Smithco Turf Spraying Guide - Manual (Page 23)

check application rate.
f. FOR SPRAYERS WITH ELECTRONIC SPRAY CONTROL SYSTEMS
On sprayers equipped with Electronic Spray Control Systems ("Spray Computers") such as
those manufactured by Spraying Systems (Tee-Jet) Raven Ind., Micro-Trak Co. &
Dickey-John Co., it is still important to select the right type and size of nozzle for the
required operation. Electronic Spray Control Systems cannot function properly if the nozzles
are not capable of delivering the programmed (desired) application rate. Nozzles which are
too large will not develop adequate pressure or satisfactory spray patterns. Nozzles which
are too small will not allow the discharge of spray material at the programmed application
rate.
Further, when calibrating sprayers which are equipped with Electronic Spray Control Systems, care
must be taken to use the mode of operation on the Spray Control System (Gallons per Acre ["US"
Mode]; Gallons per 1,000 sq. ft. ["Turf" Mode]; or Liters per Hectare [Std. International Mode], which
corresponds with the nozzle calibration charts (GPA, GPT or LPH).
g. USING THE NOZZLE CHARTS
Select the correct chart based on your nozzle type, nozzle spacing and desired expression of
application rate (GPA, GPT, LPH). If the desired operating speed is not found on the nozzle chart, it
is simple to determine application rates at different speeds by extrapolating from the application
rates at the given speed.
For example: If the desired speed is 2 1/2 MPH (4 kph) on a sprayer using Raindrop nozzles (Chart
5). The average between the application rates for 2 MPH and 3 MPH may be assumed to be the
application rate for 2 1/2 MPH. For example: RA-5 Nozzle, 50 PSI, the application rate for 2 MPH is
74 GPA and the application rate for 3 MPH is 50 GPA. Add 74 + 50 (124) then divide by 2 (62).
Therefore, the application rate at 2 1/2 MPH is 62 GPA.
Another example: The desired speed is 6 MPH. Use the application rate column for 3 MPH and
divide by 2.
h. CONVERTING NOZZLE CHART METHOD TO BRITISH GALLONS
To convert any of the Gallon Per Acre rates to Imperial Gallons per acre, (ImpGPA) multiply by .83. To
convert any of the liter Per Hectare rates to Imperial Gallons Per Hectare (ImpGPH), multiply by .22.
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. CHECKING THE ACTUAL APPLICATION RATE
After the combination of ground speed, nozzle size and operating pressure has been selected, the
sprayer should be operated to determine if the target application rate is being achieved. The
following "128" method is one way to validate the Nozzle Chart Method of calibration.
2. THE "128" METHOD OF BOOM SPRAYER CALIBRATION
a . INTRODUCTION
The "128" Method is useful for calibrating sprayers and also for checking the calibration of sprayers calibrated by
the Nozzle Chart Method and sprayers using Electronic Spray Control Systems. The "128" is based on a
convenient mathematical relationship that exists between US Gallons, liquid ounces and acres.
An ounce is 1/128 th of a (US) gallon. If an area which was "1/128 of an acre" could be found, the number of
ounces applied to that small area would be equal to the number of gallons applied to the acre. Thus, no
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