula
17. Application rate will then need to be calculated by
using one of the formulas below. For gallons per acre
see Figure 5-7. For gallons per 1000ft² see Figure 5-8.
Flow Rate of All Nozzles (gal/min) x 5940
Ground Speed (mph) x Spray Width (in.)
=Application Rate (gal/acre)
Figure 5-7. Gallons Per Acre
Flow Rate of All Nozzles (gal/min) x 136
Ground Speed (mph) x Spray Width (in.)
=Application Rate (gal/1000ft²)
Figure 5-8. Gallons Per 1000ft²
18. These formulas will give you the gallons per acre or
1000ft² that your machine is applying. If this number
does not match the application rate you need, the
nozzles may need to be replaced or a pressure
adjustment may be needed. A different nozzle size
may also be needed if these numbers are off by a
large margin.
Useful Conversions
1 Gal/Acre = 9.35396 Liters/Hectare
1 Gal/Acre = 0.0229568411 Gal/1000ft²
1 Gal/1000ft = 43.56 Gal/Acre
5.8 CALIBRATING THE SPREADER
1. Make sure the spreader is properly calibrated for the
desired application rate. Each granular material will
spread differently dependant on size, temperature, and
moisture. The machine will need to be re-calibrated
for each material(refer to the chemical manufacturer's
directions for application rate).
2. To calibrate the spreader, first make sure the spreader
system is clean and free from build up.
3. The first step is determining the spreaders effective
spread width.
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