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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