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14energyefficiencyimprovementopportunitiesinpumpingsystems
14energyefficiency improvementopportunities inpumpingsystems (onphoto:DakotaPumpPackagedWastewaterPumpingSystemsviahennesymech.com)
DetailedenergyassessmentPumpsystemsconsistofpumps,driver,pipeinstallationandcontrols(suchasASDsorthrottles)andareapartoftheoverallmotorsystem.Belowsomeoftheenergyefficiencyopportunitiesforthepumpingsystemarepresented.
Also, (ASME)haspublishedastandardthatcoverstheassessmentofpumpingsystems,whicharedefinedasoneormorepumpsandthoseinteractingorinterrelatingelementsthattogetheraccomplishthedesiredworkofmovingafluid.
Inthisstandardtheprocedureofconductinga14detailedenergyassessmentofthepumpingsystemaswellastheenergyefficiencyopportunitiesaredescribed.
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1.2.3.4.5.6.7.8.9.
10.11.12.13.14.
1.Maintenance
Inadequatemaintenancelowers ,causespumpstowearoutmorequicklyandincreasescosts.Bettermaintenancewillreducetheseproblemsandthemostimportanttosaveenergy.
Waukeshapumpsperiodicmaintenance (photocredit:hollandaptblog.com)
Propermaintenanceincludesthefollowing:
Replacementofwornimpellers,especiallyincausticorsemisolidapplications.Bearinginspectionandrepair.Bearinglubricationreplacement,onceannuallyorsemiannually.
MaintenanceMonitoringControlsReductionofdemandMoreefficientpumpsProperpumpsizingMultiplepumpsforvaryingloadsImpellertrimming(orshavingsheaves)Adjustablespeeddrives(ASDs)AvoidingthrottlingvalvesProperpipesizingReplacementofbeltdrivesPrecisioncastings,surfacecoatingsorpolishingImprovementofsealing
pumpsystemefficiency
Inspectionandreplacementofpackingseals.Inspectionandreplacementofmechanicalseals.Wearringandimpellerreplacement.Pump/motoralignmentcheck.Thelargestopportunityisusuallytoavoidthrottlinglosses.
Typicalenergysavingsforoperationsandmaintenanceareestimatedtobebetween2%and7%ofpumpingelectricityusefortheU.S.industry.Thepaybackusuallyislessthanoneyear.
2.Monitoring
Monitoringinconjunctionwithoperationsandmaintenancecanbeusedtodetectproblemsanddeterminesolutionstocreateamoreefficientsystem.Monitoringcandetermineclearancesthatneedbeadjusted,indicateblockage,impellerdamage,inadequatesuction,operationoutsidepreferences,cloggedorgasfilledpumpsorpipes,orwornoutpumps.
Thecontrol roomatColumbiaBoulevardWastewaterTreatmentPlant(photocredit:peci.org)
Monitoringshouldinclude:
WearmonitoringVibrationanalyses
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PressureandflowmonitoringCurrentorpowermonitoringDifferentialheadandtemperatureriseacrossthepump(alsoknownasthermodynamicmonitoring)Distributionsysteminspectionforscalingorcontaminantbuildup
Oneofthebestindicatorstofollowformonitoringisspecificenergyorpowerconsumptionasafunctionoftheflowrate.
3.Controls
Theobjectiveofanycontrolstrategyistoshutoffunneededpumpsortoreducetheloadofindividualpumps.Remotecontrolsenablepumpingsystemstobestartedandstoppedrelativelyquicklyandaccurately,andreducetherequiredlaborwithrespecttotraditionalcontrolsystems.
RemoteControlPumpControlPanelsForWaterBoosterPumpSystem(photocredit:stainlesssteelstoragetank.com)
4.Reductionofdemand
Holdingtankscanbeusedtoequalizetheflowovertheproductioncycle,enhancingenergyefficiencyandpotentiallyreducingtheneedtoaddpumpcapacity.Inaddition,bypassloopsandotherunnecessaryflowsshouldbeeliminated.
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Energysavingsmaybeashighas510%foreachofthesesteps.
Totalheadrequirementscanalsobereducedbyloweringprocessstaticpressure,minimizingelevationrisefromsuctiontanktodischargetank,reducingstaticelevationchangebyuseofsiphonsandloweringspraynozzlevelocities.
2500gallonwaterstorage tankwitha internalelectrical floatswitch tocontrol thesubmersiblepumpsystems (photocredit:austinlakepumps.com)
5.Moreefficientpumps
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Pumpefficiencymaydegrade10%to25%initslifetime.Industryexpertshoweverpointoutthatthisdegradingperformanceisnotnecessarilyduetotheageofthepumpbutcanalsobecausedbychangesintheprocesswhichmayhavecausedamismatchbetweenthepumpcapacityanditsoperation.
Nevertheless,itcansometimesbemoreefficienttobuyaneedpump,alsobecausenewermodelsaremoreefficient.
Anumberofpumpsareavailableforspecificpressureheadandflowratecapacityrequirements.Choosingtherightpumpoftensavesbothinoperatingcostsandincapitalcosts(ofpurchasinganotherpump).Foragivenduty,apumpthatrunsatthehighestspeedsuitablefortheapplicationwillgenerallybethemostefficientoptionwiththelowestinitialcost.
Exceptionsincludeslurryhandlingpumps,highspecificspeedpumpsorinapplicationswherethepumpneedsaverylowminimumnetpositivesuctionheadatthepumpinlet.
HighEfficiencyPumpDrive (photocredit:Grundfos)
Replacingapumpwithanewefficientonereducesenergyuseby2%to10%.Higherefficiencymotorshavebeenshowntoincreasetheefficiencyofthepumpsystem2%to5%.
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6.Properpumpsizing
Apumpmaybeincorrectlysizedforcurrentneedsifitoperatesunderthrottledconditions,hasahighbypassflowrate,orhasaflowratethatvariesmorethan30%fromitsbestefficiencypointflowrate(U.S.DOEOIT,2005).Wherepeakloadscanbereduced,pumpsizecanalsobereduced.Asmallermotorwillhowevernotalwaysresultinenergysavings,asthesedependontheloadofthemotor.
Onlyifthelargermotoroperatesatalowefficiency,replacementmayresultinenergysavings.Pumploadsmaybereducedwithalternativepumpconfigurationsandimprovedoperationsandmanagementpractices.
Whenpumpsaredramaticallyoversized,speedcanbereducedwithgearorbeltdrivesoraslowerspeedmotor.Thispractice,however,isnotcommon.Paybacksforimplementingthesesolutionsarelessthanoneyear.Oversizedandthrottledpumpsthatproduceexcesspressureareexcellentcandidatesforimpellerreplacementortrimming,tosaveenergyandreducecosts.
PumpandControlsdesignedan innovativemodularboostersystem ideal forbuildings ranging from5150storiessustaining505000gpm(photocredit:callaghanpump.com)
Correctingforpumpoversizingcansave15%to25%ofelectricityconsumptionforpumping(onaveragefortheU.S.industry).
7.Multiplepumpsforvaryingloads
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Theuseofmultiplepumpsisoftenthemostcosteffectiveandmostenergyefficientsolutionforvaryingloads,particularlyinastaticheaddominatedsystem.Alternatively,adjustablespeeddrivescouldbeconsideredfordynamicsystems.Parallelpumpsofferredundancyandincreasedreliability.
Theinstallationofparallelsystemsforhighlyvariableloadsonaveragewouldsave10%to50%oftheelectricityconsumptionforpumpingfortheU.S.industry.
8.Impellertrimming(orshavingsheaves)
Trimmingreducestheimpellerstipspeed,whichinturnreducestheamountofenergyimpartedtothepumpedfluidasaresult,thepumpsflowrateandpressurebothdecrease.
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Asmallerortrimmedimpellercanthusbeusedefficientlyinapplicationsinwhichthecurrentimpellerisproducingexcessiveheat.Inthefoodprocessing,paperandpetrochemicalindustries,trimmingimpellersorloweringgearratiosisestimatedtosaveasmuchas75%oftheelectricityconsumptionforspecificpumpapplications.
9.Adjustablespeeddrives(ASDs)
ASDsbettermatchspeedtoloadrequirementsforpumps.Asformotors,energyuseofpumpsisapproximatelyproportionaltothecubeoftheflowrate9andrelativelysmallreductionsinflowmayyieldsignificantenergysavings.Newinstallationsmayresultinshortpaybackperiods.
Inaddition,theinstallationofASDsimprovesoverallproductivity,controlandproductquality,andreduceswearonequipment,therebyreducingfuturemaintenancecosts.
Similartobeingabletoadjustloadinmotorsystems,includingmodulationfeatureswithpumpsisestimatedtosavebetween20%and50%ofpumpenergyconsumption,atrelativelyshortpaybackperiods,dependingonapplication,pumpsize,loadandloadvariation.
Pumpingcontrolpanelwithadjustablespeeddrive (photocredit:motorsandcontrol.com)
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Asageneralruleofthumb,unlessthepumpcurvesare
exceptionallyflat,a10%regulationinflowshouldproducepumpsavingsof20%and20%regulationshouldproducesavingsof40%.
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10.Avoidingthrottlingvalves
Variablespeeddrivesoronoffregulatedsystemsalwayssaveenergycomparedtothrottlingvalves.Theuseofthesevalvesshouldthereforebeavoided.Extensiveuseofthrottlingvalvesorbypassloopsmaybeanindicationofanoversizedpump.
Throttlingvalveexample
11.Properpipesizing
Energymaybesavedbyreducinglossesduetofrictionthroughtheoptimizationofpipediameters.Thefrictionalpowerrequireddependsonflow,pipesize(diameter),overallpipelength,pipecharacteristics(surfaceroughness,material,etc.),andpropertiesofthefluidbeingpumped.
Twin3,500gpmdrinkingwaterand fireprotectionpumpingsystems (photocredit:pacewater.com)
Correctsizingofpipesshouldbedoneatthesystemdesignstageswherecostsmaynotberestrictive.
12.Replacementofbeltdrives
Mostpumpsaredirectlydriven.However,somepumpsusestandardVbelts
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whichtendtostretch,slip,bendandcompress,whichleadtoalossofefficiency.ReplacingstandardVbeltswithcogbeltscansaveenergyandmoney,evenasaretrofit.
Itisevenbettertoreplacethepumpbyadirectdrivensystem,resultinginincreasedsavingsofupto8%ofpumpingsystemsenergyusewithpaybackperiodsasshortas6months.
13.Precisioncastings,surfacecoatingsorpolishing
Theuseofcastings,coatingsorpolishingreducessurfaceroughnessthatinturn,increasesenergyefficiency.Itmayalsohelpmaintainefficiencyovertime.Thismeasureismoreeffectiveonsmallerpumps.
14.Improvementofsealing
Sealfailureaccountsforupto70%ofpumpfailuresinmanyapplications.Thesealingarrangementsonpumpswillcontributetothepowerabsorbed.Oftentheuseofgasbarrierseals,balancedseals,andnocontactinglabyrinthsealscanhelptooptimizepumpefficiency.
Merc freshwaterpumpseal replacement (photocredit:bdoutdoors.com)
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Reference:IndustrialEnergyAuditGuidebook:GuidelinesforConductinganEnergyAuditinIndustrialFacilitiesAliHasanbeigi,LynnPrice
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Edvard Csanyi
EdvardElectricalengineer,programmerandfounderofEEP.HighlyspecializedfordesignofLVhighpowerbusbartrunking(
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