centrifugal pump1
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Rotodynamic Pump
Fluid enters the pump
through the eye of the
impeller.
The fluid is accelerated
radially outward from the
pump casing.
A partial vacuum is
created that continuously
draws more fluid into the
pump.
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Centrifugal PumpCentrifugal Pump
Converts kinetic
energy to pressure
energy.
Friction losses are
high for highervelocity fluids,
hence lower overall
efficiency.
This is avoided by
converting some ofthe velocity to
pressure
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CENTRIFUGAL PUMPSCENTRIFUGAL PUMPS
Prime mover
Volute casing
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ADVANTAGES OF CENTRIFUGALADVANTAGES OF CENTRIFUGAL
PUMPPUMP
High efficiency
Produces smooth and uniform flow
Wide range of capacity
Ease of operation and maintenance
DISADVANTAGESDISADVANTAGES
Loss of priming easily
Efficiency depends upon operating design head &
speed.
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Increasing the
pressure
Achieved in the casing. There
are three types of casings:Volute centrifugal
Turbine pump
Regenerative Pump
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Horizontal shaft centrifugal pump construction
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Horizontal shaft centrifugal pump components
the casing and frame are usually cast iron or cast steel, while the
impeller may be bronze or steel.
To prevent back-leakage from the exit of the impeller around the
front of it to the entry, a closely fitting wear ring is fitted into the
casing around the front rim of the impeller; this is subject to wear
by particulate matter in the water and can be replaced when the
clearance becomes large enough to cause significant loss of
performance.
Another wearing part is a stuffing box packing where the drive shaft
emerges from the back of the impeller casing. This needs to be
periodically tightened to minimize leakage, although excessive
tightening increases wear of the packing. The packing is usually
graphited asbestos, although graphited PTFE is more effective if
available.
The back of the pump consists of a bearing pedestal and housing
enclosing two deep-groove ball-bearings. This particular pump is oil
lubricated, it has a filler, dip-stick and drain plug.
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IMPELLERSIMPELLERS
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The impeller of the centrifugal pump converts the mechanical
rotation to the velocity of the liquid.
It has an inlet eye through which the liquid suction occurs.
The liquid is then guided from the inlet to the outlet of the impeller
by vanes .
The guide vanes are usually cast with a back plate, termed
shroud or back cover, and a front plate, termed front cover.
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FLOW OUT FROM IMPELLERSFLOW OUT FROM IMPELLERS
centrifugal pumps: fluidenters axially, and is
discharged radially.
mixed--flow pumps: fluid
enters axially, and leaves at anangle between radially and
axially.
axial pumps: fluid enters and
leaves axially.
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Where high flows at low heads are required (irrigation
pumps), the most efficient impeller is an axial flow.
Conversely, for high heads and low flows a centrifugal
(radial flow) impeller is recommended.
The mixed flow pump is a useful compromise to avoid the
limited lift of an axial flow pump, but still achieve higher
efficiency and larger flow rates than a centrifugal volute
pump.
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CONSTRUCTION OF IMPELLERSCONSTRUCTION OF IMPELLERS
There are three types of construction seen in an impeller. These arebased on the presence or absence of the impeller covers and shrouds.
The three types are:
1. Closed
2. Semi-open
3. Open.
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Various types of centrifugal pump impellers
iii. Centrifugal pump impeller variations
A and B are both open impellers, while Cand D are shrouded impellers.
A and C are impellers for a single-suction
pump, while B and D are for a double-
suction pump in which water is drawn in
symmetrically from both sides of theimpeller.
The advantage of a double-suction arrangement is that
there is little or no end thrust
on the pump shaft.
but double suction pumps are
more complicated andexpensive.
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CASINGCASING
A casing is provided for
housing the impeller and
supporting the bearing
provided for the shaft.
Three common types of
casings are:
Diffuser ring
Volute casing
Vortex casing
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DIFFUSER RINGDIFFUSER RING
A diffuser ring with guide
vanes surrounds the impeller
These guide vanes are placed
at such an angle that water
enters without shock. These are commonly known
as turbine pumps as they
resemble a reversed radial
flow reaction turbine.
More expensive than volutepumps. And mostly used for
developing high heads.
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VOLUTECASINGVOLUTECASING
Spiral volute pumps
incorporate a
logarithmic spiral, the
purpose of which is to
closely match the
volumetric flow-rate of
the impeller at the best
efficiency point.
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VORTEXCASINGVORTEXCASING Improvement of volute pump.
Annular space known as vortex
chamber is provided between
the impeller and volute casing.
Thus the water enters the
vortex chamber from the
impeller with a whirling motion.
Thus it increases the efficiency
of the volute chamber by
reducing the eddy formation.
suited for grit applications with
higher concentrations of solidsand sludge
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borehole pump (where
limitations on the impeller
diameter are caused by the
borehole, making multi-staging
an essential means to obtain
adequate heads
Only vertical bore holes
Higher cost of motor
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Pumping is often necessary to bring geothermal
fluid to the surface. There are primarily two typesof production well pumps
a. Lineshaft turbine pumps
b. submersible pumps
The difference is the location of the driver. In a line
shaft pump the driver, electric motor, is mounted
above the wellhead and drives the pump, whichmay be located as much as 2000 ft below the
ground surface, by means of a lineshaft.
In submersible pumps, the driver is located below
the pump itself and drives the pump through a
relatively short shaft with a seal section to
protect the motor from the well fluid.
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Submersible pump
Multi-stage and Borehole Rotodynamic Pumps
Asubmersible pump is a
device which has a hermetically
sealed motor close-coupled to the
pump body.
The whole assembly is
submerged in the fluid to be
pumped. The main advantage of
this type of pump is that it
prevents pump cavitation, aproblem associated with a high
elevation difference between
pump and the fluid surface.
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Centrifugal pump closely coupled with motor
Does not require long drive shaft
Motor operates at a cooler temperature.
Noiseless operation. High efficiency
Smooth and even flow
In case of repair full pump to be removed.
SUBMERSIBLE PUMPSSUBMERSIBLE PUMPS
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Multi-stage and Borehole Rotodynamic Pumps
Where high heads are needed, the primary means to achieve this with a single impeller
centrifugal pump are either to drive the impeller faster or to increase its diameter.
Limitations like bore hole diameter exist.
a more practical solution is to use a multiple impeller pump in which the out put from it from
one impeller feeds directly, through suitable passages in the casing, to the next, mounted on
the same shaft.
Extra pump stages can be fitted quite easily to produce a range of pumps to cover a widespectrum of operating conditions.
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MULTISTAGE IMPELLERSMULTISTAGE IMPELLERS
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