1HydraulicSystemThereareonlyfollowingthreebasicmethodsoftransmittingpower:electrical，mechanical,andfluidpower.Mostapplicationsactuallyuseacombinationofthethreemethodstoobtainthemostefficientoverallsystem.Toproperlydeterminewhichprinciplemethodtouse,itisimportanttounderstandthecharacteristicofeachmethod.Forexample，hydraulicsystemsonthelongdistanceeconomicallydeliverpowermorethanmechanicalsystems.However,fluidsystemsarerestrictedtoshorterdistancesthanelectricalsystems.Hydraulicpowertransmissionsystemsareconcernedwiththegeneration,modulation,andcontrolofsculptressandflow,andingeneralsuchsystemsinclude:l.Pumpsconvertavailablepowerfromtheprimemovertohydraulicpowerattheactuator.2.Valvescontrolthedirectionofpump-flow,thelevelofproducedpower,andtheamountoffluid-flowtotheactuators.Thepowerlevelisdeterminedbycontrollingboththeflowandpressurelevel.3.Actuatorsconverthydraulicpowertousablemechanicalpoweroutputatthepointrequired.4.Themediumisaliquid,providesrigidtransmissionandcontrolaswellaslubricationofcomponents,sealinginvalves,andcoolingofthesystem.5.Connectorslinkthevarioussystemcomponents,providepowerconductorsforthefluidunderpressure,andfluidflowreturntotank（reservoir).6.Fluidstorageandconditioningequipmentensuresufficientqualityandquantityaswellascoolingofthefluid.Hydraulicsystemsareusedinindustrialapplicationssuchasstampingpresses,steelmillsandgeneralmanufacturing,agriculturalmachines,miningindustry,aviation,spacetechnology,deep-seaexploration,transportation,Narinetechnology,andoffshoregasandpetroleumexploration.Inshort,manypeoplegetsomehowbenefitingfromthetechnologyofhydraulics.Thesecretofthesuccessandwidespreaduseofthehydraulicsystemisitsversatilityandmanageability.Fluidpowerisnothinderedbythegeometryofthemachineasisthecaseinmechanicalsystems.Also,powercanbetransmittedinalmostlimitlessquantitiesbecausefluidsystemsarenotsolimitedbythephysicallimitationsofmaterialsasaretheelectricalsystems.Forexample,theperformanceofanelectromagnetislimitedbythesaturationlimitofsteel.Ontheotherhand,thepowerlimitoffluidsystemsislimitedonlybythestrengthcapacityofthematerial.Industryisgoingtodependmoreandmoreonautomationinordertoincreaseproductivity.Thisincludesremotionanddirectcontrolofproductionoperations,manufacturingprocesses,andmaterialshandling.Fluidpoweristhemuscleofautomationbecauseoftheadvantagesinthefollowingfourmajorcategories.1.Easeandaccuracyofcontrol.Bytheuseofsimpleleversandpushbuttons,theoperatorofafluidpowersystemcanreadilystart,stop,speeduporslowdown,andprovideanydesired2horsepowerwithtolerancesaspreciseasoneten-thousandthofaninch.2.Multiplicationofforce.Afluidpowersystem(withoutusingcumbersomegears,pulleys,andlevers)canmultiplyforcesimplyandefficientlycreatetheoutputfromafractionofanouncetoseveralhundredtons.3.Constantforceortorque.Onlyfluidpowersystemsarecapableofprovidingconstantforceortorqueregardlessofspeedchanges.Itproducestheworkoutputmovingfromafewinchesperhourtoseveralhundredinchesperminute,orfromafewrevolutionsperhourtothousandsofrevolutionsperminute.4.Simplicity,safety,economy.Ingeneral,fluidpowersystemsusefewermovingpartsthancomparablemechanicalorelectricalsystems.Thus,theyaresimplertomaintainandoperate.This,inturn,maximizessafety,compactness,andreliability.Forexample,anewpowersteeringcontroldesignhasmadeallotherkindsofpowersystemsobsoleteonmanyoff-highwayvehicles.Thesteeringunitconsistsofamanuallyoperateddirectionalcontrolvalveandmeterinasinglebody.Becausethesteeringunitisfullyfluid-linked,withoutthelinkofmechanicallinkages,universaljoints,bearings,reductiongears,etc.Thisprovidesasimple,compactsystem.Inaddition,verylittleinputtorqueisrequiredtoproducethecontrolneededforthetoughestapplications.Thisisimportantwherelimitationsofcontrolspacerequireasmallsteeringwheelanditbecomesnecessarytoreduceoperatorfatigue.Additionalbenefitsoffluidpowersystemsincludeinstantlyreversiblemotion,automaticprotectionagainstoverloads,andinfinitelyvariablespeedcontrol.Fluidpowersystemsalsohavethehighesthorsepowerperweightratioofanyknownpowersource.Inspiteofallthesehighlydesirablefeaturesoffluidpower,itisnotapanaceaforallpowertransmissionproblems.Hydraulicsystemsalsohavesomedrawbacks.Hydraulicoilsaremessy,andleakageisimpossibletocompletelyeliminate.Also,mosthydraulicoilscancausetiresifanoilleakoccursinanareaofhotequipment.Now,aconcreteexampleisfollowing-weusehydraulicstationstointroducetheadvantagesofthehydraulicsystem.HydraulicStationandthedevelopmentofhydrauliccomponentsProfilesHydraulicPumpStationalsoknownasthestationsisindependenthydraulicdevice.Itisrequestedbytheoilgraduallyandcontrolsthehydraulicoilflowdirection,pressureandflowrate,appliedtothemainframeandhydraulicdevicesabilityofhydraulicmachinery.Usersjustneedtoconnecthydraulicstationandhostofimplementingagencies(motoroilorfueltanks)withtubing.Hydraulicmachinerycanrealizethesespecifiedmovementsandtheworkcycle.HydraulicpumpstationisequippedwithPumpdevice,manifoldorvalveportfolio,tanks,electricalboxes.Pumpdevice-isequippedwithmotorsandpumps.Hydraulicstationisthesourceofpowerandcantranslatemechanicalenergyintohydraulicoilpressure.Manifold-isinstalledbyhydraulicvalveandassembledchannel.Ithasthefunctionofadjustingthedirectionforimplementationofhydraulicoil,pressureandflow.Valveportfolio-platevalveisinstalledinupboard,thebackboardconnectsandhasthe3samefunctionalwithIC.Tank-plateweldingsemi-closedcontainers,alsoisloadedwithoilfilteringnetwork,airfiltersansisusedtosaveoil,oilfiltersandcooling.Electricalboxes-hasthetwopatterns.Asetofexternalfuseterminalplateandafullrangeofcontrolelectrical.TheprincipleofthehydraulicStation:themotordrivespumprotation,pumpabsorbsoilfromtheoiltank,thentranslatesmechanicalenergyintohydraulicpressureofthestation.HydraulicoilthroughManifold(orvalvecombinations)realizedthedirection,pressure.Afteradjustingflowpipe,itexternalflowstothecylinderhydraulicmachineryormotoroil,soastocontrolthedirectionofthemotivefluid,thesizeoftransformationforceandthespeedofthepace,finallyitpromoteshydraulicmachinerytothevariousacting.Firstly,AdevelopmentcourseChinaHydraulic(includinghydraulic,thesamebelow),pneumaticandsealsindustrialdevelopmentprocesscanbebroadlydividedintothreephases,namely:theearly1950stotheearly1960sistheinitialstage.The60sand70sisthegrowthstageforspecializedproductionsystem.The80s-90sisthegrowthstagefortherapiddevelopment.Meanwhile,hydraulicindustrystartedintheearly1950sfromthemachinetoolindustryproductionoffakeus-grinder,broachingmachine,copyinglathe,andotherhydraulicdrive.HydraulicComponentsfromtheplanthydraulicmachineshopisself-occupied.Afterenteringthel960s,theapplicationofhydraulictechnologyfromthemachinegraduallyextendedtotheagriculturalmachineryandmechanicalengineeringfields,attachedtotheoriginalvelocityofhydraulicshopsomestandoutaspiecesofhydraulicprofessionalproduction.Tothelate1960s,early1970s,withthedevelopmentofmechanizedproduction,especiallythesecondautomobilefactoryprovidesefficient,automatedequipment.TheHydraulicComponentsmanufacturinghasexperiencedrapidlydevelopmentofthesituation.GroupsofSMEhavebecomeprofessionalhydraulicpartsfactory.Chinaannualoutputofhydrauliccomponentshasnearly200.000in1968.Machinetools,agriculturalmachinery,mechanicalengineeringindustries,theproductionofhydraulicpartsfactoryhavebeentheprofessionaldevelopmentofmorethan100andanannualoutputmorethanonemillionin1973andanindependenthydraulicmanufacturingindustryhasbeguntotakeshape.Then,hydraulicpiecesoffakeproductshasdevelopedfromtheSovietUnionfortheintroductionoftheproductandcombiningtheproducts.Hypertensionhasdevelopedtomediumandhighpressureandthedevelopmentoftheelectro-hydraulicservovalvesandsystems,hydraulicapplicationareasfurtherexpanded.Pneumaticindustrystartedlaterthantheindustrialhydraulicyears.Until1967professionalpneumaticcomponentsfactorybegantoestablish.PneumaticComponentslookedonlyascommodityproductionandsales.Itdealwithrubberandplastics,mechanicalsealsandsealingflexiblegraphite.Intheearly1950s,itproducedordinary0-rings,rubberandplasticsextrusion,suchasoilsealsealingandsealasbestos.Untiltheearly1960s,itbeguntoproductionof4mechanicalsealsandflexiblegraphitesealingproducts.In1970s,undertheburningoftheformerMinistry,aMinistry,theMinistryofAgriculturalMechanizationSystem,agroupofprofessionalproductionplantshavebeenestablished,andtheofficialestablishmentofindustriestosealindustrialdevelopmenthaslaidthefoundationforgrowth.Sincethel980s,undertheguidelinesofcountrysreformandopeninguppolicy,withthedevelopmentofthemachineryindustry,basedmainframepiecesbehindtheconflictshavebecomeincreasinglyprominentandattractedtheattentionoftherelevantdepartments.Tothisend,theMinistryoriginatingin1982andformedthebasisofcommonpiecesofIndustry,willcentralizehydraulic,pneumaticandsealsspecializedfactoriesoriginalmachinetoolsscatteredinagriculturalmachinery,mechanicalengineeringindustriesandplacethemundercommonmanagementinfrastructurepiecesBureau,sothattheindustryintheplanning,investment,technologyandscientificresearchanddevelopmentinareasgottheguidanceandsupportofinfrastructurepiecesBureau.Sincethenitenteredaphaseofrapiddevelopmentandhasintroducedmorethan60itemsofadvancedtechnologyfromabroad,includingmorethan40itemsofhydraulic,pneumatic7.Afterdigestionandabsorptionandtransformation,nowtheyhavemassproduction,andindustry-leadingproducts.Inrecentyears,theindustryhasincreasedthetechnologicaltransformationefforts.Fom1991to1998,state,Localenterprisesandtheself-Financinghavefundtotalinputofabout20billion￥,ofwhichHydraulicwasmorethanI.6billion￥.Throughtechnologicaltransformationandtechnologyresearch,anumberofmajorenterpriseshavefurtherimprovedtheleveloftechnology,techniqueandequipment,whichhaslaidagoodfoundationinordertoformahigherStartingpoint,specialization,andrunproduction.Inrecentyears,undertheguidelinesofdevelopmentofcommonownership,differentownershipSMErapidlyhaverisetoshowgre