Operation 13
PRE-SPRAYING SYSTEM CHECK
It is highly recommended that the following checklist
be used before going to the field to spray.
1. Park sprayer, use clear water.
2. Select Rate and VPM. Turn booms on by select-
ing RUN.
3. Select Manual mode on the Rate Switch (center
position).
4. Hold the key until the display flashes “MAX”.
(This will move the valve to the maximum pres-
sure position.)
5. Start the sprayer pump and run at operating
RPM.
6. Assure that all boom valves are operational.
7. Note Maximum Volume per Minute.
8. Note Maximum pressure.
9. Hold the key until the display starts to flash
“MIN”.
10. Note Minimum pressure.
11. Note Minimum Volume per Minute.
12. Perform “Minimum Flow Rate” procedure now if
using this feature.
13. Press the key until the pressure is at some typi-
cal amount or about the middle of the range.
14. Put controller in HOLD and turn pump off.
15. Set the desired field number and chemical num-
ber. Double check that you have the correct target
Gallons Per Acre programmed in for RATE 1 and
RATE 2.
16. Clear both ACRE counts to zero, if desired.
17. Clear both VOLUME counts to zero, if desired.
You are now ready to go to the field and begin spray-
ing.
To adjust this maximum and minimum flow rate and
pressure, open or close any manual series valve, by-
pass valve, etc., to achieve a desired flow rate and
pressure range.
In general, a 4 to 1 pressure range can be used on
most nozzles. For example, 10 PSI to 40 PSI can be
used on flood-jet nozzles. Be sure to consult your
pressure nozzle charts. Using pressures that are too
low will generate a poor spray pattern. Very high pres-
sures will cause “misting” and also increase nozzle
wear-out rate.
A 4-to-1 change in pressure will only cause a 2-to-1
change in the flow rate. Therefore, the speed change
must be limited to 2-to-1. For example, a pressure
change of 10 PSI to 40 PSI (4:1) will double the flow
rate. This means the speed can also double (4 MPH
to 8 MPH) and still maintain a constant GPA (gallons
per acre).
Minimum and Maximum speed can be calculated as
follows using the formula:
Speed =
VPM x 495
Width (in feet) x Rate (in Gallons/Acre)
Example:
Using an application rate of 20 GPA and a
width of 60 feet, a minimum flow rate of 3.5 gallons
per minute would allow a minimum speed of 1.44
mph.
Minimum Speed =
Minimum VPM x 495
Width x Rate
Minimum Speed =
3.5 x 495
60 x 20
Minimum Speed = 1.4 mph
Changing to a maximum flow rate of 70 gallons per
minute will allow a maximum speed of 28.8 mph.
Maximum Speed =
Maximum VPM x 495
Width x Rate
Maximum Speed =
70 x 495
60 x 20
Maximum Speed = 28.9 mph
Calculation should be done for both Rate 1 and Rate 2.
REMEMBER, OPERATING OUTSIDE THE SPEED
RANGE FOUND IN THIS PROCEDURE (TOO FAST
OR TOO SLOW) MAY RESULT IN EXCEEDING
THE MINIMUM OR MAXIMUM RECOMMENDED
OPERATING PRESSURES FOR YOUR NOZZLE.
THIS COULD RESULT IN POOR WEED CONTROL,
ETC.
When a desired pressure cannot be obtained the
usual cause is low pump capacity. Other possible
problems are long runs of small diameter hose, low
capacity boom valves and excessive agitation flow.
