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Satya Narayan Shah
B.Sc.MechanicalEngineering(India)MSinManufacturingEngineering&Management(UK)
Basics
of
HydraulicsMajorapplicationsinEarthMovingEquipment
MajorComponentsofHydraulicSystem
HydraulicSystemDesign
BasicsofHydraulics LIQUIDSHAVENOSHAPEOFTHEIROWN.
Theyacquiretheshapeofanycontainer.Becauseofthis,oilinahydraulicsystemwillflowinanydirectionandintoapassageofanysizeorshape.
LIQUIDSTRANSMITAPPLIEDPRESSUREINALLDIRECTIONS.
LIQUIDSAREPRACTICALLYINCOMPRESSIBLE.
FORCE. Thisprinciplehelpsyoutostopalargemachinebypressingabrakepedal.
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SIMPLEHYDRAULICCIRCUIT
RESERVOIR
RELIEF VALVE
LOAD
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PUMP
ACTUATORCONTROL VALVE
HOWAHYDRAULICSYSTEMWORKS1. ThePUMPwhichmovestheoil.
2. TheCYLINDERwhichusesthemovingoiltodowork.
3. CHECKVALVES toholdtheoilflow.
4. ARESERVOIR(anditsAncillaries)tostoretheoil.
. .
6. TheRELIEFVALVE protectsthesystemfromhighpressures.
7. Gaugesshowflowandpressureatvariouspoints.
8. Accumulator (iffitted)smoothenstheperformance.
9. Filterstoseparatethecontamination.
10. Primemovertodrivethepump.
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Driveunit Hydraulicsystemsaredrivenbymotors(electrical
motors,combustionengines).
Electricalmotorsgenerallyprovidethemec an ca power or epump ns a onaryhydraulicsystem.
Combustionenginesaregenerallyusedinmobilehydraulicsystem.
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ADVANTAGES FLEXIBILITYUnlikethemechanicalmethodofpowertransmissionwhere
therelativepositionsoftheengineandworksitemustremainrelatively constantwiththeflexibilityofhydrauliclines,powercanbemovedtoalmostanylocation.
MULTIPLICATIONOFFORCEsmallforcescanbeusedtomovelargeloads.
SIMPLICITYThehydraulicsystemhasfewermovingparts,fewerpointsofwear.Anditlubricatesitself.
COMPACTNESSTheh draulics stemcanhandlemorehorse ower oritssizethaneitheroftheothersystems.
ECONOMYThisisthenaturalresultofthesimplicityandcompactnesswhichproviderelativelylowcostforthepowertransmitted. Also,powerand
frictionallossesarecomparativelysmall.
SAFETYfewermovingpartssuchasgears,chains,beltandelectricalcontactsthaninothersystems.Overloadscanbemoreeasilycontrolledbyusingreliefvalvesthanispossiblewiththeoverloaddevicesontheothersystems.
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DISADVANTAGES
EFFICIENCYWhiletheefficiencyofthehydraulicsystemismuchbetterthantheelectricalsystem,itislowerthanforthemechanicaltransmissionofpower.
NEEDFORCLEANLINESSHydraulicsystemscanbedamagedbyrust,corrosion,dirt,heatandbreakdowno luids.Cleanlinessand ro ermaintenancearemorecriticalinthehydraulicsystemthanintheothermethodsoftransmission.
FIREHAZARD Duetoneglegence.
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MajorComponentsofHydraulicSystem Reservoir
Tank
Filters Pumps
Valves
CheckValves
DirectionalValves
ReliefValves
Hydraulicaccumulators
Cylinders/Motors
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HydraulicreservoirThereservoirinahydraulicsystemfulfilsseveral
tasks.
Itactsasanintakeandstoragereservoirforthehydraulicfluidrequiredforoperationofthesystem;
Itdissipatesheat;
separa esa r,wa eran so ma er a s;
Itsupportsabuiltinorbuiltonpumpanddrivemotorandotherhydrauliccomponents,suchasvalves,accumulators,etc.
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Hydraulicreservoir Thereservoirconsistsof
Reservoirbody Intakeandreturnlines Baffleandseparatingplate Ventilationandexhaust Magneticplug
Thesizeofthereservoirde endson Pumpdelivery Theheatresultingfromoperation Thevolumeofliquid Theplaceofapplication Thecirculationtime Thesizeofthereservoirisnotclassifiedbyitsphysical
dimensionsbutitsliquidcapacity
Reservoirsize(litres)=pump(litres/min)x3
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Pump
FillerReturn
Connection
Breather
with filter
Return line
Volume of Reservoir
2 - 3 times delivery of
pump in 1 minute
Reservoir
Drain Plug
Baffles
Level indicator
Strainer
Access
panel
Suction line
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Hydraulicfilter
Thetask of the filter is to reducethe contamination in thesystem to anacceptable level in order to protect the various components fromexcessive wear.
Fillercap (breathercap)Itshouldbeairtightwhenclosed,butmaycontaintheairventwhichfiltersairenteringthereservoirtoprovideagravitypushforproperoilflow.
Oil level gauge
ReservoirAccessories
It shows the level of oil inthe reservoirwithout having toopen the reservoir.
Intake filterItis usuallya screen that is attached tothe suction pipeto filter the hydraulic oil.
Drain plug Itallowsalloiltobedrainedfromthereservoir. Somedrainplugsaremagnetictohelpremovemetalchipsfromthe
oil.
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ReservoirAccessories
Baffleplate Itislocatedlengthwisethroughthecentreofthetank
andis2/3theheightoftheoillevel.
Itisusedtoseparatetheoutlettopumpfromthereturnline.Thisensuresacircuitousflowinsteadofthesamefluidbeingrecirculated.
Thebafflepreventslocalturbulenceinthetank,allows
forei nmaterialtosettle, etridofentra edairandincreasesheatdissipation.
Suctionandreturnlines Theyaredesignedtoenterthereservoiratpointswhere
airturbulenceareleast.
Theycanenterthereservoiratthetoporatthesides,buttheirendsshouldbenearthebottomofthetank.
Ifthereturnlineisabovetheoillevel,thereturningoilcanfoamanddrawinair.
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Suctionandreturnlines
Suction line Return line
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ReservoirAccessories Hydraulic filters
Thetaskofthefilteristoreducethecontaminationinthesystemtoanacceptablelevelinordertoprotectthevariouscomponentsfromexcessivewear.
Coolers
Inhydraulicsystems, frictioncausesenergylosseswhenthehydraulicfluidflowsthroughthelinesandcomponents.
Thiscausesthehydraulicfluidtoheatup. ,
environmentviatheoilreservoir,linesandothercomponents
Thefollowingcoolingdevicesareavailable: Aircooler:differenceintemperatureofupto25C
possible. Watercooler:differenceintemperatureofupto35c
possible. Oilcoolingbymeansofairfancooler:whenlarge
quantitiesofheatmustbedissipated.
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ReservoirAccessories Heaters
Heatingelementsorflowpreheatersareusedforheatingandpreheatinghydraulicfluid.
Heatersareoftenrequiredtoensurethatoptimumoperatingtemperatureisquickly
.
Thisistoensurethatoncethesystemisstartedup,thehydraulicfluidquicklyreachestheoptimumviscosity.
Iftheviscosityistoohigh,theincreasedfrictionandcavitationsleadtogreaterwear.
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HydraulicPumpsThepumpbasicallyperformstwofunctions:
Itcreatesapartialvacuumatthepumpinletport.Thevacuumenablestheatmosphericpressuretoforcefluidfromthereservoirintothepump.
Themechanicalactionofthepumptrapsthisfluidwithinthepumpcavities,transportsitthroughthepump,and
forcesitintothehydraulicsystem. Itisoftenassumedthatpumpscreatepressure,butthe
solepurposeofpumpsistocreateflow.
Pressureiscreatedbyresistancetoflow.
Apumpisamechanismdesignedtoproducetheflownecessaryforthedevelopmentofpressure.
Itcannotitselfproducepressure,sinceitcannotprovideresistancetoitsownflow.
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Hydraulicpumps
Threebasictypesofhydraulicpumpscanbedistinguishedonthebasisofthedisplacementvolume:
Constantpumps
Fixed
displacement
volumeAdjustablepumps
Adjustabledisplacementvolume
Variablecapacitypumps
Regulationof flowrate.
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GEAR VANE PISTON
HYDRAULICPUMPS
HYDRAULIC PUMP FAMILYHYDRAULIC PUMP FAMILY
EXTERNAL INTERNAL FIXED VARIABLE
FIXED
AXIAL
BENTAXIS
VARIABLE
AXIAL
BENTAXIS
RADIAL
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Hydraulicpumps
Pumprating
Ratedbytheamountoffluidthatcanbedisplacedforeach
revolutionofthepumpshaft Specifiedincubicinchesorcubiccentimeterperrevolution
Displacementisdefinedasthevolumeofoilmovedordisplacedduringeachcycleofapump.
Therearetwoformsofdisplacement:
Nonpositivedisplacement
Positivedisplacement
Positivedisplacementpump
Deliverstothesystemaspecificamountoffluidperstroke,revolutionorcycle
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Hydraulicpumps The centrifugal pumpis an example of thenonpositive aspect, itsimply moves thefluid and allows forback flow.
Besides being positive displacementpumps, they are also categorized as
either:
Fixed displacement pumpsVariable displacement pumps
Fixed displacement pumps move the
same volume of oil with every cycle.
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This volume is only changed when the
speed of the pump is changed.
Variable displacement pumps can vary
the volume of oil they move with eachcycle - even at the same speed.
These pumps have an internalmechanism which varies the output ofoil.6/14/2011
Fixed&Variabledisplacementpumps
Fixed
Fixeddisplacementpumpsmovethesamevolumeofoilwitheverycycle.
Thisvolumeisonlychangedwhenthespeedofthepumpischanged.
Variable
Variabledisplacementpumpscanvarythevolumeofoiltheymovewitheachcycle evenatthesamespeed.
Thesepumpshaveaninternalmechanism
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Typesofhydraulicpumps Mostpumpsusedontodayssystemsareofthree
basicdesigns:
Gearpumps
anepumps
Pistonpumps
Allthreedesignsworkontherotaryprinciple;arotatingunitinsidethepumpmovesthefluid
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Gearpumps Theyarewidelyusedbecausetheyaresimpleand
economical.
Whilenotcapableofavariabledisplacement,theycanproducethevolumeneededbymostsystemsusingfixeddisplacement.
Often,theyareusedaschargingpumpsforlargersystempumpsofothertypes.
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VANE PUMPS
Vane pumps are fairly versati le pumps and can be designed as single,
double, or even triple units.
All vane pumpsmove oil using a rotatingslotted rotor with vanes fitted intothe slots.
Two types of vane pumps are most often used:
Unbalanced Vane Pumps- The unbalancedvane um usesthe bas ic r inci leof a turnin rotor wi th vanesworkin
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inside a fixed rotor ring. However, the operating cycle only happens once
each revolution. So this pump has only one inlet and one outlet port. Also,the slotted rotor is now set offside in a circular ring.
Balanced Vane Pumps-The rotor is driven by the drive shaft andturns inside an oval rotor ring. The vanes are fitted into the rotor slots and
are free to move in or out. The pump has two inlet ports, located oppositeeach other. And it has two outlet ports, also on opposite sides of the pump.
Both sets are connected to a central inlet and outlet.
VANE PUMP PRINCIPLEVANE PUMP PRINCIPLE
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Unbalancedvanepump Theunbalancedvanepumpcanhaveafixedora
variabledisplacement.
Itusesthesamebasicprincipleofaturningrotorwithvanesworkinginsideafixedrotorring.
However,theoperatingcycleonlyhappensonceeachrevolution.
Sothispumphasonlyoneinletandoneouterport.
Also,theslottedrotorisnowsetoffsideinacircularring.
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Unbalancedvanepump
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Unbalancedvanepump
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Balancedvanepumps Thebalancedvanepumpisstrictlyafixeddisplacement
typepump.
Inthebalancedvanepump,therotorisdrivenbythedriveshaftandturnsinsideanovalrotorring.
Thevanesarefittedintotherotorslotsandarefreetomoveinandout.
T i caldis lacementsto200cm /r
Typicalpressuresto280bar
Fixeddisplacementonly
Providesprimemoversoftstart
Simpledoubleassemblies
Lownoise
Goodserviceability
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Balancedvanepumps
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BALA NCED VANE PUMPBALA NCED VANE PUMP
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Unbalancedvariablevanepump
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VARIABLE VANE PUMP PRINCIPLEVARIABLE VANE PUMP PRINCIPLE
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VARIABLE VANE PUMP PRINCIPLEVARIABLE VANE PUMP PRINCIPLE
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VARIABLE VANE PUMP PRINCIPLEVARIABLE VANE PUMP PRINCIPLE
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Axialpistonpump
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Axialpistonpump
Axialpistonpump
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Axialpistonpump
Axialpistonpump
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Axialpistonpump
Axialpistonpump
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Axialpistonpump
Axialpistonpump
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Axialpistonpump
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STROKESTROKE
VARIABLE DISPLACEMENT PUMP - ZERO FLOWVARIABLE DISPLACEMENT PUMP - ZERO FLOW
Q=(No.ofPistons)x(PistonSize)x(PistonStroke)x(DriveSpeed)Q=(No.ofPistons)x(PistonSize)x(PistonStroke)x(DriveSpeed)6/14/2011 Satya Narayan Shah 73
STROKESTROKE
VARIABLE DISPLACEMENT PUMP - ZERO FLOWVARIABLE DISPLACEMENT PUMP - ZERO FLOW
Q=(No.ofPistons)x(PistonSize)x(PistonStroke)x(DriveSpeed)Q=(No.ofPistons)x(PistonSize)x(PistonStroke)x(DriveSpeed)6/14/2011 Satya Narayan Shah 74
VARIABLE DISPLACEMENT PUMP - REVERSED FLOWVARIABLE DISPLACEMENT PUMP - REVERSED FLOW
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VARIABLE DISPLACEMENT AXIAL PISTONVARIABLE DISPLACEMENT AXIAL PISTON
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Typicaldisplacementsto
500cm3/r
Typicalpressuresto350
bar
Typicaldisplacementsto
500cm3/r
Typicalpressuresto350
bar
FIXED A XIAL PISTON PUMP CHARACTERISTICSFIXED A XIAL PISTON PUMP CHARACTERISTICS
Multipleassemblies
possible
Highoverallefficiency
Compactpackage.
Multipleassemblies
possible
Highoverallefficiency
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Bentaxisaxialpistonpumps Theswashplatedoesnotturnbutitcanbetilted
backandforth.
Theangleoftheswashplatecontrolsthedistancethatthepistonscanmovebackandforthintheir
bores.
Thegreatertheangle,thefartherthepistonstravelandthemoreoilthatisdisplacedbythepump.
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Radialpistonpump Inaradialpistonpump,thecylinderblockrotatesinsideacircular
rotor.
Astheblockrotates,centrifugalforce,chargingpressure,ormechanicalactioncausesthepistontofollowtheinnersurfaceofthering,whichisoffsetfromthecentrelineofthecylinderblock.
Thepistonstakesinfluidastheymoveoutwardanddischargeitastheymovein.
Displacementsto750+cm3/r
Pressurecapabilitiesto350/400bar
Highnoiselevel
Sensitivetopoorinletconditions&contamination
Highoverallefficiency
Goodlifeexpectancy
Large,bulkyunits
Goodfluidcompatibility
Highcost.
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Pistonpumps introduction
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VARIABLE DISPLACEMENT RADIAL PISTON PUMPVARIABLE DISPLACEMENT RADIAL PISTON PUMP
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CYLINDERS PistonTypeCylindersgivestraightmovement.
SINGLEACTINGCYLINDERS giveforceonlyoneway.Pressureoilisadmittedtoonlyoneendofthecylinder,raisingtheload.Anoutsideforcesuchasgravityoraspringmustreturnthecylindertoitsstartingpoint.
DOUBLEACTINGCYLINDERS giveforceinboth
.cylinder,thenattheother,givingtwowaypower.
VaneTypeCylindersgiverotarymovement
Inaroundbarrel,theshaftandvanerotateaspressureoilenters.Oilisdischargedthroughtheoutletholeintheothersideofthecylinder.
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HydraulicaccumulatorsHydraulicaccumulatorsareusedfor:
Storingenergy
Absorbing
shockBuildingpressureregularly
a n a n ngcons an pressure
Typesofhydraulicaccumulators:
Gasloadedaccumulator
Weightloadedaccumulator
Springloadedaccumulator
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GasloadedaccumulatorsWeightloadedaccumulators Spring loadedaccumulators
TypesHydraulicAccumulators
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CharacteristicsofhydraulicaccumulatorsWeightloadedaccumulator
Constantpressureisobtained
Springloadedaccumulator
Canbemountedinanyposition
Gasloadedaccumulators
theselectionanduse ofthisaccumulatordependsuponthepressureandvolumeneedsofthe
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PNEUMATIC ACCUMULATORS
UsesinertgaseslikedryNitrogen
Oilandgaschambersareseparatedbypiston,bladderordiaphragm
Gasiscompressedwhileexcessoilistakenur ngo oa per o an expan s w en
supplyingoiltothesystem
Failureofpackingsealcausesmixingofgasandoil
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Precautions for Pneumatic Accumulators
NEVER FILL AN ACCUMULATOR WITH OXYGEN!
An explosion could result if oil and oxygen mix under pressure.
Never fill an accumulator with air. When air is compressed,water vapor in the air condenses and can cause rust. This in turnmay damage seals and ruin the accumulator. Also, once air leaksinto the oil, the oil becomes oxidized and breaks down.
Always fill an accumulator with an inert gas such as dry
nitrogen. This gas is free of both water vapor and oxygen; thismakes it harmless to parts and safe to use.
Never charge an accumulator to a pressure more than thatrecommended by the manufacturer. Read the label and observethe "working pressure."
Before removing an accumulator from a hydraulic system,release all hydraulic pressure.
To disassemble, release both gas and hydraulic pressures.
To disassemble, make sure that dirt and abrasive material doesnot enter any of the openings
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SPRING-LOADED ACCUMULATORS
In operation, pressure oil loads the piston bycompressing the spring .When pressure drops, thespring forces oil into the system.
The accumulator can be used as a gradual pressurebuilder for an automatic transmission. When the
transmission is shifted, pressure drops and the" " "accumu a or sen s a surge o o n o a e upslack." This fills the chamber behind the clutchpistons. Then pressure builds gradually for a smoothengagement of the clutch.
By controlling the flow of oil to the accumulator, thetime needed to charge it can also be controlled
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SPRING-LOADED ACCUMULATORS
Theoperationofspringloadedaccumulatorscanbevariedbychanging1)thestrengthofthespring,2)thelengthofthespring,3)thepreloadonthespring,4)
thesizeofthepistonor,5)thelengthofthepistonstroke.
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HydraulicValves
Hydraulicvalvesregulate Pressure
Direction
Volume
Typesofvalve Pressurecontrolvalves
Directionalcontrolvalves
Volumecontrolvalves
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PressureControlValves(PCV)PCVareusedtolimitorreducesystempressure
Unloadapump
Setthe ressure
ExamplesofPCVare
Reliefvalves
Pressurereducingvalves
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ReliefValvesUsedassafetyvalves
Preventstheincreaseofsystempressurefromthespecifiedpressurerange
Cracking
pressure
is
the
pressure
at
which
thereliefvalvesfirstbegintoopen
Fullflowpressureisthepressureatwhichthevalvepassesitsfullquantityofoil
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PressureReducingValvesTokeepthepressureinonebranchof
circuitbelowthanthatofmaincircuit
WhennotoperatingthisvalveisopenThespringtensioncanbeadjustedusing
screw
Thisvalvewilllimitmaximumpressureinthesecondarycircuitirrespectiveofpressurechangesinthemaincircuit
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PressuresequenceValvesTocontrolthesequenceofflowtovariousbranchesofcircuit
Valves
allow
flow
to
a
second
function
onlyafterafirsthasbeenfullysatisfied
Whenclosed thevalvedirectsoilfreel totheprimarycircuit
Whenopened,thevalvedivertsoiltoasecondarycircuit
Thesecondcylinderbeginsitsstrokeoncefirstcompletesitsstroke
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DirectionalcontrolvalvesDirectstheflowofoilinhydraulic
systemTypes
Checkvalves
poo va ves
Checkvalves:oOnewayvalve
oOpentoallowflowinonedirectionbutclosetopreventflowintheoppositedirection
oMostlyused tostopreverseflow6/14/2011 111Satya Narayan Shah
SpoolDirectionalvalveDirectsoiltostart,operateandstop
theactuatingunitsonmodernhydraulicsystem
Spoolvalvecanbecategorizedbyitspositionandwayofdirectingtheoilline
Forexamplethreepositionandfourwayvalve
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SpoolDirectionalvalve
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SpoolDirectionalvalve
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SpoolDirectionalvalve
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VolumecontrolvalvesControlsthevolumeorflowofoil
usuallybythrottlingordiverting
Speedofcylinderormotoris
regulatedbythisvalveMostlyusedinfixeddisplacement
typeofvalve
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HydraulicfilterFiltersthecontaminationfromtheoil
Itcanbetakenfromthemachineandcleanedduringservicingperiod.Ifcloggedbypassvalvecomesinaction
Isgenerallycartridgetype
Hydraulicfiltergenerallyisinbetweenreturnlineandtank
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Hydraulichoses
Carrieshydraulicoilfromonecomponenttotheanotherinhydraulicsystem
Areofhighpressureandlowaspertheoilflowline
Flexibleinnature
Canbeconnectedwithanotherpipethroughcoupling
Sometimessteelpipescanbeusedforconnectingtwocomponentsiftheyare
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Hydraulic hoses
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HydraulicfluidThehydraulicfluidisthetransmittingmediumofthehydraulicsystem.Itperformsvarioustasks:
Transmissionofhydraulicenergy
Preventionofcorrosionofmovinginternalparts
Removalofdirt,abrasivematter,etc
Dissi ationofheat
Lubrication
Sealing
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Hydraulicfluidrequirements Mustnotboil,vaporizeorfreezewithinthe
temperaturelimitsofthesystem
Mustnotcorrodetheinternalparts
Viscositymustremainstable
Mustbechemicallystable
Ca ableofresistin foamin
Capableofseparatingfromwater
Compatiblewithsealsandgaskets
Lubricatingability
Oxidationresistance
Loadcarryingcapacity
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Toohighaviscosityincreasesfriction,resultingin: Highresistancetoflow.
Increasedpowerconsumptionduetofrictionalloss.
Hightemperaturecausedbyfriction.
Increasedpressuredropbecauseoftheresistance.
Possibilityofsluggishorslowoperation.
Difficultyinseparatingairfromoilinreservoir.
Greatervacuumatthe um inlet,causin cavitation. Highersystemnoiselevel.
Andshouldtheviscositybetoolow:
Internalleakageincreases.
Excessivewear.
Pumpefficiencymaydecrease,causingsloweroperationoftheactuator.
Increasedtemperatureresultfromleakagelosses
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Typesofhydraulicfluids
Petroleumoil
Fire
resistant
fluids Waterglycols
Wateroilemulsion
Syntheticoil
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Typical hydrauliccircuit. Control valve
Tank
ressure e e
ValveL.H. CylinderR.H. Cylinder
Main pump
Hydraulic filter
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GeneralMaintenanceofhydraulicsystemCriteriaforgeneralmaintenance
Changingoffilter: Normally500hoursofoperation
Changeofoil: 2000hoursofoperationProblemarisesfromfailureofhoses
ep acemen o sea s,or ngs ncy n erp s on
Testingofpressureatdifferenttestpointsliketestofreliefvalvepressure
Internalleakagetestofpump
RefertheElectroniccontrollererrorcodeandfollowtheinstruction
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GeneralMaintenanceofhydraulicsystemForHitachiEX300excavator
Faultcode : 05
Trouble: SignalfromPVCisnottransmittedtoEC
Correctiveaction: Checkwireharness,replacePVCorECifautoidleisabnormal
Faultcode: 22
Trouble: Abnormalpumpcontrol
Correctiveaction: Harnesscheck,checkpumpdisplacementsolenoidvalve,checkanglesensor,checkPVC
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Testingofleakage anexampleLeakageofoilinsystemduetoInternalleakagefrompumpandvalve
Internalleakagefrompistoncylinder
Testingprocedure Raisethebucketwithload.Keepthebucketin
.
Ifbucketlowerscompletely,leakagefrompumpandvalve
Ifnotcompletelyretracted,leakagefromthepistonandcylindergap
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GeneralprecautiontobecarriedoutReliefvalvepressureifitistobe
resetrefertotherecommendedvaluesfrommanufacturer
Ifmetallicchipsfoundinoil,the w o eo o e us e an replacedbynewonewithfilter
Recommendedoiltofilled
Oilissensitivetothedust
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Theanaloguemechanicalsignalsarecapturedbytransducerscommonlycalledsensors
Electroniccircuitstransformtheanaloguesignaltodigitalsignalifrequired.
Relayshelpthesignalstoactivatethesolenoidvalves
Solenoidvalvesonceactivates theinputsignalgoestoElectronicControlUnit(ECU)
Thentothecorrespondingcomponentasperthesystemrequirement
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DesignofasimplehydraulicsystemWhendesigningasimplehydraulicsystem,we
needtocalculatethefollowing:
Pressure,forceandarea
pee o anactuator
Flowvelocityinpipes
Pipesizerequirements
Work,horsepowerandtorque
Reservoirsizing
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Pressureindicatesworkload Resistanceofaloadgeneratespressure.
Pressureequalstotheforceoftheloaddividedbythepistonarea.
Wecanexpressthisrelationshipbythegeneralformula:
P= ressure f=forceanda=area
A
FP =
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Forceisproportionaltopressure
andarea When a hydraulic cylinder is used to clamp or
press, itsoutput force can be computed as follows:
F = px a
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Computingpistonarea
The area of a piston can be computed by thisformula
x4
=
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Speedofanactuator
Howfastapistontravelsoramotorrotatesdependsonitssizeandtherateofoilflowintoit.
Torelateflowratetospeed,considerthevolume
thatmustbefilledintheactuatortocauseagivenamountoftravel.
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AreaTime
Volume
Speed =
x AreaSpeedTime
Volume=
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Velocityinpipes Thevelocityatwhichthehydraulicfluidflows
throughthelinesisanimportantdesignconsiderationbecauseoftheeffectofvelocityon
.
Generallytherecommendedvelocityrangesare:
Pumpinletline=0.61 1.22metrespersecond
Workinglines=2.13 6.10metrespersecond
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Pipesizerequirements
IftheLPManddesiredvelocityareknown,use
this
relationship
to
find
the
cross
sectional
area:
second)permm(inVelocity
16667xLPM)(mmArea 2 =
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Pipesizerequirements
When the LPM and size of pipe is given, use thisformula to find what thevelocity will be:
16667xLPM
Alternatively, the area can be obtained from theselection chart.
)(mmArea
2
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Pipesizerequirements
Selecttheproperconductorinternaldiameteriftheflowrateisknown.
Determineexactlywhatthevelocitywillbeiftheconductorsizeandflowrateareknown.
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Workandpower Whenaforce isexertedthroughadistance,work
isdone.
Work=forcexdistance
Workisusuallyexpressedinjoules.
Forexample,ifa50nweightislifted3m,theworkdoneis150nmorj.
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Workandpower
Thepreviousformuladoesnottakeintoconsiderationhowfasttheworkisdone.
Therateofdoingworkiscalledpower.
Time
Workor
Time
DistancexForcePower=
Theusualunitofpoweristhehorsepower(watt),abbreviatedhp(w).(1hp=746watts)
Onewattisequivalentto1newtonliftedonemetreinonesecond)
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Horsepowerinahydraulicsystem
Inthehydraulicsystem,speedanddistanceareindicatedbytheLPMflowandforceisindicatedbypressure.
Thus,wemightexpresshydraulicpowerthisway:
MetresSquare
Newtonsx
Minutes
LitresPower =
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Horsepowerinahydraulicsystem
Bychangingtheunits,weget
barxLPM
600
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Horsepowerinahydraulicsystem
Thesehorsepowerformulastelltheexactpowerbeingusedinthesystem.
Thehorsepowerrequiredtodrivethepumpwillbesomewhathigherthanthissincethesystemisnot100 e c ent.
Theformulaischangedwhentheaverageefficiency()istakenintoaccount.
x600
barxLPMkW =
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Horsepowerandtorque The following are general torquepower formulas
for any rotating equipment:
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rpm
Torque =
9550
rpmxTorquekW =
Marginoferror Whenworkingontheformulas,wemusttakeinto
considerationthemarginoferrorifitisgiven.
Workingpressure,p = operatingpressuremarginoferror
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Reservoirsizing Forindustrialuse,ageneralsizingruleisused:
Tank
size
(litres)
=
pump
lpm
x
3
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Giventhefollowing:
Load=35000N
Distance=0.5m
Operatingpressure=60bar
Marginoferror=10%
Rateofraisingload=0.15m/sec
Flowvelocity=2.5m/sec
Systemefficiency=90%
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Areaofpiston
Load is35000N
Pressureis60bar
2
5m0.0065
10x54
PressureArea ===
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Velocity
Rateatwhichloadistoberaised=15cm/sec=0.15m/sec
Whichisequalto9m/min
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RateofoilflowRateofoilf low = travelratexarea
= 9x0.0065
= 0.0585m3/min
= . litres/min
= 58.5litres/min
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Wattageofmotor
x600
barxLPMkW =
6.5kW0.9x600
60x58.5kW ==
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Insidediameterofpipe Todeterminetheinsidediameterofthepipeifa
flowvelocityof2.5m/secistobemaintained.
Usingthenomogram,for6.5LPMand2.5m/sec,weget:
Areaoffluidconductor=4cm2
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DiameterofhydraulichoseWiththeareaoffluidconductorbeing4cm2
Thediameterofthehydraulichosecanbeobtained:
2
cm2.26d
4x4d
4
=
=
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Reservoirsizing Reservoirsize
Reservoirsize =58.5x3
=175.5litres
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