1 MARINE PUMPS MARINE PUMPS Rotor Rotor- -Dynamic Pumps Dynamic Pumps Centrifugal Pumps Centrifugal Pumps Rotor Rotor-Dynamic Pumps Dynamic Pumps Rotor Rotor- -dynamic pumps can be broadly classified into dynamic pumps can be broadly classified into three main types, there are: three main types, there are: a) a) Cen tri fu gal pumps Centrifugal pumps b) b) Mi xe d fl ow pumps Mixed flow pumps c) c) Axi al flow pumps (als o k nown as prop ell er Axial flow pumps (also known as propeller pumps) pumps)
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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)
►► 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.
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)
►► 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
Air Air--PrimingPriming
►► 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.
►► 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.
Axial Axial--Flow PumpsFlow Pumps
►► 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.
►► 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.
►► 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.
Axial Axial--Flow PumpsFlow Pumps
►► 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.