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外文翻译--浅谈油管液压管路系统设计.doc

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外文翻译--浅谈油管液压管路系统设计.doc

TALKINGABOUTTHEDESIGNOFHYDRAULICCONDUCTORSERICSANDGRENTHISPAPERISACCOUNTFORUNCERTAINTYMECHANICALENGINEERING,UNIVERSITYOFCALIFORNIA,SANFRANCISCO,AVIALON503WESTMAINSTREET,POBOX96253111INTRODUCTIONINAHYDRAULICSYSTEM,THEFLUIDFLOWSTHROUGHADISTRIBUTIONSYSTEMCONSISTINGOFCONDUCTORSANDFITTINGS,WHICHCARRYTHEFLUIDFROMTHERESERVOIRTHROUGHOPERATINGCOMPONENTSANDBACKTOTHERESERVOIRSINCEPOWERISTRANSMITTEDTHROUGHOUTTHESYSTEMBYMEANSOFTHESECONDUCTINGLINESCONDUCTORSANDFITTINGSUSEDTOCONNECTSYSTEMCOMPONENTS,ITFOLLOWSTHATTHEYMUSTBEPROPERLYDESIGNEDINORDERFORTHETOTALSYSTEMTOFUNCTIONPROPERLYTHECHOICEOFWHICHTYPEOFCONDUCTORTOUSEDEPENDSPRIMARILYONTHESYSTEM’SOPERATINGPRESSURESANDFLOWRATESINADDITION,THESELECTIONDEPENDSONENVIRONMENTALCONDITIONSSUCHASTHETYPEOFFLUID,OPERATINGTEMPERATURES,VIBRATION,ANDWHETHERORNOTTHEREISRELATIVEMOTIONBETWEENCONNECTEDCOMPONENTSCONDUCTINGLINESAREAVAILABLEFORHANDLINGWORKPRESSURESUPTO10,000PAORGREATERINGENERAL,STEELTUBINGPROVIDESGREATERPLUMBINGFLEXIBILITYANDNEATERAPPEARANCEANDREQUIRESFEWERFITTINGSTHANPIPINGHOWEVER,PIPINGISLESSEXPENSIVETHANSTEELTUBINGPLASTICTUBINGISFINDINGINCREASEDINDUSTRIALUSAGEBECAUSEITISNOTCOSTLYANDCIRCUITSCANBEVERYEASILYHOOKEDUPDUETOITSFLEXIBILITYFLEXIBLEHOSESAREUSEDPRIMARILYTOCONNECTCOMPONENTSTHATEXPERIENCERELATIVEMOTIONTHEYAREMADEFROMALARGENUMBEROFELASTOMERICRUBBERLIKECOMPOUNDSANDARECAPABLEOFHANDLINGPRESSURESEXCEEDING10,000PASTAINLESSSTEELCONDUCTORSANDFITTINGSAREUSEDIFEXTREMELYCORROSIVEENVIRONMENTSAREEXPECTEDHOWEVER,THEYAREVERYEXPENSIVEANDSHOULDBEUSEDONLYIFNECESSARYCOPPERCONDUCTORSSHOULDNOTBEUSEDINHYDRAULICSYSTEMSBECAUSETHECOPPERPROMOTESTHEOXIDATIONOFPETROLEUMOILSZINC,MAGNESIUM,ANDCADMIUMCONDUCTORSSHOULDNOTBEUSEDEITHERBECAUSETHEYARERAPIDLYCORRODEDBYWATERGLYCOLFLUIDSGALVANIZEDCONDUCTORSSHOULDALSOBEAVOIDEDBECAUSETHEGALVANIZEDSURFACEHASATENDENCYTOFLAKEOFFINTOTHEHYDRAULICFLUIDWHENUSINGSTEELPIPEORSTEELTUBING,HYDRAULICFITTINGSSHOULDBEMADEOFSTEELEXCEPTFORINLET,RETURN,ANDDRAINLINES,WHEREMALLEABLEIRONMAYBEUSEDCONDUCTORSANDFITTINGSMUSTBEDESIGNEDWITHHUMANSAFETYINMINDTHEYMUSTBESTRONGENOUGHNOTONLYTOWITHSTANDTHESTEADYSTATESYSTEMPRESSURESBUTALSOTHEINSTANTANEOUSPRESSURESPIKESRESULTINGFROMHYDRAULICSHOCKWHENEVERCONTROLVALVESARECLOSEDSUDDENLY,THISSTOPSTHEFLUID,WHICHPOSSESSESLARGEAMOUNTSOFKINETICENERGYTHISPRODUCESSHOCKWAVESWHOSEPRESSURELEVELSCANBETWOORFOURTIMESTHESTEADYSTATESYSTEMDESIGNVALUESPRESSURESPIKESCANALSOBECAUSEDBYSUDDENSTOPPINGORSTARTINGOFHEAVYLOADSTHESEHIGHPRESSUREPULSESARETAKENINTOACCOUNTBYTHEAPPLICATIONOFANAPPROPRIATEFACTOROFSAFETY12CONDUCTORSIZINGFORFLOWRATEREQUIREMENTSACONDUCTORMUSTHAVEALARGEENOUGHCROSSSECTIONALAREATOHANDLETHEFLOWRATEREQUIREMENTSWITHOUTPRODUCINGEXCESSIVEFLUIDVELOCITYWHENEVERWESPEAKOFFLUIDVELOCITYINACONDUCTORSUCHASAPIPE,WEAREREFERRINGTOTHEAVERAGEVELOCITYTHECONCEPTOFAVERAGEVELOCITYISIMPORTANTSINCEWEKNOWTHATTHEVELOCITYPROFILEISNOTCONSTANTASSHOWNINCHAPTER5THEVELOCITYISZEROATTHEPIPEWALLANDREACHESAMAXIMUMVALUEATTHECENTERLINEOFTHEPIPETHEAVERAGEVELOCITYISDEFINEDASTHEVOLUMEFLOWRATEDIVIDEDBYTHEPIPECROSSSECTIONALAREAAQVINOTHERWORDS,THEAVERAGEVELOCITYISTHATVELOCITYWHICHWHENMULTIPLIEDBYTHEPIPEAREAEQUALSTHEVOLUMEFLOWRATEITISALSOUNDERSTOODTHATTHETERMDIAMETERBYITSELFALWAYSMEANSINSIDEDIAMETERANDTHATTHEPIPEAREAISTHATAREATHATCORRESPONDSTOTHEPIPEINSIDEDIAMETERTHEMAXIMUMRECOMMENDEDVELOCITYFORPUMPSUCTIONLINESIS4FT/S12M/SINORDERTOPREVENTEXCESSIVELYLOWSUCTIONPRESSURESANDRESULTINGPUMPCAVITATIONTHEMAXIMUMRECOMMENDEDVELOCITYFORPRESSURELINESIS20FT/S61M/SINORDERTOPREVENTTURBULENTFLOWANDTHECORRESPONDINGEXCESSIVEHEADLOSSESANDELEVATEDFLUIDTEMPERATURESNOTETHATTHESEMAXIMUMRECOMMENDEDVALUESAREAVERAGEVELOCITIESEXAMPLE11APIPEHANDLESAFLOWRATEOF30GPRNFINDTHEMINIMUMINSIDEDIAMETERTHATWILLPROVIDEANAVERAGEFLUIDVELOCITYNOTTOEXCEED20FT/SSOLUTIONREWRITEEQ326,SOLVINGFORDINVQD78206120203040804080EXAMPLE12APIPEHANDLESAFLOWRATEOF0002SM/3FINDTHEMINIMUMINSIDEDIAMETERTHATWILLPROVIDEANAVERAGEFLUIDVELOCITYNOTTOEXCEED61M/SSOLUTIONPEREQ335WESOLVEFORTHEMINIMUMREQUIREDPIPEFLOWAREA2320003280160020MSMVSMQMATHEMINIMUMINSIDEDIAMETERCANNOWBEFOUND,BECAUSE42DASOLVINGFORDWEHAVEMMMAD4200204000032804413PRESSURERATINGOFCONDUCTORSACONDUCTORMUSTBESTRONGENOUGHTOPREVENTBURSTINGDUETOEXCESSIVETENSILESTRESSCALLEDHOOPSTRESSINTHEWALLOFTHECONDUCTORUNDEROPERATINGFLUIDPRESSURETHEMAGNITUDEOFTHISTENSILESTRESS,WHICHMUSTBESUSTAINEDBYTHECONDUCTORMATERIALWESEETHEFLUIDPRESSUREPACTINGNORMALTOTHEINSIDESURFACEOFACIRCULARPIPEHAVINGALENGTHLTHEPIPEHASOUTSIDEDIAMETERD0,INSIDEDIAMETERDI,ANDWALLTHICKNESSTBECAUSETHEFLUIDPRESSUREACTSNORMALTOTHEPIPE’SINSIDESURFACE,APRESSUREFORCEISCREATEDTHATATTEMPTSTOSEPARATEONEHALFOFTHEPIPEFROMTHEOTHERHALFFIGURESHOWSTHISPRESSUREFORCEPFPUSHINGDOWNWARDONTHEBOTTOMHALFOFTHEPIPETOPREVENTTHEBOTTOMHALFOFTHEPIPEFROMSEPARATINGFROMTHEUPPERHALF,THEUPPERHALFPULLSUPWARDWITHATOTALTENSILEFORCEFONEHALFOFTHISFORCEORF/2ACTSONTHECROSSSECTIONALAREATLOFEACHWALL,ASSHOWNSINCETHEPRESSUREFORCEANDTHETOTALTENSILEFORCEMUSTBEEQUALINMAGNITUDE,WEHAVEWHEREAISTHEPROJECTEDAREAOFTHELOWERHALFPIPECURVEDWALLSURFACEONTOAHORIZONTALPLANETHUS,AEQUALSTHEAREAOFARECTANGLEOFWIDTHDIANDLENGTHL,ASSHOWNINFIGURE41BHENCE,THETENSILESTRESSINTHEPIPEMATERIALEQUALSTHETENSILEFORCEDIVIDEDBYTHEWALLCROSSSECTIONALAREAWITHSTANDINGTHETENSILEFORCETHISSTRESSISCALLEDATENSILESTRESSBECAUSETHEFORCEFISATENSILEFORCEPULLSONTHEAREAOVERWHICHITACTSSUBSTITUTINGVARIABLESWEHAVEWHEREGREEKSYMBOLSIGMATENSILESTRESSASCANBESEENFROMEQTHETENSILESTRESSINCREASESASTHEFLUIDPRESSUREINCREASESANDALSOASTHEPIPEINSIDEDIAMETERINCREASESINADDITION,ASEXPECTED,THETENSILESTRESSINCREASESASTHEWALLTHICKNESSDECREASES,ANDTHELENGTHOFTHEPIPEDOESNOTHAVEANYEFFECTONTHETENSILESTRESSBURSTPRESSUREANDWORKINGPRESSURETHEBURSTPRESSUREBPISTHEFLUIDPRESSURETHATWILLCAUSETHEPIPETOBURSTTHISHAPPENSWHENTHETENSILESTRESSEQUALSTHETENSILESTRENGTHSOFTHEPIPEMATERIALTHETENSILESTRENGTHOFAMATERIALEQUALSTHETENSILESTRESSATWHICHTHEMATERIALRUPTURESNOTICETHATANAXIALSCRIBELINEISSHOWNONTHEPIPEOUTERWALLSURFACEINFIG41ATHISSCRIBELINESHOWSWHERETHEPIPEWOULDSTARTTOCRACKANDTHUSRUPTUREIFTHETENSILESTRESSREACHEDTHETENSILESTRENGTHOFTHEPIPEMATERIALTHISRUPTUREWILLOCCURWHENTHEFLUIDPRESSUREPREACHESBRTHUS,FROMEQ42THEBURSTPRESSUREISTHEWORKINGPRESSUREWPISTHEMAXIMUMSAFEOPERATINGFLUIDPRESSUREANDISDEFINEDASTHEBURSTPRESSUREDIVIDEDBYANAPPROPRIATEFACTOROFSAFETYFSAFACTOROFSAFETYENSURESTHEINTEGRITYOFTHECONDUCTORBYDETERMININGTHEMAXIMUMSAFELEVELOFWORKINGPRESSUREINDUSTRYSTANDARDSRECOMMENDTHEFOLLOWINGFACTORSOFSAFETYBASEDONCORRESPONDINGOPERATINGPRESSURESFS8FORPRESSURESFROM0TO1000PAFS6FORPRESSURESFROM1000TO2500PAFS4FORPRESSURESABOVE2500PA

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