to over 80% depending on the type and
size.
Here are few samples of centrifugal pump
efficiencies:
3. Shaft seal, which allows rotation of
the rotor while preventing product
leakage around the shaft
4. Shaft and bearings, which maintain
the position of the rotor with respect
to the pump casing
10,000 gpm centrifugal pump—75 to 89%
500 gpm centrifugal pump—60 to 75% R ELIABILITY AND E FFICIENCY
100 gpm magnetic drive pump—40% The key to exemplary centrifugal pump
reliability and high overall system
efficiency is selecting the right pump for
the required application. This means that
the pump’s best efficiency flow (BEP) and
head should always closely match process’
hydraulic requirements. A poor hydraulic
match will lead to high energy bills and
maintenance costs.
100 gpm canned motor pump—35%
Basic Centrifugal Pump Construction
All centrifugal pumps have the following
common elements.
1.
2.
Impeller, which adds energy to the
liquid by accelerating it
Pump casing and volute, which
contains the liquid being pumped
and decelerates the liquid expelled
by the impeller
Centrifugal pumps like to operate close to
their best efficiency point (BEP) where:
t
Hydraulic efficiency is greatest
t Vibration and pressure pulsations are
lowest
t Shaft deflection is minimized due to
the improved pressure distribution
of internal pressure around the
impeller. This has a major positive
effect on mechanical seal life. At the
best efficiency point, the pressures
around the impeller are nearly
balanced so that radial forces on the
impeller and shaft are minimized.
t Overall mechanical reliability is
highest
BEP is the flow point where centrifugal
pump designers would like to see their
pumps to be operated. Conscientious
pump operators should always strive
to comply with the designer’s intent by
operating all centrifugal pumps near their
best efficiency point.