Lesson 04 - Pumps, Valves, Fans

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    PUMPS, VALVES,PUMPS, VALVES,& FANS& FANS

    Moving fluidsMoving fluids

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    ValvesValves

    Defn: devices whichcontrol theamountandDefn: devices whichcontrol theamountanddirection of fluid flow in piping systemsdirection of fluid flow in piping systems

    Typically made ofbronze, brass, iron, or steelTypically made ofbronze, brass, iron, or steelalloyalloy

    Components:Components:

    -- ValvebodyValvebody -- PackingPacking

    -- DiscDisc -- Packing gland/nutPacking gland/nut

    -- SeatSeat -- StemStem-- BonnetBonnet -- WheelWheel

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    Types of ValvesTypes of Valves

    Two basic groups:Two basic groups: Stop valvesStop valves -- used to shut off or partially shutused to shut off or partially shut

    offthe flow of fluid ( ex: globe, gate, plug,offthe flow of fluid ( ex: globe, gate, plug,needle, butterfly)needle, butterfly)

    Check ValvesCheck Valves -- used to permit flow in only oneused to permit flow in only onedirection (ex: balldirection (ex: ball--check, swingcheck, swing--check, liftcheck, lift--check)check)

    Special types:Special types: Relief valvesRelief valves

    PressurePressure--reducing valvesreducing valves

    RemoteRemote--operated valvesoperated valves

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    Stop ValvesStop Valves

    Globe ValvesGlobe Valves

    Mostcommon type of stop valveMostcommon type of stop valve

    Used in steam, air, water, & oil linesUsed in steam, air, water, & oil lines Discattached to valve stem rests against seatDiscattached to valve stem rests against seatto shut off flow of fluidto shut off flow of fluid

    AdvAdv: Used for throttling: Used for throttling

    DisadvDisadv: flow resistance: flow resistance

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    Globe ValveGlobe Valve

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    Stop ValvesStop Valves

    Gate ValvesGate Valves

    Used when there mustbe straightUsed when there mustbe straight--line flowline flow

    of fluid w/ min. resistanceof fluid w/ min. resistance Gate usually wedgeGate usually wedge--shaped or a vertical discshaped or a vertical disc

    AdvAdv: No flow restrictions: No flow restrictions

    DisadvDisadv: poor throttling: poor throttling

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    Gate ValveGate Valve

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    Stop ValvesStop Valves

    Butterfly ValvesButterfly Valves

    Used in water, fuel, and ventilation systemsUsed in water, fuel, and ventilation systems

    AdvAdv: small, light: small, light--weight, & quickweight, & quick--actingacting DisadvDisadv: leaks early & only low: leaks early & only low--flow throttleflow throttle

    Ball ValvesBall Valves

    Similar to butterfly valvesSimilar to butterfly valves Normally found in seawater, sanitary, trimNormally found in seawater, sanitary, trimand drain, and hydraulic systemsand drain, and hydraulic systems

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    Butterfly ValveButterfly Valve

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    Check ValvesCheck Valves

    Controls direction of flowControls direction of flow

    Operated by flow of fluid in pipeOperated by flow of fluid in pipe

    Types:Types: Swing checkSwing check -- disc moves throughan arcdisc moves throughan arc

    LiftcheckLiftcheck -- disc moves up and downdisc moves up and down

    Ball checkBall check -- ball is located atend of stem andball is located atend of stem andlifts to allow flowlifts to allow flow

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    SwingSwing--check Valvecheck Valve

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    Relief ValvesRelief Valves

    Used to protect piping system fromUsed to protect piping system fromexcessive pressureexcessive pressure

    Opens automatically when fluid pressureOpens automatically when fluid pressurebecomes too high (pressureacts againstbecomes too high (pressureacts againstspring pressure)spring pressure)

    Relieving pressure setby an adjustingRelieving pressure setby an adjustingscrewscrew

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    PressurePressure--reducing Valvesreducing Valves

    Used to automatically providea steady,Used to automatically providea steady,lower pressureto a system from ahigherlower pressureto a system from ahigher

    pressure sourcepressure source Used in air, lubeUsed in air, lube--oil, seawater, and otheroil, seawater, and other

    systemssystems

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    RemoteRemote--operated Valvesoperated Valves

    Valves thatallow operation from distantValves thatallow operation from distantstationsstations

    Types:Types: MechanicalMechanical -- uses reach rods and gearsuses reach rods and gears HydraulicHydraulic -- uses fluid and piston set upuses fluid and piston set up

    MotorMotor -- uses and electric or pneumaticuses and electric or pneumatic

    motormotor SolenoidSolenoid -- uses coil and core mechanism touses coil and core mechanism to

    open or close on an electric signalopen or close on an electric signal

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    PumpsPumps

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    PumpsPumps

    Defn: devicethat uses and externalDefn: devicethat uses and externalpower sourceto apply forceto a fluid inpower sourceto apply forceto a fluid inorder to move it from one placetoorder to move it from one placeto

    anotheranother Must overcome:Must overcome:

    (1) frictional forces from large quantities of(1) frictional forces from large quantities offluidfluid

    (2) difference in static pressurebetween two(2) difference in static pressurebetween twolocationslocations

    Must provideany velocity desiredMust provideany velocity desired

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    PumpsPumps Bernoullis TheoremBernoullis Theorem

    Pressurehead: measure of fluids mech. PEPressurehead: measure of fluids mech. PE Velocity head: measure of fluids mech. KEVelocity head: measure of fluids mech. KE

    Friction head: measure ofenergy lostthatheats fluidFriction head: measure ofenergy lostthatheats fluid

    ZZ11 + P+ P11//VV + V+ V1122/2g = Z/2g = Z22 + P+ P22//VV + V+ V2222/2g + [(U/2g + [(U22 UU11)) WW Q]Q]

    q + wq + wshaftshaft = (h= (h22 hh11) + (v) + (v2222 vv11

    22)/2 + g(z)/2 + g(z22 zz11))

    Z/z: fluid height;Z/z: fluid height; P: fluid pressure;P: fluid pressure; VV: fluid density: fluid density

    V/v: fluid velocityV/v: fluid velocity U: internal energyU: internal energy W/w: workW/w: workQ/q: heattransferredQ/q: heattransferred h: enthalpyh: enthalpy g: grav. accelerationg: grav. acceleration

    BOTTOM LINE: Total energy within thecontrol volume isBOTTOM LINE: Total energy within thecontrol volume isconstant under SS conditions.constant under SS conditions.

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    Components of PumpsComponents of Pumps

    Drive mechanism (steam, electric, gear)Drive mechanism (steam, electric, gear)

    Pump shaftPump shaft

    Impeller or pistonImpeller or piston CasingCasing

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    Types of PumpsTypes of Pumps

    Positive DisplacementPositive Displacement

    Fixed volume of fluid is displaced duringFixed volume of fluid is displaced during

    eachcycle regardless of statichead/pressureeachcycle regardless of statichead/pressurepumping againstpumping against

    Uses either a piston, gear, or screw typeUses either a piston, gear, or screw type(reciprocating, rotary gear, rotary screw,(reciprocating, rotary gear, rotary screw,

    etc)etc)

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    Positive Displacement PumpPositive Displacement Pump

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    PumpsPumps

    NonNon--positive Displacementpositive Displacement: volume of: volume offluid is dependent on staticfluid is dependent on statichead/pressurehead/pressure

    CentrifugalCentrifugal: impeller insideacase (called: impeller insideacase (calledvolute). Impeller is a disc w/ curved vanesvolute). Impeller is a disc w/ curved vanesmounted radially (likea paddle wheel)mounted radially (likea paddle wheel)

    Suction is the EyeSuction is the Eye --> fluid accelerated as it travels> fluid accelerated as it travels

    outward & then enters voluteoutward & then enters volute PropellerPropeller: uses prop insidecasing to move: uses prop insidecasing to move

    fluidfluid --> not used much in Navy> not used much in Navy

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    Centrifugal PumpCentrifugal Pump

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    PumpsPumps

    Jet pumpsJet pumps::

    Bernoullis principleand no moving partsBernoullis principleand no moving parts

    Velocity Head vs. PressureheadVelocity Head vs. Pressurehead

    hin + vin2/2 = hout + vout

    2/2

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    Jet PumpJet Pump

    Types:Types:

    EductorEductor -- used to pump liquidsused to pump liquids

    EjectorEjector -- used to pump gasesused to pump gases

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    Pump Characteristic CurvesPump Characteristic Curves

    Pump Parameters:Pump Parameters: N = pump speed, RPMN = pump speed, RPM

    V = volumetric flow rate, GPMV = volumetric flow rate, GPM

    HHpp = pump head (discharge pressure), psig= pump head (discharge pressure), psig

    P = power required, HpP = power required, Hp

    Centrifugal Pump LawsCentrifugal Pump Laws VV EE NN HHpp EE NN

    22

    WW EE NN33

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    Positive Displacement PumpsPositive Displacement Pumps

    Hp

    GPM

    N1 N2

    N2 = ____

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    Centrifugal PumpsCentrifugal Pumps

    Parallel PumpsParallel Pumps

    Hp

    GPM

    2 Pumps

    1Pump

    V2

    = ____

    Hp2 = ____

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    Centrifugal PumpsCentrifugal Pumps

    Series pumps (called staging)Series pumps (called staging)

    Hp

    GPM

    V2 = ____

    Hp2 = ____2 Pumps

    1Pump

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    Net Positive Suction HeadNet Positive Suction Head

    Defn: that pressure required attheDefn: that pressure required atthesuction ofa pump to preventcavitationsuction ofa pump to preventcavitation

    So what is cavitation?So what is cavitation?-- the formation ofbubbles dueto lowthe formation ofbubbles dueto lowpressureareaand the subsequentpressureareaand the subsequent

    collapse upon migration to ahighcollapse upon migration to ahighpressureareapressurearea

    Cavitation causes noiseand damageCavitation causes noiseand damage

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    Net Positive Suction HeadNet Positive Suction Head

    Need enough pressure on the suction sideNeed enough pressure on the suction sideso thatthe pump does not reduceso thatthe pump does not reduce

    pressure @ theeyeto cause P < Ppressure @ theeyeto cause P < Psatsat If P < PIf P < Psatsat, water flashes to vapor causing, water flashes to vapor causing

    damageto the pumpdamageto the pump

    Whatare possible means of providingWhatare possible means of providingNPSH to preventcavitation?NPSH to preventcavitation?

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    FansFans

    Same Principleas NonSame Principleas Non--positivepositivedisplacement pumpsdisplacement pumps

    Types:Types: Centrifugal: majority used for compressorsCentrifugal: majority used for compressors

    Axial (like propeller): cooling fansAxial (like propeller): cooling fans

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    FansFans

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    Questions?Questions?Questions?Questions?