Agriculture Reference
In-Depth Information
Q
A
A
, if not limited by soil intake rate.
I
=
2
, where
D
ml
is the manufacturer's rated wetting diameter of lateral
sprinkler,
F
is the overlapping factor
D
ml
1
F
S
l
=
−
2
, where
D
mm
is the manufacture's rated wetting diameter of
mainline sprinkler,
F
is the overlapping factor
Overlapping factor is normally taken as 0.5-0.75. For windy condition, over-
lapping factor may be as high as 1.0.
D
mm
1
F
S
m
=
−
A
S
l
×
(4) Number of sprinklers,
n
=
S
m
(5) Determine system capacity as
n
Q
ST
=
Q
Ai
(3.33)
i
=
1
where
i
is the number of sub-area like “
A
”
(6) Determine the power requirement to pump the water for a sprinkler system as
=
Q
ST
×
×
P
9.81
H
T
where
P
power, KW
Q
ST
=
=
total discharge rate for the system, m
3
/s
total pumping head, m
Total head consists of the following:
H
T
=
H
T
=
H
m
+
H
f
+
H
r
+
H
s
+
H
sf
where
H
m
=
pressure head required to operate the sprinklers at minimum
required pressure (m)
H
f
=
total frictional head in the lines (m)
H
r
=
maximum riser height from the pump level (m)
H
s
=
suction head (vertical difference between pump level and source
water level after drawdown) (m) (if needed)
H
sf
=
friction head loss in suction line (if suction line exists)
Procedure for calculating friction loss has been described in
Chapter 1
(
Conveyance Loss and Designing Conveyance System
), this volume.
General Guideline for Minimum Pressure of Sprinkler Irrigation System
The following pressure estimates can be used as a general guide or thumb rule for
sprinkler pressure:
Spray type sprinkler head
=
40 PSI (93 ft head)
Rotor type sprinkler head
=
45 PSI (104 ft head)
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