Marine Pumps Centrifugal

8/6/2019 Marine Pumps Centrifugal

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MARINE PUMPSMARINE PUMPS

RotorRotor--Dynamic PumpsDynamic Pumps

Centrifugal PumpsCentrifugal Pumps


RotorRotor--dynamic pumps can be broadly classified intodynamic pumps can be broadly classified intothree main types, there are:three main types, there are:

a)a) Centrifugal pumpsCentrifugal pumps

b)b) Mixed flow pumpsMixed flow pumps

c)c) Axial flow pumps (also known as propeller Axial flow pumps (also known as propellerpumps)pumps)



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Positive DisplacementPositive Displacement vsvs CentrifugalCentrifugalPositive Displacement Centrifugal

Modes of Operation Takes clearly definedvolumes of fluid from theinlet side of the pump,and transfer the fluid tothe delivery side

Relies on thehydrodynamic action of impellers, which aremounted onto the motor-driven shaft to inducefluid flow from the inlet tothe delivery side

Ability to hold pressure Seals to prevent the fluidreturning to the inlet sidewhen the pump is

stopped

Has no ability to sustainpressure when at rest;the inductive action relies

entirely on the impellermotion

Ability to generatepressure

High pressure isgenerated by displacingthe liquid against theresistance on the deliveryside.

Limited pressure on thedelivery side when kineticenergy is converted topressure by the volute.

CentrifugalCentrifugal vsvs MixedMixed--Flow PumpsFlow Pumps

Centrifugal Pump



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Centrifugal Pump Mixed-Flow Pump

http://www.youtube.com/watch?v=B8MV09HF-nY&feature=related


Centrifugal Pump Mixed-Flow Pump



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CentrifugalCentrifugal vsvs Axial Flow Pumps Axial Flow Pumps

Centrifugal Pump

Axial-Flow Pump


Centrifugal Mixed-Flow Axial-Flow

Direction of flowthrough impeller

Enters axially fromone side of impellerand flow radiallyoutwards

Enters axially fromboth sides of impeller and flowradially outwards

Enter axially andflow axiallyoutwards

Comparative

capacity (flow rate)

Lower Medium Higher

Physical size Propeller pumpscan be very large

Comparativepressure (flow rate)

Higher (up to 16bars)

Medium Lower

Number of impellers

Can be connectedin series toincrease pressure

Shaft could only fitone impeller

Shaft could only fitone impeller



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Centrifugal PumpCentrifugal Pump -- DescriptionDescriptionMain parts:

- Impeller

- Shaft

- Impeller journal

- Wear ring

- Casing

- Bearing Bush

- Packing / Mechanical seal

- Coupling spacer

- Shaft coupling

Spaced coupledSpaced coupled vsvs Closed coupledClosed coupled



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Centrifugal PumpsCentrifugal Pumps

►► Design of centrifugal pumps can vary widely inDesign of centrifugal pumps can vary widely indetailsdetails

►► Most have the characteristicMost have the characteristic volute volute shape of casing,shape of casing,necessary for efficient collection of the outflow fromnecessary for efficient collection of the outflow fromthe impeller, converting the kinetic energy intothe impeller, converting the kinetic energy intopressure energy.pressure energy.

MixedMixed--flow Pumpflow PumpMain parts:Main parts:-- ImpellerImpeller-- ShaftShaft-- Impeller journalImpeller journal-- Wear ringWear ring-- CasingCasing-- Bearing BushBearing Bush

-- Packing / Mechanical sealPacking / Mechanical seal-- Coupling spacerCoupling spacer-- Shaft couplingShaft coupling



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MultiMulti--Stage Centrifugal PumpStage Centrifugal Pump

Main parts:

- Impeller

- Shaft

- Impeller journal

- Wear ring

- Casing

- Packing / Mechanical seal

MultiMulti--Stage Centrifugal PumpStage Centrifugal PumpSeries of centrifugal pumps arrangedSeries of centrifugal pumps arrangedtoto supply one another in series andsupply one another in series andthus progressively increase thethus progressively increase thedischarge pressuredischarge pressure..

Applications: Applications:--DeepDeep--well cargo pumping (vertical),well cargo pumping (vertical),driven by electric motors or hydraulicdriven by electric motors or hydraulicmotors outside the tanksmotors outside the tanks-- Boiler feed pump (horizontal)Boiler feed pump (horizontal)



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Air Air--PrimingPriming

►► Centrifugal pumps are not self Centrifugal pumps are not self--primingpriming

►► Require some means of removing air from theRequire some means of removing air from thesuction pipeline and filling it with liquid.suction pipeline and filling it with liquid.

►► Purposes:Purposes:

To avoid running the pump dry that could damage theTo avoid running the pump dry that could damage the

sealing surfaces between journal and wearsealing surfaces between journal and wear--ringsrings To enable pumping (taking suction and deliver the fluid) asTo enable pumping (taking suction and deliver the fluid) as

soon as the pump is runsoon as the pump is run


►► Where the liquid to be pumped is at level higherWhere the liquid to be pumped is at level higherthan the pump,than the pump,

Open an air cock near the pump suction will enable the airOpen an air cock near the pump suction will enable the airto be forced out as the pipeline fills up under the action of to be forced out as the pipeline fills up under the action of gravity.gravity.

►► If the pump is below sea water level, and sea waterIf the pump is below sea water level, and sea waterpriming is permissible in the system,priming is permissible in the system,

Open a sea water injection valve and the air cock on theOpen a sea water injection valve and the air cock on thepump will effect priming.pump will effect priming.



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►► Air priming unit can be provided to individual pumps. Air priming unit can be provided to individual pumps.

AirAir--PrimingPriming – – Methods (General)Methods (General)

Manual Filling



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►► Central priming system may be connected to severalCentral priming system may be connected to severalpumping systems.pumping systems.



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Axial Axial--Flow PumpsFlow Pumps

►► Axial Axial--flow (and semiflow (and semi--axialaxial--flow) pumps areflow) pumps arefrequently used for large volumes (capacity) and lowfrequently used for large volumes (capacity) and lowheads (pressure).heads (pressure).

►► They are simple and occupy little space.They are simple and occupy little space.

►► It is an equivalent to aIt is an equivalent to a low liftlow lift centrifugal pump.centrifugal pump.


►► An axial An axial--flow pump uses a screw propeller toflow pump uses a screw propeller toaccelerate the liquid.accelerate the liquid.

►► The outlet passages and guide vanes are arrangedThe outlet passages and guide vanes are arranged

to convert the velocity increase of the liquid into ato convert the velocity increase of the liquid into apressure.pressure.



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►► An axial An axial--flow pump uses a screw propeller toflow pump uses a screw propeller toaccelerate the liquid.accelerate the liquid.

►► The outlet passages and guide vanes are arrangedThe outlet passages and guide vanes are arranged

to convert the velocity increase of the liquid into ato convert the velocity increase of the liquid into apressure.pressure.

►► They are reversible in flow direction provided thatThey are reversible in flow direction provided thatthey are driven by a reversible primerthey are driven by a reversible primer--mover.mover.



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►► Pump casing is split either horizontally or vertically toPump casing is split either horizontally or vertically toprovide access to the propeller.provide access to the propeller.

►► A stuff A stuff--box prevents leakage where the shaft leavesbox prevents leakage where the shaft leavesthe casing.the casing.

►► A thrust bearing of tilting pad type is fitted on the A thrust bearing of tilting pad type is fitted on the

drive shaft.drive shaft.


►► The axialThe axial--flow pump is used where large quantity of flow pump is used where large quantity of water at a low head is required.water at a low head is required.

►► In Steam Turbine ships, they are often used inIn Steam Turbine ships, they are often used in

condenser circulating or as a supplementary pump incondenser circulating or as a supplementary pump incondenser scoop circulating (since the pump offerscondenser scoop circulating (since the pump offerslittle resistance to flow when idling).little resistance to flow when idling).

►► With scoop circulation, the normal movement of theWith scoop circulation, the normal movement of theship will draw in water; the pump would be in useship will draw in water; the pump would be in useonly when the ship is moving slowly or stopped.only when the ship is moving slowly or stopped.



Propeller PumpsPropeller Pumps

Scoop SystemScoop System

Marine Pumps Centrifugal

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