TM 5-3740-218-13&P
The variables of 1-1000 psi have been put in this formula and calculated out. The conversion factor is necessary to put
into the formula since all nozzle flows in the charts are given for 30 psi. Any deviation from 30 psi requires a conversion
number in the formula to correct the flow rate.
Example No. 1: An application requires 12 gallons per acre at 60 mph with nozzles spaced every 8 inches on the spray
boom. The operator expects the psi to be around 35. What nozzles can be used that would be close to this
requirement?
GPM/NOZ at 30 PSI =
GPA x MPH x Nozzle Spacing
5940 x Conversion Number for New PSI
GPM/NOZ at 30 PSI = 12 x 60 x 8
=0.897
5940 x 1.08
Answer: Nozzles that will deliver close to 0.897 gpm at 30 psi are:
D 10-45
0.94
D 6-56
0.95
D 14-25
0.88
Example No. 2: A grower has an orchard sprayer with 32 nozzles and will travel at 80 mph. The swath width is 50 feet.
The grower plans to apply 16 gpa at 40 psi. What nozzle will perform to this application?
GPM/NOZ at 30 PSI =
GPA x MPH x SW
# NOZ x 495 x Conversion Number for New PSI
GPM/NOZ at 30 PSI = 8 x 60 x 50
= 1.51
32 x 495 x 1.00
Answer: Nozzles that will deliver close to 1.51 gpm at 30 psi are:
D 14-45
1.54
D 8-46
1.59
D8
1.50
G-3.
SYSTEM CALIBRATION
Three possible methods will be discussed that can be used to calibrate the system:
a. Flow Checks. The only method to calibrate a system before it leaves the ground is to time a given load of water.
With the hydraulic driven pumps, the following formula can be applied:
TIME/Load = 495 x # Gal/Load
# of Gal/Acre x SW x MPH
G-2
