centrifugal pump1

8/2/2019 Centrifugal Pump1

1/23

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.


2/23

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


3/23

CENTRIFUGAL PUMPSCENTRIFUGAL PUMPS

Prime mover

Volute casing


4/23

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.


5/23

Increasing the

pressure

Achieved in the casing. There

are three types of casings:Volute centrifugal

Turbine pump

Regenerative Pump


6/23

Horizontal shaft centrifugal pump construction


7/23

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.


8/23

IMPELLERSIMPELLERS


9/23

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.


10/23

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.


11/23

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.


12/23

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.


13/23

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.


14/23

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


15/23

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.


16/23

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.


17/23

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


18/23

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


19/23

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.


20/23

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.


21/23

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


22/23

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.


23/23

MULTISTAGE IMPELLERSMULTISTAGE IMPELLERS

centrifugal pump1

Documents