Pump Basics

Centrifugal PumpsFrom the Center of a CircleRADIAL DIRECTIONTo the Outside of a CircleA machine for moving fluid by accelerating the fluid RADIALLY outward.

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

Centrifugal PumpsA collection chamber in the casing converts much of the Kinetic Energy (energy due to velocity) into Head or Pressure.

Pump Terminology

Head is a term for expressing feet of water columnHead can also be converted to pressure"Head"100 feet43.3 PSIReservoir of Fluid

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

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.

Centrifugal ImpellersThicker the Impeller- More WaterLarger the DIAMETER - More PressureIncrease the Speed - More Water and Pressure

Two Impellers in SeriesDirection of FlowTwice the pressureSame amount of water

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

Pump Performance CurveA mapping or graphing of the pump's ability to produce head and flow

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

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

Pump Performance CurveStep #3, Mapping the Flow and the HeadPump Flow RateMost pump performance curves slope from left to right

Pump Performance CurveImportant PointsShut-off Head is the maximum pressure or head the pump can produceNo flow is producedPump Flow Rate

Pump Performance CurveImportant PointsPump Flow RateMaximum Flow is the largest flow the pump can produceNo Head is produced

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

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

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

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

Pump Flow RateThe point on the system curve that intersects the pump curve is known as the operating point.

Pump Flow RateCirculator 1Circulator 2Circulator 3PUMP SELECTION

Controlling Pump PerformanceChanging the amount for friction loss or "Throttling the Pump" will change the pump's performance

Pump Flow RatePUMP SELECTIONValve OpenValve Partially OpenValve Barely Open

Piping Design EquationsHeuristics for Pipe Diameter

Energy Loss in Piping NetworksIncompressible Fluids

Friction Loss Factors for Fittings

FittingKStandard 90o Elbow30fTStandard 45o Elbow16fTStandard Tee20fT Run60 fT BranchPipe Entrance0.78Pipe Exit1.0

Friction Loss Factors for Valves

ValveKGate valve8fTGlobe Valve340fT Swing Check Valve100fTLift Check Valve600fTBall Valve3fT

Fanning Diagramf =16/Re

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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