Hunter PGP Series User Manual

17
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16
PGP
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Rotor
PRECIPITATION RATE
Two formulas are shown below, the rst is most useful when comparing precipitation rates between different types of sprinklers
or calculating precipitation rates on areas with a single type of sprinkler and uniform head and row spacing. The second method
is better suited to areas where sprinkler head ows or spacing varies. Metric versions are shown in parenthesis.
Precipitation Rate - Method #1 - Individual Head Method
Where:
Pr = precipitation rate in inches per hour
GPM = ow for a given sprinkler of any arc, in gallons per minute
Degrees Arc = the arc of the given sprinkler in degrees
Head Spacing = the space between the heads in a row, in feet
Row Spacing = the space between rows of heads, in feet
34650 = constant for conversion of area and ow into common units
Example: What is the precipitation rate for a 270 degree sprinkler with 6.8 gpm spaced at 28' by 30'?
Pr = 34,650 x 6.8 Pr = 1.04 in./hr.
270 x 28 x 30
Precipitation Rate - Method #2 - Total Area Method
Where:
Pr = precipitation rate in inches per hour
Total GPM = total ow from all sprinklers in the given area in gallons per minute
Total Area = the given irrigated area in square feet
96.25 = constant for conversion of area and ow into common units
Example: What is the average precipitation rate for a section of turf 325' by 80' if the total ow from all sprinklers in the
area is 112 gpm.
Pr = 96.25 x 112 Pr = 0.41 in./hr.
(325 x 80)
SPRINKLER RUN TIME
The sprinkler run time formula calculates the number of minutes required to apply enough water to replace the water lost by
evapotranspiration for a specic crop irrigated with a system at a particular precipitation rate and efciency.
Where:
T = sprinkler run time in minutes
Et
o
= reference evapotranspiration rate, in inches
K
c
= crop coefcient, percent
Pr = precipitation rate of the area, in inches per hour
E
a
= application efciency of the system, percent
60 = Constant for conversion of area, ow, inches per hour and inches per day into common units
Example: Determine the sprinkler run time for an athletic eld with an accumulated Et
o
of 0.45 inches (0.15"/day for 3
days) and a crop coefcient for the warm season turf of 0.70. The sprinkler precipitation rate is 0.50 in./hr. with an applica-
tion efciency of 75%.
T = 60 x 0.45 x 0.70 T = 50.4 min.
0.50 x 0.75

Hunter PGP Series Specifications

General

Brand	Hunter
Model	PGP Series
Category	Irrigation System
Language	English