Agriculture Reference
In-Depth Information
that moves the water, the motor is the part that moves the pump. Most pumps can be
attached to several different sizes of motor. Bigger motors mean more volume and
pressure.
The second variable is the size of the impeller. The impeller spins inside the case
and this is what moves the water. Larger impellers fit tighter in the case leaving less
room for slippage. This results in higher pressures. But we don't always want higher
pressures, as pressures higher than what you need just waste energy.
12.12.3 Selecting a Pump
Significant opportunities exist to reduce pumping system energy consumption
through smart design, retrofitting, and operating practices. Operating characteristics
as supplied by the manufacturer, include relationships between flow rate, pumping
head, rotational speed, and power required. Optimum pump selection for agriculture
depends on consideration of the following:
(i) discharge rate required
(ii) source of water
(iii) well characteristics (if applicable)
(iv) quality of water to be pumped
(v) type, grade, and characteristics of the pump
Special attention must be given to the pumping plant when the irrigation sys-
tem changes, as may occur when groundwater levels decline or operating pressure
changes due to changing the type of irrigation system. Such changes may result in
temptation to add a “booster” pump or connect two or more pumps together into
a common distribution pipeline. These changes require a careful assessment if the
desired result is to be achieved. Economic operation of the entire irrigation system
can depend upon proper selection of the pump, power unit, and fuel type as well as
proper routine maintenance, testing, and adjustment. The performance of a pump
varies depending on how much water the pump is moving and the pressure it is cre-
ating. This is an important relationship because (i) it determines whether the pump
is suitable for your irrigation system, and (ii) it is the pump characteristics which
allow you to control the operation of your pump.
12.12.4 Procedure for Selecting a Pump
All pumps have oddities and special and unique requirements. Before installing a
new pump, it is better to read the manufacturer's manual.
The basic procedure for selecting a pump for a new irrigation system is
summarized below:
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