Basic Hydraulic Systems.docx

Basic Hydraulic Systems.docx

《Basic Hydraulic Systems.docx》由会员分享，可在线阅读，更多相关《Basic Hydraulic Systems.docx（62页珍藏版）》请在冰豆网上搜索。

BasicHydraulicSystems

SUBCOURSEEDITION

AL0926A

BASIC

HYDRAULICSYSTEMS

ANDCOMPONENTS

BASICHYDRAULICSYSTEMSANDCOMPONENTS

SubcourseNumberAL0926

EDITIONA

USArmyAviationLogisticsSchool

FortEustis,Virginia23604-5439

4CreditHours

EditionDate:

September1994

SUBCOURSEOVERVIEW

Thissubcourseisdesignedtoprovideinstructionontheconceptandoperationofthebasiccomponentsofthehydraulicsystem.Italsodescribesthevariouscomponentsofatypicalhydraulicsystem,theirconstructionandfunctions,andtheirrelationshiptoeachother.

Whenthetermhydraulicsisappliedtoaircraft,itmeansamethodoftransmittingpowerfromonelocationtoanotherthroughtheuseofaconfinedfluid.Thefunctionsperformedbyhydraulicsystemsinaircraftincludeassistinginflightcontrol,extendingandretractinglandinggear,positioningflaps,operatinghoists,raisingandloweringcargodoors,andstartingengines.

ThehydraulicsystemsusedinArmyaircraftaredependableandrelativelytrouble-free.Themaintenancerequirementsaresmallincomparisontotheworkthesystemperforms.

iAL0926

Thissubcourseistobecompletedonaself-studybasis.Youwillgradeyourlessonsasyoucompletethemusingthelessonanswerkeyswhichareenclosed.Ifyouhaveansweredanyquestionincorrectly,studythequestionreferenceshownontheanswerkeyandevaluateallpossiblesolutions.

Therearenoprerequisitesforthissubcourse.

Thissubcoursereflectsthedoctrinewhichwascurrentatthetimeitwasprepared.Inyourownworksituation,alwaysrefertothelatestofficialpublications.

Unlessotherwisestated,themasculinegenderofsingularpronounsisusedtorefertobothmenandwomen.

TERMINALLEARNINGOBJECTIVE

ACTION:

Youwilldemonstrateaknowledgeofthebasiccomponentsofthehydraulicsystem,includingthedeviceswhichactuate,discharge,andcontroltheflowofhydraulicfluidandthosedeviceswhichsense,control,andlimithydraulicpressure.

CONDITIONS:

Youwillusethematerialinthissubcourse.

STANDARD:

Youmustcorrectlyanswer70percentofthequestionsonthesubcourseexaminationtopassthissubcourse.

iiAL0926

TABLEOFCONTENTS

SectionPage

SubcourseOverviewi

TerminalLearningObjectiveii

AdministrativeInstructionsiv

GradingandCertificationInstructionsiv

Lesson1:

HydraulicReservoirs,Filters,Pumps,

Accumulators,andMotors1

PracticeExercise19

AnswerKeyandFeedback22

Lesson2:

BasicConstructionandOperationofHydraulic

ActuatingDevices,FlowControl,andDirectional

Devices25

PracticeExercise43

AnswerKeyandFeedback46

Lesson3:

HydraulicPressure-Limiting,Controlling,and

SensingDevices49

PracticeExercise55

AnswerKeyandFeedback58

Examination61

Appendix:

Glossary69

StudentInquirySheets

iiiAL0926

GRADINGANDCERTIFICATIONINSTRUCTIONS

Examination:

Thissubcoursecontainsamultiple-choiceexaminationcoveringthematerialcontainedinthissubcourse.Afterstudyingthelessonsandworkingthroughthepracticeexercises,completetheexamination.Markyouranswersinthesubcoursebooklet,thentransferthemtotheACCPExaminationResponseSheet.Completelyblackouttheletteredovalwhichcorrespondstoyourselection（A,B,C,orD）.Useanumber2leadpenciltomarkyourresponses.WhenyoucompletetheACCPexaminationresponsesheet,mailitinthepreaddressedenvelopeyoureceivedwiththissubcourse.Youwillreceiveanexaminationscoreinthemail.YouwillreceiveFourcredithoursforsuccessfulcompletionofthisexamination.

ivAL0926

LESSON1

HYDRAULICRESERVOIRS,FILTERS,PUMPS,ACCUMULATORS,ANDMOTORS

STPTasks:

552-758-1063

552-758-1071

OVERVIEW

LESSONDESCRIPTION:

Inthislessonyouwilllearnthebasicoperationofthehydraulicreservoirs,filters,pumps,accumulators,andmotors.

TERMINALLEARNINGOBJECTIVE:

ACTION:

Afterthislessonyouwilldemonstrateknowledgeofhydraulicreservoirs,filters,pumps,accumulators,andmotors.

CONDITIONS:

Youwillstudythematerialinthislessoninaclassroomenvironmentoratyourhome.

STANDARD:

Youwillcorrectlyanswerallthequestionsinthepracticeexercisebeforeyouproceedtothenextlesson.

REFERENCES:

Thematerialcontainedinthislessonwasderivedfromthefollowingpublications:

AR310-25,AR310-50,FM1-500,FM1-509,TM1-1500-204-23Series,TM55-1510-Series（FixedWingMaintenanceManuals）,TM55-1520-Series（RotarywingMaintenanceManuals）andTM4301A050267（AirForce）

1AL0926

INTRODUCTION

Ameansofstoringhydraulicfluidandminimizingcontaminationisnecessarytoanyaircrafthydraulicsystem.Thesefunctionsareperformedbyreservoirsandfilters.Thecomponentwhichcausesfluidflowinahydraulicsystem--theheartofanyhydraulicsystem--canbeahandpump,power-drivenpump,accumulator,oranycombinationofthethree.Finally,ameansofconvertinghydraulicpressuretomechanicalrotationissometimesnecessary,andthisisaccomplishedbyahydraulicmotor.

HYDRAULICRESERVOIRS

Thehydraulicreservoirisacontainerforholdingthefluidrequiredtosupplythesystem,includingareservetocoveranylossesfromminorleakageandevaporation.Thereservoircanbedesignedtoprovidespaceforfluidexpansion,permitairentrainedinthefluidtoescape,andtohelpcoolthefluid.Figure1-1showstwotypicalreservoirs.Comparethetworeservoirsitembyitemand,exceptforthefiltersandbypassvalve,noticethesimilarities.

Fillingreservoirstothetopduringservicingleavesnospaceforexpansion.Mostreservoirsaredesignedwiththerimatthefillerneckbelowthetopofthereservoirtopreventoverfilling.Somemeansofcheckingthefluidlevelisusuallyprovidedonareservoir.Thismaybeaglassorplasticsightgage,atube,oradipstick.Hydraulicreservoirsareeitherventedtotheatmosphereorclosedtotheatmosphereandpressurized.Adescriptionofeachtypefollows.

VentedReservoir.Aventedreservoirisonethatisopentoatmosphericpressurethroughaventline.Becauseatmosphericpressureandgravityaretheforceswhichcausethefluidtoflowtothepump,aventedreservoirismountedatthehighestpointinthehydraulicsystem.Airisdrawnintoandexhaustedfromthereservoirthroughaventline.Afilterisusuallyinstalledintheventlinetopreventforeignmaterialfrombeingtakenintothesystem.

PressurizedReservoir.Apressurizedreservoirissealedfromtheatmosphere.Thisreservoirispressurizedeitherbyenginebleedairorbyhydraulicpressureproducedwithinthehydraulicsystemitself.Pressurizedreservoirsareusedonaircraftintendedforhighaltitudeflight,whereatmosphericpressureisnotenoughtocausefluidflowtothepump.

Inreservoirspressurizedbyenginebleedair,theamountofairpressureisdeterminedbyanairpressureregulator--usually10to15poundspersquareinch（psi）gage.Anexampleofa

2AL0926

hydraulicallypressurizedreservoirusedintheCH-47hydraulicsystemisshowninFigure1-2.

Thisreservoir,ortankasitisreferredtobyBoeing-Vertol,isconstructedofametalhousingwithtwointernalpistons,onefixedandtheotherafloatingpistonwhichslidesalongacentraltube.AttachedtothefloatingpistonisalargertubethatprojectsthroughtheforwardendofthetankandiscalibratedtoindicateFULLandREFILLfluidlevelsforramp-upandramp-downpositions.

Figure1-1.TypicalHydraulicReservoirs.

Hydraulicfluidat3,000psiflowsintothecentraltubeasshowninFigure1-2,passesthroughtwooutletholes,andappliespressureatthepistonareabetweenthetwotubes.Becausethesmallerpistonhasa.5-square-inch（sqin）exposedsurfaceandthefloatingpistonhasa30-sq-inexposedsurface,the3,000-psipressureactinguponthesmallerforwardareaproducesanopposingpressureof50psionthereturnfluidstoredattherearofthepiston.

3AL0926

AdditionalReservoirComponents.Manyreservoirs,asshowninFigure1-1,areconstructedwithbafflesorfinstokeepthefluidfromswirlingandfoaming.Foamingcancauseairtobecomeentrainedinthesystem.

Filtersareincorporatedinsomereservoirstofilterthefluidbeforeitleavesthereservoir.

Abypassvalveisusedtoensurethatthepumpdoesnotstarveifthefilterbecomesclogged.

Astandpipeisusedinareservoirwhichsuppliesanormalandanemergencysystem.Themainsystemdrawsitsfluidfromthestandpipe,whichislocatedatahigherelevation.Thisensuresanadequatefluidsupplytothesecondarysystemifthemainsystemfails.

Figure1-2.HydraulicReservoirPressurizedWithHydraulicFluid.

HYDRAULICFILTER

Contaminationofhydraulicfluidisoneofthecommoncausesofhydraulicsystemtroubles.Installingfilterunitsinthepressureandreturnlinesofahydraulicsystemallows

4AL0926

contaminationtoberemovedfromthefluidbeforeitreachesthevariousoperatingcomponents.Filtersofthistypearereferredtoaslinefilters.

LineFilterConstruction.AtypicallinefilterisshowninFigure1-3.Ithastwomajorparts--thefiltercase,orbowl,andthefilterhead.Thebowlholdstheheadthatscrewsintoit.Theheadhasaninletport,outletport,andreliefvalve.Normalfluidflowisthroughtheinletport,aroundtheoutsideoftheelement,throughtheelementtotheinnerchamber,andoutthroughtheoutletport.Thebypassvalveletsthefluidbypassthefilterelementifitbecomesclogged.

Figure1-3.TypicalLineFilterAssembly.

TypesofFilterElements.ThemostcommonfilteringelementusedonArmyaircraftisthemicronictype.Itisadisposableunitmadeoftreatedcelluloseandisfor