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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

whichvariestheoutputofoil.6/14/2011 Satya Narayan Shah 34

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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QQ

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

QQ

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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

Compactpackage.6/14/2011 Satya Narayan Shah 77

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

closedtoother6/14/2011 135Satya Narayan Shah

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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