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英文原文WaterbasedhydraulicsystemsWaterbasedhydraulicsystemstraditionallyhavebeenusedinhotmetalareasofsteelmills.Theobviousadvantageofwatersystemsintheseindustriesistheirfireresistance.Waterbasedhydraulicsystemsalsohaveobviouscostadvantagesoveroilbasedfluid.First,nontoxic,biodegradablesyntheticadditivesforwatercost5to6pergallon.Onegallonofconcentratecanmake20gallonsofa5solution,sothecostofwaterbasedhydraulicfluidactuallycanbelessthan30centspergallon.Consideringthecostsassociatedwithpreventingandcleaningupenvironmentalcontamination,waterbasedhydraulicsystemsholdthepotentialfortremendouscostsavingsattheplantlevel.Oilthathasleakedalreadybecomesaveryimportantproblem.Itmustbecollected,properlycontained.Watercontainingsyntheticadditives,however,canbydumpedintoplanteffluentsystems.Costsavingsattheplantleveldon39tstopatthelowercostofthefluidanditsdisposal.Becausewaterbasedhydraulicfluidconsistsof10partswaterandonepartsyntheticadditive,5gallonsofadditivemixeswithwatertomake100gallonsofwaterbasedfluid.A50galloncontaineriscertainlyeasiertohandlethantwo55gallondrums,sowarehousingissimpler,cleaner,andlesscluttered.Transportationcostsalsoarelower.5opa6|NeOtherpotentialplantwidesavingsincludeimprovedsafetyforworkersbecausethewaterbasedfluidisnontoxicaswellasnonflammable.Theseattributescanreduceplantinsurancerates.Spillscostlesstocleanupbecausegranularabsorbentsorabsorbentsocksareunnecessary.WaterisquothotquotagaingDWzTheoilembargointhe1970ssparkedinterestinwaterbasedfluidsasalesscostlyalternativetooils.Eventhemostexpensivewateradditivesbecameattractivewhendesignerslearnedthatonegallonofconcentratewouldmake20gallonsoffluid.Y9y7qd,rAsoilpricesgraduallydropped,sodidinterestinwaterbasedhydraulics.Inretrospect,interestinwaterbasedfluidscenteredaroundtheircostsavingpotential.Mostdesignerslostinterestwhentheydiscoveredthattheycouldnotjustchangethefluidintheirsystemsfromoiltowaterwithoutmakingothersubstantialchanges.Theythenbecomereluctanttoacceptotherquotdisadvantagesquotreadsubstantialchangesofswitchingovertowaterbasedhydraulics.4wG,Ruj7e4p._8IWhatwereviewedasdisadvantageswerereallydifferentrulesthatapplytowaterbasedhydraulicsystemsDesignersprobablyresistedlearningmoreaboutwaterbasedhydraulicsbecausetheywereintimatedbyalltheworkrequiredtoleanabouthowtodesignanewsystemorretrofitanoldersystem.Byclosingtheirmindstothisdifferenttechnology,theymissedthemanyotheradvantagesofwaterbasedfluidbeyondinitialcost.Nowthatenvironmentalconcernshaveaddeddisposalcoststothepriceofhydraulicfluids,waterbasedhydraulicshasagainbecomeahottopic.Fightingfreeze9W,yJ4j0I8o6VF9yWaterbasedhydraulicsystemsdo,ofcourse,havelimitstotheirapplications.Onelimitationisthepotentialoffreezing.Thispossibilityisprobablythemostsignificantblockadetomorewidespreadapplicationofwaterbasedsystems,especiallyinthemobileequipmentindustry.Longwallminingisbyfarthelargestsectorofmobileequipmentthathasbeenabletotakeadvantageofwaterbasedsystems.Temperaturesundergrounddonotapproachthefreezingpointofwater,andfireresistanceisessential.Mobileandevenmarineequipmentusedintemperateclimatescouldcashinonetheadvantagesofwaterbasedsystems,butthereisnoguaranteethatsuchequipmentalwayswillbeusedinabovefreezingtemperatures.Nevertheless,addinganantifreezetoawaterbasedfluidcandepressitsfreezingtemperaturetowellbelow32°F.Ethyleneglycolusedinautomotiveantifreezeistoxicandisnotbiodegradable,soitsuseforantifreezeinwaterbasedhydraulicfluidwoulddefeattheenvironmentaladvantagewaterbasedfluidhas.Thereisanalternative.Propyleneglycolisnottoxicandisbiodegradable.Itcostsmorethanethyleneglycolandisnotquiteaseffectiveantifreeze,soitmustbeusedinslightlyhigherconcentrations.Twomoretechniquestoreducefreezingpotentialaretokeepfluidcirculatingcontinuouslyandusehosewherepractical.Sealingthesystem9nia.ViUuJTwomoreperceivedproblemswithwaterhydraulicsystemsarebacterialinfestationanddifficultyinmaintainproperconcentrations.Sealingthesystemfromatmospherecanholdbacterialgrowthincheck.Additionofanantibacterialagenttothefluidcanhavealastingeffectonpreventingbacterialbuildupifairisexcludedfromthesystem.th0B8P1KisAsealedreservoireliminatesanotherproblemsufferedbymanyhydraulicsystemswateringression.Thisaddressesanothermisconceptionaboutwaterbasedsystemswaterbasedsystemsnotsealedfromtheatmospheremustbecloselymonitoredtoensurethattheadditiveconcentrationstayswithintolerance.Thatisbecausewaterevaporatesfromthereservoirmorereadilythantheadditivedoes.Consequently,waterevaporationcausestheadditiveconcentrationtoincrease.Whennewfluidisaddedtoasystem,samplesoftheexistingfluidmustbetakentodeterminetheconcentrationofadditiveinsolution.Theseresultsthenrevealtheratioofadditivetofluidthatmustbeaddedsothatfluidconcentrationiscorrect..pz\vNnWithasystemthatsealsfluidfromtheatmosphere,theevaporationproblemisvirtuallyeliminated.Fluidthatescapesbyleakageisasolutioncontainingwaterandadditive.Therefore,thequantityoffluidinthesystemchanges,butconcentrationdoesnot.Systemfluidisreplenishedsimplybyaddingapremixedsolutionofwaterandadditivetothereservoir.3s1v6YvSSpecialconsiderationsWaterbasedhydraulicsystemscanbemorepronetopumpcavitationiftheyarenotproperlydesigned.Generousportingandotherpassagewaysshouldbeprovidedtokeepfluidvelocitiesbelow20ft/secpreferably,below15ft/secinpressurelines.Velocityinsuctionlines,ingeneral,shouldnotexceed23ft/sec.Velocitiesinreturnlinesshouldbeheldbelow510ft/sec.Higherreturnvelocitiescanpromotefoamingwhenfluidreentersthereservoir.Componentsshouldalsobecarefullysizedbecauserapidchangesinfluidpressureandvelocitycancausedissolvedairtoprecipitatefromsolutionandcausedamagesimilartothatproducedbycavitations.m/nqu0XXAnimportantconsiderationforwaterbasedsystemsisthatmajorcomponentsshouldbedesignedspecificallyforusewithwaterfluid,ratherthanmodifiedfromversionsoriginallyintendedforoilservice.Tubing,hose,andfittingsusuallycanbeidenticaltothoseforoilsystems.Pumps,valves,andactuatorsforwaterservice,however,exhibitsomesignificantdifferencesfromcomponentsforoilsystems.Pumpgears,forexample,shouldbemadeofsuperhardalloystoresistwear.Apump39sgearfaceshouldbewiderthanthatofanoilpumpbecausewater39slowviscosityrequiresalargerareatoformanadequatelubricantfilm.Cylindersusedinwatersystemsshouldhavebronzecladpistonstominimizewearbetweenpistonsandcylinderwalls.SpringorOringenergizedsealsshouldbeusedtominimizeleakageacrossthepiston.2dY_.ZValvesforwaterValvesforwaterbasedfluidusuallyarepackedwithsealsseparatingmetalpartstopreventmetaltometalcontact.Thisisbecausewaterevenwithlubricantadditivesdoesnotprovidethefullfilmlubricationofoil.Metalsurfacesinrelativemotioninvalvesforwaterbasedfluidareseparatedbybearingtypematerials.xg8f0uValvesforwaterservicealsoareslightlylargerthanthoseforoil.Thismaybeanotherreasonwhywaterbasedsystemshavenotgainedwideacceptance.Originally,thelargersizeofcomponentsforwaterbasedfluidcreatedahandicapwhendesigningsystems,andmorecostlyconstructioninflatedpricesofvalvesforwaterbasedfluidtothreetimesormorethatofvalvesforoil.Now,however,valvesizesarecomparabletothoseforoil.ManyvalvesareavailablewithstandardNFPAfootprints.Thepricedifferentialhasalsobecomeless.Componentsforwaterbasedfluidstillmaycostperhaps3morethanthoseforoilsystems,butthismaybeabargainwhenyouconsiderthecostsavingpotentialofwaterbasedsystems.x9YbFluidleakageLeakagecontinuestobeanaggingprobleminmanyhydraulicsystems.Newsealmaterialsanddesigns,andOringfacesealfittingsarepowerfulweaponsinthebattleagainstleakage.Butthebattleisfarfromoverbecauseofmisapplication,improperinstallation,orsimplelackofunderstanding.Althoughthere39snoexcuseforleakageinmostsystems,itstilloccurs.Assumingthatleakagewillnotbeeliminatedinthenearfuture,waterbasedfluidcandramaticallyreducethecostsassociatedwithleakage.QP/UR4ahInternalleakagecanbejustaswasteful.Thisleakagecancarburizetheoilbygeneratingheat.Internalleakagetypicallyisroutedbacktotank,sothistechniquetransformsmechanicalenergyintoheatinsteadofusefulwork.UsingastainlesssteelspoolwithPTFEsealsinavalveforwaterbasedfluideliminatestheneedforclearancebetweenmovingcomponents.Becausethereisnoclearance,thereisnointernalleakage.,O,aw,i4cButbeyondtheobviousandintangiblecostsoffluidleakage,disposingofthefluidthathasleakedfromasystembecomesaconcern.Allowinghydraulicoiltoenterplanteffluentsystemsbecomesanexpensivepropositionwhenremovalanddisposalcostsareconsidered.Realizingthatcleanupanddisposalcostswillonlygoup,andthatthepriceofoilisunstablesuggeststhatwaterbasedhydraulicscanbeaneconomicalsolutiontoenvironmentalproblems.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,D2b9Ol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加仑的桶更容易处理,因此储藏更简单、更清洁、更不凌乱,运输成本也较低。.J0_72iZa其他工厂范围下潜在的节约是为工人改善安全,因为水基液是不含毒性,并且非易燃。这些特点可以减少工厂的保险费率。泄漏的成本比清理低,因为不再需要颗粒吸收剂或吸附棉条。水基流体再次变成热门话题3uY3lsr,D9Q在20世纪70年代石油禁运引发了较低成本的水基液压流体替代高昂的液压油的兴趣。当设计师们获悉,一加仑聚合物可以制造出二十加仑的流体时,即使是最昂贵的水添加剂都更有吸引力。Oe2LdJ由于石油价格逐渐的回落,因此人们对水基液压也没有那么大的兴趣了。回想起来,对水基流体的兴趣集中在其节省成本的潜力上。当设计师发现他们不能在他们的系统中改变流体从液压油到水的状况并且也没有其他重大的改变时,他们就失去了兴趣。然后,他们不情愿的接受其他的缺点–了解到很大的变化又切换到水基液压。适用于水基液压系统的不同的规则被认为是缺点。设计师可能不愿意学习更多关于水基液压,因为他们被暗示,所有的工作需要依靠如何设计一个新的系统或改造旧系统的知识。因为他们结束了对这另外技术的思维,他们错过了除水基流体初始成本以外的许多其他的优点。现在,环境问题,增加了液压油处理成本的价格,水基液压便再次成为热门话题。,m5NS3N3Dy5I6o抵抗凝固.7Dmhtk8A当然,水基液压系统确实在应用上有它的局限性。一个限制就是潜在的凝固。这个可能性可能是更广泛地应用水基系统,特别是在移动设备业最重要的阻碍。长壁开采法是迄今为止最大的能够充分利用水基系统的移动设备部门。地下的温度不接近水的凝点和耐火性是必不可少的条件。用于温带气候海上设备和移动设备获利于水基系统的优点,但不能保证这些设备将始终用在上述凝固温度。不过,给水基流体加入防冻液可以使其凝固温度远低于32华氏度。用在汽车上的防冻液乙二醇是有毒的,是不能生物降解的,因此它在水基液压中添加防冻液将击败水基液压流体在环境上的优势。7V有一个替代的方法。丙二醇是没有毒性,而且是可生物降解的。它比乙二醇花费更多,并且是不太有效的一种防冻液,因此它必须使用较高浓度的溶液。减少凝固潜力的另外两个技术是要保持流体的不断循环和在实际中使用胶管。系统的密封水基液压系统的两个个容易被察觉的问题是细菌的大批出没,并且很难保持适当的浓度。大气下的
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