1 FUNDAMENTALS OF CORIOLIS METERS AGA REPORT NO. 11 Stan Calame Oil and Gas Business Development Manager Emerson Process Management- Micro Motion, Inc. 7070 Winchester Circle Boulder, CO80301 Introduction Sincetheearly1980s,Coriolismetershavegained worldwideacceptanceingas,liquid,andslurry applicationswithaninstalledbaseofmorethanone millionunits.Throughsignificantdesign,enhancements intheearly1990sCoriolismetershaverapidlygained worldwideacceptanceingasphaseapplicationswith over100,000metersinstalledworldwideandmost notablythepublicationofthesecondeditionofAGA ReportNumber11,MeasurementofNaturalGasby Coriolis Meter. Havingtheabilitytobidirectionalmeasurealmostany gasfrom-400to+660degreesFahrenheitwithlittleto noconcern oferrorcausedby flow profile disturbances, pulsations, orflow surges, Coriolismeters are becoming the meter of preference in many applications. Coriolisisasmalltomediumline-sizetechnology; currentlythelargestofferingfromanyvendorforgas applications is a 250mm (10) equivalent flow diameter. ThepressuredropandflowrangeofaCoriolismeter drawsadirectrelationshiptotheactualflowarea throughthemeter.WhencomparingCoriolistoother metering technologies; i.e. the flow area trough a turbine meteristheareanotdisplacedbytheturbineinternals and rotor, the flow area of an orificemeter is that of the orificediameter.Becauseofthisrelationship,aCoriolis meterwilltypicallybeonepipesizesmallerthana turbinemeterandseveralsizessmallerthananorifice whilehaving similar pressuredrops at flowing pressures in the 300 ANSI class and above. 200mm (8) Coriolis meter installed in 250mm (12) line Beingatechnologywithoutwearingparts,Coriolis meters are immune to flow factor shift as they age. Most recently,resonantmodalanalysistechniques incorporatedintosomeCoriolismeterdesignsallowing flow accuracyverificationon-line,withoutdisruptionin flow, and without visual inspection of the flow element. Overall,Coriolismetersgreatlyreducemeasurement uncertaintyandmaintenancecostsascomparedtoother gas flow technologies. This paper will discuss the theory ofoperation,application,maintenance,andprovide examplesofCoriolismeterapplicationingas measurement. Theory of Operation A Coriolismeteris comprisedof twomain components, a sensor (primary element) and a transmitter (secondary). Coriolismetersdirectlyinferthegasmassflowrateby sensingtheCoriolisforceonavibratingtube(s).The conduit consists of one or more tubes that vibrate at their resonantfrequencybyaDriveCoil.Sensingpickoff coilslocatedontheinletandoutletsectionsofthe tube(s),oscillateinproportiontothesinusoidal vibration. 2 Coriolis Sensor Components Duringflow,thevibratingtube(s)andgasmassflow coupletogether,duetotheCoriolisforce,causing twistingoftheflowtube(s),frominlettooutlet, producing a phase shift between the signals generated by thetwo-pickoffcoils.Thephaseshiftordifferencein time is directly proportional to mass flow rate. Coriolis Sensing/Pickoff Signals Notethatthevibrationfrequencyoftheflowtubesis proportionaltotheflowingdensityofthefluid.Forgas applications,theflowingorlivedensitymeasured by the Coriolis meter is not used for gas measurement, as itspotentialerrorinrelationtogasdensitiesisnot acceptableforgasflowmeasurementpurposes. Althoughthisisthecase,densitymeasurementingas applicationscanbeusedasanindicatorofchangeina Meter Selection - Temperature ThetypicaloperatingtemperaturerangeofCoriolis meters is -400 to +400 degrees Fahrenheit (-240 to +200 degrees Celsius). Some advanced designshave extended the high temperature operating range up to +660 degrees Fahrenheit (+350 degrees Celsius). Otherthantemperaturecompensationfortheeffectof Youngsmodulus,flowingtemperaturemeasurementis not requiredfor themeasurement ofmass, basevolume, or energy with Coriolis meters. Meter Selection - Pressure Most Coriolis meters are designed to operate at pressures upto1480psi(600ANSI),withmetersconstructedof hastalloyandduplextubescapableofoperatingat pressures up to 3600 psi (1500 ANSI). Changesinoperatingpressurecanproduceabiasoften referredtoastheflowpressureeffectthatcanbe compensated for. The "flow pressure effect" of a Coriolis meteriscausedbythestiffeningoftheCoriolisflow tube(s)asthefluidpressureinthemincreases.This effect issimilar to abicycle innertube as itsinternal air pressure is increased; the inner tube ismore flexible at a lower pressure than at a higher pressure. Highfluidpressurescausetheflowtubetobemore resistanttothetwistingforceof theCoriolis Effectthan theyareatlowpressures.Astheinternalflowtube(s) pressureincreases,theCoriolisEffectortwistingofthe flowtube(s)observedforagivenmassflowrate decreases.Likewise,astheinternalpressuredecreases theCoriolisEffectobservedforagivenmassflowrate increases. Every Coriolis meter design and size has a different flow pressure effect specification. To correct for flow pressure effecttheflowpressureeffectcompensationfactor detailed below is applied to the indicated mass flow rate. 1 Coriolis meters flow factor and/or clean vs. dirty. Coriolis is a direct inferential mass meter eliminating the Where: Fp = 1 + ((P Effect /100) * (P Static P)) Cal requirementtoquantifygasvolumetricallyatflowing conditions; i.e. the need to measure flowing temperature, flowingpressure,andcalculateaflowing compressibility.Equationsandmethodsforthe conversionofmasstobasevolumearedocumentedin AGA Report Number 11, Measurement of Natural Gas Fp PEffect PStatic PCal =Flow pressure effect compensation factor = Pressure effect in percent psi = Measurement fluid static pressure in psi = Calibration static pressure in psi by Coriolis Meter and AGA Report Number 8, Compressibility Factors for Natural Gas and Other Hydrocarbon Gases. MostCoriolistransmittershaveprovisionsforapplying anaverageflowpressureeffectcorrectionandthe monitoringastaticpressuretransmittertofacilitatelive pressure compensation. 3 Meter Selection - Compressibility, Density, Viscosity, and Reynolds Number Althoughchangeincompressibility,density,viscosity, andReynoldsNumberareaconcernwithalmostall meteringtechnologies,theinferredmassflowrateofa curvedtubeCoriolismeterisinsensitivetoerrorcaused by these changes. Meter Selection Rate of Change High rates-of-change in flow or flow surges are the most commoncauseofdamageinflowmeterswithrotating flowelements;e.g.Turbine,Rotary,Positive Displacement,etc.Highratesofchangeinflowcause thesemeterstoover-speedandaretypicallyinherentto engine, boiler, and burner fuel gas applications. Duringaflowsurge,theinletflow splitterofaCoriolis meter chokesflow to the diameter of theflow tubes and theflowingdensitiesofnaturalgasmixturesdonot provide enough inertialforce to be imparted on theflow tubestodamagethem.Thiscoupledwiththeabilityof advanceddesignstomeasureuptochokevelocities removesanyrate-of-changeconcernintheuseof Coriolis. Meter Selection - Over Range Overrangingoftencausesmechanicaldamageand/or loss of measurement in the use of almost any flow meter. Some Coriolis meter designs can measure gas flow up to sonic velocity or choke point (approximately 1400 ft/sec with naturalgasmixturesfrom atmosphericto 2220psi) withoutlossofmeasurementordamage.Manufacturers shouldbeconsultedonthemaximumvelocitylimitof their particular Coriolis meter design. Pipingerosioncausedbyhighflowvelocitiesisa commonconcerningasapplications.Althoughthis concern is valid for carbon steel piping, it is not valid for stainlesssteelpipingorCoriolismeters.Foragasto erode ametal, themetalssurfacemustfirst oxidize and thenhighgasvelocitieserodethesoftoxidelayer.In mostgasapplications,moistureinthegascauses oxidationofcarbonsteelpipingdrivingthevelocity concernsofmanypipingengineers.ACoriolismeters immunitytohighvelocitygaserosionissimilartothat of an orificeplate or sonicnozzle, in that they aremade of stainless steelorothernickelalloyswhicharehighly immunetocorrosion/oxidationandthushighvelocity gas erosion. If abrasive contaminants (sand, welding rods, rocks, etc.) are present in the gas flow stream, erosionor damage of thewettedmetercomponentscausedbythisdebris travelingathighflowvelocitiesisofconcern.These concernsareapplicationspecific,butwhenpresent, filtration should be used to protect the meter. Meter Selection - Flow Pulsation The pulsation of flow is typically ofhigh concernin the useofeveryflowmeteringtechnology.Pulsatingflow cancausemeasurementerror(e.g.fluidicoscillation, orifice/differentialhead,rotary,turbine,andultrasonic meters)andmechanicaldamageinmetering technologieswithloadbearingsandgears(e.g.rotary, andturbinemeters).Flowpulsationsaretypicallya concernonfuelgaslinestoreciprocatingengines,the inletandoutletcompressionlinesofreciprocating compressors, and the inlet and outlet lines of regulators. AdvancementsinCoriolisflowmeterdesignhave yielded designs that maintain accuracy over a wide range ofpulsatingflowconditions.AlthoughCoriolismeters, forthemostpart,areimmunetoerrorcausedbyfluid pulsations, they are sensitive to pulsations at the resonant frequency of themeters flow tubes. In gas applications, Coriolismeters typically operate at resonantfrequencies above100Hzor6000cyclesperaminute,wheregas pulsations are typically not found. Meter Selection - Gas Quality Shoulddebris(i.e.sand,gravel,weldingrods,welding slag) exist that could erode, scar, or plug theflow tubes, filtrationshouldbeutilizedinthemeteringsystem designtoprotectthemeter.Althoughfinesoftparticles likeironoxide,oils,anddustwillnotdamagetheflow tubesofaCoriolismeter,build-upofthisdebriscan causeanimbalanceintheflowtubesandoutof specificationshiftinthemeterszero.Coriolismeters havehigherrorimmunitytodirtyprocessesbecausean outofspecificationzerocausedbydebrisbuildupwill induce detectable errors only at the low end of ameters flow range and are typically insignificant/undetectable at flows in the high end of the flow range. Inmostapplications,gasvelocitiesthroughtheflow tubesatthehighendoftheflowrangearetypically sufficienttomaintainameterscleanliness.AZero Checkperformedduringmaintenancewillidentifyif debrisbuilduporcoatingisaffectingthemeters measurementaccuracy.Ifanoutoftolerancecondition exists,themeterszerocanberecalibratedtoregain accuracy. Meter Selection - Bidirectional Coriolismeters are bidirectionalmeters, duringflow the signal from the inlet pick-off coil lags the outlet pick-off 4 coilsignal,bydeterminingwhichpickoffsignalis lagging flow direction is determined. Meter Selection - Measurement Accuracy Themeasurement accuracy of a Coriolismeter is design andfluidspecific.MostbendingmodeCoriolismeters canmeasuregasmixturesataccuraciesbetterthan1%. SomeadvancedCoriolisdesignscanachieveaccuracies of +/- 0.35%. Meter Selection Flow Range Theflow rangeof aCoriolismeteris determinedonthe lowendbyminimumacceptableaccuracyandworst- casedriftinameterszero,referredtoasZero Stability.ZeroStabilityisthepotentialerrorinall indicatedflowrates.Duetothisfact,aCoriolismeters accuracynaturallyimprovesasmassflowrateincreases until amaximum accuracy, dictated by meter design and measurement fluid,is reached. ThehighendofaCoriolismetersflowrangeis determinedbyflowvelocity.MostCoriolismeterscan measuregasvelocitiesupto200ft/secandadvanced designscanmeasuregasflowatvelocitiesuptosonic velocityorchokepointwithoutlossofmeasurementor damage.AlthoughsomeCoriolismeterdesignscan measuregasflowsuptosonicvelocity,amaximum allowablepressuredropdictatedbytheapplicationin whichtheywillbeappliedtypicallydetermines maximumflow.Thisisquitedifferentfromtraditional flowtechnologieswheremaximumflowiswhere measurementislostand/orflowdamageoccurstothe flow element. Therefore,theappropriatesizeofCoriolismeterforan application is determined by the following. -Allowable Pressure Drop @ Maximum Flow -Minimum Acceptable Accuracy @ Minimum Flow Sinceflow throughthemeterincreaseswithsquareroot of static pressure change and the minimum flow through themeterisconstantandrelativetotheminimum acceptableaccuracy,applyingameterathigher pressures,ineffect,increasesoperatingrangeand turndown. Coriolis Turndown versus Operating Pressure Insummarytheoperatingrangeforagivenpressure dropcanbeincreasedbyinstallingaCoriolismeterat high-pressurelocationsorupstream of regulationversus downstream. Meter Selection Low Flow Thefollowingequationisthemostutilizedmethodfor determining the minimum flow rate of a Coriolis meter. MinFlow = ZeroStabilty Accuracy% /100 Since Zero Stability can be expressed in standard volume (scf)unitsforagivenrelativedensity,the minimum standardvolumeflow rateatauserspecifiedacceptable accuracyneverchangesregardlessofpressureor temperatureforagivenmeterdesignandsize.Thisis differentfrom othergasmeasurement technologieswere theminimumflowratevarieswithpressureand temperature. Meter Selection - Maximum flow SomeCoriolismeterdesignscanmeasuregasflowsup tochokepointoraflowvelocityequivalenttosonic velocity(Mach1)ofthegasmixture(Approximately 1400 ft/secfornatural gasmixtures from atmospheric to 2220psi).Althoughthisisthecase,Coriolisare typicallysizedwithinanacceptablepressuredroplimit dictatedbytheapplication.Utilizingasetofgas referenceconditions,oftenfoundinthemanufacturers specifications, thefollowing equation can be utilizedfor calculatingtheflowratethroughameteratagiven pressure drop. 5 ( b vf vb f f b vf vb f f f APAppGas f ( RefGa s ( Installation - Meter Mounting APRe fGas Q RefGa s f Ap p Ga s Ap p Ga s f Ap p Ga s = Q Ap p Ga s Considerationshouldbegiventothesupportofthe sensorandthealigEnqm. e(6n.t3o) ftheinletandoutletpiping flanges with the sensor. For field fabrication of piping, a spool piece should be used in place of the meter to align Where: APAppGas RefGa s APRe fGas Ap p Ga s Q RefGa s Ap p Ga s Q Ap p Ga s = Maximum allowable pressure drop across the Coriolis meter with an application gas density ( ) in psi Ap p Ga s = Density of reference gas at flowing conditions in lb/cf = Reference differential pressure across Coriolis meter with reference gas density ( ) in psi RefGa s = Density of application gas at flowing conditions in lb/cf = Volume flow rate of reference gas at flowing conditions ofand RefGa s APRe fGasin cf/hr = Density of application gas at base conditions in lb/cf = Volume flow rate of application gas at base conditions in cf/hr or scf/hr pipe-workpriortoweldingtheCoriolissensormating flanges; i.e. slip fit is ideal. Pipingshouldfollowtypicalindustrypipingcodes. Meterperformance,specificallymeterzero,canbe affectedbyaxial,bending,andtorsionstresses.When thesestressesexist,pressure,weight,andthermal expansioneffectscanamplifythem.Althoughmost Coriolismetersaredesignedtoberelativelyimmuneto theseeffects,utilizingproperlyalignedpipe-workand pipingsupportsinsurestheutmostperformanceofany meterdesignandinmanycasesyieldsperformance better than the manufacturers specifications. Installation - Meter Orientation Coriolismetersareimmunetoorientationeffectswhen measuringsingle-phasefluids,manyfluidsarerarely alwaysinasinglephaseorfreefromsporadic contaminatesintheoppositephase.Asaruleingas measurement,theCoriolissensorshouldbeorientedin suchawayastominimizethepossibilityofheavier components,likecondensate,settlinginthesensorflow tube(s).Solids,sediment,plugging,coatings,ortrapped liquidscanaffectthemeterperformance,especially whenpresentduringzeroingofthemeter.Allowable sensororientationswilldependontheapplicationand Installation - Electrical Classification MostCoriolismetersaredesignedtomeetClass1, Division1,andClass1,Division2hazardousarea classifications. Installation Up and Downstream Piping InstallationeffectstestingperformedbySouthwest ResearchInstitute(SwRI)andsponsoredbytheGas ResearchInstitute(GRI)in2002confirmedbenttube Coriolismeterstobemostlyimmune,withinthe uncertaintyoftheflowlab,toupstreaminstallation effects.ThetestresultscanbefoundinGRITopical Report GRI-01/0222. Perturbation testing including pulsation and regulator valves placed in close proximity of a bent tube Coriolis meters has also been conducted by other organizations and independent parties and has shown flow conditioning or straight pipe up and downstream of a Coriolis meter is not required. thegeometryofthevibratingflowtube(s).Ingas service,theidealorientationofthesensoriswiththe flow tubes in the upright position. Installation Piping Configuration Curved or bent tube Coriolis flow sensors are immune to velocityprofiledistortionandswirleffects,thus allowingthedesignerflexibilityrestrictedonlybygood pipingsupportpracticestominimizestructuralstresses on the sensor body. The piping configuration of a Coriolis installation should consistofblockvalvesupanddownstreamofthe Coriolismeterwithbleedvalvestofacilitatepurgingof thepiping,zeroingofthemeter,andmaintenance procedures.Abypassshouldbeinstalledaroundthe meterifinterruptionofservicetothecustomerisan issue. Althoughthepressureportforflowpressureeffect compensationhasapreferredlocationupstreamofthe Coriolissensor,itcanbelocatedupordownstreamof 6 theCoriolissensor.Atemperatureportforverification of theCoriolis sensorsmeasuredtemperatureshould be located upstream of the sensor due to the Joule Thomson effect at high differential pressures across the sensor. Typical Coriolis Meter Installation Metrology - Calibration Duetothevariabilityofmanufacturingprocesses,all Coriolismetersrequireaflowcalibrationtoadjusttheir performancetotheaccuracylimitsinherenttotheir particulardesign.AsacommonpracticemostCoriolis calibrationoverawatercalibrationonCoriolismeters intendedforgasmeasurement.Althoughthisisthecase theusershouldreview industry recommendedpractices, standards,andregulatoryrequirementswhen establishing calibration policy for Coriolis. Coriolismetersareanattractivetechnologywhenthe availability,capability,oreconomicviabilityofgas calibrations is limited. Highly accurate water calibrations andconstructionofwatercalibrationfacilitiesare achieved at a fraction the cost of their gas counterparts. Metrology Volume Measurement ToaccuratelyquantifythemassoutputofaCoriolis meterappliedatpressuresotherthancalibration pressure,aflowpressureeffectcorrectionmustbe applied.EveryCoriolismeterdesignandsizehasa differentflowpressureeffectspecification.Inorderto correct fortheflow pressureeffectin aCoriolismeters indicatedmassflow rate, thefollowing correctionfactor should be applied to the indicated mass output. 1 manufacturerscapitalizeontheeconomicsandhigh stabilityofawatercalibrationtoperformthese calibrations.SomeadvancedCoriolismeterdesignsare immunetofluidphase,density,andviscosity;enabling water calibrations to transferto all otherfluids; i.e.gas, Fp = 1 + ((P Effect Where: /100) * (P Static P)) Cal liquid, and slurries. TestingbynumerousEuropeanandNorthAmerican flowlabshasconfirmedthetransferabilityofwater calibrationdataonaCoriolismetertogasapplications. MostnotablytestingsponsoredbytheGasResearch Fp PEffect PStatic PCal =Flow pressure effect compensation factor = Pressure effect in percent psi = Measurement fluid static pressure in psi = Calibration static pressure in psi Institutein 2004anddocumentedinreportGRI-04/172, whichcoverswatertogastransferabilityandwetgas performanceofCoriolismeters.Conclusionsinthe report state, The single fluid calibrationtests show that a water calibration of a Coriolis mass flow meter can be usedfornaturalgasapplicationswithoutlossof accuracy. Forgasapplications,themeasurementaccuracyof densitymeasuredbyaCoriolismeterisrelativetoa liquiddensitometersaccuracy,thisdoesnotmeetthe accuraciesrequiredforgasmeasurement.Thereforethe on-linedensityfromthemeterisnotusedforflow measurement with gas; rather the relative density or base densityofthegasisenteredintoaflowcomputeras determinedfrom eithersamplingmethods or on-linegas analysis. It should be noted that the gas physical property informationrequiredbyAGA8GrossMethod1,Gross Method 2, or Detail Method and proceduralmethodsfor applyingthisinformationintheuseofaCoriolismeter areidenticaltothoserequiredbyvolumetricmeters;i.e. Turbine,Orifice,Rotary,andUltrasonic.Coriolis technologyusesthefollowingcalculationstooutputa highly accurate standard or normal volumetric output. GRI 04/0172 Water, Air, and Gas Transferability Data SCF (gas)= Mass(gas) F p b(Gas) Industry testing has shown there is minimal benefit, from a calibration uncertainty perspective, in performing a gas SCF= Mass(gas) F p 7 (gas) Grx (Gas)b( Air ) 8 = Pb x Mrb will affect a Coriolis meters accuracy more at low flows than at high flows. If the buildup is causing ashift in the meter zero, cleaning and re-zeroing will bring the Where: Zb xR x Tb meters performance back to its original specification. At anygivenlevelofcoating,ifthecoatingisstable,the metercanbere-zeroed,withoutcleaning,andmeter performancecanberestored.Ifcoatingofthesensor SCF( gas) =Gas volume atTb andPb continues, the zero may continue to drift. Mass=Weight of gas (Coriolis output) Inspection and Re-zeroing b = Density atTb andPb Tb= Temperature at base conditions Pb= Pressure at base conditions Zb= Compressibility at base conditions ( Tb Toinspectorre-zeroaCoriolismeter,thermal equilibrium ofthemetershouldbeestablished.Flowing at a flow rate above the transitional flow rate can be used toestablishthermalequilibrium.Oncethermal equilibrium is achieved the meter is to be blocked in and themeters zero verified. Even though thestream isnot and Pb ) flowing, theflow metermay indicate a small amount of flow bias, either positive ornegative. Causesfora bias Gr(Ga s)=Real Gravity atTb andPb in the zero are usually related to the differences between previous and current zero flow conditions, which R= Universal gas constant M r = Molar Weight Fp =Flow pressure effect compensation factor Field Maintenance and Meter Verification ThefieldmaintenanceofaCoriolismeterisan inspection process consisting of the following 1)Transmitter Verification 2)Sensor Verification 3)Sensor Temperature Verification 4)Sensor Zero Verification AGA11 states the user should use meter verification data toguidethemontheneedtore-zerotheCoriolismeter and when to flow test. Field Maintenance Zero Verification Themeterzeroshouldbeverifiedperiodicallyand recalibratedifitisnotwithinthemanufacturers specification.Ataminimum,inspectionofthemeters zeroshouldbeperformedseasonallyinthefirstyearof operation to identify and installation or process condition issues.After thefirstyear of operation, zero verification intervalscanbeextendedbasedonthehistoric performance of the meters zero for the application. Drift in Zero Reading Productbuildup,erosion,orcorrosionwillaffectthe meterzeroperformance.Productbuildup(coating)may biasthemeterzero.Itshouldbenotedthatazeroshift include. -Differences between thecalibrationmedia density and the gas density -Differences in temperature Themetershouldreadamassflow ratethatislessthan themanufacturer is zero stability specificationunder the no-flow condition. If the zero iswithin specification re-zeroing themeter is unwarranted.Ifoutsideofspecificationthecurrentzero valueandmetertemperatureshouldberecordedfor futurereferenceandthezeroingprocedurespecifiedby the meter manufacturer should be followed. Field Maintenance Diagnostics DiagnosticLED(s)anddisplay aretypically providedto indicatetheoperatingstatusofthesensorand transmitter.ThediagnosticsoftheCoriolistransmitter verifytheintegrityoftheCPUandinsureoperational parametersarewithintolerance.Coriolissensor diagnosticsverifythesensingcomponentsofthesensor arenotdamagedandoperatingwithinnormallimits. Sensordiagnosticsalsoprovideinsightintotheprocess flowconditionsandpotentialmeasurementproblems with them. SomeCoriolissensordesignsalsoprovideon-line verificationoftheflowtube(s)structure.Theflowtube structure of a Coriolis sensor dictates its flow calibration factor. This method of verification measures flow tube(s) stiffnesstoinferdensityandmasscalibrationfactoras unchanged. Utilizing resonantmodal analysis techniques thetransmitteractivelyteststheflowtube(s)stiffness 8 duringflowingconditionsanddeterminesifanoutof tolerance stiffness change has occurred. Coriolismeterverificationbyresonantmodalanalysis methodisasignificantadvancementinCoriolis technology.Thiscapabilityallowsforverificationa Coriolis meters accuracy without interruption in flow or inspection of the meters components for damage. CAPEX CapitalExpenditures(CAPEX)toimplementCoriolis measurementwillvarydependentuponmeterdesign, size,pressureratings,materialsofconstruction,and accuracy.Typicalcapitalexpendituresrequiredinthe implementationofaCoriolismeteringsysteminclude the following. -Coriolis Sensor -Flow Computer or Transmitter -Power System -Installation and Startup Coriolistechnologyreducesoreliminatesseveralofthe capitalexpendituresrequiredintheapplicationofother gasflowtechnologiesandtypicallyassociatedwith naturalgasmetering.Typicalcapitalexpendituresthat are reduced or eliminated are as follows. -Pressuremeasurement-Typicallynotrequired forflowmeasurementandifrequired,ahigh accuracy transmitter is unwarranted -Temperature measurement- Integral to Coriolis sensor design -Specialtyupstreamanddownstreampiping and/or flow conditioning Not required -Gasflowcalibrationofsensor-Factorywater flowcalibrationtransferstonaturalgas measurement -Installation and startup OPEX OperatingExpenditures(OPEX)tomaintainCoriolis measurementwillvarydependentuponmeterdesign, powersystem,cleanlinessofprocess,andverification proceduresrequiredbymeterdesign,adoptedbythe usersorganization,ordictatedbyregulatory requirements. Typical operating expenditures required in the use a Coriolis metering system include the following. -Routineverification/inspectionofsensorzero and meter diagnostics -The replacement of battery backup power cells, if used, when their efficiency has declined. Coriolistechnologyreducesoreliminatesseveralofthe operatingexpendituresassociatedwithgasflow technologies.Typicaloperatingexpendituresthatare reduced or eliminated are as follows. -PressurecalibrationAlthoughpressure measurement,ifused,willrequireperiodic verificationitsrecalibrationwithaprecision reference is typically not required. -Temperaturemeasurement-Although temperaturemeasurementwillrequireperiodic verificationitsrecalibrationwithaprecision reference is typically not required -Inspectionandcleaningofspecialtyupstream anddownstreampipingand/orflow conditioning -Validationofflowfactor-Coriolismeterscan bevalidatedwithwaterflowreferences,which are typically more economical than that of their natural gas counterparts. Some Coriolis designs incorporatestructuralintegritydiagnosticsthat verifythesensorsflowfactororidentifythe requirementforrecalibration.Structural diagnosticseliminateunnecessaryflow validations or recalibrations. Application Examples Coriolismetersareappliedinawidevarietyof applications,fromthewellheadtotheburnertip. Coriolismetersareprimarilyasmallertomediumline sizemeter,ideallysuitedtothefollowinggasmetering sweet spots: -Line sizes 250mm (12) and smaller -300 ANSI through 900 ANSI -High turndown requirements -Dirty,wet,orsourgaswheremaintenancecan be an issue with other technologies -There is no room for long straight-runs -Changing gas composition and density -Suddenchangesingasflowvelocity(fueland production gas applications) -Pulsatinggasflows(fuelgasandcompression gas in the use of reciprocating compressors) -Applicationswereabnormallyhighflowrates can occur. Coriolismeterscanbesizedforverylow-pressuredrop (100H2O),butcanalsobeinstalledupstreamofthe pressure regulator with high-pressure drops for increased turndown without concern of damage or malfunction due toflownoise.Forinstance,inoneapplicationfor custody transfer of nitrogen, a 50-psid drop (1390 H2O) 9 wasallowedacrosstheCoriolismeterandthepressure regulator adjusted accordingly.This allowed the use of a 1Coriolismeterinsteadofa3meterdownstreamof theregulatoranda40:1useableturndown(Betterthan 1%accuracyatminimumflowandanaverage0.35% basevolumeaccuracyover95%oftheupperflow range). Separatorgas:SaudiAramcousesanumberofCoriolis metersonboththeliquidandgassideofseparators. Thisapplicationisofparticularnotebecausethegas streamiswet,withentrainedhydrocarboncondensates. Measurement of this stream iswithin a few percent over awiderangeofconditions,greatlyenhancingseparator operationandaccuratelyquantifyingthevalueofthe liquid hydrocarbon entrained stream. Coriolis Liquid and Gas Separator Measurement Fuel Control: A major US vendor of gas turbines designs ahigh-efficiency,lowemissionsoffering.Thisdesign utilizesatrioofCoriolismeterstomeasurethenatural gasburnedineachofthreecombustionzones.The combination of no damage due to flow rate-of-change at start-up,highturndown, highaccuracy,immunityto vibrationinaveryhighvibrationenvironment,along witheaseofinstallationduetonostraightpiperun requirement, makes Coriolis the technology of choice. Coriolis Fuel Gas Measurement on a Gas Turbine Natural Gas Fiscal Transfer: One specific example of gas measurementcapabilityisatanaturalgasutilityin WesternAustralia.Two3metersareusedinparallel withathirdusedasahotspareformonthly verifications of the transfer meters. The justification for using the Coriolis meters was based oninstallationandcalibration/maintenancecost improvementsoverthemoretraditionalgasmetering systems.SinceCoriolismetersrequirenostraightruns or flow conditioning the installed costswere reducedby fivetimes,evenwiththeparallelmetersrequiredto handle the highest flows. Additionally,periodicmaintenancecostswerereduced duetotheintrinsicreliabilityofCoriolismeters(i.e.no movingparts).Similarly,reliabilityimprovements reduced calibration and proving costs. Internalchecksbythecustomerhaveshownagreement tobetterthan0.1%onallgastransfersovera6-year period. Western Australia: Previous installation using turbine meters for 50:1 turndown After installation since 1996, with two operating and one hot spare meter for 80:1 turndown. 10 Natural Gas Storage: A storage field in Hungary utilizes 27two-inchCoriolismetersfortheinjectionand withdrawalmeasurementofnaturalgas.Thestorage reservoirconsistsofamultilayersandstoneformation withanaquiferflowingthroughit.Duetothe complexityofmanagingthewaterlevelinasandstone formation on the injection and withdrawal of natural gas, multiple smallwells are required. Thewithdrawalgas is alsofully saturated,containsH2S,andduringhighflow thewells producesand.In this difficultapplicationonly Coriolismeterscanprovidebidirectionalmeasurement, long-termaccuracy,andachievethewideturndowns required for reservoir management. Coriolis Natural Gas Storage Measurement in Hungary Energy Metering:EnergyperSCFcanvary asmuch as 10timesthatofenergyperaunitweightfor Hydrocarbons. Ifthetotal concentration ofCO2andN2 inthenaturalgasmixtureremainsconstantandmostof thevariationincompositionisrelatedtohydrocarbon concentrations,anaverageheatingvaluecanbeutilized forenergymeasurementallowingCoriolistoachieve totalenergyaccuraciesunparalleledbyvolumetric metersutilizingthesameaveragevalue.ACoriolis meterbyitselfoffersaveryaffordablemethodof inferring energy flow rates on some natural gas streams. Combustioncontroltoboilers:Inthisapplication,a Pulpmill in Quebec sought amore reliableway tomeet EPAemissionsrequirements.Combustioncontrolwas easier,basedonthemassratiobetweenthenaturalgas andcombustionair.Highturndownandconcernover damagetothemeasurementelementduetoflowsurge when the boilers fired drove the selection of Coriolis for this application. Combustion control application to boilers Ethylene gas transfer: Ethylene is commonly viewed as a difficult tomeasuregas, due to itsnon-idealnature. In thisapplication,Coriolismetersareusedforintra-plant transfers attainingaccuraciesunattainablebyvolumetric meters,helping tomeet both unitmass-balance goals, as well as reactor feed rate requirements. Ethylene application, where ethylene is fed continuously to a polymerization reactor Summary Although a relatively new technology for the natural gas industry,Coriolismetershavegainedworldwide acceptanceastheidealmeterformeasurementofmany fluidsinotherindustries.Withaworldwideinstalled baseofoveronemillionunits,Coriolistechnologyis seeingexpandeduseforbothliquidpetroleumand naturalgas.Mostcountriesandmeasurement organizationshaveapprovedorpublishedstandardsfor theuseofthetechnology.MostnotablyisAGAand 11 APIwhohavejointlypublishedAGAReportNo.11/ APIMPMSChapter14.9,MeasurementofNaturalGas by Coriolis Meter. Technologylimitationsofearlierdesignshavelargely beenovercome,withhighaccuracymeasurementnow possibleatlow-pressuredrop.Coriolissweetspots arelinesizesof300mm(12)andsmaller,300to900 ANSI,wherehighturndownisneeded,flow conditioningwithothertechnologiestomeetAGA requirementsiscostly,flowsurgesoccur,pulsationsare present, energy metering is required, and/or the gas is of dirty, sour, or changing composition. Coriolistechnologymeritsseriousconsiderationasa bonafidecontendertocomplementUltrasonicinlow costofownershipmeteringfornaturalgasapplications. Thesetwotechnologiesoverlapinthe100mm(4)to 300mm (12) line size range. Parallel3 Coriolis and 16 ultrasonic in a fuel gas metering installation. Third-partydatafromCEESI,Pigsar,SwRI,andothers showlittleifanyeffectofflowprofileandthe transferabilityofafactorywatercalibrationtonatural gas measurement applications. CommonCoriolisgasapplicationsrangefromwellhead separator,mediumtohigh-pressurefiscalmetering,and fuelgastopowerturbines,reciprocatingengines,and boilers.AsusersofgasmetersinvestigateCoriolisthey are finding it to be the fiscally responsible choice for gas measurementintodayscompetitivebusiness environment. References -AGA Engineering Technical Note XQ0112, Coriolis Flow Measurement for Natural Gas Applications, American Gas Association, 400 N. Capitol Street, N.W., 4th Floor, Washington, DC 20001 -AGA Report No. 3, Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids, American Gas Association, 1515 Wilson Boulevard, Arlington, VA22209 -AGA Report No. 7, Measurement of Gas by Turbine Meters, American Gas Association, 1515 Wilson Boulevard, Arlington, VA22209 -AGA Report No. 8, Compressibility Factors of Natural Gas and Other Related Hydrocarbon Gases, American Gas Association, 1515 Wilson Boulevard, Arlington, VA22209 -AGA Report No. 9, Measurement of Gas by Multipath Ultrasonic Meters, American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209 -AGA Report No.11, Measurement of Natural Gas by Coriolis Meter, American Gas Association, 1515 Wilson Boulevard, Arlington, VA22209 -ANSI B16.5, Pipe Flanges and Flanged Fittings, American National Standards Institute, 25 West 42nd Street, New York, NY 10036 -API Manual of Petroleum Measurement Standards Chapter 21.1, September 1993, Flow Measurement Using Electronic Metering Systems, American Petroleum Institute, 1220 L Street NW, Washington, DC20005 -ASME MFC-11M, 2006, Measurement of Fluid Flow by Means of Coriolis Mass Flowmeters, American Society of Mechanical Engineers, Three Park Avenue, 23S2, New York, NY 10016-5990 -ISO 10790, 1999, Measurement of fluid flow in closed conduits Coriolis meters, International Organization for Standardization, Case Postale 56, CH-1211 Geneve 20, Switzerland -GTI Topical Report, GRI-01/0222, Coriolis mass flow meter performance with natural gas, Gas Technology Institute, 1700 South Mount Prospect Road, Des Plaines, Illinois60018 -GRI Topical Report, GRI-04/0172, Coriolis mass flow meter performance with water, air, dry - gas, & wet gas, Gas Research Institute, 1700 South Mount Prospect Road, Des Plaines, Illinois 60018