10 steps to selecting an air compressor - industrial air power · 10 steps to selecting an air...
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ingersollrandproducts.com 137
What are you using the compressed air for?Thetypeofworkyoudoisprobablythemost
importantfactorindeterminingcompressorsize.Doyouintendtouseairsixhoursperday/
fivedaysaweek,oronlyoccasionally?Areyourdemandsforcompressedairrelativelyconstant
duringtheday,ordotheyvarywidely?Purchaseacompressordesignedforadutycyclewhich
equalsorexceedsspecifiedrequirement.
Where will the compressor be located? Outdoorapplicationsrequirespecialprotectionagainst
waterandfreezing.Indoors,sufficientventilationiscrucialforsuccessfuloperationsincemost
reciprocatingcompressorsareaircooled.Don’tputthecompressorinacloset,forexample.
Placethecompressoratleastthreefeetfromthewalltoensureproperairflowandbesurethe
installationsiteissufficientlyventilatedtohandletheheatgeneratedbythecompressorduring
operation..
How much pressure (psi) do you require? Thepsi,orpoundspersquareinch,capabilityofa
compressormustmatchorexceedthepsirequirementofyourhungriestairtoolsandpneumatic
equipment.Checkthemanufacturer’sspecificationsandpressurerequirementforallyour
equipment.Thepressurealsodetermineswhethertheunitshouldbeasingle-stage(max135psi)
oratwo-stage(max175psi)compressor.
How much air flow (cfm) do you require? Cubicfeetperminuteorcfmisameasureofairflowthecompressorcancreate.CFMisstatedintwodifferentforms,pistondisplacement(PD)oractualcubicfeetperminute(acfm).Alwaysconsidertheacfmasitreflectstheamountofusableairavailableforwork.Readthefineprintandmakesureyouunderstandwhetherthecfmratingis“pistondisplacement”or“actualdeliveredair”ataspecifiedpsi.
What motor horsepower do you require? Horsepowerisdirectlyproportionaltocfmrating
ofacompressor;typically,thehigherthehorsepowerthemoreair(cfm)thecompressorcan
produce.Don’trelysolelyonhorsepowerorattempttobuythehighesthorsepowercompressor
youcanafford.Letyourcfmandpsirequirementsdeterminehorsepowerforyou.Bevery
carefulwiththecompressorsthatclaimhighhorsepowerratingwithlowairflowperformance,this
oftenindicatesan“occasional-use”aircompressor.Theseproductsaredesignedwiththemotor
operatingatmaximumspeed,whichtypicallyresultsinamotorthatwillrunhotwithseverely
shortenedlifespan.
10 Steps to Selecting an Air Compressor
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138 ingersollrandproducts.com
10 Steps to Selecting an Air Compressor (continued)
What size and type of air tank do you require?Airtankshelpeliminatepulsationinthe
airlineandprovidestoragewhendemandforairexceedsthecapacityofthecompressor.The
largerthetank,themorepressurizedairisavailableforoutput.Thesmallerthetank,themore
thecompressorhastoworktokeepupwiththedemand.Decideifyourapplicationrequires
averticalorhorizontaltank;thisisdeterminedbythephysicallocationofthecompressorand
one’spersonalpreference.Verticalcompressorshaveasmallerfootprintthanahorizontaldesign;
verticaltanksareonlyavailableonmodelsratedupto10horsepower.
What compressor features should you consider? Lookforthefollowingfeaturestosuitmore
demandingapplications:
•100%cast-ironconstructiondesignedforreliabilityanddurability.
•Minimalmovingpartsreducesmaintenancecostandserviceintervals.
•Splashlubricationprovidessimple,reliabledesignreducinginitialpurchaseprice
•Stainlesssteelfingervalveseliminatecorrosionwhileinsuringlongservicelife.
•One-piececonnectingrodseliminateinternaladjustment.
•Oilmonitoringdevicetopreventlow-oildamage.
•Separatecastcylindersintwo-stagecompressorsforbettercoolingandextendedlife.
What are the electrical requirements of the installation? Incomingelectricalserviceisvery
importanttoidentifyandunderstandbeforepurchasingacompressor.Voltagewilldeterminethe
horsepowercapacityavailablewithoutexpensivemodifications.Thestandardvoltageforhomes
is110volts.Thisvoltagewillonlyoperatecompressorsuptothreehorsepower.IntheUnited
States,Canada,Mexicothefollowingvoltagesandphasesareavailable:
•Single-Phase1.110-1-602.208-1-603.230-1-60
•Three-Phase1.308-3-602.208-e-603.460-3-604.575-3-60
NOTE: Always have a qualified electrician review electrical requirements prior
to procuring an air compressor.
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10 Steps to Selecting an Air Compressor (continued)
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What control system do you require?Allreciprocatingaircompressorsrequireoneofthe
threecontrolsystemsinordertoregulateoperationinaccordancewithairdemand:
•Start/StopControlisusedforapplicationswhereairisnotrequiredcontinually,
allowingthecompressorsufficientcoolingtime.Whensystempressurefallsbelowtheset
start-uppressure,thecompressorwillautomaticallystart.Whenthecut-offpressureis
reached,thecompressorwillautomaticallyshut-offandwillnotstartagainuntilthesystem
pressurefallsbelowtheminimumstartpressure.
•ConstantSpeedControlkeepsthecompressorfromexcessivelystartingand
stopping.Aswithstart/stopcontrol,ithasaminimumstartpressureandamaximumcut-
offpressure.Thisfeaturepreventsprematuremotorfailureandminimizesoperatingcosts
associatedwithhighamp-draw.Here’saruleofthumb:ifthecompressorstartsmorethansix
toeighttimesperhour,youshouldoperateconstantspeedcontrol.Ifthecompressorstarts
lessthansixtimesperhour,start/stopcontrolisrecommended.
•DualControlallowsthecompressortooperateineitherstart/stopmodeor
constantspeedcontrolmodebyadjustingthecompressorauxiliaryvalve.Thiscontrolmethod
allowstheusertoeasilyadjustthecontrolmodedependentuponcompressedairusage.Know
yourrequirementsandpurchaseaccordingly!
Additional buying tips
•Allcompressorsratedfivehorsepowerandaboveshouldhaveamagneticmotorstarterfor
thermaloverloadprotection.Motorstartersaresizedaccordingtohorsepoweraswellas
byincominglinevoltage.Thestartercanbemountedtothecompressororbepositioned
remotely.Besuretochecklocalelectricalcodesandrequirementsandhaveallwiringdoneby
alicensedelectrician
•Useofproperoiliscriticaltothelong-termoperationofyourcompressor.Sincecompressors
areshippedwithoutoilinthecrankcase,besuretocheckwithyoursupplierregardingany
start-up/lubekitrequirements.Also,manymanufacturersnowofferextendedwarrantieson
thecompressorifyoupurchaseaspecificlubricant.
•Moistureisthenumberoneenemyofcompressedairsystems.Awidevarietyofmoisture
removalproductsareavailable,rangingfrominlinefiltersandmoisturedrainstoaftercoolers
andairdryer.Consultwithyourlocalcompressedairspecialistregardingyourspecificneeds.