Download - Pump Basics1
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Pump Basics
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Centrifugal PumpsFrom the Center of a CircleRADIAL DIRECTIONTo the Outside of a CircleA machine for moving fluid by accelerating the fluid RADIALLY outward.
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This machine consists of an IMPELLER rotating within a case (diffuser)
Liquid directed into the center of the rotating impeller is picked up by the impellers vanes and accelerated to a higher velocity by the rotation of the impeller and discharged by centrifugal force into the case (diffuser).Centrifugal Pumps
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Centrifugal PumpsA collection chamber in the casing converts much of the Kinetic Energy (energy due to velocity) into Head or Pressure.
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Pump Terminology
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Head is a term for expressing feet of water columnHead can also be converted to pressure"Head"100 feet43.3 PSIReservoir of Fluid
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Conversion Factors Between Head and PressureHead (feet of liquid) =Pressure in PSI x 2.31 / Sp. Gr.Pressure in PSI = Head (in feet) x Sp. Gr. / 2.31PSI is Pounds per Square InchSp. Gr. is Specific Gravity which for water is equal to 1For a fluid more dense than water, Sp. Gr. is greater than 1For a fluid less dense than water, Sp. Gr. is less than 1
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HeadHead and pressure are interchangeable terms provided that they are expressed in their correct units.The conversion of all pressure terms into units of equivalent head simplifies most pump calculations.
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Centrifugal ImpellersThicker the Impeller- More WaterLarger the DIAMETER - More PressureIncrease the Speed - More Water and Pressure
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Two Impellers in SeriesDirection of FlowTwice the pressureSame amount of water
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Multiple Impellers in SeriesPlacing impellers in series increases the amount of head producedThe head produced = # of impellers x head of one impellerDirection of FlowDirection of Flow
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Pump Performance CurveA mapping or graphing of the pump's ability to produce head and flow
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Pump Performance CurveStep #1, Horizontal AxisThe pump's flow rate is plotted on the horizontal axis ( X axis)Usually expressed in Gallons per MinutePump Flow Rate
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Pump Performance CurveStep #2, Vertical AxisPump Flow RateThe head the pump produces is plotted on the vertical axis (Y axis)Usually express in Feet of WaterHead
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Pump Performance CurveStep #3, Mapping the Flow and the HeadPump Flow RateMost pump performance curves slope from left to right
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Pump Performance CurveImportant PointsShut-off Head is the maximum pressure or head the pump can produceNo flow is producedPump Flow Rate
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Pump Performance CurveImportant PointsPump Flow RateMaximum Flow is the largest flow the pump can produceNo Head is produced
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System Performance CurvesSystem Performance Curve is a mapping of the head required to produce flow in a given systemA system includes all the pipe, fittings and devices the fluid must flow through, and represents the friction loss the fluid experiences
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System Performance CurveStep #1, Horizontal AxisSystem Flow RateThe System's flow rate in plotted on the horizontal axis ( X axis)Usually expressed in Gallons per Minute
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System Performance CurveStep #2, Vertical AxisPump Flow RateThe head the system requires is plotted on the vertical axis (Y axis)Usually express in Feet of WaterHead
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System Performance CurveStep #3, Curve MappingThe friction loss is mapped onto the graphThe amount of friction loss varies with flow through the systemPump Flow RateFriction Loss
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Pump Flow RateThe point on the system curve that intersects the pump curve is known as the operating point.
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Pump Flow RateCirculator 1Circulator 2Circulator 3PUMP SELECTION
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Controlling Pump PerformanceChanging the amount for friction loss or "Throttling the Pump" will change the pump's performance
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Pump Flow RatePUMP SELECTIONValve OpenValve Partially OpenValve Barely Open
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Piping Design EquationsHeuristics for Pipe Diameter
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Energy Loss in Piping NetworksIncompressible Fluids
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Friction Loss Factors for Fittings
FittingKStandard 90o Elbow30fTStandard 45o Elbow16fTStandard Tee20fT Run60 fT BranchPipe Entrance0.78Pipe Exit1.0
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Friction Loss Factors for Valves
ValveKGate valve8fTGlobe Valve340fT Swing Check Valve100fTLift Check Valve600fTBall Valve3fT
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Fanning Diagramf =16/Re
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Energy Loss in ValvesFunction of valve type and valve positionThe complex flow path through valves can result in high head loss (of course, one of the purposes of a valve is to create head loss when it is not fully open)Ev are the loss in terms of velocity heads
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