5MINUTEFIXTOTROUBLESHOOTADIAPHRAGMPUMP

Air-operateddoublediaphragmpumps(AODD)arepreferredintransferapplicationsduetoasimpledesignthatmakesthemeasytooperateandcosteffectivetorepair.Butitisimportanttoinstallandoperatethepumpcorrectlytoachievetopperformance.Highlightedbelowaresixquickandeasyfixestocommonproblemsyoumayencounterduringinstallationandoperation.

Step1.ChecktheInletAirLineSizeandPressure

InstallingtoosmallofanairlineisthemostcommonmistakerelatingtoanAODDpump.Byusingtoosmallofanairline,youarestarvingthepumpofthefuel-compressedair-itneedstooperateatpeakperformance.Doublediaphragmpumpscomeinallshapesandsizes,basedontheapplicationandfluidrequirements.LargerAODDpumps,oneinchandgreater,requiremorecompressedairandlargerairlinestooperateatfullcapacitycomparedtosmallerpumps.Youcanfindtheappropriateairlinesizeforyourpumpinthemanufacturer’sinstallationandoperationmanuals.AsageneralguidelineforAODDinletairlinesizes,itisbestpracticetomatchtheairlinehosesizetotheairinletportsizeontheairvalve.

Inletairpressurealsoplaysakeyroleingettingthemostoutofyourpump.Diaphragmpumpsoperateona1:1ratio,meaningthepressureoftheinletairyoufeedthepumpisdirectlyrelatedtothefluid

pressureattheoutletofthepump.Forexample,ifthetargetoutletpressureofa1inch,50gpmpumpis100psi,theinletairpressureenteringtheairvalveofthepumpmustbegreaterthanorequalto100psi.

Systembackpressureandfluidviscositywillimpacttheoutletfluidpressure.Toolittlebackpressuremaycausethepumptoruninefficientlybecausetheballchecksmaynotcheckasquickly.Toomuchbackpressurecancausethepumptostallifthefluidpressureovercomestheairpressuretothepump.Tocontroltheperformance(flowandpressure)ofanAODD,itisimportanttohaveanairregulatorassemblyinstalledtocontroltheincomingairpressure(seeFigure1,C).InstallingthecorrectairlinesizewithanairregulatorwillsolvethemostcommoninstallationproblemfoundwithAODDpumps.

Step2.InspectforMufflerIcingandRestrictions

Diaphragmpumpscangeneratehighdecibellevelsatfullspeed,whichiswhymufflersareincludedandrecommendedatinstall.TheAODDairmotorrequirescompressedairtooperate.Asthecompressedairenterstheairvalveandischanneledthroughthepumpcentersectiontoexhaustthroughthemuffler,rapidchangesintemperatureoccur.Atthemufflerexhaust,airtemperatureiswellbelowfreezingandcancauseicing-relatedissues,increasinglycommoninhumidenvironments.

Ifyourpumpisoperatingerratically,oriftheinletairhashighlevelsofmoistureoryouseefrostontheoutsideofyourmuffler,theseareallindicationsyouarehavinganissuerelatingtoicingthatisdecreasingyourpumpefficiency.Suggestedbelowaresolutionsyoumayimplementtoeliminatetheseissuesandrestoreyourpumpperformance.

• Decreasetheairpressuretothepump

• Increasesizeofpumptooperateatlowerspeed(i.e.,lowerairpressure)

• Exhausttheairtoaremotelocationviaanexhaustporttube

• Addanairlinefilterwithawatercatcheranddraintocollectcondensation

• Installanairlineheater,raisingtheexhaustairtemperatureabovefreezing

• Adjustpressuredewpointtemperaturewithanaircompressordryer

Step3.InspectSealingSurfacesforLeaking

Leakingisaverycommonprobleminalltypesofpumps.ButtherearesomesimplefixestoensurethefluidstaysinyourAODDpumpandnotontheground.First,itisimportanttoknowthatpumps,especiallyplasticpumps,needtobetorquedtothemanufacturer’srecommendedrating.Reasonbeing,materialsrelaxovertime,oftenreferredtoascoldflowing,whichcancausesealingsurfacestoloosenandcreateleakpaths.Alwaysrefertothepumpmanualfortorquevaluesandfollowtheboltingpatternsillustratedtoreducethethreatofleakage.

Awisemaintenancetechnicianoncesaid,“Therearetwotypesofpumps–thosethatleakandthosethataregoingtoleak.”

ReuseofPTFEo-ringsisanothercauseofleakingatsealingsurfaces.PTFEisaversatilematerial,butoneofitsdownfallsisresilience.OnceaPTFEo-ringhasbeencompressed,itisnotcapableofregeneratingitsoriginalshape.SoreplaceallpumpPTFEo-ringswhenservicinganAODDpump.Afterproperlytorquingyourpumppermanufacturerrecommendationsandensuringallsealingo-ringshavebeenreplacedafterservice,yourAODDshouldbeleak-free.

Step4.EnsureProperTubingandPipingSize

Pumpinletandoutletfluidportdiametersvarybasedontheflowraterequired.Itiscriticalthatinletandoutlethosesizesmatchthesizeofthepump.Ofprimaryconcernistheriskofcavitationandthenegativeeffectithasonthepump,causingmorefrequentrepairsandhighermaintenancecosts.

Forexample,ifa1inchpumphasa½inchinlethoseconnected,thepumpwillnotbeabletooperateatfullcapacitywithouttheriskofcavitation.Thisriskincreasesdramaticallyasthedesiredfluidviscosityrises.Inthisexample,the1inchpumpshouldhavea1inchinletandoutlethoseattachedtoavoidcavitationandmorefrequent,costlyrepairs.

ItisalsorecommendedthatanAODDpumpbeinstalledwithaflexibleinlet/outletconnectionratherthanbeinghardplumbed.Aspumpspeedincreases,vibrationincreases.Asvibrationincreases,theriskoflooseningahardplumbconnectionincreases,creatingthepotentialforleaking.

Step5.SlowthePumpDowntoPrime

AODDpumpsarepopularwhenselfprimingisrequired.Creatingalowpressurezone,lessthantheatmosphericpressureof14.7psi,insidethefluidbowlsishowtheAODDpumpdrawsfluid.Iftheair

pressuresuppliedtothepumpistoohigh,thiswillcausethepumptochangeovertooquicklyandnotallowenoughtimeforthefluidtobedrawnintothepump.

Tosolvethisprimingissue,usetheairregulatortodecreasetheairpressureenteringtheairvalveandslowdownthepump.Oncethepumpspeedhasbeenreducedandthefluidhasbeenprovidedenoughtimetoenterthepump,youcanincreasetheairpressureandoperatethepumpatafasterspeed.

Step6.ClearanyFluidLineRestrictions

Thelaststeptoensureoptimalpumpperformanceistoclearanyfluidlinerestrictions.Theserestrictionscreatebackpressurethatmaynegativelyaffectthepumpandpotentiallycreatecavitationthatwillincreasefrequencyofmaintenance.Thingstolookforatboththeinletandoutletofthepump:

• Closedorpartiallyclosedvalves

• Clogsorkinksintheline

• Toomuchhoseorlengthofdistance

Conclusion

ThesequickfixeswillsolvemostofthecommonproblemsyoumayencounterwithanAODDpump.Remembertolistentothepump.Manytimes,carefullylisteningtothepumpoperatewilltellyouwhatyouneedtodotoreachoptimumpumpperformancelevels.Listenforerraticoperation,whichmaybecausedbyaninlethosethatistoosmalloraproblemrelatingtoicing.Ifyouhearwhatsoundslikegravelrunningthroughthepumporyouseeflashingaroundthemanifoldelbows,youarecavitatingandneedtocorrecttheinletoroutlettubingsizeorreducethepumpspeedtominimizeunnecessarymaintenance.Keepaneyeoutforkinksinyourinletandoutletlinesoranyvalvesthatcouldbeclosedorrestricted.Withthesetips,youwillachievetopperformanceoutofyourAODDpumpandspendlesstimetryingtofigureoutproblemsandmoretimepumping.