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?