select the appropriate pumps and controls. © irrigation association understanding basic pump...
TRANSCRIPT
Select the Appropriate Pumps
and Controls
© Irrigation Association
Understanding Basic Pump Selection Considerations
• Matching the pump and system
• Flat vs. steep curves
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Water Horse power
where:WP = water power output, hpH = total operating head, ftQs =design discharge of the irrigation
system, gpm
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3960
QHWP s
Brake horse power
where: BP= power input required by the pump, hpEp = the pump efficiency, %.
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)100/E(3960
QH
100/E
WPBP
p
s
p
Total power input
where: KW = pumping plant power input, kwEp = the pump efficiency, %. Em = the motor efficiency, %.
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)100/E()100/E(5308
QH
)100/E(100/E
WP746.0KW
mp
s
mp
Hf + Hm
Hp
Q
PUMPS - HORSEPOWER DETERMINATION
He
Hs
Total Dynamic Head (TDH) is the energy that the pump imparts to the water for a specific flow rate (measured in feet)
mfesp HHHHHTDH
• Hp = pressure at outlet of discharge pipeline• Hs = lift (+) or head (-) from water surface to pump• He = lift (+) or fall (-) from pump to outlet of discharge
pipeline• Hf = friction loss in discharge pipeline• Hm = miscellaneous losses (e.g., valves, reducers, etc.)
avitySpecificGr
psiessureftHead
31.2)(Pr)(
Total Dynamic Head (TDH)
Practice example
The GIR requirement is 1 inch per 3 days and the fraction of operating time is t = 0.9. The irrigated area is 130 acres. The pumping lift (Hlift) from water surface in sump to the ground surface is 10 ft and includes the friction loss in the pump intake pipe. The pressure requirement at the pump outlet, Pout, is 79 psi.
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© Irrigation Association
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Steep v.s. flat
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System curves
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System Curves
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Big Nozzle approach
where:Qs= design system discharge, gpmKs = system discharge coefficientTDH = total dynamic head (system head), ftE = total elevation change in the system, ft
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ETDHKQ ss
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Understand Types of Electronic Controls
Available
• System protection and shut
down
• Automated controls
• Remote controls
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Integrate Pump and Pivot Controls
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Inside the Alignment Box
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Chemical Injection Equipment
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Electronic Controls
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Computer Management
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Computer Management
Controls
• Pressure actuated Safety switch– Loss of prime, broke pipe, loss of
fuel, etc.• Demand switches• Startup control
– Controlled startup of flow • Back flow devices• Shut off
– Pivot stuck or stopped
• Oil pressure– High or low
• Time delay limit switch• Flow switch
– No flow, high flow• Phase monitor• timers
Alarms
• High or low pressure• High or no flow• Low oil• Low pressure• Etc.
Variable speed devices
• Potentially Ideal Applications– Widely varied flow Requirements– Less total head needed as flow
requirements are dropped (Extreme friction loss or major draw-down changes in a well)
– Single Well serving a very large acreage
– Long operating hours at less than full flow – Varied crops, multiple systems on one pump
– Steep pump curves
© Irrigation Association
Let’s Go to Our Manuals and See What We Can
Learn