外文翻译--水基液压系统.doc

英文原文Water-basedhydraulicsystemsWater-basedhydraulicsystemstraditionallyhavebeenusedinhot-metalareasofsteelmills.Theobviousadvantageofwatersystemsintheseindustriesistheirfireresistance.Water-basedhydraulicsystemsalsohaveobviouscostadvantagesoveroil-basedfluid.First,non-toxic,biodegradablesyntheticadditivesforwatercost$5to$6pergallon.Onegallonofconcentratecanmake20gallonsofa5%solution,sothecostofwater-basedhydraulicfluidactuallycanbelessthan30centspergallon.Consideringthecostsassociatedwithpreventingandcleaningupenvironmentalcontamination,water-basedhydraulicsystemsholdthepotentialfortremendouscostsavingsattheplantlevel.Oilthathasleakedalreadybecomesaveryimportantproblem.Itmustbecollected,properlycontained.Watercontainingsyntheticadditives,however,canbydumpedintoplanteffluentsystems.Costsavingsattheplantleveldon'；tstopatthelowercostofthefluidanditsdisposal.Becausewater-basedhydraulicfluidconsistsof10partswaterandonepartsyntheticadditive,5gallonsofadditivemixeswithwatertomake100gallonsofwater-basedfluid.A50galloncontaineriscertainlyeasiertohandlethantwo55-gallondrums,sowarehousingissimpler,cleaner,andlesscluttered.Transportationcostsalsoarelower.5o:p#a6|%N!e!Otherpotentialplant-widesavingsincludeimprovedsafetyforworkersbecausethewater-basedfluidisnon-toxicaswellasnon-flammable.Theseattributescanreduceplantinsurancerates.Spillscostlesstocleanupbecausegranularabsorbentsorabsorbentsocksareunnecessary.Wateris"；hot"；again#g#DW*zTheoilembargointhe1970ssparkedinterestinwater-basedfluidsasaless-costlyalternativetooils.Eventhemostexpensivewateradditivesbecameattractivewhendesignerslearnedthatonegallonofconcentratewouldmake20gallonsoffluid.Y9y7q&?*d,rAsoilpricesgraduallydropped,sodidinterestinwater-basedhydraulics.Inretrospect,interestinwater-basedfluidscenteredaroundtheircostsavingpotential.Mostdesignerslostinterestwhentheydiscoveredthattheycouldnotjustchangethefluidintheirsystemsfromoiltowaterwithoutmakingothersubstantialchanges.Theythenbecomereluctanttoacceptother"；disadvantages"；-readsubstantialchanges-ofswitchingovertowater-basedhydraulics.&4w:G,R)u#j7e4+p._8IWhatwereviewedasdisadvantageswerereallydifferentrulesthatapplytowater-basedhydraulicsystems?Designersprobablyresistedlearningmoreaboutwater-basedhydraulicsbecausetheywereintimatedbyalltheworkrequiredtoleanabouthowtodesignanewsystemorretrofitanoldersystem.Byclosingtheirmindstothisdifferenttechnology,theymissedthemanyotheradvantagesofwater-basedfluidbeyondinitialcost.Nowthatenvironmentalconcernshaveaddeddisposalcoststothepriceofhydraulicfluids,water-basedhydraulicshasagainbecomeahottopic.Fightingfreeze9W,y+J4j0I8o6V-F9yWater-basedhydraulicsystemsdo,ofcourse,havelimitstotheirapplications.Onelimitationisthepotentialoffreezing.Thispossibilityisprobablythemostsignificantblockadetomorewidespreadapplicationofwater-basedsystems,especiallyinthemobileequipmentindustry.Longwallminingisbyfarthelargestsectorofmobileequipmentthathasbeenabletotakeadvantageofwater-basedsystems.Temperaturesundergrounddonotapproachthefreezingpointofwater,andfireresistanceisessential.Mobileandevenmarineequipmentusedintemperateclimatescouldcashinonetheadvantagesofwaterbasedsystems,butthereisnoguaranteethatsuchequipmentalwayswillbeusedinabove-freezingtemperatures.Nevertheless,addingananti-freezetoawater-basedfluidcandepressitsfreezingtemperaturetowellbelow32F.Ethyleneglycol-usedinautomotiveanti-freeze-istoxicandisnotbiodegradable,soitsuseforanti-freezeinwater-basedhydraulicfluidwoulddefeattheenvironmentaladvantagewater-basedfluidhas.Thereisanalternative.Propyleneglycolisnottoxicandisbiodegradable.Itcostsmorethanethyleneglycolandisnotquiteaseffectiveantifreeze,soitmustbeusedinslightlyhigherconcentrations.Twomoretechniquestoreducefreezingpotentialaretokeepfluidcirculatingcontinuouslyandusehosewherepractical.Sealingthesystem9n$i$a.Vi$U$u；JTwomoreperceivedproblemswithwaterhydraulicsystemsarebacterialinfestationanddifficultyinmaintainproperconcentrations.Sealingthesystemfromatmospherecanholdbacterialgrowthincheck.Additionofananti-bacterialagenttothefluidcanhavealastingeffectonpreventingbacterialbuildupifairisexcludedfromthesystem.t!h0B8P1K:i&sAsealedreservoireliminatesanotherproblemsufferedbymanyhydraulicsystems:wateringression.Thisaddressesanothermisconceptionaboutwater-basedsystems:water-basedsystemsnotsealedfromtheatmospheremustbecloselymonitoredtoensurethattheadditiveconcentrationstayswithintolerance.Thatisbecausewaterevaporatesfromthereservoirmorereadilythantheadditivedoes.Consequently,waterevaporationcausestheadditiveconcentrationtoincrease.Whennewfluidisaddedtoasystem,samplesoftheexistingfluidmustbetakentodeterminetheconcentrationofadditiveinsolution.Theseresultsthenrevealtheratioofadditivetofluidthatmustbeaddedsothatfluidconcentrationiscorrect.pz-&vN:n$Withasystemthatsealsfluidfromtheatmosphere,theevaporationproblemisvirtuallyeliminated.Fluidthatescapesbyleakageisasolutioncontainingwaterandadditive.Therefore,thequantityoffluidinthesystemchanges,butconcentrationdoesnot.Systemfluidisreplenishedsimplybyaddingapre-mixedsolutionofwaterandadditivetothereservoir.3s1v6Y；v*SSpecialconsiderationsWater-basedhydraulicsystemscanbemorepronetopumpcavitationiftheyarenotproperlydesigned.Generousportingandotherpassagewaysshouldbeprovidedtokeepfluidvelocitiesbelow20ft/sec-preferably,below15ft/secinpressurelines.Velocityinsuctionlines,ingeneral,shouldnotexceed2-3ft/sec.Velocitiesinreturnlinesshouldbeheldbelow5-10ft/sec.Higherreturnvelocitiescanpromotefoamingwhenfluidre-entersthereservoir.Componentsshouldalsobecarefullysizedbecauserapidchangesinfluidpressureandvelocitycancausedissolvedairtoprecipitatefromsolutionandcausedamagesimilartothatproducedbycavitations.(m/n-q+u*0X#XAnimportantconsiderationforwater-basedsystemsisthatmajorcomponentsshouldbedesignedspecificallyforusewithwaterfluid,ratherthanmodifiedfromversionsoriginallyintendedforoilservice.Tubing,hose,andfittingsusuallycanbeidenticaltothoseforoilsystems.Pumps,valves,andactuatorsforwaterservice,however,exhibitsomesignificantdifferencesfromcomponentsforoilsystems.Pumpgears,forexample,shouldbemadeofsuper-hardalloystoresistwear.Apump'；sgearfaceshouldbewiderthanthatofanoilpumpbecausewater'；slowviscosityrequiresalargerareatoformanadequatelubricantfilm.Cylindersusedinwatersystemsshouldhavebronze-cladpistonstominimizewearbetweenpistonsandcylinderwalls.Spring-orO-ring-energizedsealsshouldbeusedtominimizeleakageacrossthepiston.2d；Y-_.Z(ValvesforwaterValvesforwater-basedfluidusuallyarepackedwithsealsseparatingmetalpartstopreventmetal-to-metalcontact.Thisisbecausewater-evenwithlubricantadditives-doesnotprovidethefull-filmlubricationofoil.Metalsurfacesinrelativemotioninvalvesforwater-basedfluidareseparatedbybearing-typematerials.；x#g8f0u-Valvesforwaterservicealsoareslightlylargerthanthoseforoil.Thismaybeanotherreasonwhywater-basedsystemshavenotgainedwideacceptance.Originally,thelargersizeofcomponentsforwater-basedfluidcreatedahandicapwhendesigningsystems,andmorecostlyconstructioninflatedpricesofvalvesforwater-basedfluidtothreetimesormorethatofvalvesforoil.Now,however,valvesizesarecomparabletothoseforoil.ManyvalvesareavailablewithstandardNFPAfootprints.Thepricedifferentialhasalsobecomeless.Componentsforwater-basedfluidstillmaycostperhaps3%morethanthoseforoilsystems,butthismaybeabargainwhenyouconsiderthecost-savingpotentialofwater-basedsystems.$x9Y*b)FluidleakageLeakagecontinuestobeanaggingprobleminmanyhydraulicsystems.Newsealmaterialsanddesigns,andO-ringface-sealfittingsarepowerfulweaponsinthebattleagainstleakage.Butthebattleisfarfromoverbecauseofmisapplication,improperinstallation,orsimplelackofunderstanding.Althoughthere'；snoexcuseforleakageinmostsystems,itstilloccurs.Assumingthatleakagewillnotbeeliminatedinthenearfuture,water-basedfluidcandramaticallyreducethecostsassociatedwithleakage.!Q:P/U(R4a:hInternalleakagecanbejustaswasteful.Thisleakagecancarburizetheoilbygeneratingheat.Internalleakagetypicallyisroutedbacktotank,sothistechniquetransformsmechanicalenergyintoheatinsteadofusefulwork.UsingastainlesssteelspoolwithPTFEsealsinavalveforwater-basedfluideliminatestheneedforclearancebetweenmovingcomponents.Becausethereisnoclearance,thereisnointernalleakage.,O,a；w,i4c；Butbeyondtheobviousandintangiblecostsoffluidleakage,disposingofthefluidthathasleakedfromasystembecomesaconcern.Allowinghydraulicoiltoenterplanteffluentsystemsbecomesanexpensivepropositionwhenremovalanddisposalcostsareconsidered.Realizingthatcleanupanddisposalcostswillonlygoup,andthatthepriceofoilisunstablesuggeststhatwater-basedhydraulicscanbeaneconomicalsolutiontoenvironmentalproblems.中文译文水基液压系统传统上水基液压系统已经应用在钢铁厂炼铁领域。这些产业中水基液压系统的明显的优点是它们的耐火性。而且水基液压系统在费用上也优于油基的液压系统。首先，无毒的、可被生物分解的综合性添加剂每加仑花费5到6美元。一加仑集中可生成20加仑的5%溶液，因此实际上水基液压流体的费用可以比油基的每加仑少30分。在工厂的水平下，考虑到相关费用、防止和清理环境的污染，水基液压系统拥有节省巨大成本的潜力。液压油的泄漏已经成为一个非常重要的问题。它必须被收集、妥善控制。不过，含有合成添加剂的水，可以倾倒入工厂的污水系统。j,L,(D2b9O(l*在工厂水平下，节省成本不停留在流体的较低成本及其处理上。因为水基液压液由十部分水和一部份合成添加剂，5加仑添加剂与水的混合物构成100加仑水基流体。50加仑的容器当然比两个55加仑的桶更容易