Centrifugal Pumps Sup27jul

7/31/2019 Centrifugal Pumps Sup27jul

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http://en.wikipedia.org/wiki/Image:Warman_centrifugal_pump.jpg


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depends on various factors likeProcess liquid characteristics i.edensity,viscosity.Size of pump and its inlet and outletsections.Size and shape of cavities between thevanes.Pump suction and dischargetemperature and pressure conditions.

Velocity of flow in suction pipe.


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It is the measurement of the height of aliquid column.

Various head terms used are:Static suction head.Static discharge head.Friction head.Pressure head.Total suction head.Total discharge head.Total differential head.


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Head resulting from elevationof liquid relative to the pumpcenterline.

If the liquid level is abovepump centerline,then thestatic suction head is positive.

If the liquid level is belowpump centerline then thesuction head is negative andthis condition is commonlydenoted as a suction liftcondition


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:

CASE I:Suction from source under pressure

other than atm, and located abovepump centerline.

CASE II:Suction from source under pressure,andlocated below pump centerline.


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This involves asuction supplyunder a press otherthan atm,andlocated above thepump centerline.

Includes allcomponents of thesuction head.


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Suction fromsource under atmpressure, andlocated belowpump centerline.Used in cases

where the tank isunderground orsuction from largereservoirs


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It is the head required to overcome theresistance to flow in the pipe and

fittings.It is dependent upon the size, conditionand type of the pipe, number and type of pipe fitting, flowrate, and nature of liquid.h f = 4fLu 2

2Dg


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Pressure head must be considered whena pumping system either begins orterminates in a tank which is under some

pressure other than atmosphere.Pressure head refers to absolute press onthe surface of the liquid reservoir

supplying the pump suction.If the system is open,h p equals atmpressure head.


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hps = Suction tank pressure head

h s = Static suction headh fs = Friction headhpd = discharge tank pressure head

hd = Static discharge head


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determines the requiredsuction head (maximum suction lift).

is determined by the pipesystem on the suction (inlet) side of the pump.

You must configure your system so. Failure to meet

this requirement will cause reducedflow rate, cavitation, and vibration of the pump.


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= pressure on the liquid surfacein the supply tank

= suction head (+) orsuction lift (-)

= vapor pressure= friction loss in the suctionpiping


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Slower speeds.

A double suction impeller.Inducer.Several smaller pumps in parallel.


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is a general term used todescribe the behavior of bubbles in aliquid.

Two classes of : : Bubblein a liquid rapidly collapses, producing a

shock wave: Bubble in a fluid

is forced to oscillate due to some form of

energy input.


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It occurs when the pump suction isunder a low pressure/high vacuumconditionThis vapor is carried over to thedischarge side of the pump and iscompressed back into a liquid by the

discharge pressure.This imploding action occursviolently and attacks the face of theimpeller.


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Discharge cavitation occurs when thepump discharge pressure is extremely

high.The high discharge pressure causesthe majority of the fluid to circulateinside the pump instead of beingallowed to flow out the discharge.Discharge cavitation is believed to bethe cause of cracking of joints.


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Centrifugal Pumps Sup27jul