Slide 1
A rotating impeller transfers energy to liquid
A centrifugal pump uses a rotating impeller to transfer mechanical energy to liquid. The casing guides that moving liquid toward the outlet.
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The surrounding system determines how much flow results. A pump connected to a short, wide pipe operates differently from the same pump connected to a long, restrictive line.
Slide 2
Pump head measures energy per unit weight
Engineers describe pump output using head: mechanical energy per unit weight of fluid. Head can support pressure, height or fluid motion.
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For the same head, a denser liquid corresponds to a larger pressure difference. This is why pressure alone is an incomplete description when comparing pumps handling different liquids.
Slide 3
The pump and system curves describe the operating demand
A pump curve relates delivered head to flow at a stated speed. A system curve describes the head that the connected installation requires.
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Their intersection defines a possible steady operating point. Opening a valve changes the system curve, while changing rotational speed changes the pump curve.
Slide 4
An oversized pump can work inefficiently
A pump is usually most efficient within a particular operating region. Selecting a much larger machine can create unnecessary energy use and maintenance.
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Operating far from the intended region can increase internal recirculation and mechanical loads. A large nameplate capacity therefore does not guarantee a robust or economical installation.
Slide 5
Speed control saves energy according to the system’s needs
Variable speed can adjust a pump to changing demand. The saving depends on the system, especially the amount of fixed elevation or pressure it must overcome.
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In an ideal friction-dominated system, reducing speed can sharply reduce power. A system with substantial static head behaves differently, so a simple cubic estimate should not be applied blindly.
Sources
- Improving Pumping System Performance: A Sourcebook for Industry
U.S. Department of Energy