10-centrifugal pumps construction 1

7/29/2019 10-Centrifugal Pumps Construction 1

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OF CENTRIFUCONSTRUCTIONGAL PUMPS


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Construction of Centrifugal Pumps

Casing

Casing generally are two types:

I. Volute casings for a higher head.

II. Circular casings for low head and high

capacity.


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CasingVolute casings:

A volute is a curved funnel

increasing in area to the

discharge port.


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Running volute-style pumps

at a lower capacity than the

manufacturer recommendscan put lateral stress on the

shaft of the pump,

increasing wear-and-tear

on the seals and bearings,and on the shaft itself.


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Double- volute casings are

used when the radial

thrusts become significantat reduced capacities.

the main purposes of a

volute casing is to help

balance the hydraulicpressure on the shaft of the

pump at the manufacturer's

recommended capacity .


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CasingCircular casings:

have stationary diffusion vanes surrounding the impeller

periphery that convert velocity energy to pressure energy.

Solid casing is one casting or fabricated piece.

Split casing consists of two or more parts are fastened together.
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Split casing

Horizontally split or axially split casing.


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Split casing

Vertically split or radially split casing.


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Casing

Shaft

weight

Sha

ftdeflection

Cost=


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CasingThe ideal design would be one which reduces radial thrust

to an acceptable level.

How?


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CasingSome pump casings use a split volute design instead of a

double volute.


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Casing

Some pump casings use a split volute design instead of

a double volute.

Diffuser pump casings:

The liquid leaves the diffuser at

a higher pressure than it leaves

the impeller, then enters the

casing annulus and finally

leaves at the discharge branch.


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Casing

Diffusers are frequently used in

multi-stage pumps and are

more efficient than volute typesof casing.

Diffuser pump casings:

However, diffuser designs are

more costly than volute designs

and therefore single-stagediffuser pumps are not used as

often as volute types because

of the expense.


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CasingMulti-stage pumps:


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Diffuser



Diffuser

Impeller

1. Guides the liquid flow from one

impeller to the next.

2. acts in a similar manner to a volute

by converting velocity energy (kinetic

energy) into pressure energy.


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LP

LP

HP

HP

LP HP HP LP

LP

LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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LP

LP

HP

HP

LP HP HP LP

Normal thrust

on rotor

Normal thrust

on rotor


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CasingSuction and Discharge nozzle:


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End suction/Top discharge:

1) Always an overhung type.2) Typically has lower NPSHR.


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Top suction/Top discharge:

1) Always a radially split case pump.2) It can be either an overhung type

or between bearing type..


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Casing

Side suction/Side discharge:

This pump can have either an axially orradially split case type.

Suction and Discharge nozzle:


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CasingSeal Chamber and Stuffing Box:

If sealing is by mechanical seal, the chamber is referred to as a

Seal Chamber.

If sealing is by packing, the chamber is referred to as a StuffingBox.

They either integral with or

separate from the pump

case housing that forms theregion between the shaft

and casing where sealing

media are installed.


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Throat

bushing

Throttlebushing

GlandInternal circulating device


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Bearing housing

10-centrifugal pumps construction 1

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