CompressorsThemaindifferencebetweenpumpsandcompressorsisthatthefluiddeliveredbycompressors--air--iscompressedandunderpressureatthetimeitisdelivered,evenifthereisnoloadonthesystem.Mostdevicesusedtocompressairareverysimilarinconceptand--perhapseveninhardware--tohydraulicpumps,andselectionconsiderationsaresimilar.Theonlyothersubstantivedifferenceisthatmosthydraulicsystemsarepoweredbyasinglepumpthatisactuallyapartofthesystem,whereasahostofpneumaticsystemsareoftenpoweredbyasinglecompressor,whichisalmosta"utility"intheplantlikewaterorelectricservice.Nevertheless,manysmallcompressorsareavailableforspecific,discretejobs;typicallytheyarepositive-displacementcompressors.Dynamic,ornonpositive-displacementcompressorsaretypicallylarger,facility-typeunits.Compressorsarefairlysimpledevices,capableoflongperiodsofmaintenance-freeoperationifproperlyintegratedintopneumaticsystems.Yettimeandagaintheysufferfromearlyfailuresbecauseobviousprecautionswereignoredduringsystemdesign.Fourbasicrulescanprovidesubstantialimprovementincompressorlifewithonlymoderatedesigneffort:? Pumpsandcompressorsshouldbesizedtoprovideatleasttherequiredpressureandflow,andpreferably10to25%more.? Filtersshouldbeselectedtoprotectthepumpingunit,andsometimestoprotectdownstreamcomponentsorproductsaswell.? Reliefvalvesshouldbeselectedtokeeppressureorvacuumatappropriatelevels.? Pumpingunitsshouldbeplacedinaclean,cool,dryenvironment.Bellowscompressorsconsistofaweldedmetalbellowsconnectedtoinletandoutletportswithcheckvalves.Thesecompressorstypicallycoverthepressurerangeupto10psig,andareusedinpollutiondetectingandmeasuringdevices,gas-samplinginstruments,andmedicalapplications.Lubricationisnotneeded,allowinghighpuritiestobemaintained.Vanecompressorsaresimplemachineswithfewmovingparts.Liketheirhydrauliccounterparts,vanepumps,thecompressorsareinexpensive,withlowoperatingcost,andlowstarting-torquerequirement.Theyarecompactandrelativelyvibrationfree,withlittlepulsationinthecompressoroutput.Theslidingvanesarecloselyfittedintherotorslotsandwearverylittleduringoperation.Thesecompressorsareavailableinpowerrangesfrom10to500hp,atpressuresto150psi.Reciprocatingcompressorsconsistofapistonmovingwithinthecylindertotrapandcompressthegas.Inprinciple,suchaunitislikeanautomobileengine,withthepistonscompressingthegasandvalvescontrollingitsinletandoutflows.Sizesrangefromlessthan1toover5,000hp.Reciprocatingcompressorshavegoodpartloadefficienciesandareusefulforwidevariationsinoperatingconditions.Diaphragmcompressorsareamodificationofthereciprocatingcompressor.Compressionisperformedbytheflexingofametalorfabricateddiaphragmwhichiscausedbythemotionofareciprocatingpistoninacylinderunderthediaphragm.Thespacebetweenthediaphragmandthepistonisusuallyfilledwithliquid.Lobed-rotorcompressorshavetworotatingelementsthatrevolveinoppositedirectionsinachamber.Inmostcompressors,therotorsdonotactuallytouchanddonotdriveeachother,beingdriveninsteadbytiminggears.Becausetherotorsdonotactuallytouch,airleaksbetweenthematasmallbutconstantrate.Thisleakage,called"slip,"isconstantforagivencompressoratagivenpressure.Forhighestefficiency,thesecompressorsshouldbeoperatedatmaximumspeed.Theyareavailableinpowerrangesfrom7to3,000hp,deliveringpressuresto250psi.Becausetheinternallobesdonotcontact,theyneednolubrication.Liquidpistoncompressorshavenomovingpartsinwearingcontact.Arotorwithmultipleforward-curvedbladesrotatesinanellipticalcasing.Fluid,trappedwithinthecasing,iscarriedaroundtheinnerperipherybytheblades.Spacebetweenthebladeschangesvolumeduetotheellipticalfluidpath,andtheinnersurfaceoftheliquidringtrappedbetweenthebladesservesasthefaceofaliquidpiston.Thesecompressorsacceptliquidslugsandfineparticleswithoutseriousdamage.Lubricationisrequiredonlyinbearingslocatedoutsidethepumphousing.Thesecompressorsdeliverupto150psithroughouttherangeof10to500hp.Centrifugalcompressorsarebestsuitedtomovinglargevolumesofairatrelativelylowpressures.Basically,theyconsistofahigh-speedrotatingimpeller,adiffusersectionwherevelocityisreducedandpressureincreased,andacollectorsectionthatfurtherreducesvelocityandincreasespressure.Centrifugalcompressorscanhandlehighflowdemandswell,butwhendemanddecreasesmuchbelowratedflowandoutputpressurerises,thecompressorscansurge.Insurge,thepressurefieldatthecompressoroutletvariesrandomly.Ifallowedtocontinue,thisconditioncandamagebearings,blades,andeventhehousingitself.Centrifugalcompressorstypicallyusefromtwotosixstages,supplyingfrom400to3,000cfmatspeedsto20,000rpm.Regenerativeblowers(alsoknownasperipheralblowers)useadisclikeimpellerwithbladesmountedarounditsoutsideedge.Astheimpellerrevolves,airisdrawnintothespacebetweentheblades.Centrifugalforcemovestheairinaspiralpathoutwardtothehousing,whereitslipsbytheinitialbladeandreturnstothebaseofthesucceedingblade,wheretheprocessisrepeated.Insomemodels,aflowsplittercreatestwoflowpaths,sothattheairmustmaketwocircuitsaroundtheimpeller.Inothermodels,thesplitterisomitted,andtheairmakesonlyonecircuitbeforeexiting.Regenerativeblowersprovideairflowsupto1,000cfmandpressuresto8psi.Helicalcompressorslookliketwogiantscrewsmeshingtogether;theyworkmuchlikehydraulicscrewpumps.Maximumpressurefromthesemachinesisapproximately125psiinsingle-stageconfigurations.Helicalcompressorsmaybeeitheroilfloodedordry.Dryhelicalcompressors,likelobedunits,requiretiminggearstomaintainproperclearancebetweentherotatingelements.Theseunitsaremostefficientlyoperatedathighcontinuousspeeds.Floodedcompressorsdonotrequireanytiminggears,becausetheoil-ladenscrewsurfacescandriveeachother.However,oilseparatorsareneededtoremovetheoilfromtheairasitleavesthecompressor.Theyareavailableoverapowerrangeofabout7to300hp.Single-screwcompressorsarebasedonthesameprincipleashelicalcompressors.Asthecentralscrewrotates,airtrappedbetweenthescrewteethiscompressedagainstthestar-shapedrotors.Thesecompressorstendtohavelowvibrationandnoiselevels,andlowdischargepressures.Lubricationisrequired.PumpsvacuumpumpsInprinciple,industrialvacuumpumpsaremerelycompressorsrunwiththeinletattachedtothevacuumsystemandtheoutletopentoexhaust.Insmallersizes,compressorsandvacuumpumpsareoftenidenticalmachines.However,inthelargesizesthatmightpoweraplant-widevacuumsystem,themachinesdifferinminorwaysthatareintendedtoenhanceefficiencyforoneapplicationortheother.Manufacturersstronglyadvisethatthesamemachinenotbeusedforbothvacuumandcompressionatthesametime.Theheavyloadswilldamageit.Threecriteriacontrolpumpselection:degreeofvacuumproduced,rateofairremoval,andpowerrequirement.However,applicationssuchasfiltrationmaysubjecttheunittotheingestionofforeignmaterial.Thefirstpumpperformancecriterionisthevacuumitproduces.ManufacturersprovideamaximumvacuumratingexpressedasabsolutepressureinmmHg,orvacuuminin.Hg.Largerunitsareusuallyratedonlyforcontinuousduty,butsmallerunitsmayhaveahighervacuumratingforintermittentduty.Insmallerunits,temperature-riseconsiderationslimitthevacuumthatcanbeproduced.Continuousandintermittentvacuumratingsaredeterminedforstandardatmosphericpressure:29.92-in.Hg.Lowerambientpressuresreducethevacuumthatcanbeproduced.Theratingisdeterminedfrom:whereVa=adjustedvacuumrating,in.Hg;Vo=originalvacuumratingatstandardconditions,in.Hg;andPa=anticipatedatmosphericpressureattheapplicationsite,in.Hg.Rateofairremovalisthesecondcriterion.Vacuumpumpsareflowratedaccordingtothevolumeofairexhaustedwithnopressuredifferentialacrossthepump.Manufacturersprovidecurvesshowingfreeairdeliveryatratedspeedforvacuumlevelsrangingfrom0-in.Hg(so-called"opencapacity")tomaximumvacuumrating.Somemanufacturersalsoprovidecurvesofcapacityatdifferentspeedsforagivenvacuum.Thelastpumpcriterionispowerrequirement.Comparedwithaircompressors,vacuumpumpsrequirerelativelylittlepower.Atlowflows,vacuum(orpressuredifferential)ishigh;athighflows,vacuumislow.Therefore,power,whichisproportionaltoflowandpressuredifferential,isgenerallylow.Poweroutputofthepumpcanbefoundfrompressure-flowcurvesprovidedbymanufacturers.Inputpowerandspeedrequirementsarealsoshowninthedata.Overallpumpefficiency(includingbothvolumetricandmechanicalefficiency)canbeevaluatedbycombiningthisdata.Thisisdonebydividingthefree-aircapacityofthepumpattherequiredvacuumlevelbydrivepowerrequiredatthatcondition.Theresultisproportionaltotheproductofgagevacuumandair-flowrateandisrepresentativeofefficiency.Allthreeperformancecriteria--vacuum,flowandpower--canbeaffectedbypumptemperature.Athighervacuumlevels,littleairflowsthroughthepump,solittleheatistransferredtotheair.Muchoftheheatgeneratedbyfrictionmustbedissipatedbythepump.Thisheatgraduallyraisespumptemperatureandcandrasticallyreduceservicelife.Temperatureexcursionsareespeciallyimportanttointermittent-dutypump,whichcanoverheatifontimegreatlyexceedsofftime.Vacuumpumpsareclassifiedaseitherpositiveornonpositivedisplacement.Apositive-displacementpumpcreatesvacuumbyisolatingandcompressingadistinct,constantvolumeofair.Thecompressedairisventedoutoneport,andavacuumiscreatedattheotherportwheretheairisdrawnin.Thisgeneratesrelativelyhighvacuum,butlittleflow.Anonpositive-displacementpump,ontheotherhand,usesrotatingimpellerbladestoaccelerateairandcreateavacuumattheinletport.Whilenonpositive-displacementpumpscannotproducehighlevelsofvacuum,theyprovidehighflowrates.Principaltypesofpositive-displacementvacuumpumpsincludepiston,diaphragm,rocking-piston,rotary-vane,lobed-rotor,rotary-screw,andliquid-ringdesigns.Reciprocating-pistonpumpsgeneraterelativelyhighvacuums--from27tomorethan29in.Hg--underavarietyofoperatingconditions.Typicalpumpsofthistypehaveoneormorepistonslinkedtoarotatingcrankshaft.Thealternatingpistonactionmovesairpastcheckvalvesinthecylinderheadtocreateavacuumattheinletport.Lubricatedpistonpumpsarequieter,producelessvibration,haveahighercapacity,andfeatureamuchlongerlifethanoillessdesigns,buttheyarealsoheavierandmoreexpensive.Diaphragmpumpsoffertheadvantageofthefluidchamberbeingtotallysealedfromthepumpingmechanisms.Aneccentricconnectingrodmechanicallyflexesadiaphragminsidetheclosedchambertocreateavacuum.Thisresultsinsomewhatlowervacuumcomparedtothatproducedbyareciprocatingpiston.However,thediaphragm'slowercompressionratio--lowflow,largediameter,andshortstroke--makesforquiet,economical,andreliableoperation.Thedesignisavailableinbothoneandtwo-stageversions.Single-stagepumpsprovidevacuumupto25.5in.Hg,whiletwo-stageunitsareratedto29in.Hg.Rocking-pistonpumpscombinethecompactsizeandquiet,oillessoperationofthediaphragmpumpwiththehigh-vacuumcapabilitiesofthereciprocating-pistonpump.Here,apistonisrigidlymounted(nowristpin)ontopofthediaphragmunit'seccentricconnectingrod.Anelastomericcupskirtsthepistonandfunctionsbothasaseal--equivalenttotheringsonapistoncompressor--andasaguidememberfortherod.Thecupexpandsasthepistontravelsupward,thusmaintainingcontactwiththecylinderwallsandcompensatingfortherockingmotion.Theabsenceofawristpinisthekeytothepump'slightweightandcompactsize.Single-stagerocking-pistonpumpsproducevacuumto27.5in.Hg;two-stagedesignscangenerate29in.Hgormoreofvacuum.Rocking-pistonpumpsarealsorelativelyquiet,operatingatsoundlevelsaslowas50dBA.Adrawbacktorocking-pistonpumpsisthattheycannotgeneratealotofairflow.Eventhelargesttwin-cylindermodelshaveflowratesoflessthan10cfm.Rotary-vanepumpsuseaseriesofsliding,flatvanesrotatinginacylindricalcasetogeneratevacuum.Asaneccentricallymountedrotorturns,thevanesslideinandout,trappingaquantityofairandmovingitfromtheinletsideofthepumptotheoutlet.Rotary-vanepumpsusuallyhavelowervacuumratingsthanpistonpumps,inthe20to28in.Hgrange.However,thereareafewexceptions.Sometwo-stage,oil-lubricateddesignshavevacuumcapabilitiesupto29.5in.Hg.Pumpswithrecirculatingoilsystemsreachstillhighervacuums,inthelessthan1-torrrange.Thepumpsofferanumberofadvantages,includinghighflowcapacities,lowstartingandrunningtorquerequirements,vibration-freeoperation,andcontinuousairflow.Novalvesrestrictfloworrequiremaintenanceintherotarydesign.Thecompactunitsarealsoquiet,generatingaslittleas45dBAorsound.Dependingontheapplicationandvacuumlevelrequired,aneconomicalalternativetousingahigh-vacuumpumpistwostandard,stagedrotary-vanepumps.Or,ahigh-volume,low-dutypumpratedforcontinuousdutyof20in.Hgsometimescanbeoperatedatrestrictedairflowor"blanked-off"conditionsforshortperiodsoftimetoprovidehighervacuums.Aswithothertypesofpumpsavailableinbothlubricatedandoillessconfigurations,lubricatedrotary-vanepumpsarecapableofslightlyhighervacuumcomparedtooillessdesigns.Liquid-ringpumpsfeatureamultibladeimpeller,mountedeccentricallyinacylindricalcasethatispartlyfilledwithwater.Astheimpellerrotates,liquidisthrownoutwardbycentrifugalforcetoformaliquidringconcentricwiththeperipheryofthecasing.Duetotheeccentricpositionoftheimpeller,theairspaceintheimpellercellexpandsduringthefirst180°ofrotation,creatingavacuum.Duringthenext180°ofrotation,theairspaceisreduced,dischargingcompressedairandwater.Inadditiontobeingthecompressionmedium,theliquidringabsorbstheheatofcompressionaswellasanypowderorliquidslugsentrainedintheair.Rotary-screwandlobed-rotorvacuumpumpsaretwoothertypesofpositivedisplacementpumps.Neitherlubricateddesignisaswidelyusedasrotary-vaneandpistonpumps,especiallyinsmallersizes.Duetothesizeofthegearsandrotors,bothdesignslendthemselvestolargerinstallations.Arotary-screwpump'svacuumcapabilitiesaresimilartothoseofpistonpumps,withtheaddedadvantageofbeingnearlypulse-free.Twomeshingrotorswithhelicalcontourstrapairasthescrewsturninoppositedirections.Thisactioncreateschambersofdecreasingvolumebehindandincreasingvolumeinfrontoftherotorchambers.Lobed-rotorpumpsbridgethegapbetweenpositiveandnonpositive-displacementunits.Thepumpshaveapairofmatinglobedimpellersthatrotateinoppositedirections,trappingairandwithdrawingitfromthesystem.High-speed,multistagedcentrifugalblowersandregenerativeblowersarethemajortypesofnonpositive-displacementpumps,generallyoperatingathighspeedsandattainingmoderatevacuumlevels.Centrifugalblowers,forexample,areanexcellentchoicewhereonlyintermittentuseisrequired.Tokeepcostsdown,ashort-lifebrush-typeacordcmotorpowerstheseblowers,whicharewidelyusedinvacuumcleaners.Regenerativeblowershavemanyadvantagesbecauseindividualairmoleculespassthroughmanycompressioncycleswitheachrevolutioncomparedtothesinglecompressionperstageformultistagedcentrifugaltypes.Atfirstglance,regenerativeblowersaresimilartorotary-vanepumps,buthaveaspecialbladeandhousingconfiguration.Astheimpellerrotates,centrifugalforcemovestheairmoleculesfromthebladeroottoitstip.Leavingthebladetip,theairflowsaroundthehousingcontourandbackdowntotherootofasucceedingblade,wheretheflowpatternisrepeated.Thisactionprovidesaquasi-stagingeffecttoincreasepressuredifferentialcapability.Thespeedoftherotatingimpellerdeterminesthedegreeofpressurechange.Theendresultisnotaparticularlyhighvacuum--approximately100-in.H2Oinsingle-stagemodels.Butflowcapacityisveryhigh,uptoseveralhundredcfm.Multistageversionsproducehighervacuumlevels,butatlowerflowrates.壓縮機泵和壓縮機主要區別是：流體被壓縮機傳送—氣體—在它被傳送的同時被壓縮并處于壓力之下，即使系統在沒有載荷的情況下。大多數用于空氣壓縮的裝置原理上非常相似--甚至在零部件上-如液壓泵，考慮和選擇是相同的。它們本質上唯一的不同是大多數的液壓系統由單一泵供給能量，并且泵實際上是系統的一部分，而大多數的氣動動力系統往往由單一壓縮機供給能量，像廠區內的水、電力服務一樣它幾乎是廠區“公共設施”。不過有許多小型壓縮機用于特殊、不連續的工作場合。他們通常是可移動型壓縮機。動力型的或非移動型壓縮機通常是大型的單元設備。壓縮機裝置比較簡單，如果納入適當的氣動系統則使壓縮機能長期維持運轉，由于在系統設計中忽視了明顯的注意事項導致了壓縮機一次又一次的前期故障。只要適度的努力遵循四項基本規則可大大提高壓縮機設計壽命：泵和壓縮機應該以最低壓力和流量來分級，最好在10至25%以上；應選擇過濾器來保護泵單元，并且有時也保護下游產品和部件；應選擇安全閥來保持壓力或真空度在適當的水平；泵單元應安放在一個干凈、通風、干燥的環境。波紋管式壓縮機：包括金屬焊接波紋管，由截止閥連接在進、出端口。這種壓縮機主要用于各種壓力高達10磅/平方英寸左右，用于污染檢測和測量儀器、氣體取樣工具、醫療設備。不需要注潤滑油，因而使其保持在較高的純凈度。葉輪式壓縮機：由一些簡單的轉動零件構成。相對于它們水力的相似物-葉輪泵-來說，壓縮機價格便宜,操作成本低和低的開車需求。它們結構緊湊，并且在壓縮機輸出時相關的自由顫動、壓力波動小?；瑒拥娜~輪在轉子溝槽中緊密配合并且在操作時很少磨損。這些壓縮機可用在動力范圍在10至500惠普，壓力為150磅/平方英寸。往復式壓縮機：由一個活塞在汽缸內移動而吸入并壓縮氣體。原則上，像汽車發動機一樣的單元由活塞壓縮氣體并且有控制閥控制氣體的吸入與流出。尺寸范圍規模小于1個調和級數到5000惠普。往復式壓縮機具有良好的部分負載效率可廣泛用于各種操作條件。隔膜式壓縮機：是一種正在改進的往復式壓縮機。壓縮是由一片有彈性的金屬或預制的隔膜它的運動由在隔膜子下的氣缸中的往復運動的活塞所引起的。隔膜與活塞之間的空間通常充滿液體。葉片-轉子式壓縮機：有兩個旋轉元件它們在工作腔中以相反地方向進行旋轉。在大多數壓縮機中轉子實際上并不相互接觸而且并不相互驅動,而是由驅動齒輪來間接傳動。因為沒有實際相互接觸它們之間的空氣泄漏率很小而且保持恒定。這個泄漏量，被稱為“錯漏”因為某一特定壓縮機有一個特定的壓力。為了保持高效率，壓縮機應該以最高轉速運轉。他們可利用在動力范圍為7至3000惠普，傳送壓力達到250磅/平方英寸。由于內部葉片沒有相互接觸，它們不需要注潤滑油。流體活塞壓縮機：沒有移動部件處于磨損接觸。一個帶多片向前彎曲葉片的轉子在橢圓形外殼中旋轉。流體被截留在殼體隨著葉片的旋轉被帶到內部殼體的邊緣。葉片之間的空間隨著橢圓形通道的改變而改變，并且被截留在葉片之間的液環的內表面被看作流體活塞的表面。這些壓縮機可以承受液滴和好的微粒而不產生嚴重的破壞。潤滑油只須注在泵機架外的軸承上。這種壓縮機可傳送壓力高達150磅/平方英寸動力范圍為10至500惠普。離心式壓縮機：最適合運送大容量壓力較低的空氣?；旧?，他們包括高速旋轉葉輪,一個擴散節，在擴散節中流動速度降低但壓力增高,還有一個收集部件，在其內部進一步降低速度，增高壓力。離心式壓縮機可處理高流量需求的井道，但是當需求量大大低于額定流量和壓力升高，壓縮機將產生喘振。如果產生喘振壓縮機出口的壓力范圍將產生隨意的改變。如果任其繼續下去，這種情況會破壞軸承、葉片，甚至自己的機架。離心壓縮機通常使用二至六級，可供應量為400至3000立方英尺/秒，轉速可達20,000轉/分。再生式鼓風機（又名環形滑道式鼓風機）：采用了邊緣外安裝了葉片的推動葉輪。由于這個旋轉推動葉輪，空氣被吸入葉片之間的空間。離心力使空氣呈螺旋形路線離開葉輪室，空氣由初始的葉片泄漏并返回低一級的葉片，在這一級這個過程被重復。有些型號一個流程被分離成兩個流程途徑,因此使空氣沿推動葉輪要做兩次循環。其它型號，分離被省略了，因此空氣在離開時只做一次循環，再生式鼓風機提供空氣流速多達1000立方英尺/秒和壓力達8磅/平方英寸。螺旋式壓縮機：像兩根巨大的螺桿嚙合在一起；它們的操作很像液壓螺桿泵。這些壓縮機的單級結構最大壓力大約為125磅/平方英寸。螺旋式壓縮機可以是有油潤滑也可以是無有潤滑。無油潤滑螺旋式壓縮機：像葉片式單元一樣，需要傳動齒輪使旋轉元件保持適當的清潔。這些單元在高速連續不斷的操作中的效率非常高。有油潤滑式壓縮機：不需要任何調整齒輪，因為螺桿表面的石油可以帶動對方相互驅動。不過當石油離開壓縮機時，需要用石油分離器從空氣中分離出石油。他們有較廣泛使用的動力范圍約為7至300惠普。單螺桿式壓縮機：與螺旋式壓縮機基于同樣的原則。由于主螺桿旋轉截留在螺桿旋齒中的空氣沿著與星型回轉體相反的方向壓縮。這些壓縮機趨于低振動、低噪音、低排放壓力.需要注潤滑油。泵真空泵原則上，工業真空泵與壓縮機類似，只是它的入口連接在真空系統而出口直接排入大氣，在小型號中，壓縮機與真空泵往往是相似的機器。不過，在大型號中它們為成套的真空系統提供能量、在中型真空泵方面有所不同它一方面為了提高效率或有其它用途。廠商強烈呼吁在同一機器不能在同一時間同時進行抽真空和壓縮。沉重的負載將會破壞真空泵。三個標準來控制泵的選擇:抽真空程度，空氣采集量和電力需求。不過，由于過濾系統的應用受到對等過濾外來物質的影響。泵性能的第一標準是它所產生的真空度。廠商所提供的最高真空度用毫米汞柱或英寸汞柱絕對壓力表示。通常大的單元只用連續負載評定、但是小單元可以用較高的真空度為間歇性負載。在小單元中由于要考慮溫度上升補償因此限制了泵所能產生的真空度。持續或間歇真空度值為標準大氣壓所確定為:29.92英寸汞柱。較低的環境溫度壓力將降低泵所能產生的真空度值，數值由下式所確定：

而Va=調整真空度值，英寸汞柱；Vo=標準條件下的原始真空度數值，英寸汞柱；Pa=當地大氣壓數值，英寸汞柱。第二標準是輸送空氣值。真空泵額定流量是根據通過泵的沒有壓力差的排出空氣量所決定的。廠商提供的在標準傳送速度下的自由空氣的真空度級別的顯示曲線范圍從0英寸汞柱（所謂“開放容量”）到最大真空度值。一些廠家還提供某一給定真空度的不同速度得容量曲線。最后一個泵的標準是功率需求。與空氣壓縮機相比，真空泵需要較少的功率。在低流量、高真空度（或壓差）；在高流量、真空度也是低的。因此，功率-它是流量與壓差之間的比例關系，因此它通常也偏低。泵的輸出功率可以由廠商提供的壓力-流量曲線圖中查得。輸入功率和需求的速度也顯示這些數據中。因此全部泵的效率（包括容積效率和機械效率）可用這些相關的數據進行評價。這一點在劃分泵的自由空氣容量所需開車功率時所必須的真空度級別時被完成的。除以自由空氣的能力水平的真空泵的驅動力所需的必要條件。其