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Understanding
Ultrasonic Level
Measurement
third edition SIEMENS
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AcknowledgementsAsyoucanimagine,aprojectlikethisinvolvestheeffortsandcontributionsofmanypeople.Tobeginwith,theauthorswanttothankthegenerationsofengineers,designers,applicationspecialists,salespeople,supportstaff,andmanagementwhohavedevelopedthetechnologyandtheproductsovertheyears.Allofusalsooweahugedebtofgratitudetoourcustomerswhohaveallowedustogrowandtoshareintheirsuccessesbyparticipatinginourvision.Alltogether,theyhavecreatedtheSITRANSLUT400,therevolutionaryultrasoniccontrollerwithonemillimeteraccuracythemarketshavebeenwaitingfor.
Theauthorsalsowanttothankallofthewritersandphotographerswhohavecontributedmaterialusedinthisbook,bothinspecificcontentandforgeneralbackgroundinformation.Theyaretoonumeroustomention,buttheirenthusiasmforthetechnologyandtheireffortsaremuchvalued.TheartisticcontributionsofPeterFroggattarealsoappreciated.Overtheyears,hisdrawingsandphotoshavehelpeddefinetheproductline,andhisworkgracesmanyofthepagesinthishumbletome.Thosewhotookthetimetoeditandprovidecommentsandotherinputalsohaveourgratitude.
Specifically,wewanttothanktheeditingandorganizationalskillsofJamieChepeka.Herdedicationtotheprojectwasunwavering,eveninthefaceofloomingdeadlinesandcreativeangst.Withouthermanagementguidance,wewouldstillbestaringatourscreens.
Lastly,theauthorsapologizeinadvanceforanyandallmistakes,inaccuracies,andomissions.Wetakefullresponsibilityandassureyouthatwewilldobetternexttime.
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Contents
ChapterOneHistoryofultrasonicsUltrasonicsandlevelmeasurementProductdevelopmentmapUltrasonictheorySoundUsingsoundFrequencyandwavelengthMeasurementprincipleThemediumandthemessageSoundintensitySoundvelocityandtemperatureSoundvelocityandgasSoundvelocityandpressureSoundvelocityandvacuumSoundvelocityandattenuationSoundreflectionSounddiffractionSoundpressurelevel(SPL)Soundintensitychanges
Summary
ChapterTwoUltrasonicinstrumentationThetransducerTransducerenvironmentsTransduceraccuracyTransducerresolutionandaccuracyImpedancematchingAxisoftransmissionBeamwidthBeamspreadingRingdownThecontrollersDigitalfilteringAveragingechoesEchoextractionalgorithms
Summary
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ChapterThreeThesoundandtheslurryTopicsTransducersandultrasonicsystemsSinglesystemsCompoundsystems
TransducersTemperatureandtransducermaterialTemperaturesensors
SoundanddifferentialamplifiersSingle-endedreceiverDifferentialreceiverApplicationtemperatureHousingmaterialRangeandpowerConditionsTransducerselectionBlankingdistanceandheightplacementTemperatureInstallationTransducerdesign:theheartofthematter
Summary
ChapterFourEchoprocessingTopicsEchoprocessing-intelligenceUnderstandingechoprocessingShotsandprofilesFindingthetrueechoEchoqualityFigureofmeritEchoparameterfinetuningEchoprofilesProfilecomponentsEchoprofileRingdownTVTcurve(TimeVaryingThreshold)EchomarkerEcholockwindowEchoprocessingparametersEchoconfidenceTheechoEchostrength
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NoiseNoiseinterferenceDeterminingthenoisesource
Non-transducernoisesourcesCommonwiringproblemsReducingelectricalnoiseAcousticnoiseReducingacousticnoise
Summary
ChapterFiveInstallationTopicsSelecttherighttransducerLocationObstructionsClosedvesselsTanksTankaccessOpenvesselsOpenchannelmeters:weirsandflumesFlumesTransducerlocationLiftstationsPositioncontrolHazardousapprovalsApprovalsControllerinstallation
Summary
ChapterSixApplicationsApplicationsTopicsCementMiningChemicalstorageAggregateBlendingsilosandstoragebunkers
EnvironmentalCollectionsystem:liftstation/pumpstation/wetwellWastewatertreatmentplantEnvironmentalapplicationsFoodindustryChemicalindustry
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Otherindustries
ChapterSevenBestinclass–theultrasonicproductlineSITRANSLUT400Keybenefits
SITRANSProbeLUKeybenefits
TheProbeKeybenefits
MultiRanger100/200Keybenefits
SITRANSLU10Keybenefits
HydroRanger200Keybenefits
EchomaxTransducersXRS-5Keybenefits
XPS/XCTSeriesKeybenefits
XLTSeriesKeybenefits
ST-HKeybenefits
Conclusion
GlossaryWorksCited
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ChapterOne
HistoryofultrasonicsHowsweetthatjoyoussound,wheneverwemeet.1
SiemensMilltronicsProcessInstrumentshasalongandsuccessfulhistoryspecializinginthemanufactureofequipmentforindustrialprocessmeasurement.BasedinPeterborough,Canada,SiemensMilltronics(PI2)isnowakeymemberoftheSensorsandCommunicationdivisionwithintheSiemensIndustrydivision,supplyinginstrumentationacrosstheglobe.
Foundedin1954byStuartDaniel,aformeremployeeofCanadianGeneralElectric,thecompanybeganasMilltronicsandengineeredelectronicballmillgrindingcontrolsforthecementandminingindustry.Fromthis,thecompanyexpandedanddiversifieditsproductlinetodevelopawiderangeofprocessmeasurementdevices.Ithasbecomealeaderinlevelmeasurementtechnology.TheSiemensMilltronicsrangeofinstrumentationnowincludesultrasonic,radar,andcapacitancetechnologies,butthefoundationofitsinnovationandsuccessfuldesignandtechnicalexpertiseliesinitsultrasonicecho-rangingtechnology.
SiemensMilltronicsultrasonicecho-rangingtechnologycompriseshighlysophisticatedinstrumentationapplyingdigitalcircuitrytoultrasonicecho-ranging.Thisinnovationhasproducedarangeoftechnologicallyadvancedproductscapableofmonitoringliquidandsolidslevelsfromafewcentimeterstoover60meters(200ft).Todate,over1,000,000pointsoflevelonadiverserangeofmaterial,includingsolids,liquids,slurries,andresins,aremonitoredacrosstheglobebySiemensMilltronics,manyinhostileandhazardousenvironments.
TheSiemensMilltronicsultrasonicproductlineisconstantlyimprovingastechnologicaladvancesareimplemented,newproductsaredeveloped,andnewapplicationsaretackledandwonover.Complementedbyateamofhighlyskilledapplicationsengineers,servicepersonnel,andadedicatedSiemenssalesforce,SiemensMilltronicscontinuestoprovide
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reliableandinnovativelevelsolutionstoindustryacrosstheglobe.
UltrasonicsandlevelmeasurementThemeasurementoflevelhasbeenintegraltohumandevelopmentsincepre-industrialtimes.
“Egypt,”Herodotusremarkedmorethan2000yearsago,referringtothevastirrigationprojectthatsustainsthatcountry’sagriculture,“isthegiftoftheriver.”EveryJune,assnowmeltsfromtheTanzanianHighlandsandspringrainfromtheCongobeginaccumulatingintheNile,itselevationbeginstorise.ItrisesgentlytoacrestinlateSeptemberorearlyOctober,thensubsidesbylateDecember.Seedgoesintotherich,freshlydepositedsiltassoonasthefloodrecedes.
Egyptianengineersbegancapturingtheriverforirrigationprojectsabout7,000yearsago.Becausethesystemreliesonacomplicatedsystemofgatestodistributewateracrossabroad,relativelyflatarea,it’svitalthatengineersknowtheheightoftheriverinadvanceofitsarrival.Thefirstsolutionwastosimplymarktheriverbanksandconveyinformationbacktoheadquartersviarunners.Later,engineersdevelopedalargevarietyof“nilometers,”devicesusedto
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measuretheriverheight.Most,however,consistedofordinarygraduatedscalesthatprojectedverticallyupwardfromtheriverbedandwerereaddirectly.
Today,theU.S.GeologicalSurveyandtheNationalOceanicandAtmosphericAdministrationusesimilardevices:graduatedpolesstuckintothewater.Techniciansreadmostofthemmanually,buttherearesomeinflood-proneareasthattransmitinformationdirectlytotheagencyviaradio.Thoughmillennia-oldsolutionsformeasuringriverlevelarestillinuse,therearethousandsoflevel-determinationproblemsinindustrythatdemandmuchmoresophisticatedsolutions.Liketheirforebears,contemporaryengineershaverespondedwithimpressiveingenuity.2
IngenuityisalsothekeytothesuccessofSiemensMilltronicsultrasonictechnologyasitmeetsthedemandsoflevelmeasurementintheprocesssystemsmarket.TheneedforprocessmeasurementdatesbacktotheIndustrialRevolutionwhenthedevelopmentofthesteamenginecreatedarequirementfortheaccuratemeasurementoftemperature,pressure,andflow.
Bytheearlytwentiethcentury,processengineersweredeterminingprocessmeasurementsusingavarietyofmechanicaldevicesincludingfloats,sightglasses,thermometers,gauges,andarmatures.Accuracywasoftenelusive,andthesedevicesweresupplementedbyhumanexperience.Processengineersoftenreliedontheirsensestocomplementthetechnology:usingsight,sound,touch,smell,andeventexture,engineerswouldexamineprocesssmoke,liquidclarity,texture,andsmelltodetermineproductquality.However,chemicalcompounds,safetyrestrictions,systemcomplexity,andawarenessnowmakethistypeoftactileverificationimpossible,requiringmeasurementtobemadebytheinstrumentalone.
Processmeasurementincorporatesavarietyofsolutions,frompressureandtemperaturetoflowandlevel.WhileSiemensSCPIoffersinstrumentationtomeasureallofthese,SiemensMilltronicsspecializesinthecalculationoflevel.
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Levelmeasurementinstrumentationcurrentlyemploysavarietyofsophisticatedtechnologies,withultrasonicmeasurementasthecornerstone.Theoriginsofultrasonicmeasurementtechnologylieinearlyusebysubmarinesofsonarfordepthgaugingandmarinedetection,butitwasn’tuntil1949thattheseprincipleswereappliedtolevelmeasurement.BobRedding,ofEvershedandVignoles,developedanultrasonicinstrumentwithservocontrolthatautomaticallymeasuredoillevelandthentransferredthatinformationtoaremoteindicator.
OthertechnologieswerealsoappliedtoremotelevelmeasurementbycompanieslikeMagnetrol,whichapplieditsmagneticswitchingtechnologytothecontrolofpumpsandotherdevicesforuseinwaterlevelalarming.Thedevicetransmittedlevelchangestotheswitchmechanismwithoutanymechanicalorelectricalconnectionandeliminatedmechanicaldevicessuchasdiaphragmsandstuffingboxes.
In1963,MagnetrolintroducedModulevel©3,thefirstmagneticallycoupledpneumaticproportionallevelcontrol.Thefirstsignificantsensinginstrument,itledthewaytonewmarketsincontinuousprocesslevelcontrol.Bythe1970s,ultrasonictechnology,alreadyusedinshipandplanedetection,wasdevelopedforthemeasurementindustries.Sonarprincipleswereappliedtouseinair,usingmodifiedlowfrequencysonarequipmentwithpiezoelectriccrystalstogenerateechoranging.Thesenewsensorswereappliedtoprocesscontroltaskssuchaspointlevel,continuouslevel,concentration,andfullpipeapplications.Inthemid-1980s,analoginstrumentationwentdigitalandoffered4to20mAsignal,openingupcommunicationpossibilities,andgreatlyincreasingitsvalueascontrolinstrumentation.
Milltronicsenteredthemarketintheseearlydaysofultrasonicdevelopment.In1973,afterbeingthemainRaytheon®4distributorinCanadaandtheUSA,MilltronicsacquiredtheRaytheonUltrasonicRangingbusinesssegmentandtheAiRangerIIproduct.Overthenext30years,Milltronics®5hasbecomethemarketleaderandthemosttrustednameinultrasonicslevelmeasurement.AftertheSiemensacquisitionin
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2000,theMilltronicsbrandhascombinedwiththeTotallyIntegratedAutomationvisionofSiemenstoofferultrasoniclevelmeasurementequipmentasanintegralcomponentofcompletesystemdesign.
Productdevelopmentmap
Ultrasonictheory
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Ultrasonicmeasuringtechnologyoperatesonthesimpleprincipleofmeasuringthetimeittakessoundtotraveladistance.Whiletheideaissimple,theprocessofcreating,controlling,andmeasuringthesoundtravelisnot.
SoundSoundistheinterpretationofelectricalsignals.Thesesignalsarederivedfromacousticpressurewavesthatactivateatransducersimilartothehumanear.Thisorganictransducerinterpretstheelectricalsignalschanneledintotheearcanal.
Thesoundsignalsarecausedbythemechanicalvibrationoftheobject.Thevibrationistransferredtothegasmodulesinthesurroundingmediumwithinwhichitiscontained.Thetransferoccursasthevibrationsalternatelycompressanddecompressthemoleculesnexttotheobject,spreadingoutwardliketheringsinapondintowhichastonehasbeenthrown.Astheobjectmovesintothegas,itsmoleculescompressintoasmallerspace.
Astheobjectmovesoutofthegas,itsmoleculesdecompressintoalargerspace.Thispatternorwaveofcompressionanddecompressiontravelsoutwardfromthevibratingobjectthroughthegasandmanifeststhephenomenoncalled“sound.”Ifthereisnogas,asinaperfectvacuum,thentherewillbenopropagationofsound.
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Soundlevelsintheeverydayworld
Thesound,ornoise,ofeverydaylifesurroundsusfromourbreakfasttohouseholdchores,work,andtravel.Soundiseverywhereanditsoccurrenceseemsanaturalpartofourenvironment.Sound,however,canalsobeused,notjustfordirectcommunicationasinspeechormusic,butalsoasaresourcetobeharnessedandthenappliedtoamethodofmeasurement.
UsingsoundSoundcanbeusedasameasurementtoolbecausethereisameasurabletimelapsebetweensoundgenerationandthe“hearing”ofthesound.Thistimelapseisthenconvertedintousableinformation.Ultrasonicsensingequipmenthastheabilitytogenerateasoundandthenthecapacitytointerpretthetimelapseofthereturnedecho.Itusesatransducertocreatethesoundandsensetheecho,andthenaprocessortointerpretthesoundandconvertitintoinformation.
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Frequencyandwavelength
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Vibrationofthesoundwavesisrelatedtotimeandiscalled“frequency.”FrequencyismeasuredinHertz(Hz)andreferstothenumberofcyclespersecond.Apuresoundwaveofaparticularfrequencyexertssoundpressurewhichvariessinusoidallywithtime.Onewavelengthorcycleisdefinedasthedistancefromonecompressionpeaktothenext.Thewavelengthofaspecificfrequencyisrelatedtothevelocityatwhichthesoundtravels:
ThenumberofcyclesthatoccurinoneseconddefinesthefrequencyinHertzatwhichthesoundisbeinggenerated.Forourpurpose,thefrequencyisconstant.Atbest,thehumanearcandetectsoundsrangingfrom20to20,000Hertz.Thesoundrangeabovethisfrequencyisknownasultrasonics.
MeasurementprincipleApiezoelectriccrystalinsidethetransducerconvertsanelectricalsignalintosoundenergy,firingaburstofsoundintotheairwhereittravelstothetarget,afterwhichitisreflectedbacktothetransducer.Thetransducerthenactsasareceivingdeviceandconvertsthesonicenergybackintoanelectricalsignal.Anelectronicsignalprocessoranalyzesthereturnechoandcalculatesthedistancebetweenthetransducerandthetarget.Thetimelapsebetweenfiringthesoundburstandreceivingthereturnechoisdirectlyproportionaltothedistancebetweenthetransducerandthematerialinthevessel.Thisverybasicprincipleliesatthemeasurementheartofthetechnologyandisillustratedinthisequation:
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Thespeedofsoundthroughairisaconstant:344meterspersecondwithinanambientairtemperatureof20°C.Therefore,ifittakes58.2millisecondsfortheechotobedetected,wehavethisresult:
ThemediumandthemessageForanultrasonicmeasuringsystemtohaveanyvalue,itmustprovideaconsistentoutputvalueforthesamephysicallevelconditionsoveralongperiodoftime.Thisrepeatabilitydependsmostlyonconditionsofthesoundmediaandthetargetmaterial.Thevelocityofsound(344m/sec)isdeterminedthroughthestandardmediumofairandattheidealtemperatureof20°C.However,oftentheconditionsunderwhichultrasonicmeasurementoccurarenotidealastherecanbenumerousfactorsinfluencingthemedium,therebyalteringthesoundtransmissionspeedandaffectingmeasurement:
temperaturemediumtype(gas)mediumstratificationvacuum
SoundintensitySoundintensitydescribeshowmuchenergythereisinawaveofsound.Theunitsofsoundintensityarewattspersquaremeter(W/m2).Whensoundintensitiesarecomparedtooneanother,itisusualtousethedecibelasaunitofmeasure.TheratiooftwosoundintensitiesI1,andI2isgivenbythisequation:
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Forsoundinair,theusualreferenceintensitychosenasthe0dBpointis0dB=10-12W/m2.Usingthatreferencepoint,120dBdescribesasoundintensitythatis120dBlargerthanthe0dBreferenceintensity,whichisanintensityof1W/m2.120dBisconsideredthethresholdofpainforthehumanear.Thedecibelscaleisusedbecauseofitsabilitytoeasilycomparesoundintensitieswhichmayvaryoveranenormousrangeofvalues.
SoundvelocityandtemperatureTemperaturechangesaffectthevelocityofsoundinair,andthevariationsintemperaturerequirecompensationtocalculateaccuratemeasurement.Ifthetemperatureoftheairbetweenthetransducerandthetargetisuniform,thencompensationisachievedandanaccuratemeasurementcanbemade.
Thetemperatureoftheapplication,orthemediumthroughwhichthesoundtravels,isrequiredtocalculatethevelocity.However,SiemensMilltronicstransducershavebuilt-intemperaturesensors,andatemperaturereadingistakeneachtimethetransducerisfiredtocompensatefortemperaturefluctuations.
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Thischarttrackstheincreaseinthevelocityofsoundasthetemperatureincreases.
SoundvelocityandgasThevelocityatwhichsoundpropagatesinagasisconstant,aslongastherearenochangesinthegas.Thefollowingformulacalculatesthevelocityforagas:
Example
At(20Celsiusor293Kelvin),thevelocityofsoundis:
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Notethatthespeedofsoundvarieswithabsolutetemperature.Inairatnormalambienttemperatures,whichisabout300K,achangeof1KorC(to301K)causesthespeedofsoundtoincrease:
SoundvelocityandpressureSoundvelocityinamediumexperiencingvariablepressuresiscalculatedusingthefollowingformula:
Thisformulasuggeststhatthespeedofsoundvarieswithpressureasitdoeswithtemperature.
Thevaporsaturationinairofvariouschemicalsmustalsobeaccountedfor.Thesaturationlevelisrelevanttothedifferentvaporpressuresofeachchemicalasillustratedinthenextchart.Notethatthecurvedlinesarefor100%saturationandthetruesoundvelocityisinbetweentheapplicablecurveandthatshownforair.
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SoundvelocityandvacuumIfatreefallsinavacuum,doesitmakeanynoise?No.Soundrequiressomethingtovibrate,andinavacuum,thereisnomediumtovibrate.Thusanapplicationthatoperatesinavacuumhastorelyonanalternatetechnologyforlevelmeasurement.
SiemensMilltronicshasacomprehensivelineofradarinstrumentsfornon-contactingmeasurement,andathoroughrangeofcapacitanceinstrumentsandguidedwaveradarforlevelandinterfacecontactmeasurement.Allthesetechnologiesoperateperfectlywellinavacuum.
SoundvelocityandattenuationAttenuationreferstoadecreaseofsignalstrengthasitmovesfromonepointtoanother.Forsoundsignals,ahighdegreeofattenuationgenerallyoccurswheretherearehighlevelsofdust,humidity,orsteam.Attenuationalsooccurswheretargetmaterialsarehighlyabsorbentto
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sound,foamforexample.Insuchapplications,impedanceandfrequencyselectionareessentialinordertotransferasmuchpoweraspossiblefromthetransducerintotheairandviceversa.
Wherethemediumbetweenthetransducerandthetargetisotherthanthenaturalcompositionofair,thevelocityofsoundcanalsochange.Ifthemediumishomogeneous,compensationcanbeachieved.If,however,themediumisstratifiedsothepropagationofsoundundergoeschangesinvelocityatvariouslevels,thenonlyanapproximationcanbemadebyusingtheaveragevelocityofthemediumtocalculatethedistancethatthesoundhastraveled.
SoundreflectionWhenasoundwavearrivesataninterfacebetweenmediaofdifferentdensity(e.g.airandwater),someofthesoundenergyisreflectedandsomeofitistransmittedthroughthesecondmedium.Theratioofenergyreflectedtoenergytransmittedisdependentupontheacousticimpedancesofeachmedia.Thegreatertheratioordifference,thegreatertheamountofenergythatwillbereflected.
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Theangleofthereflectedsoundwave(onasmoothsurface)isequaltotheangleoftheincidentsoundwave,buttotheoppositesideofthenormaltotheplaneofthesurface.Ideally,formeasuringlevel,thisangleiskepttoaminimum.
Asurfaceisconsideredsmoothiftheroughness,expressedasthepeaktovalleydifference,is1/8orlessoftheincidentwavelength.Anyabsorptionofthesonicenergyisignoredforthisexample.
SounddiffractionDiffractionoccurswhenthesoundwavebendsaroundanobjectsuchthatthereislittleornoreflection.Foragivensizeobject,diffractiondecreaseswithadecreaseinwavelength(increaseinfrequency).
Soundpressurelevel(SPL)Soundpressurelevel(SPL)isthepressureofsoundincomparisonwiththereferencepressurelevelwherePrefisthereferenceforsoundpressureinair(20.4mPaat1KHz).TheSPLcanbemeasuredbyamicrophone.
SoundintensitychangesWhensoundpropagateswithinagas,itspreadsoutsothattheenergyitcarriesisdiffusedoveranincreasingareaasthewavetravelsfurtherfromitssource.Excludinglossescausedbyotherfactorsdescribedlater,soundintensitydecreasesataratethatisinverselyproportionaltothesquareofthechangeindistance.
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Thatistosay,iftheintensityofsoundisXatapointlfromthesource,thentheintensitywillbeX/4atadistanceof2lfromthesource.
SummaryThesoundwavesareaffectedbymanyfactorswithintheapplicationenvironment,andtheapplicationengineermustalwaysverifythatalltheseconditionsareknownbeforesettinguptheapplication:
temperaturemediumabsorbency(dust,steam)mediumtypepressuremediumstratificationvacuumreflectivityofmaterial
SiemensMilltronicsultrasonicinstrumentationtacklesapplicationsthatinvolveoneormoreoftheseconditions.Ourexperiencedsalesapplicationengineerswilldesignaninstrumentconfigurationthatwillprovidereliableandaccuratemeasurement.
1VanMorrison,“JoyousSound.”APeriodofTransition,1977.2Felton,Bob.“LevelMeasurement:AncientChore,ModernTools.”ISA,August2001.3ModulevelisaregisteredtrademarkofMagnetrol.4®RaytheonisaregisteredtrademarkoftheRaytheoncompany.5®MilltronicsisaregisteredtrademarkofSiemensMilltronicsProcessInstruments.
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ChapterTwo
UltrasonicinstrumentationStop,children,what’sthatsound1
Measurementrepeatabilityisdependentonthesignalprocessorbeingused.Thespecifiedaccuracyvaluestakeintoaccountsuchfactorsaslossofresolution,supplyvoltagevariation,operatingtemperature,circuitlinearity,andloadresistance.Thesefactorsdependontheinstrumentationhardwareandsoftware,nottheapplicationconditions.
Ultrasoniclevelmeasurementinstrumentationrequirestwocomponents,onetogeneratethesoundandreceivetheecho(transducer),andonetointerpretthedata,deriveameasurement,andaffectareactionofthecontroller.Eventhoughsomeultrasonicinstrumentscombinethecomponentsinoneunit(SITRANSProbeLU,PointekULS200),theindividualfunctionalityremainsdistinct.Theoperationandtechnicalspecificationsregardinginstrumentperformancewillbediscussedindetailinsubsequentchapters.
ThetransducerAdvancesinthedesignofultrasonictransducershavesignificantlycontributedtothesuccessofultrasonicsasalevelmeasurementtechnology.Transducersarethevocalchordsandearsofanultrasoniclevelmeasurementsystem.Thesoundpulseiscreatedbythetransducerwhichconvertstheelectricaltransmitpulseintosonicenergy,effectivelyradiatingthatsonicenergyintotheairandtowardsatarget.
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Afterthetransmissionprocessiscomplete,thetransducerthenactsasthereceivingdeviceforthereturningechosignal.Thisinformationisthenprocessedandturnedintoameasurementvalue.
Theeffectiveacousticenergyisgeneratedfromthefaceofthetransducerandisradiatedoutward,decreasinginamplitudeatarateinverselyproportionaltothesquareofthedistanceastheunitenergyisdissipatedoveralargerarea.Maximumpowerisradiatedaxially(perpendicular)tothefaceinalinereferredtoasthe“axisoftransmission.”Whereoff-axispowerisreducedbyhalf(-3dB)withrespecttoanon-axispointequidistantfromthetransducer,aconicalboundaryisestablished.Thediametricalmeasurementoftheconeindegreesdefinesthehalf-powerbeamangle.Althoughthebeamangleforaroundfacetransducercanbederivedempirically,itcanbepredictedbythefollowingformula:
TransducerenvironmentsTransducerscarryafullrangeofhazardousapplicationapprovalsfromCSAandFMtoATEX(EuropeanUnionExplosiveAtmospheresprotection).Constructedfromthemostadvancedmaterialcompounds,transducersareavailableforsomeoftheharshestindustrialenvironments:
Forcorrosiveapplications,transducersarefabricatedwithmaterialssuchasPVDForPTFE,allowingultrasonicstobeusedwithacidsandsolvents.Industyapplications,acousticimpedancematchingmaterialssuchaspolyurethaneandpolyethylenefoamareusedbecausetheirelasticpropertiesamplifythecrystal’svibration.
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Forlong-rangesolidsapplications,long-rangetransducersdeliverhighpoweroutputtomeasuresolidmaterialsaccuratelytodistancesover200feet.Theflexuralmodetransducerdeliversmorepowerbydrivingalargecentraldiscwiththecentralpiezoelectriccrystal.Thelargemetaldiscismadetovibratealongwiththepiezoelectriccrystal,producingastandingwaveonitssurface.Holespunchedinconcentricringsalloweveryotherantinodetobedelayedtothepointthattheybecomeinphasewiththeothers.Theneteffectisanintensesoundpressurewavewhichistransmittedintotheair.Thistypeoftransducerisverywellsuitedfordustyenvironments.
TransduceraccuracyTheaccuracyofanyinstallationisdependentonthecaretakentoensuretheelectronicsagreewiththephysicalmeasurementandtheaccuracyofthiscalibration.Duetothedesignoftheelectronics,insitucalibrationiseasyandhighaccuracyisreadilyobtainable.Traceabilitytoknownstandardsisdependentonthemethodandequipmentusedasthereference.
TransducerresolutionandaccuracyTheminimumchangeorincrementofdistancethatcanbedetectedisreferredtoastheresolutionofthemeasurementsystem.Resolutionisdependentonthewavelengthandthetimingresolutionoftheelectronics.Theshorterthewavelength,thesmallertheincrementthatcanberesolvedgivenaspecificsignalprocessor.TheSITRANSLUT400,hasadesignresolutionoflessthanonemillimeter(0.078")andaonemillimeteraccuracyspecification.
Inscience,engineering,industryandstatistics,accuracyisdefinedashowclosethemeasurementsystemquantityistothemeasurementofthatquantity’sactualvalue.
Impedancematching
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Thevibrationofthetransducerfaceactsuponthesurroundingairtoproduceasoundwave.However,forefficienttransferofpowerfromthecrystaltotheair,impedancematchingmaterialsmustbeused.Matchingmaterialstepsdownthehighimpedanceofthecrystaltothelowimpedanceofair.OnSiemensMilltronicstransducers,aspeciallowdensitymaterialisusedasaninterface.
Theimpedancematchingcanbefurtherenhancedbyanadditionalfacingmaterial.However,thisisnotalwaysrequirednorpracticalfromanapplicationstandpoint.
Acousticimpedancematchingisimprovedbythesematerialsastheirelasticpropertiesamplifymagnitude(D)ofthecrystal’svibration.Asexpressedbythisformula:
Moreamplitudeisnowpossiblewithagivenforcebyincreasingthedistancethevibrationhastraveledthroughthetransducerface.
AxisoftransmissionSoundenergyisgeneratedfromthefaceofthetransducerandradiatesoutward.
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Theenergygeneratedatthefaceofthetransducerdecreasesinamplitudeatarateinverselyproportionaltothesquareofthedistancetraveled.Maximumpowerisradiatedaxially(perpendicular)tothefaceinalinereferredtoasthe“axisoftransmission.”
BeamwidthBeamwidthisdefinedas“twicetheangleatwhichoff-axistransmissionis3dBlessthanthetransmissionaxisacousticpressurelevels(asmeasuredequidistantfromthetransducerface).”Therefore,adiametricalpowermeasurementoftheconeindegreesdefinesthehalf-powerbeamangle.
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Beamwidthisafunctionofthetransducerradiatingsurfacearea,frequency,andplane.
Forultrasoniclevelmeasurement,widedispersionisundesirable.Thenarrowerthebeamwidth,thelesslikelyvesselobstructionswillbedetected.
Forshortandwidevessels,a12°beamwidthisidealtosimplifyaiming.Fortall,narrowvessels,a5°to6°beamwidthwillavoidvesselwallseamorcorrugationdetectionformaximumreliability.
BeamspreadingAswellasthemainbeam,sidelobesofamuchlowerintensitymayradiateintheformofaconicalshell,concentrictothemaincomponent.Themaincomponentandthesidelobesmaybedepictedonapolarplotinordertovisualizethepatternofsound.Itisdesirabletohaveasmuchenergyaspossibleconcentratedinthemainbeaminordertoreduceunwantedechoesgeneratedfromthesidelobes.Similarly,itisnecessarythatenergybepreventedfromradiatingfromtheendoppositethetransducerface.Aswellasgoodoutputpower,thetransducermustbesensitivetotheweakreturnechoesasnoamountofelectronicscan
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compensatefornon-detectionofanecho.Thus,propertransducerdesignisfundamentallyimportantinputtingthetheoryofultrasonicechorangingintopractice.
RingdownTheprimaryactivecomponentofthetransducerisapiezoelectriccrystalthatexhibitsanexpansionandcontractionofitslengthwhensubjectedtoalternatingvoltage.Whenthevoltageisremoved,thecrystalisnolongerexcitedanditsmechanicalvibrationbeginstodecay.Theinherentnatureofthecrystalandthesurroundingtransducermassistocontinuevibrating.Thisvibrationiscalled“ringing.”Thetimeittakesforthisringtostopisoftencalled“ringdown.”
Thelevelofringingdependsnotonlyonthecrystalitselfbutalsoonthematerialsandconstructionoftheentiretransducer.Moderntransducershavesignificantlylessringdownthanearlierversions.Duetoresearchintothelatestconstructionmaterialsandtechniques,theblankingdistanceofthenewestultrasonicinstrumentsliketheSITRANSProbeLUisnowonly0.25meters(10").
Thecontrollers
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Thetransducerscanbelikenedtothescoutsofalevelmeasurementsystem.Theygooutandgettheinformationandbringitback.Thecontrollersanalyzethatinformationandthenturnitintosomethinguseful.
Sinceitsinception,ultrasoniclevelmeasurementtechnologyhasimprovedgreatlywithadvancesinelectronicsignalprocessors.Digitalsystemstransmitinthesamemannerasanalogsystems,butdigitizetheanalogreceivedsignalofthereturnechoandstorethecompleteechoasaprofile.
Theprocessor,insidethecontroller,thenanalyzestheprofileusingsoftwarealgorithms,extractingoneechofromtheprofileasthemostprobabletobethetargetecho.Then,thesignalprocessorconvertsthetimedifferentialbetweenthetransmitandthetimeoftheselectedtargetechointodistance.
Digitalultrasonicmeasurementalsohastheabilitytousesoftwarefilteringtechniquesandintelligentechoextractionalgorithmstodeterminedistance.Themicroprocessorgivesthesignalprocessortheabilitytoperformhighspeedmanipulationofthedatagatheredfromanechoprofile.Usinganalog-to-digitalconversion,echoprofilesreceivedbythetransduceraredigitizedbythereceivingdeviceandstoredinmemoryforfutureevaluation.Storingtheechoprofileinmemorymakesitpossibletoperformthemanytestsonthedatanecessarytodeterminethetruematerialecho.
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DigitalfilteringDigitalfilteringremovesunwantednoisefromtheechoprofile,includingelectricalnoisealwayspresentinanindustrialenvironment.
Forexample,variablespeedmotordrivesproducehighlevelsofelectricalnoisethatareusuallyveryhighinamplitudeyetveryshortindurationwhencomparedtothedatabeinggatheredfortheechoprofile.Therefore,digitalfilteringisusedtoremoveanydatafromtheprofilebelowagivenlimitinduration,significantlyreducingtheeffectofthenoiseontheoverallmeasurementquality.
AveragingechoesInapplicationsthatcreatehighlevelsofdustoracousticnoise,highspeeddatamanipulationpermitstheaveragingofmanyechoprofilestodevelopacompositethatcanbemoreaccuratelyanalyzed.Averagingofechoprofilesperformsseveralusefultasks:randomsourcesofinterferencesuchasacousticnoiseoraircurrentsareaveragedoutoftheechodataandechoesareenhancedindustyandotherwisechallengingapplications.
EchoextractionalgorithmsEchoextractionalgorithmsaresoftware-basedfunctionsusedtoevaluateanechoprofile.Anechoprofilecanbeevaluatedinmanyways,witheachmethodhavingparticularadvantagesindifferentapplications.Beforemicroprocessors,analogsignalprocessorsevaluatedtheechoprofileasitreturnedandthenthereceiverlookedforanyechoaboveasetthreshold.Onceanechoofsufficientamplitudewasdetected,thedistancewascalculatedandtheoutputwasgenerated.Unfortunately,analogsignalprocessorswereunabletodifferentiatebetweenrealbuterroneousreturnsandthetrueechoindifficultapplications.
Digitalsignalprocessorsapplyechoextractionalgorithmsaftertheentireechoprofilehasbeenreceived,andthenusemanytechniquestodeterminewhichechorepresentsthetruemateriallevel.
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Onemethodofechoextractioninvolvesstoringaprofileoftheemptybin.Thisstoredprofileisthenusedasatemplate,allowingtheprocessortoignoreobstructionsinthebin.Forexample,inabinfabricatedwithbracingaroundtheinsidesurface,thereturnechoescanindicatebracingandnotlevel.Whentheechoprofilefortheemptybiniscaptured,theprofileshowsechoreturnsindicatingthebracings.Inordertodiscriminateagainsttheseerroneousechoes,thesignalprocessorcompareseachechoprofiletothetemplateprofileinitiallytakenandstoredinmemory.Thistemplateprofilecontainstheechoesproducedbythebracing.Thus,usingthiscomparison,theechoesfromthebracingareignoredandthetruematerialechoisselected.Anothermethodevaluatestheechoprofilebasedonthecharacteristicsoftheechoanditslocationintheechoprofile.Thismethodfirstselectsthemostlikelyechointheprofilebyusingathresholdsimilartothatusedbytheanalogsignalprocessor.Oncethemostlikelycandidateshavebeenselected,thealgorithimsbegintoevaluateeachechobasedonthetypeofmaterialbeingmeasured.Ifthematerialisliquid,thentheprogramevaluatestheechoonamplitudeanditslocationintheechoprofile.Forexample,whenmeasuringaliquidsurfacethecharacteristicechoisnarrowandhighinamplitude.Liquidisveryreflectivetoultrasonicfrequencies;therefore,thetrueliquidlevelwillusuallybethefirstechoreceived;andinaliquidapplication,thealgorithmwouldselectthefirstechoreceivedwiththehighestamplitude.Forsolidsmeasurement,theprocessorselectsthemostlikelyechoesinthesamemanner,onlyusingdifferedselectioncriteriabasedonthedifferingcharacteristicsofthatsolidmaterial.Inthiscase,theprogramlooksforanechowhichisoflesseramplitudeandwiderthanthatofaliquidecho.Theechoiswiderbecausemostsolidmaterialshaveanangleofreposewhichreflectsmanydifferentechoesfromdifferingpointsontheangleofrepose.Thealgorithmmustnowlookfortheselectedechowhichisthehighestinamplitudeandthewidest.Therefore,theprocessorwillselecttheechowiththegreatestarea.
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SummaryDigitalsignalprocessingandadvancedechoextractionalgorithmsmakeultrasonicsareliableandaccuratemethodofmeasuringsolidsandliquids.Ultrasonicinstrumentationisthusavaluableadditiontomanyoperations,providinglongtermandcost-effectivemeasurement.Thisbookprovidesathoroughlookatultrasonicleveltechnology,attheinstrumentation,andatthewidevarietyofapplicationsbestsuitedforitsuseasthisproventechnologycontinuestobeapreferredsolutiontomanymeasurementneeds.
1BuffaloSpringfield,“ForWhatIt’sWorth.”BuffaloSpringfield,1967.
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ChapterThree
ThesoundandtheslurrySomebody'sshoutingUpatamountain
Onlymyownwordsreturn1
Thetransduceristhespeakerandmicrophoneintheultrasoniclevelsystem,producingtheultrasonicwavesandthensensingtheechoesastheyreturnsothecontrollercanrespondasprogrammed.SiemensMilltronicstransducershaveaprovenandextensiveapplicationhistory,andarethereliableeyesandearsofthousandsofapplicationsaroundtheworld.
Thischapterexaminestheroleofthetransducerinanultrasonicsensingsystem,howitismade,andhowitworks.
Topicsultrasonicsystemstransducersblankingdifferentialamplifiersechoprocessingreducingnoisebeamangleprofiles
TransducersandultrasonicsystemsTheultrasonicsensingsystemisavailableintwoformats:
singlesystems:thetransducerandthecontrollerelectronicsareintegratedintooneenclosure
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compoundsystems:thetransducerandthecontrollerareseparateentities
SinglesystemsAsingleunitsystemisoftenreferredtoasa“leveltransmitter.”TheSiemensSITRANSProbeLUleveltransmittercombinestheelectronicsandtransducerinacompactsystemideallysuitedforliquidlevelmeasurementupto12meters(40ft).
ThetransducerportionoftheSITRANSProbeLUisinthelowerhalfofthedevice;thecontroller,electronicsandwiringareaareintheupperhalf.Leveltransmittersareversatileandaresuitableformanyapplications,includingbothgeneralpurposeuseinsafeareasanduseinhazardousareas,dependingonapprovals.
CompoundsystemsCompoundsystemsseparatetheultrasonictransducerfromthecontroller.Thetransducerismountedonthevesselwhilethecontrollerisinasafeareaawayfromtheapplicationinacontrolroomorafieldmountedelectricalpanel.Siemensoffersawidevarietyofcontrollersandtransducers,liketheSITRANSLUT400andEchomaxXRS-5,thatcanbematchedtosuitmanyapplications.
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Transducerscarrymanysafetyapprovalsformountingandforuseinhazardousareas,andtheyaredesignedtowithstandruggedindustrialenvironments.Thetransducerisconnectedtothecontrollerbycable(eitherco-axialortwistedpair),receivestheelectricaltransmitpulse,andthensendsthereturnechopulsealongthesamewire.Thetransducerandcontrollercanbeseparateduptoadistanceof365meters(1200ft).
TransducersAtransducerissimplyadevicethatconvertsoneformofenergyintoanother.Thus,devicessuchasthespeakersconnectedtoanentertainmentsystemaretransducersbecausetheyconvertelectricalsignalsgeneratedbytheamplifierintothemusicyouhear.Amicrophoneisthereverseofaspeaker:atransducerconvertingsoundintoelectricalsignals.
Thetimerequiredtochangefromtransmittoreceivemodeisfinite.See“Blanking."
Theultrasonictransducerperformsbothfunctions.Likeaspeaker,itconvertsthehighfrequencyelectricalpulsefromthecontrollerintohighfrequencysound,andthenprojectsthesoundintothevessel.Andlikeamicrophone,itconvertsthesoundechobackintoanelectricalpulse,transmittingthissignalbacktothecontrollerforprocessing.Thetransducerdoesnottransmitandreceivesimultaneously,butconstantlychangesfromtransmitmodetoreceivemodemanytimespersecond.
Theheartoftheultrasonictransducerisapiezoelectricceramiccrystalthatvibrateswhenahighvoltagepulseisapplied,sendingoutsoundwaves.Conversely,whenthesoundwavesreturn,thevibrationscausethepiezoelectriccrystaltoproduceanelectricalsignalwhichisthensentbacktothecontrollerforinterpretation.Thedifferencebetweenthe
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transmittedsignalandreceivedsignal,issignificant,andtheoutgoingtransmitcanbeseveralhundredvolts,whilethereceivedsignalisinthemicrovolttomillivoltrange.
Becausethereturnsignalissoslight,itcanbeaffectedbyanynumberofsituationalinfluences:mediumtemperatures,attenuation,andobstructions.Toachievemaximumperformancebenefitfromtheultrasonicsystem,alltheapplicationconditionsneedtobeconsideredwhendesigninganultrasoniclevelsystem.
TemperatureandtransducermaterialThetemperatureoftheapplicationcanaffecttheperformanceofthetransducer,asdoesitsconstancy,becausefluctuationsalsoaffectthereadingreliability.Transducerscompensatefortheseconditionsbyincorporatingtemperaturesensorsandbyusingtemperatureresistantmaterialsintheirconstructionsothatthereadingsareunaffectedbytheseconditions.Thetemperaturevariationeffectisgenerally0.17%foreverydegreecentigrade;soforeverydegreetheapplicationtemperaturefluctuates,thelevelmeasurementisaffectedby0.17%.
TemperaturesensorsWhentransducerswerefirstdeveloped,temperaturevariationsweremediatedbytheuseofanexternalsensorwhichtransmitteddatatothecontroller,whichthencompensatedforfluctuationsbyadjustingthereadingaccordingly.Theneedfortheexternalsensorwaseliminatedwhenanambientairtemperaturesensorwasincorporatedintothebodyofthetransducer.Makingthesensorpartofthetransducercircuitryalso
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allowsthesensortousethesamewiresettotransmittemperaturedatatothecontroller.Siemensaddedtothisconveniencebyplacingthetemperaturesensorinapocketjustbehindthetransducerfaceandbyimprovingthecircuitry,enhancingsensorfunctionbyacceleratingthetemperatureprocessing.
Built-intemperaturecompensationimprovestheaccuracyofthesystemandreducesinstallationcost.
SoundanddifferentialamplifiersWhilenoisecanaffectthesystemfromoutside,itmayalsooccurwithinthesystemitself.Thisinfluenceisaconsequenceofthesystem'selectricalfunctionalityandthecablingrequirementsthatcreateoramplifynoise.Siemenshasdevelopedadifferentialreceiverinterfacethateliminatesorgreatlyreducesinducednoiseonboththepositiveandnegativewiresofatwistedpaircable.2
Transmissionandreceiptofbothelectricalandultrasonicsignals
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Figure1:Theelectricalpulsesreceivedbythetransceivertendtobesmallerthantheinitialpulsesoutputbythedevice.
Therefore,accuratedistancemeasurementrequiresamplificationoftheelectricalsignals.
Forthedevicetocalculateadistanceaccurately,itmustamplifythereturningelectricalpulsesandanalyzethereturneddatausingechoprocessingalgorithms.Unfortunately,theamplificationprocedureusedonthereturningsignalsissensitivetotheeffectsofnoiseandthisiswherethedifferentialreceiverinterfacehasanumberofadvantagesoverthecommonsingle-endedreceiverinterface.
Single-endedreceiverTheamplifierwithinthecontrollerisresponsibleformagnifyingthereturningelectricalpulsesexistingbetweentheamplifier’spositiveandnegativeinputs.Forthecommonsingle-endedreceiverinterface(seeFigure2),thepositiveinputoftheamplifierisconnectedtothepositiveterminalofthetransducer,andthenegativeinputisconnectedtoground.Whenthedevicereceivessignalsfromthetransducer,itamplifiesthesignalexistingatthepositiveterminalwithrespecttoground.Fornow,ifthegroundisassumedtobeideal,theoutputoftheamplifierwillsimplybeamagnifiedversionofthesignalreturningalongthepositiveterminal.
Commonsingle-endedreceiverconnection
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Figure2:Inacommonsingle-endedreceiverconnection,thepositiveinputoftheamplifierisconnectedtothepositiveterminalofthetransducerandthenegativeinputisconnectedtoground.
Intheeventwherethesignalalongthepositiveterminaliscontaminatedbynoise(i.e.environmentalnoiseproducedbymotors,near-byantennae,wirelessdevices,etc.),sincethegroundisassumedtobeideal,theamplifierwouldmagnifythisnoise(seeFigure3).Thisnoisecouldleadtoinaccuratedistancecalculationsbythedevice.
Theeffectsofnoiseonacommonsingle-endedconnection
Figure3:Theeffectofnoiseonacommonsingle-endedconnectionismagnifiedandmayleadtoinaccuratedistancecalculationsbythetransceiver.
DifferentialreceiverInthedifferentialreceiverconnection,thevoltageexistsbetweenthepositiveandnegativewiresofthecable.Thepositiveinputoftheamplifierconnectstothepositiveterminalofthetransducerandthenegativeinputconnectstothenegativeterminal.
Differentialreceiverconnection
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Figure4:Inadifferentialreceiverconnection,thepositivewireisconnectedtothepositiveterminalofthetransducersandthenegativeinputisconnectedtothenegativeterminal.
Wherethepositiveandnegativewiresareinverycloseproximitytoeachother(common),anyenvironmentalnoiseoccurringononewirewillalsoexistontheother.Sinceadifferentialamplifiermagnifiesthedifferencebetweenthetwowires,anynoisecommontobothwires(hencetheterm“common-mode”noise)willnotappearattheoutputoftheamplifier(seeFigure5).
Theeffectsofnoiseonadifferentialconnection
Figure5Becauseadifferentialamplifiermagnifiesthedifferencebetweenthetwowires,anynoisecommontobothwireswillnotappearattheoutputoftheamplifier.
WhenaconnectionbetweenadevicewithadifferentialreceiverinterfaceliketheSITRANSLUT400andatransduceristobemade,ashieldedtwisted-paircableshouldbeused.Inthiscase,thepositivewireconnectstothepositiveterminalofthetransducer,thenegativewireconnectstothenegativeterminal,andtheshieldconnectstoground.Notethatneitherthepositivenorthenegativeterminalsarelinkedtoground.Sincethepositiveandnegativewiresaretwistedtogether,thereisahighlikelihoodthattheenvironmentalnoiseexistingonbothwireswillbe
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essentiallythesame.Therefore,environmentalnoisewillbepresentintheformofcommon-modenoise,whichtheamplifierwillbeabletoeffectivelyremove.Alsovoltagesinducedontheshieldduetogroundloopswillhavenoeffect,sincethesignalexistsacrossthepositiveandnegativewires.
Differentialinterfacecombinedwiththephysicaltwistingofthewiresinthetwistedshielded-paircableenhancesthecommon-modenoiserejectionability,helpingtonegatenoiseinterference.
Applicationtemperature3
Ultrasonicinstrumentshaveahightemperaturetolerance.Formostapplications,hightemperatureisnotanissue,butinhotprocessapplicationswherethematerialcomesfromakilnordryer,thetransducerrequiresahightemperaturetolerance.Tomeetthesedemands,designadvanceshaveextendedthemaximumtemperaturerangeofmanytransducersto150°C(300°F).
Ultrasonictransducersremainextremelystableovertheiroperatingrangebecauseoftheiron-boardsensorsandtwo-wiredatatransmission,evenduringextremetemperaturefluctuationscommontomanyoperations.
HousingmaterialChemicalcompatibilityisanimportantapplicationconsideration;thetransducerhastobecompatiblewiththematerialbeingmeasured.Transducersareavailableinavarietyofmaterials,includingPTFE,ETFE,PVDF,CPVC,andCFM,andcanbematchedwithavarietyofapplicationmaterialconditions.
Attenuationisthedecreaseinthesoundsignalasitpassesthroughvariousmediaandtheinitialpower/vibrationofthesoundisabsorbedbyotherinfluences.
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Theusershouldalwaysverifymaterialsuitabilitybycontactingthetransducermanufacturerorbyusingachemicalcompatibilitychartprovidedbythetransducermaterialmanufacturer.ChemicalcompatibilitychartsarealsoreadilyavailableontheInternet.
RangeandpowerThemaximumrangeofatransducerisnormallyproportionaltotheamountofpoweravailableandthefrequencyoftransmission.Thehighertheinitialtransmitpower,thebetterthechanceofgettinganecho.Thethickerthemediumthroughwhichthesoundtravels,themoreforceisrequiredtopushthesoundthroughit.Lowerfrequenciesarelessattenuatedwhentheypassthroughair,whichiswhyfoghornsaresolow-pitched.
Rangesquotedinthespecificationsheetsandinstructionbooksshouldbetakenasamaximum.Donotexceed!
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Thematerialspresentinthemediumabsorb(attenuate)thesoundandaffectperformance.Thisgraph4showstheattenuationindecibelsofvarioussoundfrequencieswhenthetemperatureandhumiditylevelsareconstant:
Soat41kHz,theroundtripattenuationisapproximately55dBatarangeof15meters(50ft).Anechoof30dBatthemaximumratedrangeofatransducerisstrongenoughtoprocessandexceedthenoiselevelsinherentinmanyapplications;however,insomeinstances,echoesasweakas5dBcanbeprocessedwithhighconfidence.Knowingthis,thecontrollermustsendoutapulsetothetransducerthatisstrongenoughsothatintheafter-round-tripattenuationof55dBat41KHzata15meterrange,thereissufficientreturnechostrengthtoprocessthesignal.
Long-rangetransducersaredesignedtooperateatlowerfrequenciestotakeadvantageoflowerattenuationratesthatprovideastrongerechotothetransceiverforprocessing.Inexchangefortheextrapower,however,someresolutionislost.Butinlong-rangeapplicationsofgrains,powders,orpellets,thisgenerallydoesnotpresentaproblemasaccuracyrequirementsmaynotbeasstringent.
ConditionsConditionsaffectperformancebecausethesoundwavesneedtogothroughthemediumandareinfluencedbyotheroccupantsofthatspace.Dust,steam,andhighhumidityattenuatesoundandtherequireddistanceformeasurementmaynotbemet.Withoutanecho,thereisnothingfortheelectronicstoworkwith.Conversely,withaverysmallstainlesstank,itmaybebettertogotoalowerpowertransducerbecausemultipleechoesmayrequirechangingthealgorithm,aninconveniencetothecustomer.
Rule:iftheapplicationisonthelimitofthetransducer’srange,stepuptothenexttransducerforbetterreliability!
Dust
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Mostsolidapplicationsaredusty.Inareaswheredustisextremelyheavy,keepingthetransducercleaniscriticalbecausematerialbuildupreducesthetransducer’sabilitytotransmitandreceive.Siemenstransducersusematerialswithgoodreleasecharacteristicswhich,combinedwithpulsatingdisplacement,oftenpreventbuild-upfrombeginning.
StillingwellsIfanapplicationisveryagitated,dusty,orhasalotofsurfacefoam,theseconditionsmaybeneutralizedusingastillingwell.Thestillingwellisasecondarypipeaccessingthetankcontentsandreflectingthesamecontentlevel.
Inaverysmallstainlesstank,gotoalowerpowertransducerbecausemultipleechoesmayrequirechangingthealgorithm.
Withstillingwells,lowerpowermaybebettersincethereisnospreadinglossbecausethesonicenergyiscontainedwithinthepipe.Inlaboratoryconditionsequivalenttoanemptywarehouse,oroutsideonacalmday,echoeshavebeenobtainedatmuchgreaterdistancesthanthenominalratingofthetransducers.However,inreal-worldapplications,usetheguidelinesdetailedabove.
Foamfacing
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Impedancematchingfoamfacingcanimproveatransducer’spowerandrange.Impedancematchingprovidesgreateracousticpoweroutputandisveryusefulindustysituationswheretheparticlesintheaircauseattenuation.
Animpedancematchingpolypropyleneclosed-cellfoamfaceisdesignedforEchomaxXPStransducers.Theclosedcellpolypropylenehasahightemperatureratingof95°C(203°F)andisnotbotheredbydustormoisturegettingintothefoam.
MoistureontransducerfaceThefaceoftheXPStransducersisactiveandwillultrasonicallyevaporatethedroplets.Ifthereisabitofaslopetothetransducer(mountadegreeortwooffvertical),theextravibrationwillcausethedropletstomovetotheedgeandfalloff.
TransducerselectionSelectingtherighttransduceraffectsperformance,andthecriteriashouldbebasedonrange(distance)andpower.Forexample,insomepowderandplasticpelletapplications,ashorterrangeEchomaxXPS-15(operatingat44KHz)ismoreappropriatethanalong-rangeEchomaxXPS-40(operatingat21KHz)becausethehigherfrequencyyieldsabetterreflectionfromthematerialsurface.Alltheapplicationconditionsneedtobeconsidered,notjustdistance.
BlankingdistanceandheightplacementThelocationofthetransduceralsoinfluencesperformance.Theheartofatransducerisapiezoelectriccrystal;whenatransducerissentatransmitpulse,thepiezoelectriccrystalexpandsandcontractslengthwisetoproducetheultrasonicsoundsignal.Whenthetransmitpulsestops,thecrystalisnolongerexcitedanditsmechanical
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vibrationbeginstodecay.Thisdecayhasafinitetimeperiodandisoftenreferredtoas“transducerringdown”duringwhichthetransducercannotreceiveanecho.
Properaiming,location,andmountingareotherimportantfactors.
Thetimeoftheringingisthenconvertedtodistance(D=VT)andrepresentsthespaceinfrontofthetransducerfacewheremeasurementisnotpossible.Thisspace,alsoknownasthe“blankingdistance”or“deadzone,”hasdecreaseddramaticallyovertheyearsastechnologyandresearchadvancedultrasonicmeasurementtechnology.Initially,theblankingdistancewasameterorevenmore,butithasbeenreducedto25centimeters(0.82ft)inthemostrecentsystems.
Otherfactorsliketemperatureandinstallationtechniquesalsoaffecttheblankingdistance:
Theringdownquantitydependsonthecrystalitselfaswellasthematerialsandconstructionoftheentiretransducer.
TemperatureHightemperaturetransducershavealongerblankingdistance.Whileringdowntakesthesameamountoftimeregardlessofthetransducer’stemperature,thespeedofsoundincreaseswithtemperature.ThereforewhenusingD=VT,agreatervelocityresultsinanincreaseddistance.Theblankingdistanceisstatedatthemaximumtransducertemperaturerating.
InstallationIfthetransducerisconnecteddirectlytoametalcouplerorifthemountingthreadsaretorquedtootightly,themountingarrangementactsaspartofthetransducerandwill“ring”witheachtransmitpulse.Toreduceringingonly,hand-tightenthetransducerintoablindflangeorontoaconduitadapter.Ifpossible,useaplasticconduitadapterratherthanametalone.
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Foraflangedtransducer,usethesuppliedplasticboltsanddonotover-tighten.Useagasketbetweenthevesselflangeandthetransducerflange.
Transducerdesign:theheartofthematterThephysicaldesignoftoday’stransducerhousesdecadesofresearchandenhancements,distinguishingSiemensfromtherestoftheplayers.ThesetransducerdevelopmentshavemadeSiemensthebestinthebusinessandtheworldleaderinthefield.
Measuringdistanceisnotassimpleastimingthesoundwhenitbouncesback.Italsorequiresintelligencebecausesoundisindiscriminate.Itbouncesfromanythingandeverything,andsincemostapplicationsarefilledwithobstructionsandotherclutterthatinterfereswiththepathofsound,itrequiressophisticatedequipmenttodistinguishthereallevelechofromtherestofthebouncebacks.
Siemensultrasonicinstrumentationhasthesophisticatedtechnologythatevaluatestheechoesanddetermineswhichonesaretrueandwhicharefalse.
SummaryThetheoreticalprincipleofsoniclevelmeasurementissimple.Atransducerlocatedatthetopofabinorwelltransmitsapulseofsoundenergy.Thesoundreflectsfromthematerialsurfaceandtravelsbacktothetransducerwhereitisconvertedintoanelectricalpulse.Thetimedelayfromtransmissiontoreceivedechoisconvertedintodistanceandthemateriallevelisdetermined.
Inpractice,soniclevelmeasurementisabitmorecomplicatedasthereisnotjustasingleechofromthematerial,butmanyechoesreflectingfrombinwalls,beams,pipes,andwiresinthesoundpath.Furthermore,theactualechoqualitiescanvarygreatlyforthefollowingreasons:
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soundattenuateswithdistance;thus,thedesiredechofromthematerialsurfacemaybeweakerthantheundesiredechoesthematerialsurfaceofsolidsisusuallyinclined,andthisspreadsandweakenstheechoelectricalnoisefrommotorsorcontrollerscaninterfereorbestrongerthantheecho
Distinguishingamongthemanyechoescanthusbeverydifficult,butitiscrucialforthesystemtobeeffectiveandtherealechoneedstobefound.Thehistoricalprogressionofthetechnologyisbasedonthissearchforthetrueecho.
1DeepPurple,"PicturesofHome."MachineHead,1972.2Thissectionwasfirstpublishedas,Ausder“Klemme”Füllstandmessung-intelligenteSchaltungstechnikvergrößertRauschabstand.GordonLi.MSRMagazin(Messen,Steuern,RegelnundAutomatisieren).Issue1-2(January/February2005)pages:16-17.3DougDuncan.“Ultrasonicsensors:Nowanevenbetterchoiceforsolidmaterialdetection,”InstrumentationandControlSystems.November1998.4From“TheTheoryofUltrasonicsandEchoRanging.”
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ChapterFour
EchoprocessingMakinggooddecisionsisacrucialskillatanylevel.1
Ultrasonicstechnologyhasbeenusedforindustrialbinlevelmeasurementsincethe1940s.Sincethen,thetoolshaveevolvedtoovercometheacousticproblemsfacedinrealworldapplications.Complexcircuitrywithtimevaryinggain,automaticgaincontrol,rangetrackinggates,nearandfarblanking,noisesuppressionfilters,phaselockedloops,andotheradvanceshaveexpandedthecapabilitiesofsoniclevelmeasurement.Thesedevelopmentsallhaveonethingincommon:real-timeanalogprocessingofthesignalasitwasreceived.
Whileanalogprocessinggreatlyadvancedultrasonictechnologyaslevelmeasurementinstrumentation,italsohadtwomaindisadvantages:
First,askilledtechnicianwithascrewdriverandanoscilloscopewouldcarefullyadjusttheinstalledelectronicsforeachapplication,andthishadtobedonewhilethebinlevelwascycledupanddownseveraltimes.Thisisacostlyandtime-consumingprocess.Second,sincethesignalisprocessedasitisreceived,thereisnoopportunitytoanalyzeandcomparetheinformationstatisticallytoseeifitisevenpossibleorcorrect.Thusdataloggingwasnot
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possible.
Siemensrecognizedthatanalog-basedinstrumentswouldneverbesufficientandfocuseditseffortsonmovingawayfromreal-timeprocessing.Engineerssoonrealizedthatplacingtheentirestreamofechoesintoastoredechoprofileinacomputer’smemorygavetheunittheopportunitytoexamineitsshots.Thecomputerthenprocessesandanalyzesthestoredechoprofiletoselectthetrueechoinamorereliablefashion.ThefirstproducttousethisrevolutionarytechniquewastheMilltronicsAiRangerIV,introducedin1984,andthissystemhasbeenineveryinstrumentsincethen,includingSITRANSLUT400andSITRANSProbeLU.Asaresult,echo-processingadjustmentsarenotgenerallyrequiredinmostapplications.
ThischapterpresentsSonicIntelligencefunctionalityandhowitrefinestheanalyticprocessdeterminingtrueechoandlevel.
TopicsEchoprocessingShotsandprofilesFiltersTimevaryingthreshold(TVT)EchoselectionFigureofmeritEchoprofilesEchoprocessingparametersNoise
Echoprocessing-intelligenceThepatentedecho-processingtechnologyembeddedinultrasoniclevelmeasurementproductsfromSiemensisknownasSonicIntelligence™2.SonicIntelligencedifferentiatesbetweentrueechoesfromthematerialbeingmeasuredandfalseechoesgeneratedbyobstructionsorelectricalnoise.Theresultisrepeatable,fast,andreliablemeasurement.
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SonicIntelligenceisfield-proveninover1,000,000applicationsworldwide.
Thistechnologicaladvancementwasdevelopedinconsultationwithfieldserviceengineersandsupportedbyfielddatagainedfromdecadesofexperiencewithapplicationsinmanyindustriesandcontinuestoevolvetoday.Usinghigherordermathematicaltechniquesandalgorithmstoprovideintelligentprocessingofechoprofiles,this“knowledge-based”techniqueproducessuperiorperformanceandreliability.
SITRANSLUT400usesnextgenerationSonicIntelligenceforechoprocessing,providingadaptivedigitalfilteringofthetransducersignal.Forexample,whennoiselevelsarehigh,filtersareadjustedtomaximizethesignaltonoiseratio.ThisadvancedSonicIntelligencenotonlyallowsforbetterfiltering,butprovidesimprovedtrackingofechoes,andmoresophisticatedechopositioningalgorithms.
UnderstandingechoprocessingEchoprocessingisasimpleconceptandacomplexrealityastheinstrumentlooksateachgroupingofechoes(ashot)andprocessesthereturntodeterminethetrueecho.
Theshortshotusesanarrowtransmitpulsewhichreducestransducerringingtoprovideimprovedreliabilityforthedetectionofneartargets.Thelongshotusesawidetransmitpulsetoprovideastrongerreturnechotodetectmoredistanttargets.Bothshortandlongshotsareprocessed,andthenthebestisselectedwithabiasinfavoroftheshortshot.Onceanechoisselected,variousfiltersareappliedtostabilizethereading.
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EventhoughSonicIntelligencewillselectthecorrectechoaftereverymeasurement,thereadingitselfmayfluctuateasaresultofchangingconditionswithinthebin.Averagingthereadingsreducesthefluctuationsbutcausesalaginresponsewhenthemateriallevelchanges.SonicIntelligenceusespowerfulstatisticaltechniques,togivestablereadingswhilestillallowingrapidresponsetoactualchangesinthemateriallevel.
ShotsandprofilesSolet’slookathowthesoftwarereadstheshotsandwhatitseesasthefollowingareimplemented:
filtersTimeVaryingThreshold(TVT)application
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echoanalysis
TheechoprofileThecompleteprofileincludingtransmitandringdownisdisplayedandtheamountofblankingindexedinthesoftwareisshownonthebottomtrace.Theecholockwindow(orwindow)locksontotheselectedechoinordertoignorespuriousechoesfromagitatorbladesorrandomelectricalinterference.ATimeVaryingThreshold(TVT)curveprovidesareferenceforcomparingechoes.
SITRANSLUT400usesnextgenerationSonicIntelligenceforechoprocessing,providingadaptivedigitalfilteringofthetransducersignal.Forexample,ifnoiselevelsarehigh,filtersareadjustedtomaximizethesignaltonoiseratio.ThisadvancedSonicIntelligencenotonlyallowsforbetterfiltering,butprovidesimprovedtrackingofechoesandmoresophisticatedechopositioningalgorithms.
WhattheLUT400sees(or,moreaccurately,“hears”)fromatransmitpulseinanapplicationisstoredinadigitalformatandisreferredtoasan“echoprofile.”Thisprofileisadigitalrepresentationofthereturnedechoenergyversustime.
Findingthetrueecho
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Astheechoesbouncebackfromthesurface,SonicIntelligencesoftwareparsestheinformationinitsgoaltofindthetrueecho.Theprocesscomprisesthreeactivecomponentsworkingtogetherintheselectionprocess:
1. Filters: enhancing the echoes and using Time Varying Threshold(TVT)toselect.
2. Trueecho:selection.
3. Selectedecho:verification.
One:FiltersFiltersarealgorithmprocessesinthesoftwarethattuneoutoutsideinterferencesandenhancetheechoesreturnedfromtheapplication.
ClippingfilterRemovesthehighspikesinthetimedomain,resultinginlessringinginthefilterandreducingtheimpactofhighnoiseontheprobabilityofpickingtherightecho.
DigitalbandpassfilterThismethodpermitsthedesignoftheoptimummatchedfilter,creatingthehighestprobabilityofselectingtherightechoovernoise.Eachtransducerhasabandpassfilterbasedonitstransmissionfrequency.
KalmanfilterThisalgorithmsmoothesandappliesdampingtoreadings,removingjitterandinstability.
TemperaturefilterAKalmanfilteralgorithmthatremovesjitterofthereportedtemperaturevaluecontributestoaccuratecalculationofthesoundvelocity.
SpikefilterElectricalnoiseproducesfalseechoeswhicharenarrowandhighcomparedtowiderechoesfromthematerialbeingmeasured.ThespikefilterinSonicIntelligenceusesthisdifferencetoidentifyandremove
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electricalnoise.
Thespikefiltermeasuresthewidthofeachspikeandcutsoffanyspiketoonarrowtobeanecho.Theecholockwindowisthefirstlineofdefenseagainstrandomelectricalnoise,butthespikefiltereffectivelycorrectsforelectricalinterferencefrommachinerysuchasvariablefrequencydrives(VFDs).Thespikefilterwillneverremoveavalidecho.
NarrowechofilterManybinshavetargetsinthepathofthesoundwavethatproducefalseechoesthatcouldinterferewiththemeasurement.Thesemaybepipes,cables,orevenseamsinthebinwall.Inanarrowbin,itmaybeimpossibletomovethetransducerfarenoughawaytoavoidthesetargets.Thesetargetsproduceechoeswhichmakeitdifficulttoselectthecorrectechofromthematerialsurfaceinareliablemanner.
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Insolids,theNarrowEchoFiltercanremoveundesiredechoesfromhardtargetssuchaspipes,beams,windows,orseams.That’sbecausetheseechoesarenarrowerthanthetrueechofromaninclinedsolidmaterialsurface.Inuse,thefilterisincreasedbysmallamountsuntiltheundesiredechoesareeliminated.Itisadvisabletomonitoroperationoveracompletefillandemptycycletoavoidsettingtoohighafiltervaluethatcouldwipeoutthetrueechoaswell.Thistechniquedoesnotapplytoliquidmeasurementwherethetrueechoisasnarrowastheundesiredecho.
ReformechoIndeepbins,thesoundwavefacesmanyobstaclesinitsjourneyfromtransducertomaterialsurfaceandbackagain.Theseobstaclesincludereflectionfromthebinwall,dust,aircurrents,changesinairdensity,andirregularitiesatthematerialsurface.Alltheseobstructionscombinetocreateafragmentedorsplinteredecho.Reformechobuildsthefragmentedechobackintoasingle,strong,well-definedechopulse.
Byincreasingreforminsmallamounts,theoperatorcanjointhepeaksofafragmentedechotoproducealarge,smoothecho.Usethisfeaturewithcautionbecauseifthereformistoolarge,thepeaksofunrelatedechoeswillbejoinedtogether.
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EchoselectionalgorithmsAftertheechoprofilehasbeenenhanced,thefinaltaskisselectingthebestecho,ataskdeterminedbythebinconditions.
Two:Trueechoselection(selectionofechoreflectedbytheintendedtarget)ThisselectionoccurswhentheportionoftheechoprofileabovetheTimeVaryingThresholdmeetstheevaluationcriteriaofSonicIntelligence.Insignificantportionsoftheechoprofileoutsideofthemeasurementrange(e.g.FarRange)andbelowtheTVTcurveareautomaticallydisregarded.Theremainingportionsoftheechoprofileareevaluatedusingtheechoselectalgorithmandtheechoprofileportionprovidingthebestecho(confidence)isselected.
NOTE:Aconfidencevalueisastatictestofasinglesnapshotprofiletomaintainavalidreading;itrequiresthateachindividualprofilemaintainsitspeakabovethethreshold.Thewindowmaybelockedontheprofileforhoursorevendays,soiftheprofiledropsbelowtheTVTcurvejustonce,lossofechomayoccur.
TimeVaryingThreshold(TVT)Thetimevaryingthreshold(TVT)isusedasareferencetocompareechoesatdifferentpositionsintime.Afarechowillbeweakerbecausethesoundhastraveledagreaterdistance,butnearandfarechoesmust
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becomparedinordertoselectthetrueecho.
Foragivenconditionofdust,temperature,orhumidity,theattenuationofsoundisusuallyuniformthroughoutthebin;therefore,theidealTVTisalinewithaslopeequaltotheattenuationofsoundindB/m.Thisslopeiscalculatedfromthedecliningportionoftheechoprofile.
TVTshaper(manualadjustment)TheshaperdividestheTVTcurveintoequalsegments,eachofwhichcanbeadjustedupordown.AnundesiredechocanbeignoredbyliftingtheTVTcurveatthepositionoftheecho.IftheTVTcurveisraisedtoomuch,however,thetrueechowillnotbedetectedwhenitisinthisregion.ItisnotnecessaryfortheTVTtocleartheundesiredecho,justcuttingitinhalfisusuallyenoughtode-emphasizetheundesiredecho.
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TheadjustmentsrideupanddownwiththeTVTandmovehorizontallywhenthevelocitychanges.Allcalibrationpointsandrangesshouldbesetbeforeusingtheshaper.
Theshapercannotbeusedonechoesfromreflectionsofmaterialhang-upsbecausethefalseechopositionwillchangeifthematerialfallsoutofitshungupposition.
Autofalse-echosuppression(automaticTVTshaping)Thisfeatureautomaticallydetectsandsuppressesechoesfromvesselobstructions.PriortoactivatingtheAutoFalse-EchoSuppression,emptythetankasmuchaspossible.Ifthereisanagitator,itshouldbeoperating.DuringtheTVTLearnsession,thecontrollerfirespulsesandshapestheTVTaroundanyechofromanobstructionliketheagitator.ThisshapingiseasytoperformanddoesnotrequireaPC.
TheTVTwillthennotdroplowerthanthelearnedposition.
SITRANSLUT400hasadvancedtrackingabilityandcanfindtherealechoamongststationaryclutterechoes.Therefore,eveniftheechodropsbelowtheTVTcurve,itcanbeidentifiedwithnearcertaintyforapproximately30seconds.ThiscapabilityismeasuredbytheFigureofMerit(FoM)setting.
Therearefourselectionmethods:
measuretheareaofeachechomeasuretheheightofeachecho
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measurethefirstmovingechoselectthefirstsignificantecho
FortheMultiRanger,LargestorFirstarethepreferredalgorithms.FortheAiRanger,togetherit’sALF.
ThesemethodscanbereferredtoasArea,Largest,andFirstalgorithms(ALF).AnothermethodusesTrackerwheretheuserselects/deselectsthealgorithmstandardsettings.SonicIntelligenceusesallfouralgorithmsoneachmeasurement.Foreachalgorithm,ascoreorconfidenceiscalculatedforeachechothatcrossestheTVTcurve,thenthescoresareaddeduptogiveatotalscoreforeachecho.Theechowiththehighesttotalscoreisdeemedtobethetrueechofromthematerialsurface.Thenetechoconfidenceistheconfidenceofthechosenechominustheconfidenceoftheechowiththenexthighestconfidencelevel;i.e.netconfidenceofthefirstchoiceisfirstchoiceminussecondchoice.
Occasionally,onealgorithmwillgivealowscoretothetrueechoandabetterscoretoafalseecho,buttheotheralgorithmswillpullthetotalscoreofthetrueechoup,andpushthetotalscoreofthefalseechodown.ThefinalselectedechoiscorrectbecauseSonicIntelligenceincorporatesadiversifiedportfolioofapplicationexperience.Foragivenbincondition,asinglealgorithmwillgivehigherechoconfidencebut,asbinconditionschange,anotheralgorithmmayberequired.Generally,usingallfouralgorithmsprovidesformorereliableoperationovertime.However,trainedoperatorscanadjustthedeviceparametersandfine-tunethealgorithmstosuittheirapplication.
SiemensMilltronicsequipmentalsocontainsanechoprocessingalgorithmcall“bLF,”alsoknownas“BestofLargestatFirst.”ThisalgorithmrunstheLargestalgorithmandFirstalgorithmandselectstheechowiththehighestconfidencevalue.ItdoesnotsumthevaluesasintheALFalgorithm.bLFisthebestchoiceforshortrangeliquidapplications.
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AnotheralgorithmisTrueFirst(TF).ThisalgorithmselectsthefirstechothatcrossestheTVTcurve.Useinliquidsapplicationsfreeofobstructionswhenconfidenceoffirstechoishigh.
TheTR(TR)Trackeralgorithmselectstheechothatclosesttothetransducerandismoving.AnechothatisbelowtheTVTlineandmovingcanbedetectedbythisalgorithmandwhenitisnottrackinganecho,itbehavesthesameasbLF.
NOTE:OnlyuseTRalgorithminprocessapplicationswitheitherofthesetwoconditions:
continuouslevelchangesariskoffixedobstructionsthatcouldinterferewithtruelevelresultinginlowconfidence.
Three:SelectedechoverificationThisverificationisautomatic.Theposition(relationintimeaftertransmit)ofthenewechoiscomparedtothatofthepreviouslyacceptedecho.WhenthenewechoiswithintheEchoLockWindow,itisaccepted,updatingdisplays,outputs,andrelays.Ifthenewechoisoutsideofthewindow,itisnotaccepteduntilecholockrequirementsaresatisfied.
ThesethreeprocessesworkawayinthebackgroundastheSonicIntelligencesoftwaredeterminesthebestecho.However,theechoescanbefurthertunedshoulditbenecessary.
EchoqualityEchoqualityandconfidencecanbefurthertunedusingtheinformationprovidedbythedevicefromthefollowingfeatures.
Figureofmerit
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FigureofMerit(FOM)measuresthequalityofthereportedprocessvalue:highervaluesrepresentbetterquality.Evenwhenalowconfidencevalueexists,ahighFOMwillensurethetrueechohasbeenselected.Approximately20readingsareusedtosupporttheFOMvalue.
EXAMPLEFOMgreaterthan75%=goodqualityFOMlessthan50%=poorqualityContributionstotheFoM:
successofthetracking(howcloselycanthenextlevelversustheactualnextlevelbepredicted)levelofnoiseconfidenceofthelastechotimeintervalsincelastvalidechospeedatwhichtheprocessismovingqualityoftheechoshapeandhowithelpsthecalculationoftheechoposition
NOTE:IfFoMislow,reducethenoiseintheprocess,orchecktheinstallationtoincreasesignalquality.
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EchoparameterfinetuningSonicIntelligencesoftwareeliminatestheneedforecho-processingadjustmentsinallbutthemostdifficultapplications(lessthan1%).Iffinetuningisrequired,operatorscanusethemoreadvancedadjustmentparametersavailableinSiemenstransceivers.
Onlyoneortwoecho-tuningparametersshouldbeadjustedatatime,sothattheimpactofeachadjustmentcanbecarefullymonitoredforacompletefillandemptycycle.Adjustmentsmadetoreachaconfidencefigureatacertainbinlevelmaynotholdunderchangingbinlevels.Donotrelysolelyontheconfidencefigure,butlookattheechoprofileanddecideiftheechoiswelldefinedundervariousconditionsandwillprovidereliabletrackingoflevelsfromemptytofull.Thisisespeciallyimportantduringaimingandmounting.
EchoprofilesTheechoprofile,agraphicrepresentationofthereflectedechoreceivedbythetransducer,isanimportantdiagnostictool.Digitallygenerated,theprofileisstoredbythetransceiverandcanbeviewedusingseveraltypesofconfigurationsoftware,includingSIMATICPDM(ProcessDeviceManager),AMS,FDTs,DolphinPlus,andSuperSonex.
Theechostartsoutasananalogsignal:
Thissignalisdigitizedbythetransceiver’sA/Dconverterandchangedintoanechoprofile,whichisameasurementoftheechoenergyversustime.
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Toreadtheprofile,startattheleftside,whichrepresentsthetanktop,andmoveacross.Thefartherright,thefartherdownintothetanktheshotgoes,readingthedistance.Theupwardspikesindicateechoesandthestrengthindecibels.
ProfilecomponentsThereareseveralcomponentstoanechoprofile,eachrevealingasignificantaspectoftheecho.Theechoprofilecomponentsareshowninthefollowingdiagrams:
Echoprofile
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Theleadingedgeoftheechoprofileisthedecayofthetransmitpulse,alsoknownasthe“transducerringdown.”Thisistheportionoftheechoprofileshowingthegradualrecoveryofthecrystalafterashothasbeentaken.
TVTcurve(TimeVaryingThreshold)
TheTVTcurveisadigitallygeneratedthresholdlevelthatactsasavalidationpointforthereceivedechoes.Itisadynamicthresholdlevel;anypartoftheprofileabovethecurvewillbeincludedintheechovalidationprocess.
Echomarker
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Theechomarkerrepresentswhatthecontrollerhasprocessedasthecorrectecho(ormateriallevel)forthatparticularechoprofile.Itmayormaynotpresentthisasthelevelreading.TheEchoLockWindowcontrolsthelevelreadingoutput.Theheightofthemarkerrepresentstheechoconfidence;thelargertheheight,thebettertheconfidencethatthisistheechothatmostrepresentsthetruelevelforthisparticularprofile.
Echolockwindow
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TheEchoLockWindow(orsimplytheWindow)controlshowfarthelevelcanchangebetweenshots.Fromshottoshot,thelevelchangecannotexceedthewidthoftheecholockwindow.Iftheechomarkerfallswithinthewidthofthewindow,thecontrollerwilloutputthelevelasindicatedbytheechomarkerandre-centerthewindowontheecho.Iftheechomarkerfallsoutsidethewindow(e.g.marksanechofromabladeofanagitator),thenthecontrollerwillignorethemarkedechoandoutputalevelrepresentedbythewindow(whichalsorepresentsthelastvalidreading).
Thewidthofthewindowissetbythemeasurementresponse(ordamping)parameter.Iftheapplicationlevelchangesrapidly(aprocessvessel),programafastmeasurementresponseandthewindowwidthwillbequitewide.Iftheapplicationhasaslowmovinglevel(astoragevessel),thensetthemeasurementresponseparametertoslowandthewindowwidthwillbequitenarrow.
Ifthereisasuddenchangeinlevelandtheechomarker(thistimerepresentingthetruelevelandnotafalseechofromanagitatorblade)isoutsidethewidthofthewindow,thecontrollermaintainstheleveloutput
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atthelevelrepresentedbythewindow,thelastvalidreading.Italsobeginstowidenthewindowatthemeasurementresponserate.Iftheechomarkerpointsatthesameechooutsidethewindowforfiveshotsinarow,thecontrolleracceptsthatthisisnowtruelevelandchangestheleveloutput(thedisplay,mAoutput,ordigitaloutput)atthemeasurementresponserateinthedirectionofthetruelevel.Thewindowcontinuestowidenatthemeasurementresponserateandoncethetrueechoiswithinthewindowwidth,thewindowwillshrinkbacktoitsnormalsizeandre-centeritselfonthetrueecho.
Echoprocessingparameters
Thevaluesofsomeoftheadvancedechoprocessingparametersareplacedontheechoprofileasaconvenienceandcanbeusedasareferencewhensubsequentlyviewingtheprofiles.
Includedarethevaluesforthefollowing:
echoalgorithmspikefilter
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narrowechofilterechoreformTVTtypeconfidencethresholdshortshotrangeshortshotbiaswindowsillpercentagenearTVTdB
Echoconfidence
Echoconfidencerepresentsthecertainty,orconfidence,thatthechosenechoisthecorrectecho.ThevalueisgeneratedfromoneoftheechoprocessingalgorithmslikeALForbLF(seeSonicIntelligence).Confidenceisshownintwoareas:attheselectedechoandbesidetheechomarker.Thevaluesbesidetheechoshowtheconfidencevaluesgeneratedbyindividualalgorithms.IntheaboveprofileitshowsL:20and
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F:20–meaningthattheLargestalgorithmandtheFirstalgorithmeachgeneratedaconfidencevalueof20.Theconfidencevaluebesidetheechomarkerisshownas:
Thisindicatestheshortshotconfidenceis0,thenetlongshotconfidenceis20,andthebracketsaroundthe20indicatethatthelongshotwasusedtoprocessandoutputthelevelmeasurementreading.
Theecho
Thisgraphshowsanecho,withspikesthataresharporgradual(dependingonthematerial)risingintheechoprofile.Sharpechoesarisefromflatmaterialsurfaceslikeliquids,asintheaboveprofile.Gradual,widerechoescomefromsolidmaterial;clinker,coal,orgrains,aremoregradualintheirrise,andoftenlookliketheechobelowfromplasticpellets:
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EchostrengthThestrengthoftheselectedechoindBabove1microvoltRMSiscalculatedasechostrength.
Theechoprofilesareaninvaluableassetwhentroubleshooting,andatechniciancandeterminethefollowingfromtheprofilebasedontheechoes:
goodechostrengthandlowconfidencemeansmultipleechoestogetthelevelreadinglowechostrengthandlowconfidencecanmeantheechoisweak,theresultofpooraiming,orhighattenuationfromdust,steam,orC02.Thesurfacemayalsobefoamyorpoorlyreflectivefromextremeturbulence.
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NoiseNoiseinanultrasonicsystemcanalsobegeneratedbyelectricalinterferencereceivedfromthetransducercables.Thisinterfereswiththeechoreadingandentersthecontrollerfrommanysources:
mainpowermAoutputexternaltemperaturesensor(ifused)radiatedfromnearbyelectricaldevices
Theelectricalnoiseispickedupontheprofile.Thetwolinesatthebottomleftrepresentthenoiseparameter.ThetopoftheboldverticallineisthepeaknoiseindB;thesmallhorizontallineindicatestheaveragenoise.Inthisexample,thepeaknoiseis5dBandtheaveragenoiseis-3dB.
Thebestmethodforensuringthelowestnoisepossibleistousetherecommendedtransducercable.ThenewerSiemensMilltronicscontrollers(SITRANSLUT400,MultiRanger100/200,HydroRanger200)useshieldedtwistedpaircablewhileestablishedmodels(SITRANSLU)
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useRG62A/Ucoaxialcable.Theshieldsmustbeproperlyconnected,andusegroundedmetalconduittoshieldthecablefromelectricalnoiseandtophysicallyprotectthecablefromdamage.
Ingeneral,averagenoiselevelsabove30dBarecauseforconcernandnoiseshouldbereduced.
ThelevelsofnoisepresentatthereceiverinputcanbeviewedonthedeviceLocalUserInterfaceastheaveragenoiseandthepeaknoise.Ingeneral,themostusefulvalueistheaveragenoisebecausethepeaknoiseisaspikethatcanbefilteredout.Averagenoise,however,istheoverallbaselinenoise.Iftheechostrengthdoesnotexceedthebaselinenoise,therewillbeproblemsdiscerningtheechofromtheambientnoise.
AdaptiveprofileblendingWhennotinahighnoiseapplication,theLUT400processeseveryshotindividually.Ifnoiselevelsincreaseaboveathresholdof35dB,theSITRANSLUT400blendsmultipleprofilestogether,increasingthereliabilityofechoselectionandpositiondetection.Thisreplacesthepreviousprocessofaveraginganumberofshotsandrespondsmorequicklytofastchangingmateriallevels.
NoiseinterferenceWithnotransducerattached,thenoiseisunder5dB,whichiscalledthenoisefloor.Ifthevaluewithatransducerattachedisgreaterthan5dB,thensignalprocessingproblemscanoccurbecausethegreaterthenoise,thelessthedistancethatcanbemeasured.Anyaveragenoiselevelgreaterthan30dBisgenerallycauseforconcernunlessthedistanceismuchshorterthanthemaximumspecifiedforthetransduceranditpowersitswaythroughthenoise.
Determiningthenoisesource
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Noisecanbefromeitherelectricalinterferenceorfromanacousticobstructionthatintervenesanddistortstheintendedecho.Thus,thefirststepistodeterminethenoisesource.
Startbydisconnectingthetransducerfromthetransceiver.Ifthemeasurednoiseisabove5dB,gotoNon-transducernoisesourcesbelow.Fornoiselevelsbelow5dB,proceedwiththefollowing:
1. Connectonlytheshieldwireofthetransducertothecontroller.Ifthemeasured noise is below 5 dB, continuewith the next step. If thenoiseisabove5dB,gotoCommonwiringproblems.
2. Connect the white and black transducer wires to the controller.Recordtheaveragenoise.
3. Remove the positive wire of the transducer. Record the averagenoise.
4. Reconnect thepositivewireand remove thenegativewire.Recordtheaveragenoise.
UsetheNoiseModificationtabletodeterminetheappropriatenextstep.Thetermshigher,lower,andunchangedrefertothenoiserecordedintheprevioussteps.
Noisemodificationtable
noise -removed +removed Goto:
higher higher
unchanged
lower
Reducingelectricalnoise
Commonwiringproblems
Reducingacousticnoise
unchanged higher
unchanged
lower
Reducingelectricalnoise
ContactSiemens
Reducingacousticnoise
lower higher
unchanged
lower
Commonwiringproblems
Commonwiringproblems
Reducingacousticnoise
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Non-transducernoisesourcesRemoveallinputandoutputcablesfromthecontrollerindividuallywhilemonitoringthenoise.Ifremovingacablereducesthenoise,thatcablemaybepickingupnoisefromadjacentelectricalequipment.Althoughcontrollersaredesignedtoworknearheavyindustrialequipmentsuchasvariablespeeddrives,donotlocatethemnearhighvoltagewiresorswitchgear.
Becauseofhighcosts,filteringcablesarenotrecommendedunlessallotheroptionshavebeenexhausted.
Ensurethatlowvoltagecablesarenotbeingrunadjacenttohighvoltagecablesorneartoelectricalnoisegeneratorssuchasvariablespeeddrives.
Movingtheelectronicsafewmetersawayfromthesourceofnoisewillfixtheproblem.Shieldingtheelectronicsisanotheroption,albeitexpensiveanddifficulttoinstallproperly;theshieldingboxmustenclosethecontrollerelectronicscompletely,andallwiresmustbebroughttotheboxthroughgroundedmetalconduit.
CommonwiringproblemsTheinstallationwiringcanalsopresentnoiseproblems.
makesurethatthetransducershieldwireisconnectedattheelectronicsendonly.Donotgrounditatanyotherlocation.donotconnectthetransducershieldwiretothewhitewire.(AppliesonlytotheSITRANSLUT400,MultiRanger100/200,HydroRanger200,andSITRANSLUC500)theexposedtransducershieldwiremustbeasshortaspossible.connectionsbetweenthewiresuppliedwiththetransducer,andanycustomerinstalledextensionwireshouldbedoneingroundedmetaljunctionboxes.
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ForSITRANSLUT400,LUC500,MultiRanger100/200,andHydro-Ranger200,thetransducerextensionwiremustbeshieldedtwistedpair.ForSITRANSLUseries,AiRangerseries,HydroRangerPlus,andMiniRangerPlus,useRG-62A/Uco-axialcablefornoisereductionpurposes.Seetheinstallationsectionofthecontrollermanualforcorrectcablespecifications.
NOTE:OnSiemenstransducers,thewhitewireisnegativeandtheblackwireispositive.Iftheextensionwireiscoloreddifferently,makesurethatitiswiredconsistently.
Reducingelectricalnoiseensurethatthetransducercabledoesnotrunparalleltoothercablescarryinghighvoltageorcurrentmovethetransducercableawayfromnoisegeneratorssuchasvariablespeeddrivesputthetransducercableingroundedmetalconduitfilterthenoisesource
AcousticnoiseToconfirmthattheproblemisacoustical,placeseverallayersofcardboardoverthefaceofthetransducer.Ifthenoiseisreduced,thenoiseisdefinitelyacoustical.
Reducingacousticnoisemovethetransducerawayfromthenoisesourceuseastillingwellinstallarubberorfoambushingorgasketbetweenthetransducerandthemountingsurfacerelocateorinsulatethenoisesourcechangethefrequencyofthenoise.Thecontrollerisonlysensitivetonoisebetween25KHzand65KHz
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SummarySonicintelligencebeatsattheheartofSiemensultrasonictechnology.Derivedfromthecumulativeexperienceofoveramillionultrasonicapplications,thissophisticatedechoprocessingfocusesalasersharpeyeonthetruelevelintheapplication.
1Drucker,Peter.1909-2005.2™SonicIntelligenceisatrademarkofSiemensMilltronicsProcessInstruments.
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ChapterFive
InstallationThereisjoyinrepetition,
thereisjoyinrepetition,thereisjoyinrepetition.1
Ultrasoniclevelmeasurementinstrumentationoffersnon-contactingtechnologythatisvirtuallymaintenancefreeandcosteffectiveinmanyapplications,fromthewaterandwastewaterindustriestosolidsandliquidsmeasurementinavarietyofindustrialsettings.
Ultrasonicsystemsuseatransducertosendelectronicpulsestoacontrollerwhichinterpretsthemanddeterminesleveldistance.IntegratedsystemsliketheSITRANSProbeLUhousethetransducerandcontrollertogetherandcanalsofunctionastransmitterswithinanetwork,usingthelatestincommunicationhardwareandsoftwaretotransmitdatabacktoitssourceforimmediateprocessing.Theycanoperatepumpsandalarmsdirectlyorsenddatathroughcommunicationsystems.
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Othersystemsseparatethetransducerfromthecontroller,andonlythetransducerisactuallyattheapplication.Thecontrollercanbeasfaras365meters(1200ft)away.Theapplicationcanbeconfiguredandmanagedfromadistance;thusindangerousorawkwardsituations,nooneneedstoreturntothesiteaftertheinitialinstallation.
Ultrasonictransducersareveryeasytoinstallandmaintain,ensuringmanyyearsofreliableoperation.Thischapterdiscussesinstallationrequirementsandbestpracticestomaximizethebenefitsofanultrasonicapplication.
Topicstransducerselectionlocationandobstructionsvesselstanksandaccessnozzles,standpipes,stillpipescablingopenvessels,flumes,weirsliftstationspositioncontrolapprovals
InstallationconditionsarethesameforthetransducersensorsonlyorfortransmittersliketheSITRANSProbeLU.Thecontrollersaregenerallymountedawayfromtheapplicationswheretheycanbeconfiguredin
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comfortandsafety.
SelecttherighttransducerTheEchomaxXRS-5isapopulartransducerchoice.Withameasurementrangeof0.3meters(oneft)toeightmeters(26ft)onliquidsandslurries,itissuitableformostshorttomid-rangeapplicationsinthewaterandwastewaterindustries.
Forshort-rangesolidsapplications,theEchomaxXPS-10providesahighpoweroutputsuitablefordustyapplications.
Forapplicationsbeyondeightmeters(26ft)andupto15meters(50ft),EchomaxXPS-15transduceroffersthemostaccurateperformanceforsolids,liquids,andslurryapplications.
Applicationsbeyond15meters(50ft)requiretheXPS-30orXPS-40transducerswithlowerfrequenciesandmorepowerfuloutput.
Manyconditionscanaffecttheperformanceofyourultrasonicsystem,andtheyneedtobenotedwhenchoosingatransducer.Theapplicationenvironmentalsoinfluencestheperformance,andinthischapterwediscusstheactualinstallationcriteriaforthetransducersafteryouhavedecidedwhichtransducerisappropriateforyourapplicationandiscompatiblewiththecontroller.
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LocationTheactualphysicallocationofthetransducerisveryimportantforoptimalperformance,andthereareanumberoffactorsthatmustbeconsidereddependingontheapplicationtype.Thusthetransducermountingformeasuringopenchannelflowisdifferentfrommeasuring
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liquidsinavesselanddifferentagainfrommeasuringsolids.However,regardlessoftheapplicationtype,theonecommonconditiontoavoidinanyapplicationistheobstruction.
Keepobjectsoutoftheultrasonicconetoreducefalseechoes.
ObstructionsObstructionsarethemostimportantapplicationelementstobeawareofastheyblockthesoundsignalpath.Typicalvesselobstructionsincludeladders,pumps,braces,lights,agitators,walkways,andloadingchutes.Ifobstructionsareunavoidable,choosethelocationwheretherearetheleastnumberofobstructions.Thetransducermustbeableto“see”thematerialbeingmeasured,andabeam,pipe,orstructuralbracewillblocktheviewandaffectthereading.Obviously,theclearertheaccesstothematerial,thebettertheperformance.
Becausetheultrasonicpulseradiatesinaconeshapefromthefaceofthetransducer,keepingobjectsoutsideofthissignalconereducesthechanceoffalseechoesbeingrecorded.Thetransducerbeamanglespecifiesthedegreeofthecone(seeillustrationbelow)wheretheultrasonicpulse’spowerislowerbythreedB(decibels).
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ClosedvesselsInclosedvessels,locatethetransduceronastandpipeorstillpipe,oranyaccessportornozzlethatoffersanunobstructedviewofthesurfacetobemonitored.Thestandpipeorstillpipecannegatetheblankingrequirementsbydistancingthetransducerfromthematerial.
TanksThevarietyofvesselsmeasuredbyultrasonicsisextensive,fromsmallonemeterhigh(3.3ft)plasticcontainersofwoodglueresinstothreemeterhigh(10ft)stainlesssteeltanksfulloficecreambaseto60meter(200ft)concretegrainsilos.Ultrasonicmeasurementhasveryfewlimitationswhenitcomestovesselsizeorgeometry;itsimplyneedsaclearpathforthesoundtotraveltothematerialbeingmeasured.Theshapeofthetankmatterslittle.
Althoughtankorvesselsizescanvary,themajorityarevariationsononlyafewstandardshapes.Transducerlocationcanchangeslightlydependingupontheshapeofthevessel.
Theseshapesinclude:
FlatbottomtanksCommonapplicationsincludewastewaterwetwells.Locatethetransducerasclosetothecenteraspossibleandawayfromobstructionsinthebeampath.Ifmountinginthecenterisnotpossible,maintaina10:1ratiowhenmountingclosetothesideofthevessel.
NOTE:Foreverytenmetersverticalmeasurement,locatethetransduceronemeterfromthesidetopreventanyinterferingechoes.
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Conebottom/parabolicbottomtanksFortanksusedinliquidmaterialapplications,mountthetransducerinthecentersothatmeasurementtothebottomoftheconeispossible.Ifthisisnotpossible,programthecontrollersothatthebottomofthetankisthetopofthecone.
Ifthematerialisasolid(i.e.grain),thenatransducerwithanaimingdeviceshouldbeusedandthetransduceraimedtowardsthebottomoftheconetoensuremeasurementintothedrawpoint.
HorizontaltanksMountthetransducerasclosetothetopcenterofthevesselaspossibletomakeuseofalltheavailablespan.
NOTE:Echoprocessingsoftwarecanignorereflectionsfromsupportbeams,weldbeads,ladder,ormaterialbuildupalongthevesselsides.
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TankaccessTherearemanywaystoaccessasealedtankorvessel:
cutholeand/orEasyAimernozzlesstandpipesstillpipessidepipes
Cuthole/EasyAimer:sometanksorvesselshavenoentryroutes,butcanbeaccessedbycuttingaholeorusinganexistingtrapdoortomountthattransducer.TheSiemensMilltronicsEasyAimerassistsinaimingthetransducerthroughanaccessportintothevesselatananglerequiredtogettheaccuratereading.Attachthetransducertotheaimingkitusingthecouplingprovidedwiththekitandthenaimpastthetransducersothatthesoundpathisperpendiculartothematerialsurface.
NOTE:Besuretolocatetheaccessportsothatnoobstructionsareinthebeampath.
TheEasyAimeraimsthetransducertothelowleveldrawpoint.Thetransducercanberevolvedthrough360°andangledat0to27°offvertical.Itcanwithstand100kPa(onebaror15psigauge)pressurewithaggressiveenvironments.
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Nozzles:aprotrudingaccesspipelocatedonthesurfaceofthevessel.Ashortoutlet,orinlet,pipeprojectingfromtheendorsideofahollowvessel.
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Standpipe:anaccesspipethatprotrudesthroughavesselwallandispresentonboththeoutsideandtheinsideofthetank,andmaybeusedasamountingplatform.
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Beawareofthefollowingwhenusinganozzleorstandpipe.Whenmountingflangedtransducerstoclosedtopvessels:
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besurenobuildupformsinsidethestandpipe(maycreatefalsereadings)eliminateweldsandseamsastheyhavethesameeffectasbuildupheightshouldbelessthanthreemultiplesofthediameter(H<3D)minimumdiameteris76millimeters(3")ifheightislessthan150millimeters(6"),factoryblankingcanbeused.Ifheightisgreaterthan150millimeters,increaseblankingto150millimetersbeyondthebottomofstandpipe,orextendstandpipeintotankandcuttheendata45°angle.
StandpipeinstallationCuttheendofthestandpipeona45°angleandremoveanyburrsfromcutting.Thisanglewillhelpmatchtheimpedanceoftheairinsidethepipewiththerestoftheapplicationenvironment.A90°cutcouldcreate
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aninterferingechoattheendofthestandpipeandreducetheconfidencevalueoftherealecho.
Forstandpipeinstallations,useafactorybondedflangedtransducerorsplitflangekitthatwillreadilymatetotheflangedstandpipe.Anotheroptionistohangthetransducerfromablindflange.
Thestandpipeshouldbeasshort,andthediameteraslarge,aspossible.The-3dBconeofthesoundbeamshouldnotintersectthestandpipewallinapplicationsopeningintoavesselorlargerarea.Otherwise,additionalblankingwillberequiredtocompensatefortheinterferencezonecreatedbytheopening.
Stillpipes/StillingtubesAstillpipe(essentiallyanextendedstandpipe)maybeusedforturbulentliquidapplicationsasitextendsfurtherdownintothevessel,andisalsohelpfulinfoamyconditionsbyisolatingthesurface.
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Astillpipeissimplyasmoothwalledpipethatextendsfromthetopofthevesseltothebottom.Thelowerendofthepipeisopentoallowthecleanfreeflowingliquidtomoveupthepipe.Inanapplicationwherethevesselisemptiedcompletely,itmaybepossibleforthefoamtoenterthebottomofthestillpipe.Inthiscase,aJ-tubeisrecommended.TheJ-tubeisastillpipewithan180°elbowatthebottom.Whenthevesselisemptiedtherewillalwaysbeasmallamountofliquidintheelbow,anditwillnotallowanyofthefoamtopassintothestillpipe.
Thesameconsiderationsforastandpipeshouldbeappliedtostillpipe:
donotperforateordrillholesalongthelengthofthestillingwellweldsandcouplingscanaffectthereliabilityoflevelmeasurementavoidbuilduporotherdebrisontheinsideofthewellwallensurethereisaventholeatthetopofthestillingwell
SidepipesSidepipesaresimilartostillpipesbutareontheoutsideofthevesselandiscomparabletoasightglass.Thelevelisreflectedinthejoinedpipe.Sidepipeseliminatefalseechoesfromobstructionsandfillstreams,and
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areoftenusedinsumpsandwells.Thefollowingmustbenoted:
pipesshouldbeseamlesswithaminimum150millimeter(6")diameterpipeshouldbeventedatthetoppipemustbekeptcleanofbuildup
FlangesTransducerscanbemountedwithavarietyofflanges:
bondedflangesfornon-corrosiveapplicationsPTFE–facedflangesforcorrosiveapplicationssplitflangesforfieldretrofitformountingonaflangedstandpipe
Overtighteningthemountinghardwarecanleadtotransducerringing.
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Tightentheflangeboltsevenlytoensureagoodsealbetweenthematingflanges,butdonotovertighten.Thiscanadverselyaffectperformance.Handtighteningshouldbesufficient.
LiquidapplicationsForbestresultsinliquidlevelmeasurement,thetransducermustbeperpendiculartothematerialsurface.Whetheritisthroughastandpipe,nozzle,orpositionedinthevesselusinganexistingopeningoranewlycutone.
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Solidsapplications
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Notethefollowingwheninstallingthetransduceronatank:
Inmosttanks,thetransducershouldbecenteredasmuchaspossible(withoutinterferencefrominlet)foroptimumreadingrange.Whetherthetankisemptyorfull,itmustcontainitsnormalvaporconditions.Whetherthetankisemptyorfull,itshouldbeatitsnormaltemperature.Thetransducershouldbeperpendiculartotheangleofreposeofthematerial,whichusuallymeansmountingittoonesideandatanangle.
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Inconebottomtanks,aimthetransduceratthedrawpointatthecenterofthecone.Aimthetransducerawayfromseams,structuresandirregularitiesinthebinwall.Locatethetransducerawayfromthematerialinflow.Onfluid-likesolids,aimthetransducerperpendiculartothematerialsurface.Ondualdischargebins,aimthetransduceratthedrawordischargepointtoensureaccuratereadingsonemptying.UseEasyAimer.Keeptransducerawayfromfillpoints,asthematerialenteringthevesselcouldreflectthesoundpulseandgiveanincorrectlevelreading.Lookoutforratholingwherethedischargehascreatedadrainholethatcangiveincorrectlevelreadings.Bridging,wherethedischargedmaterialdoesnotshow,alsoleadstoincorrectlevelreadings.
ProtectionForsolidsapplicationswherethetransducercancomeincontactwithmaterial,suchasinarockboxorcrusher,protectthetransducerfromflyingrocksbysurroundingitwithawirecage.Securetheinstallationby
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connectingasafetychainfromthetransducertothemountingsurface.
UsepropercablingCableselectionisaveryimportanttoensureproperfunctioningofthetransducer.Allwiring,conduit,andjunctionboxesaretobeinstalledaccordingtoalllocallaws,rules,andregulationsand/orinsurancecompanyrequirements.Refertoproductmanualsforwiretypeandconnectionsforspecifictransducermodels.
Installametaljunctionboxandtwoconductorterminalstripsataneasilyaccessiblelocation.Terminatecablesperthetransducerinstallationmanual.Ensurethatthecableshieldsareisolatedfromtheground.Failuretoproperlyinsulatethetransducershieldcancauseashorttotheground.
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Groundedmetalconduitisrequiredbetweenthetransducerandthemetaljunctionbox.Groundedflexconduitisacceptable.Rigidmetalconduitshouldbeinstalledfromthejunctionboxtotheelectronicspackage.InthecaseofmultiplepointsystemsliketheSITRANSLU10,asingleconduitcanbeusedforalltransducercables.Iftransducercablesruninthesameconduitorincloseproximitytoeachother,besuretosynchronizethetransceivers(seedeviceinstructionmanual)topreventcrossinterference.
Transducersallhaveintegralcableswith“pigtail”leadsattheend.Thelengthofintegralcablecanbeselectedwhenorderingandareavailableinlengthsofupto100meters(328ft);however,thefivemeter(16.5ft)andtenmeter(32ft)lengthsaremostpopular.
Thepigtailendscanbedirectlyconnectedtothecontroller’sterminalblocks,orthecablecanbeextendedusingafield-mountedjunctionboxandadditionalcable,uptoatotallengthof365meters(1200ft).Theadditionalcabletypedependsonthecontroller,notthetransducer.Forextendedrunsbeyondthetransducer’sintegralcablealwayschecktheproductmanualforrecommendedcabletype.Somecontrollers,likethe
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SITRANSLUT400andMultiRanger200,use18AWGshielded,twistedpaircable;othermodels,liketheSITRANSLU10,useRG62Ucoaxcabletoextendthelengthofthetransducercable.
Alltransducercableshouldbemountedingroundedmetalconduittoprovidethebestelectromagneticnoiseshieldingandphysicalprotectionofthecableitself.Donotruncablesnearhighvoltageorcurrentruns,contractors,orSCRcontroldrives.
DiagnosticsoftwareFordifficultinstallationsinvolvingexcessivedust,turbulence,obstructions,orverynarrowwells,diagnosticsoftwareisavailabletohelpfine-tunethetransducer’saimandtosetparameters.SiemensMilltronicsusesSIMATICPDMforviewingechoprofilesandtodiagnoseechoproperties.SupportforDTMsandothertypesofconfigurationsoftwareisavailableforsomemodels.
MatchenvironmenttemperatureIfatransducerbecomessignificantlywarmerorcoolerthantheaverageairtemperatureintheapplicationenvironment,itmayaffectaccuracybecausethespeedofsoundchangeswithtemperature.Althoughsome
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transducershavebuilt-intemperaturecompensationfeatures,it’salwaysbesttomountatransducerwhereitwillsharethesameairtemperatureastherestoftheapplicationenvironment.
Fortransducersmountedoutdoorsindirectsunlight,provideasunshield.Ifthereisasignificanttemperaturedifferencebetweenthemediumandthesensorsurface,connectanexternaltemperaturesensortothecontrollerforincreasedaccuracy.
OpenvesselsLocatethetransducerascloseaspossibletothemaximumheightofthematerialbeingmeasuredwithoutinfringingontheblankingdistance.Theblankingdistancevariesamongmodels,sochecktheproductmanualforblankingdistanceinstructionsrelatedtoyourtransducer.
MountingbracketsTheseversatilebracketsprovidesturdyplatformsforopenvesselsandforopenchannelmonitoring.Manufacturedfrom304stainlesssteel(1.4301),thesebracketscomeinavarietyofshapestofitanyapplication.
Openchannelmeters:weirsandflumesOpenchannelflowoccurswhenliquidflowsinachannelwithafreesurfaceopentoatmospheresuchasstreams,rivers,irrigationcanals,andditches.Non-pressurizedpartiallyfilledpipes,includingstormsewers,sanitarysewers,andculvertsalsoqualify.Openchannelflowconditionsarecommonlyfoundinwastewatertreatmentsystems,industrialwastesystems,andirrigationsystems.
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Inanopenchannel,pressureisnottransmittedfromoneendtotheotherendofthefluidlikethatinafullyflowingpipe,andonlytheforceofgravityonthefluidcausestheopenchannelflow.
Oneofthetime-provenandcommonmethodsofmeasuringflowusesaprimarydevicetorestricttheflowofliquidsothatamathematicalrelationshipexistsbetweentheliquiddepth(headlevel)andtheflowrateorvelocityofthewater.
Therearetwotypesofprimarydevices:weirsandflumes.
WeirsWeirsarethemostcommontypeofprimarydevicesusedtomeasureopenchannelflow.Aweirisadambuiltacrossachannelandtheliquidflowsoverit,oftenthereisacutoutornotch,andtheweirisgenerallynamedfortheshapeofthenotch.Aweiristhesimplestandoldesttypeofchannelflowmeasuringdevice.
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Amathematicalrelationshipcanbederivedtocalculatethedischargethroughthesharp-crestedweirs.
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FlumesAflumeisaventuridevice2placedwithinachanneltorestricttheflowandproduceahead(level)/flowraterelationship.TheflowinducedisbetweencriticalandsupercriticalflowlevelssoonlyoneheadmeasurementisrequiredtomeasureflowQ.
Mostflumesaredesignedtopasstheflowsthroughacriticalstateforaspecifiedheadrange,providedflumesareinstalled,maintained,andoperatedwithinthespecifiedrange.
Commonflumesinclude:
ParshallflumeRectangularflumePalmer-Bowlusflume
Ultrasoniclevelmeasurementdevicesareideallysuitedtomeasuringwaterlevelinprimarydevices.Thenon-contactingnatureofultrasonicsallowsformeasurementwithoutdisruptingtheflow;contactdevicesusedformeasuringheadlevelwouldactuallydisruptthelaminarflowandaffectthehead/flowrelationshipandtheoverallaccuracyoftheflowmeasurement.Thesurfaceofthewaterissmooth(ideallythereisnoturbulence)andthisprovidesaperfectreflectingsurfaceforsoundwaves.Ultrasonicdevicescanalsoprovideintegrationoftheinstantaneousflowratetoatotalizedamount.
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Theoverallaccuracyofopenchannelflowmeasurementisdependentonthefollowing:
theprimaryelementselectionanddesignproperinstallationoftheprimarydevicetheeffectoftheapproachflowtheeffectsofthedischargeflowtheliquidbeingmeasuredthesecondarymeasuringdevicefieldcalibrationoftheprimaryelement(provingthatitdoesperformasintended)fieldcalibrationofthesecondarydevice
Thissectionfocusesonthesecondarydevice,theultrasonicopenchannelmeter,andthefield-mountedtransducer.Manytextsandguidelinesareavailablethatfocusontheprimarydeviceanditsinstallationcriteria;pleaserefertotheseforselectingandinstallingaflumeorweirproperly(seeISCOHandbook)orwww.usbr.gov/pmts/hydraulics_lab/pubs/wmm/cover.html
Theprimaryrequirementforaccuratemeasurementisthattheapproachingflowintoaflumeoroveraweirmustbetranquilandnon-turbulent.Thisisperhapsthemostimportantcriteriawheninstallingaprimarydeviceandalsohasaneffectontheaccuracyofthesecondarydevice.Iftheflowisturbulentintheapproachchannelthenthelevelwillnotbestable,causingdifficultiesforthesecondarydevicetolockontoalevelthatisrepresentativeoftheactualflowrate.
TransducerlocationThelocationofthetransducer,eveniftheflowissmoothandtranquil,isimportantiftheheadversusflowrelationshipistobemaintained.Forstandardweirs,thetransducershouldbelocatedupstreamminimumthreetimesthemaximumheadlevelasshownbelow:
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BS-3680V-notchweirISO1438/1(BS-3680)thinplateV-notchweirrequiresthatthetransducerbelocatedfourtofivetimesthemaximumheadlevelbackfromtheweirplate:
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ParshallflumesForflumes,thelocationofthetransducerdependsupontheflumetype.CommoninNorthAmerica,Parshallflumeshavetheheadmeasuredat2/3thelengthoftheconvergingsectionfromthebeginningofthethroatsection:
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BS-3680/ISO4359rectangularflumeAnISO4359(BS-3680)rectangularflumeheadlevelmeasuresfourtofivetimesthemaximumheadlevelupstreamasshowninthefollowingdiagram:
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PipelineflumesTwotypesofflumesaredesignedtofitdirectlyinpipelinesinmanholes:Palmer-BowlusflumesandLeopoldLagcoflumes,andtheyaresizedaccordingtothepipediameter.Thetransducerlocationsdifferbetweenthesetypes;however,bothdependuponthepipediameter.TheupstreamlocationofthetransducerinaPalmer-Bowlusflumeisthepipediameter‘D’dividedbytwo,asshown:
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TheLeopoldLagcoFlumeheadlevelmeasurementrequiresthetransducertobelocatedasshowninthefollowingtable:
Flumesize(pipediameter
ininches)
Pointmeasurement
centimeters inches
12 2.5 115 3.2 1.25
18 4.4 1.75
21 5.1 224 6.4 2.530 7.6 342 8.9 3.548 10.2 454 11.4 4.560 12.7 566 14.0 5.572 15.2 6
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Tipsforeffectiveopenchannelflowmeasurement
Ensuretheprimarydevice(weirorflume)istherighttypeandsizefortheexpectedflowrate,andensureitisinstalledproperly.Discrepanciesfromthestandarddesign,dimensions,orsetupwilladverselyaffecttheaccuracyofflowmeasurementdevices.Ensurethatitisproperlycleanedandmaintained.Anybuildupofsedimentorvegetationcaninfluenceflowandflowmeasurement.Checkupstreamconditionsthatmaycreatewavesorsurging.Hydraulicjumps,flowpipes,ordropsinapproachpipeslocatedclosetotheflumecaninterferewithmeasurement.Wheninstallingflowmeasurementdevices,followtheinstallationguidelinesintheinstructionmanualtoensurecorrectsetupandtobeawareofanylimitations.Fieldcalibrationoftheprimaryelementwilltellyouiftheactualheadcorrespondstothehead-to-flowcalibrationinformationsuppliedbythemanufacturer.Ifnot,anewcurvecanbedeterminedthrough
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fieldtesting.Thisisessentialonspecialapplicationsornon-standardweirsandflumes.Installtheheadmeasuringdeviceinarelativelycalm,stableportionofthechannel.Itshouldnotbepositionedinachannelapproachthathashighvelocityofwater,turbulence,gates,valves,pumps,orasuddenchangeinsection.Makesurethemeasurementdevicehasbeenproperlyzeroedinreferencetotheprimarydevice.Whentheflumeisempty,yourlevelsensorshouldreadzero.
MaintenanceIfsignificantperformancechangesareobserved,shutdownthelevelmeasurementsystemandinspectit,startingwiththetransducer.Ensurethetransducerisstillfirmlymounted,wipethefaceifithasbecomesoiled,andcheckthewiringconduittoensureitisallsound.Ifthetransducerworksproperly,checkthevesselsidesfornewobstructionsormaterialbuildup.
Ifthesoundpathisclear,performdiagnosticsatthecontroller.Troubleshootinginformationisclearlymarkedintheinstructionmanual,andotherproceduresincludeanalyzingtheechoprofileforechoquality(strength,confidence,andnoise).
Generally,lowmaintenanceisakeyadvantageofultrasonictransducers.Thepowerfulpulsingactionmakesthefaceself-cleaning.Becausetransducersarenon-contacting,thereisnomaterialbuildup,avoidingthenuisance,danger,andexpenseinvolvedincleaning,adjusting,andrepairingcontactingdevices.
LiftstationsLiftstations,alsoknownaspumpstationsorwetwells,areessentiallyverticallymounted,flatbottomvesselsthathappentobebuiltintotheground.Theyarepartofgravityfedsewagecollectionsystemsandareusedtocollectsewageatonepointandthenpumpit(orliftit)toahigherelevationtoeventuallyendupatthewastewatertreatmentfacility.
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Liftstationsarealsofoundattheinlettothewastewatertreatmentfacilityitself.Thewetwelldiffersfromasimpleverticallymountedflatbottomvesselbythepresenceofequipmentinsidethewell:pumps,chains,inletanddischargepipes,back-upfloats,powerlinestothepumps,andladderrungs.Liftstationenvironmentsarealsoverycorrosiveanddirty,andthewatercancontainsolids;thuscontactdevices,likefloats,canprovetobeunreliableovertimeasmaterialbuildupandconstantcontactwearsonthesedevices.Ultrasonictransducers,anon-contactingtechnology,aremountedabovethesewageandonlycomeincontactwithsewageduringabnormalfloodconditions.Thusultrasoniclevelmeasurementprovidesnearmaintenance-freeoperationformanyyears.
Installthetransduceronasturdybracketorhangfrommetalconduit.Themountingheightshouldatleast30centimeters(12”)abovetheexpectedmaximumlevel;locatethetransducerasfarawayaspossiblefromtheinletpipe,pumps,ladderrungs,floats,thewetwellwall,andotherobstructions.Ifextremelyturbulentorfoamy,useastillingwellandfollowtheinstallationguidelines.
Wetwelltransducerselection:
shortrangewetwells[0to8m(0to26ft)]:XRS-5shortrangewellswithobstructedbeampath:XPS-15deeperwells:XPS-15verynarrowwetwells:XPS-30
Floodalert
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Ifthetransducerissubmerged,especiallyinapplicationssuchasafloodedwetwell,useatransducerwithasubmergenceshieldthatmaintainsanairpocketinfrontofthetransducer.Thecontrollerrecognizestheuniqueechocreatedbytheairpocket,andthecontrolleroutputsahighlevelreading.
Wheninstallingasubmergenceshield,ensureitisproperlyseatedandevenacrossthetransducer.Checkforleaksbyplacingtheassembledunitinabucketofwaterandseeifanybubblesleakout.Leaksindicatetheshieldhasnotbeenpulleddownfarenoughtoproperlyseatthepressureclips.
NOTE:Asyouselectthetransducer,youalsoneedtoselectacompatiblecontrollertoprocessthesignalfromthetransducertoprovidethefollowing:
levelmonitoringdataloggingadvancedecho-processingtechnologypumpcontrolfunctionsremotemonitoring
Allcontrollermodelsofferbacklitdisplaysforeasyreadabilityandotheradvancedfeaturesthatcanimproveplantefficiency.Consideryourspecificapplicationneedsagainstthemanyfeaturesthatareavailable.
Positioncontrol
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Ultrasonicsensingtechnologyhasotherusesthatareoutsideoflevelmeasurementbutthatoperateonsimilarprinciples.Thetransducersactasdistancesensors,indicatingproximityandactivatingalarmsormotorsorswitches.Thisultrasonicpositioningcontrolrequiresthetransducertobemountedhorizontallyandisveryeffectiveintheshippingindustryforoperatingoverheadcargocranesandintheminingindustryformanagingcoalloadingconveyors.
HazardousapprovalsTransducerandtransmittersareinstalledinpotentiallyexplosiveenvironments.Greatcareandeffortistakenduringthedevelopmentoftransducerstoensuretheyaresafeforuseandmeetorexceedtheapprovalrequirementsnecessaryforinstallationintheseenvironments.Notonlymusttheyperformtothedistanceandtemperaturerangesspecified,theymustalsodososafelyinhazardousorexplosiveenvironments.
Undermostgoverningelectricalcodes,itisuptotheusertoensurethatthetransducerortransmitterbeinginstalledhasthenecessaryapprovalstomeettheminimumareaclassificationoftheapplication.TransducersfromSiemensMilltronicscomewithawiderangeofapprovalstomeetthedemandsoftheapplicationsthathaveexplosiveenvironments.Theyvaryslightlyfromcountrytocountryastheworldhasnotadoptedaschemeforglobalapprovals.
ApprovalsSiemensultrasonictransducersaredesignedtomeettherequirementstobeusedinbothgasanddustatmospheresandarecertifiedbyvariousagenciesaroundtheworld.Itisimportantwhenspecifyingandinstalling
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anyequipmentinalocationthatisclassifiedashazardoustofollowalllocalelectricalcodesandguidelinesandtopayparticularattentiontothespecifiedratings.
NOTES:Thefiretriangleorcombustiontriangleillustratestheconditionsrequiredformostfires.Threeelementsareneeded:heatorspark,fuel,andanoxidizingagent(usuallyoxygen).Fireispreventedorextinguishedwhenanyoftheconditionsareremoved.
Intheworldofelectricalengineering,ahazardouslocationiswhenconcentrationsofflammablegases,vapors,ordustsoccur.Electricalequipmentinstalledintheselocationsisespeciallydesignedandtestedtoensureitdoesnotinitiateanexplosionthrougharcingcontactsorhighsurfacetemperature.
ControllerinstallationWhilethetransducer/compoundinstrumentinstallationmustbecarefullyplannedbecauseofitsproximitytotheapplication,thecontrollerinstallationcanbedeterminedbytheoperator’srequirements.Thus,iftheoperatorisneartheapplication,thecontrollercanbeplacedcloseby.However,becausethecontrollercanbeinstalledasfarawayas365meters(1200ft),itcanalsobeplacedindoorsandawayfromtheelementswhereitmaybeinstalledindependentlyorinarackasoneofanumberofinstruments.
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Whethertheunitiswallmountedorinstalledinarackorpanelwithotherinstrumentsdoesnotaffectperformance.Theyarethesame,regardlessofmountingdesigns.
MountinginstructionsThewallmountandpanelmountunitsinstalldifferentlyandthemanualscontainthespecificinstructions.
Wallmountedunitsmustbemounteddirectlytoawallortoelectricalcabinetbackpanel.Alternatesurfacesmustbestrongenoughtosupportfourtimestheweightoftheunit.
Rackandpanelmountedunitswillfitintoexistingslotsor,aswiththeSITRANSLUT400,willrequiremakingacutouttoaccommodatetheunit.Afullsizecutouttemplateisprovidedwithyourunitormaybedownloadedfromwww.siemens.com/level.
WiringCableisbroughtineitherdirectlythroughthecableglandsorthroughconduit,dependingontheinstallationrequirements:
Cableglands:ifthepurchasedunitdoesnothavepre-drilledcableglandholesorknockout,youneedtodrilltheentryholes.Makesureyouremovethemainboard,beingcarefulnottodamagetheelectronicswithstaticelectricity.Makesurecableglandholesdonotinterferewiththelowerareasontheterminalblock,circuitboard,orcommunicationcard.
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Afterlooselyattachingtheglandstotheenclosure,threadthecablesthrough,keepingthepowercableseparatefromthesignalcables.Thentightenglandtoaensurewaterproofsealwhenwiringiscompleted.
Conduit:youneedtodrilltheentryholesorremovetheknockouts,somakesureyouremovethemainboard,beingcarefulnottodamagetheelectronicswithstaticelectricity.Makesureconduitholesdonotinterferewiththelowerareasontheterminalblock,circuitboard,orcommunicationscard.Attachtheconduittotheenclosureusingonlyapprovedsuitablesizehubsforwatertightapplication.Reinstallthemainboardwiththemountingscrews.
NOTES:
PerforminstallationonlybyqualifiedpersonnelandinaccordancewithlocalgoverningregulationsFollowpropergroundingprocedures.Thisproductissusceptibletoelectrostaticshock.Allfieldwiringmusthaveinsulationsuitableforatleast250V.HazardousvoltageispresentontransducerterminalsduringoperationSupplyACandDCterminalsfromapprovedsourcesUsegroundingtypebushingsandjumperssothenon-metallicenclosuredoesnotprovidegroundingbetweenconduitconnectionsEnsureambienttemperatureisalwayswithinitsapprovedrange.Typically-20to50°C(-5to122°F)Mountunitsodisplaywindowisatshoulderlevelandeasyaccessforprogrammingisprovided.MakesuremountingsurfaceisfreefromvibrationLeavesufficientroomtoswingunitlidopenforclearaccessAvoidexposuretodirectsunlight(Provideasunshieldtoavoiddirectsunlight.)Avoidproximitytohighvoltage/currentruns,contacts,SCR,orvariablefrequencymotorspeedcontrollers
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SummaryUltrasonicsisaversatileandfriendlytechnologyformanylevelapplications,buttheinstallationrequirementsmustbemetforoptimalperformance.Situatingthesensorortransducerinthepropervessellocation,followingallthesafetyregulationsandapprovalrequirements,andaccountingfortemperatureandpressureconditionswillallensurereliable,accurateperformance.Alwaysaccountfortheconditionswhenchoosingaleveltechnology,andthosewhicharemoreproblematicforultrasonics–dust,vacuum,interference–canbehandledbytheSITRANSradarline.
1Prince,“JoyInRepetition.”GraffitiBridge,1990.2Anydevicethatrestrictstheflowandregulatesitthroughameasurablepoint.
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ChapterSix
ApplicationsI’macosmopolitansophisticateofculture
andintelligence.Theculminationoftechnologyandcivilizedexperience.1
Ultrasoniclevelinstrumentsarenotexclusivetoanyoneindustryandarewidelyusedacrossmanybusinessesandapplications.However,therearecertainapplicationswhereSiemensMilltronicsultrasoniclevelinstrumentsoperateparticularlyeffectivelyandaccurately.Acrosstheglobeandoveramillionstrong,theseultrasonicleveldevicesarefoundinthewater/wastewater(W/WW)industry;inmining,aggregate,andcement(MAC)applications;andinthechemicalmarkets.
Regardlessofthetypeofapplication,however,theprimaryrequirementforallindustriesistobeabletomeasurelevelaccurately,consistently,andcosteffectively.Ultrasoniclevelmeasurementmeetstheseneeds
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andhasbecometheselectedsolutionformanyindustriessincethe1970s.
ApplicationsMarketslikewater/wastewaterandmining,aggregate,andcementemploylevelmeasurementformanydifferentpurposes,includingprocesscontrolandinventorymonitoring.Eachindustryhasarichhistoryofinstrumentationdevelopment.Ascompetitiongrowsandresourcesarestrained,controllingprocessesandinventoriesisincreasinglycrucialtothebottomline.Accuracyandreliabilitybecomeparamountandcloserattentionispaidtotheinstrumentsusedtomeasureinventoryandcontrolprocesses.Measuringandcontrollingthelevelofmaterialscontainedinstorageandprocessvessels,suchastanks,wells,reservoirs,ponds,bins,andhoppersisoneofthemostcommonproceduresofindustrialinstrumentation.
Inalltheseapplications,ultrasonicsprovidestwotypesoflevelmeasurement:
pointmeasurementcontinuous
Thepointlevelcanalsobecombinedwiththecontinuousleveltoprovidesafetyredundancy.
Notthatlongago,binsandsilosweremeasuredbyknottedropesorbysightlines,withemployeesclimbingtothetopofthecontainerorinsomecasesintothecontaineritself.Thistypeofmeasurementbecameimpractical,andoccasionallydangerous,andcompaniessoughtoutinstrumentationwhichwasaccurateandreliable,andcouldbemonitoredincontrolroomsoractivatedfromremotelocations.Plumbbobsandcontactswitchescouldnotstanduptothestrenuousdemandsofmanyoftheapplications,sonon-contactingultrasoniclevelmeasurementasdevelopedbySiemensMilltronicsinthe1970sand1980swasintroduced
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tothemarket.TheruggedreliabilityofSiemensMilltronicsinstrumentslikeTheProbeandtheMultiRangerquicklyproveditselfinvaluableforthefollowing:
reducespillage(overflow)–environmental,losscontrol,legislationcostaccounting–inventoryqualitycontrol–processcontrolbylevelreductionofinventoryinprocess–smallervesselspumpprotection–protectfromrunningdry
TopicsThischapterdiscussestheseapplications,focusingonthefollowingindustries:
cementminingwater/wastewaterfoodchemical
Cement
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Thecementindustry,similartomining,reliedonrudimentarylevelmeasurementsystemsformanyyears.Plumbbobsoryo-yos,tiltswitches,andmanualdipsprovidedmostoftheinventoryandprocessinformation.Inthe1970sand1980s,ultrasonicmeasurementappearedonthescenewithsomeoftheearlyMilltronicsAiRangersandLRtransducers,findingmanyusesinthecementindustry.
Theproductionoffinishedcementrequiresnumerouslevelinstrumentsalongtheway,operatingintwocapacities:
asprocesscontrollers,activatingpumps,belts,alarms,andotheractionsasinventorymanagers,monitoringmateriallevelsinsilosandbins
Thecementprocesschartindicatesthemanyareaswhereultrasonicinstrumentsoperateinthecementproductionprocess.OtherSiemensMilltronicsequipment,likebeltscales,weighfeeders,andprocessprotectioninstrumentsalsoplayvitalrolesintheproductionofcement,reinforcingSiemens’roleasatotalsolutionprovider.
PrimarycrushersGyratoryconecrushersarethemostcommon,andtherearegenerallytwomainapplicationsattheprimarycrusher.
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Truckpositioning–thetransducerishorizontallymountedinthepathofthereversingtruckandiswiredintoacircuitwhichcontrolsredandgreenlights.Asthetruckapproaches,theultrasonicsystemcontinuouslymonitorsitsposition.Whenitistheproperpositionfordumping,analarmrelayclosesandthegreenlightisactivated,signalingtothedriverthattheloadmaybesafelydumpedintothecrusher.
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Rockbox–locatedbelowthecrusher,theultrasonicsystemmonitorsthelevelofthecrushedrock.Alarmsaresettoindicateaclogintheoutfeedandtoindicatewhenaloadcanbesafelydumpedintothecrusher.Alowlevelalarmcanbeprogrammedtomaintainaprotectivelayeroforeintherockboxtopreventfeederdamage.
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QuarrystockpilesThecrushedlimestoneistransportedfromthecrushertoastockpilebyastackerconveyor.Theultrasonictransducermonitorsstackoutprofilesandprovidesinventoryestimatesinstockpilestoensureuniformstackout.
Anultrasonictransducermountedontheheadoftheconveyormonitorsthedistancefromthedischargetothetopofthestockpile.Whenthedistancebetweenthetworeachestheprogrammedsetpoint,analarmtriggers,signalingtheneedtoraiseorrotatetheconveyortoanewposition.Thisinventorymanagementisacommonapplicationforultrasonicssystemswheretheruggeddesignandremotepositioningofthecontrollermakeitanidealtechnologyfortheseconditions.
SecondarycrusherInthesetypicallynoisy,wet,anddirtyapplications,ultrasonictransducerssensethelevelofmaterialinthesurgebins.Ultrasonicsystemsarealsousedatin-feedchutestocrushers,monitoringforpluggedchutes.
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Here,thePointekULS200monitorsthechuteattheendofaconveyor.Ifthechuteplugs,arelayintheULS200closesimmediately,notifyingtheuserthataproblemexistsandshuttingdowntheconveyor.
RawmillfeedsilosCrushedoreistransportedfromthesecondarycrusherstotherawmillfeedstoragesilo.Hereanultrasonicsystemmonitorstheleveloforeinthesilo.
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Thisapplicationisstrictlyinventorymanagement,astheultrasonicsystemmonitorsthecontentlevelsonly.
RawmillTherawmillistypicallyarollermillthatpulverizesrawmaterial,includingadditives,intoafinepowderwhichisthentransportedtothekilnfeed.Blendedrawmaterialsarecontinuouslyfedintotherawmill.
Theultrasonicsystemmonitorstheheightofthemillrollersabovethetable,essentiallymonitoringbeddepth.Operatorsintegratematerialfeedratewiththerollerheighttomaintainaconsistentbeddepth,improvingmillingefficiencyandpreventingtherollersfromstrikingthemilltable.
KilnfeedsiloCrushedmaterialfromtherawmillistransportedtothekilnfeedsilo(sometimescalledContinuousFeedSiloasmaterialisconstantlyfedinandoutofthissilo)whereitisstoredandpreheatedinpreparationfordeliveryintothekilnitself.Ultrasonicsmonitorsthelevelwithinthesesilos,butwithonlyalimitedrangeduetotheextremelydustyandturbulentenvironment.
Inrecentyears,manykilnfeedsiloshavebeenoutfittedwithSiemensSITRANSLR560radarleveltransmitterswithgreatsuccessatovercomingtheharshenvironments.Ultrasonicsmaywork,however,
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dependingonthedustlevels,andisacost-effectivealternativetoradarinappropriateapplications.
Clinkerstorage
Thematerialleavingthehotkilniscalledclinker.Ranginginsizefromdusttofistsizedclumps,theclinkerisstoredinsilosbeforebeinggroundintoafinepowder.Becauseithascomeoutofthekiln,theclinkerisquitehot.
Toworkeffectively,powerfulhightemperaturetransducersliketheXLT-60measurethelevelintheclinkersilos.Becauseclinkerapplications,althoughdusty,arenotasdustyaskilnfeedsilosorfinishedcementsilos,ultrasonicsisaviablechoiceforthisapplication;however,moreusersareswitchingtoSITRANSLR560radarbecauseofitsimprovedperformance.
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AdditivebinsandcoalstoragesilosThesebinscontainmaterialsthatareaddedtotherawmillprocessandaremixedwiththecrushedlimestonebeforethekiln.Theyalsoholdthematerialsthatareaddedduringthefinalgrindingoftheclinker.Thesebinscontainsand,ironore,flyash,gypsum,plaster,orothermaterialsusedtoadjustthecompositionofthecement.
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Thecoalsilosstorethecoalthatisburnedinthekiln–theheatfromtheburningcoalisresponsibleforthechemicalchangesoftherawfeedintoclinker.Ultrasonicsystemsmonitorthelevelinthesebinsforinventorypurposes.
FinishedcementsilosThesesiloscontainfinishedcement.Oncetheclinkerandotheradditiveshavegonethroughtheballmills,thematerialisreducedtoaveryfinepowderandisconveyedtostoragesiloswhereitwaitsforbulkshippingviatrainortrucking,orforfurtherproductionintobagged,finishedcement.
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Finishedcementisextremelyfineandthereisverylittlemoisture,whichmakesthisapplicationverydusty.Theperformanceofultrasonicsystemsonthisapplicationisinconsistent–itdependsonmanyfactorsincludingsiloheight,dustcollectionsystem,transducerlocation,transduceraiming,andmethodoffilling.Likethekilnfeedsilos,thisapplicationwastraditionallymonitoredbyanultrasoniclevelsystem.Incaseswherethedustistoogreat,aSITRANSLR560radarleveltransmitteroperateswithgreatsuccess.
MiningInventorymanagementandprocesscontrolintheminingindustrywasaroughbusiness.Thenatureoftheproductmadeitdifficulttoassessvolumeaccuratelyandmostofthecontrolwasdonemanually.Mechanicalmeasurementreliedonyo-yos,oroccasionallynuclearmeasurementforpointlevelcontrol.However,nucleartechnologyisveryexpensiveandhasitsownsafetyconcernsandyo-yosarepronetobreakdown.Processeswerealsovisuallymonitoredbutoftenbrokedownwhenthemonitorwasnotwatchingorawayfromhispost.Crushersjammedupfromtoomuchloadorranemptywhenbinsdrained
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early.Efficiencywasthusdifficulttomaintain.Safetywasalsoaproblemasworkersoftenhadtoenterstoragebinstochecklevelsortorepairjammedequipment.
Theimplementationofultrasonicmeasurementhasgreatlyimprovedoperationalefficiencyandsafetyinmining.Thenon-contactingtechnologyallowsforinventoryandprocessmanagementfromthesafetyofacontrolbooth.Crushersandfeedbeltsoperatewithoutinterruptionandloadsareaccuratelyandefficientlyprocessed.Ultrasoniclevelmeasurementoperatesinvariouslocationsthroughoutmining.Someofthem,liketheprimaryandsecondarycrushers,areidenticaltothoseusedinthecementindustry.Otherapplications,asshownintheprocessdiagrambelow,requiretheuseofultrasoniclevelequipmentforprocesscontrolandinventorymanagement.
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CrusherOrelevelsinsurgebinsaremeasuredbyultrasonicsystemstomonitorthefeedintoacrusher.Thetransducers,althoughruggedindustrialdevices,mustbemountedfarenoughawayfromthefeedtoreducerepeatedcollisionsfromtheoreitself.
Thecrusherreducestheoretoamuchfinerconsistencysoitcanbeaddedtoanotherprocess.
FineorebinsTheXPStransducerseriesareidealformeasuringfineorelevels,atypicallydustyenvironment.ThemultipointSITRANSLU10controllercanmonitorlevelinthebinsandcanbeprogrammedforpriorityscanningtomonitorbinsthatarefillingatahigherratethanstaticbins.
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FlotationcellsTheflotationprocessusedinmineralprocessingbeginsbyinjectingafrothingagentintomineralslurry,thenitpumpsthematerialintoanagitatedopentankoranaeratedflotationcell.
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Thevaluablemineralsclingtothefroth,whichisthenscrapedfromthetopoftheslurry,afterwhichthefrothingagentisremovedfromthemineral-richconcentrate.Theconcentratesaredewateredandthewasteisdiscardedastailings.Foranefficientextractionprocess,itisessentialtomonitortheleveloftheslurryandtheleveloffroth.
Duringtheflotationprocessboththeheightandthicknessofthefrothmustbecalculatedtodeterminethedosageoftheexpensivechemicalreagents.Accuracyisimportantasitsavesmoneybyusingonlytherequiredamountofreagentsandbyremovingthemaximumamountofmineralsfromthefroth.
TwotransducersorSITRANSProbeLUsaremountedovertheflotationcell.Thefirstmeasuresthelevelofthefroth;thesecondmeasuresthelevelofthepulp.Thepulplevelisdeterminedbyusingafloatball/targetplateassembly:thefloatballfloatsontopofthepulp,arodwithatargetplateisattachedtotheballandthetransducermonitorsthelevelofthetargetplate.Thelevelofthetargetplateisdirectlyproportionaltothelevelofthepulp.Thesignalsfromthetransducersaresenttoaprocesscontrolsystemwhichcalculatesthefroththicknessandcontrolsthedosageofthechemicalreagentsaccordingly.
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ChemicalstorageManychemicalsareusedaspartofmineralprocessingandarestoredonsite.Ultrasonicsystemsareusedforinventorymonitoringofthesechemicals.Non-contactingmeasurementisidealforthistypeofinventorymonitoring,astheaggressivenatureofmanychemicalsmakecontactdangerousorimpossible.
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Slurrytanks
Shortrangeultrasonictransducersareflange-mountedaboveslurrytankstomeasuretheamountofliquid.ThePVDFenclosuresprotectthetransducersfrommostchemicalsfoundinslurrytanks.
SumppumpwellsManysumpwellsataminingsitecanbemeasuredbyshortrangeultrasonictransducersformorereliableperformance,especiallywhencomparedtosimplefloatsorothercontactswitches.Themanagementofwater,whetheritbetocontrolfloodingoraspartoftherefinementprocess,iscrucialtothemineoperation.
Orestoragebinsorstockpiles
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Oftenoreisstoredinbinsorstockpilesbetweenprimaryandsecondarycrushingstages.Ultrasonicsystemsmonitorlevelinthebinsorstockpiles.Thisapplicationissimilartothequarrystockpilingofmaterialusedforcementproduction.
DiskfiltersAftertheconcentratehaspassedfromtheflotationcellsandthethickeners,diskfiltersdewatertheconcentratebeforeitproceedstothesmelterprocessing.Ultrasonicsystemsmonitorthelevelwithinthefilters
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andactivatealarmsifthefilteredcake(thedewateredconcentrate)backsup,thuspreventingaspill.
Applicationone:measuringlevelinflotationcellsOneoftheworld’sleadingproducersofcopperandmolybdenumoperatesacoppermineinthewesternUSA.Theoperationusesaseriesofconecrushersandballmillstoreducecopperoretoveryfineparticleswhicharepulped(mixedwithwater)tocreateaslurry.Smallamountsofspecialreagentsareadded,includingafrotherandacollectorchemicalthatcausesthecoppermineralstosticktothebubbles.Thismaterialispumpedtoaseriesoffrothflotationcellstoconcentratethecopperwhereairisblownintotheflotationcelltank,andthepulpmixtureisvigorouslyagitatedlikeinahigh-speedblender.Risingbubblescarrythecopperparticlesupandovertheedgeoftheflotationtankwherethebubblesbreaksoonaftertheyflowovertheedge.Thecopperisthengroundevenfinerandpurifiedbyadditionalflotationprocesses.
Conditions
needtomeasurethelevelofboththepulpandthefrothtoensureoptimumcopperconcentrateproduction.Thoselevelsprovidefeedbacktotheplant’sprocesscontrolsystemsooperatorscanmakeappropriatechangestovariableslikepulpandairflowaswellastheadditionofchemicalreagents
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difficultforlevelmeasurementbecauseofmaterialbuild-upandpluggingthatoccursonmosttypesofleveltechnologiesnarrowmeasurementrequirements:spanforthepulpmeasurement(usingtheProbeLUwithtargetandfloatassembly)is25.5centimeters(10")andthefrothlevelProbeusesaspanofonlyfivecentimeters(2")harshconditionsrequireaveryrobustdevice
SolutionTheSITRANSProbeLUultrasoniclevelmonitorcombinessensorandelectronicsinasinglepackageforeffectiveliquidlevelmeasurementinopenorclosedvessels.ThepatentedSonicIntelligenceecho-processingfiltersoutfalseechoesfromacousticalorelectricalnoisesandagitatorbladesinmotion,givingsuperiormeasurementreliability.
EachflotationcellisequippedwithaProbeLUtomonitorthefrothlevelwhileasecondProbeLUmeasuresthepulplevelbasedonametaltargetattachedtoamechanicalfloatassembly.The4to20mAanalogoutputfromtheProbeLUfeedsflotationcelllevelinformationintotheplant’scontrolsystem.
BenefitsTheSITRANSProbeLUsareveryeasytoprogramandtheyrequirenomaintenance.Theonlysetuprequiredisprogrammingthespanfortheanalogoutputwhichisreadilyaccomplishedintheinstrumentshoporduringinstallation.
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AggregateTheaggregateindustryissimilartocementandmininginthatitinvolvesmanyofthesameprocessesandmuchofthesamematerial.Thedifferenceisthatitoccupiesthemediumstage,andwhiletherearesomeprocessesinvolved(seediagram),muchoftherequirementisforinventorymanagementandtransfercontrol.Applicationsrequiringprimaryandsecondarycrushers,aswellasorestoragebinsorstockpiles,areverysimilar,ifnotidentical,totheapplicationsinthecementindustry.Others,likethetertiarycrusher,arethesameasthosefoundintheminingindustry.Therearesomeapplicationsuniquetotheaggregateindustry,andtheseareshownintheprocessdiagram.
Blendingsilosandstoragebunkers
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Theselargebunkersstorethecrushedore.LongrangetransducerswithEasyAimersprovidemaximumperformance.Loadingisoftendonebytrippercars,unmanneddevicesthatmovealongatrackoverthebunkers.Thetrippercarspositionthemselvesoveremptybunkersandloadtheore.
Screeningstation
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Atthescreeningstation,amultipointultrasonicleveldeviceliketheSITRANSLU10measurestheindividualinventoryofbinsbasedonmaterialsize.
SummaryUltrasoniclevelinstrumentsplayanimportantroleintheMining,Aggregate,andCement(MAC)industries.Therugged,non-contactingtechnologyiscost-effective,accurate,andreliable;andcanbeusedforprocesscontrol,inventorymanagement,andevenasdistancelocatorsforcraneoperators.
EnvironmentalTheenvironmentalindustryisthebiggestmarketforultrasonicsensors.Fromwater/wastewatersystemstocleanwatersystems,sensorsmeasureflow,runpumps,activatealarms,andcontroladditiveinventories.
Collectionsystem:liftstation/pumpstation/wetwellInmunicipalitiesandcitieswithwatertreatmentfacilities,anunderground,gravity-fedcollectionsystemtransportsrawsewagefromresidentialandindustrialuserstothesewagetreatmentplant.Pumpstations(aka:liftstations)aredistributedthroughoutthesysteminplaces
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wheregravityneedsahelpinghand.Insidethepumpstation,sewageiscollectedinthewetwell,atransitionpointfromwhichitispumpedout,orlifted,untilitreachesthetreatmentfacility.
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Ultrasonicsystemsmonitorandcontrolthelevelofsewagewithintheliftstation.Asyoucanseefromthephotosoftheinsideofaliftstation,therearemanyobstructionsinthewells–thenarrowbeamangleandthenon-contactingnatureofultrasonicsmakeitanidealtechnologyformonitoringwetwelllevels.
AdvancedfeaturesincorporatedintoSiemensMilltronicscontrollersprovidemorethansimplepumpcontrol.TheSITRANSLUT400canmonitorpumpruntime,pumpfaults,pumpstarts,androtatepumpstoeventhewearonthepumpsorwearonepumppreferentially.
TheLUT400hasuniquetimingfeaturesthatadduptogreatbenefits.PumpON/OFFsetpointscanbechangedautomaticallybasedonthetimeofday,avoidingpumpingduringpeakelectricitypriceperiodsandgeneratingenergysavings.TheLUT400realtimeclockcontrolallowspumpsetpointstoalteraccordingtothetimeofday.Inatypicalwetwellinstallation,thiscouldmeanpumpingoutthewellbeforepeakrateandthendeferringpumpinguntilaftertheexpensiveperiod.Penaltiesimposedbyelectricitysuppliersforusageduringpeakhourscanbeavoidedinmostinstances.
TheLUT400pumpcontrolandlevelmeasurementsystemprovidestheoptimumsolutiontomanagecollectionnetworks.Pumpstatusandpumpedvolumearemonitoredusingtheprimaryleveldevice.Digital
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inputscapturesiteandpumpdataprovidingacompletelyintegratedsystem.
Pumpingstationsaredesignedtohandlespecificflowrates–establishedbypopulationserved–butdemographicchangesalterrequirementsovertimesodesignvolumecannotbeassumed.Pumpedvolumeprovidesrealtrendingdataforcollectionsystemefficiencymonitoring.
Itisimpossibletomaintaincompletelysealedpipeworkfrompumpingstationtotreatmentworks.Groundwaterinfiltrationisinevitable.Pumpedvolumemonitoringcanprovidenetworkinformationtodetermineinfiltrationlocations.
NetworkcapacitycanbeeffectivelyusedbymonitoringcollectionflowsandtransmittingdataviatelemetrytoaSCADAsystem.Thisallowseffectiveassetmanagementandhelpstodiagnosestructuralproblems.
Combinedseweroverflows(CSO)Combinedsewagesystemscollectindustrial,residential,andstorm(rainwater)inthesamesewernetwork.Undernormalconditions,allofthesewageispipedtothesewagetreatmentfacilityfortreatmentanddischargedbackintotheenvironment.However,duringstormconditions,flowsincreasedramaticallyduetorunoffandoverflowsoftenoccur.Whenthishappens,thesewageandrainwateroverflowsaredischargedwithouttreatmentintotheenvironment–stream,ponds,orrivers.Theseoverfloweventsmustbeloggedforregulatorycompliancewiththetime,amount,andlocationrecorded.Ultrasonicsystems,liketheLUT400,canmonitorCSOsandrecordoverflowswhichcanbeusedforregulatorycompliance.
StormwaterpondsInsomecaseswhereoverflowsoftenoccur,stormwaterretentionpondsareinstalledtocollectthesewageandrainwaterandpreventrunofftoneighboringstreams.Oncethestormhassubsided,thewaterispumped
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backintothecollectionsystemfortreatment.Ultrasonicsystemsareinstalledtomonitorthelevelinthesepondsandalertuserstothepresenceofstormwaterandofpossibleoverfillingofthepond.
Wastewatertreatmentplant
MainliftstationThemainstationisalargeliftstationlocatedatthesewagetreatmentfacility–alltheremoteliftstationswithinacityeventuallypumptheirsewagetothiscentralstation.Thisapplicationissimilartotheremoteliftstation;however,thewetwellismuchlargerandtherearegenerallyfewerobstaclesorobstructions.Ultrasonicsystemsmonitorthelevelandcontrolthepumpsthatconveythesewageintotheplantaswellasthesewageholdingsandprocessesintheplantitself.
Overflow/stormtankThisoverflowtanklocatedatthesewagetreatmentfacilityprovidesthesamefunctionasstormwaterponds.Actingasholdingfacilities,theycollectthecombinedsewageandstormrainwaterwhenthetreatmentplantisworkingatitsmaximumcapacity.Oncetheincomingflowtotheplantdropsbelowmaximumcapacity,theoverflowispumpedintothetreatmentworksforprocessing.
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Intakeflow(influentflume)Flowtothefacilityneedstobemonitoredandcontrolledtomaintainplantefficiency.Ifinletflowexceedstheratedcapacity,itisdivertedtostormholdingtanks(seeabove)andlaterpumpedbackthroughtheinletonceflowsreturntonormal.
InletflowisoftenmonitoredusinganopenchannelprimarymeasuringdevicelikeaflumeorweirandSITRANSLUT400,asecondarymeasuringdeviceprovidinghighaccuracylevelmeasurementusingultrasonictechnology.
Flowdatamustbeloggedtoensurethefollowing:
thatthetreatmentplantoperateswithintolerancescompliancereportingforlocalenvironmentalregulationsisaccurate
BarscreenInorganicdebrisandmaterialiskeptfromenteringthetreatmentplantbybarscreensplacedintheinletchannel.Abuildupofdebrisontheupstreamsidecausesareducedlevelonthedownstreamsideofthe
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screen.Whenenoughdebrisaccumulates,arakeisactivatedtoclearthescreenandmaintainflow.Thedebrisismaceratedanddriedbeforedisposal.
ASiemensHydroRanger200usestwoultrasonictransducerslocatedateithersideofthescreentomeasuretheupstreamanddownstreamlevels.ArelayonboardtheHydroRanger200activatestherakeatauser-defineddifferentialleveltocleardebris.Theuseofnon-contactingultrasonictransducersensuresyearsofmaintenancefreeoperation.
Solidslevelmeasurement
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Sandanddebrisremovedbytherakeandgritchambersiscollectedinavessel(oragarbagedumpster)monitoredbyanultrasonicsystem.Oncefull,theultrasonicsystemprovidesanalarmtotheusersothatthevesselcanbereplacedwithanemptyone.
ChemicaltanksChemicals,likethealumusedasaflocculentinclarifiersorthechlorinethatdisinfectsthewaterbeforefinaldischarge,arestoredon-sitefordailyuse.Ultrasonicsystemsmonitorthelevelinthesevesselsforinventorypurposes.
Finaleffluent/dischargeflow
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Alltreatmentplantdischargestotheenvironmentmustconformtodistrictlegislationregardingquantityandquality,soaccuracyiscriticalatthisstage.Primarydevicessuchasweirsorflumesthroughwhichtheflowischanneledprovidehighaccuracymeasurementandareoftenused.Thequalityofthedischargemustbemonitoredandistypicallydonewithasampler.
Toachieveaccurateflowmonitoringandcomplywithlegislationrequirements,aprimarymeasuringdevicecombinedwiththeLUT400openchannelmonitorcanbeused.TheLUT400convertshighaccuracyultrasoniclevelmeasurementtoaflowvalueusingknownheadversusflowformulaorBritishandISOStandards.Fulldataloggingcapabilitiesareavailabletologdailyflowtotalsandflowrates.
SludgetreatmentThesludgethatisleftafterthewaterhasbeenremovedisatoxicsoupofwasteproductsthatmustbetreatedverycarefully.Itshandlingishighlyregulatedandallprocessesarecarefullyscrutinized.Measurementofinventorythusplaysanimportantroleinsludgemanagement.
Digestergas
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Biogases(methane)fromthedigesterareoftenstoredinagasholderwitha“floating”roof.Thesegasesarere-usedtoprovideheatingfortheplantorforlocalpowergeneration.Ultrasonicsystemsareappliedtomonitortheheightoftheroofandthustheamountofgaspresent.
DigesterlevelThisapplicationwasoftendonewithultrasonicswithlimitedaccuracyduetheeffectsofmethaneonthespeedofsound.Currently,radardevicesliketheSITRANSLR200andProbeLRprovideamoreaccurate,cost-effectivereadingandarereplacingultrasonicsasthefirstchoicetechnologyforthisapplication.
Dewatering/vacuumfilterThelevelofsludgeinthevacuumfilterismonitoredbyultrasonicsandcontrolsapumpthatwillcallformoresludgetothefilterfromthesludgetankwhenthelevelistoolow.
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Environmentalapplications
Applicationone:liftstationcontrolAmunicipaldistrictinEuropeneededtoupgradeitswatertreatmentsystemandturnedtoSiemenstorenewthelocalmeasurementdevices,andcontrolequipmentandautomationsystem.Theyalsowantedtoincreaseremotemonitoringcapacity.
ConditionsTheprojectneededtointegrateexistinglevelmeasurementsolutionssuchashydrostaticpressuresensorswithanewultrasoniclevelmeasurementsystems,liftpumpcontrolmonitoring,anddataacquisition.
116pumpingstations18associatedcommunitiespopulationof140,000
SolutionSiemensinstalledthefollowingsystem:
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SITRANSLUT400–thehighlyaccurateultrasoniccontrollerfromSiemenswaschosenforthepumpstationmonitoringandequipmentcontrol.EchomaxXRS-5ultrasonictransducerswereinstalledtomeasurelevel.
WithpatentedSonicIntelligenceecho-processingtechniques,theLUT400monitorsandcontrolsliquidlevelsinwellsand/orliquidflowinflumes,weirs,oropenchannels.ItsthreerelayscontrolalarmsorpumpsThesystemmonitorsliftstationsandcollectsdatasuchasstateofoperationandpumpruntime.Ateachliftstation,anLUT400controllerprocessessignalsreceivedfromlevelmeasurementtransducers.
DataistransmittedvialandlineusingSITRANSRD500tothecontrolroomatthedistrictheadoffice.TheSITRANSRD500hasabuilt-inwebserver,FTP,andemailclientwhichallowstheprocesstobemonitoredremotely.AlarmnotificationsarecommunicatedthroughemailandSMStextmessagestooneormorerecipientstoensurethatappropriateactionsaretakenbypersonnel.
BenefitsTheSITRANSLUT400provedareliableandcost-effectivesolutionforpumpcontrol,requiringlessmaintenancethanthepressuresensors.SITRANSLUT400increasedefficiencyandreducedmaintenancecosts.
InstallingSITRANSLUT400alsooptimizedspaceintheelectricalcabinetbyrationalizingcomponentsandreducingwiringtimes.ExistingequipmentwaseasilyintegratedwithLUT400andithooksseamlesslyintothecentralcontrolsystem.
Applicationtwo:wastewaterplantcontrolAmajorCanadiancitywithapopulationexceeding300,000neededtoupgradeitswastewaterplantsandpumpstations.
Allthelocationsweretolinkintoanewhigh-speeddatacommunicationsnetwork,integratingthemintoaSCADAsystem.Toensureaccuratedatagathering,thecityrequiredreliablefieldinstrumentsthatcouldintegrate
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intothenetwork.Afterconductingaseriesofrigoroustestsonultrasonicleveltechnologiesfromseveralsuppliers,thecitychoseSITRANSLUT400withitsonemillimeteraccuracyandSiemensreliability.
Conditions
sixwastewatertreatmentplantshandlingatotalof208millionliters(55milliongallons)perdaythirty-eightpumpingstationswithcapacitiesrangingfrom0.75–21millionliters(0.2millionto21milliongallons)perday.twenty-fiveofthe38areduplexpumpingstations;therestarecomplexpumpingstationswithhugevariablefrequencydrive(VFD)pumps
SolutionSiemensinstalledtheLUT400inthe25duplexpumpingstationsforcontinuouslevelmonitoringandpumpcontrolandputSiemensEchomaxtransducers©2intothewetwells.
TheuniquepanelmountdesignoftheSITRANSLUT400madeforquickinstallation,andforeasyaccess.ThecontrollerswerenetworkedintoaPROFIBUScommunicationsystem.TheSCADAsystemreceivesinformationfromallstations,aswellasotherplantinformation,onthenetwork.AtthemorecomplexpumpingstationsemployingVFDpumps,theLUT400measureslevel,andtheanalogoutputisfedintoaPLCforpumpcontrolandremotetelemetry.
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BenefitsTheultrasonicsystemsperformreliably,anddatacollectionfromthemanysitesisnowfastandaccurate.Operatorscanmonitorandcontroltheplantsitesfromthecentrallocation.Theautomatedsystemismoreefficient,andhasgeneratedsavingsinenergyandmaintenancecosts.StandardizingonLUT400simplifiedinstallationandtraining,savingstafftimeandmoney.
Applicationthree:smallcityoperatesatahighlevelAsmallbutgrowingCanadiancityneededtoincreaseitsfreshwateroutputduetoasteadilygrowingpopulation.Thisneedwascombinedwitharequirementtocontrolcostsandimproveefficiency,allthewhileimplementingnewregulationsrequiringenhancedsafety,training,andenvironmentalprotection.
Conditions
Populationof74,000andgrowingThesystembringswaterfromariver,cleansandtreatsit,thendistributesittoresidentsApproximately400kilometers(250miles)ofwatermainsPumpsanaverageof45millionliters(12millionUSgallons)ofwateraday
SolutionThewaterplantembracesfullyautomatedoperations.AllprocesspointsareintegratedfullyintoacentralSCADAsystemforcontinuousmonitoringandcontrol.Levelmonitoringisacriticalneedforawaterplant,andSiemensinstalledmorethan40pointsoflevelinthemainplantovertheyears.Theymonitortheriverlevel,gatepositionintheriver,aswellaslevelintheflocculationtanks,sedimentationbasins,settledwatertrough,filterbeds,finishedwaterstoragereservoirs,chemicaltanks,andotherapplications.Anultrasonicdevicemonitorsthefloorasasafeguardtodetectanyspillagefromaleakorrupturedpipe.
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Atthecity’svariousstations,reservoirs,andelevatedwatertanks,thereareanother20pointsoflevelbeingconstantlymonitored.Signalsfromremotesitesaretransmittedbyradiolinktotheplantcontrolcenter.
BenefitsTheaccurateandresponsiveSiemenssensorsconstantlymonitortheriverrateofchange,acriticalmeasurement.Theyalsoprovedtheirpreventativevaluewhenoneoftheinteriortanksdevelopedaleakandanalarmwasimmediatelytriggered,preventingaseriousproblem.BecauseSiemenshasbeenthevendorofchoiceforquitesometime,theplantactuallyhasanumberofolderinstrumentmodelsoperating.Theseinstrumentsstillperformreliablyandaccurately,keepingmaintenancecostsdown.TheplantoperatorscreditSiemensultrasonicsystemswithhelpingthemintheireffortstodeliverqualitywaterefficientlytocityresidents.
Applicationfour:protectingwaterqualityAUKwatercompanyoperatesalargesubmergedmicrofiltrationplantthatservicesanentirecitywithpotablewater:
Theplantcapacityis84megalitresadaySixfiltrationcellsthatremoveparticlesassmallas0.2microns,includingbacteria,algae,andmicroorganisms.
ConditionsTwotypesoflevelmonitoringisrequired:
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monitoringwaterlevelsiscrucialbecausethefltersrequireperiodicbackwashingwithfiltrateandair,andwithchemicalswhenthemaximumtransmembranepressureisreached.Afilterblockagemakesthewaterlevelrise,signalingtheneedforabackwash.monitoringthelevelsofthechemicalsonsite,includingsodiumhypochlorite,sulphuricacid,sodiumbisulphate,andsodiumhydroxide(causticsoda).Reliablelevelmeasurementofthechemicalstoragetanksiscrucialtosuccessfulprocesscontrol,inventorymanagement,andoverflowprevention.Levelsmustalsobemeasuredintheclean-in-placetank(CIP)andthewashwatertank.
Solution
SiemensEchomaxXRS-5ultrasonictransducersareinstalledona“tophat”sectionofeachchemicaltankusingaflangemounting.Thesetransducersarehermeticallysealedinchemicallyresistantenclosuresforreliableoperationinharshenvironmentsorchemicalapplications.ThetransducersarewiredtotheSITRANSLUT400controllerswhichfeedthe4to20mAoutputdirectlyintotheSCADAcontrolsystem.
Operatorscannoweffectivelymonitorthelevelineachofthestoragetanks.Theultrasonicsystemsworkeffectivelywithoutthecomplexityofhigherpricedsolutionsandwithouttheproblemsofcontactingandmechanicaldevices.PatentedSonicIntelligenceadvancedecho-processingtechnologyisbuilt-intoprovidesuperiorreliability.
Benefits
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Non-contactingultrasonictechnologyrequiresalmostnomaintenance,andeliminatesworriesaboutchemicalcompatibility.Thereisnodriftfrommechanicalwear,andtheyarenotaffectedbydensitychangessothereisnoneedforrecalibration.
Theyareeasytoinstallandreplace,withnoneedtodrainthetank.Topmountingeliminatestheneedforisolationvalvesrequiredforside-mountedpressuretransmitters.
FoodindustryLikemanyotherindustries,foodapplicationscanbedividedintotwotypes,storageandprocess.Furthermore,storagecanbedividedintosolidsandliquids.Theseapplicationsarequitedifferentandeachpresentsitsownunique,butnotinsurmountable,challengesforlevelmeasurement.Forexample,a30meter(100ft)silofullofcornstarchisverydifferentthana1.5meter(5ft)stainlesssteelcookervesselfullofspaghettisauce.
SolidsSolidstorageapplicationsarecommon;mostfoodfactoriesneedtostorealargesupplyofrawmaterials.Cerealmillingcompanies,grainshipping,petfood,andbreweriesstorerawgrains(wheat,corn/maize,barley)inlargetallsilosorconcretebunkers;anXPS-30mountedwithanEasyAimerIImeasuringgrainatabrewingcompanyisshownhere.
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Generally,longerrangetransducersareusedastheapplicationsareusuallygreaterthan15meters(50ft)andtheextrapoweroflongrangetransducersovercomesattenuationduetodust(evenondustyapplicationsthatmaybelessthan15meters(50ft)).EasyAimersarerecommendsothetransducersaremountedperpendiculartothematerialsurfacesthatoftenhaveasteepangleofrepose.Onexcessivelydustyapplications,theSITRANSLR560radaristherecommendedinstrument.
Often,manyofthesametypeofvesselsarefoundtogether,acerealmanufacturerstoringalargeinventoryofgrain,forexample,anditisbeneficialtouseamulti-pointsystemliketheten-pointSITRANSLU10tomeasureinventoryoftenvesselswithonecontroller.
SanitaryconnectionFoodprocessingvessels,whetherblendingfruitjuices,cookingsauces,ormixingicecreamflavours,aremuchsmaller,aremadeofstainlesssteel,andarecleanedregularly.Asanitarymountingprocessconnectionisrequiredtoensurecleanliness.TheProbeleveltransmitterandtheXCT-8transducerareavailablewitha4-inchsanitaryclampstyleprocessconnection.
Temperature
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Thetransducerhastobeabletowithstandthecleaningtemperaturesduringthesanitizingprocess.Inmostcasesthetemperatureisintherangeof80°Candamildcausticsolutionissprayedontheinsideofthetank.Iftheleveldevicecannotwithstandthecleaningtemperaturethenitmustberemovedandsanitizedseparately;ifthecleaningtemperatureiswithintherangeofthetransducerthenitcanbecleanedinplace(oftenreferredtoasCIP).
ObstaclesTheinsideofaprocesstankhasnumerousobstaclesthatthelevelsystemhastotakeintoaccount.Theroundballisacleaningballandthesanitizingsolutionissprayedintothetankfromthisball.Whenmountingatransduceronafoodprocessvessel,makesurethatthecleaningballisnotwithinthebeampath.
LiquidsLiquidstoragevesselsarethemoststraightforwardmeasurementsforultrasonicsystemsinthefoodindustry.Thevesselsaregenerallylessthanfivemeters(16.5ft)inheightandhavelittleornoagitation.Theycontainfoodoils(vegetableoils),sugarsyrups(glucose,molasses),cleaningsolutions,water,acids,orfats.
Chemicalindustry
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Applicationswiththechemicalindustryaregenerallylimitedtorawmaterialstoragevesselsorfinishedgoodsstorage–theprocess/reactorvesselsareusuallytoohotortoohighpressureforultrasonictechnology.However,otherancillaryapplicationsinthechemicalindustryrequireultrasonictechnology.Forexample,thesemaybethevesselsstoringlubeoilsforon-sitemachinerymaintenanceorcontainingthepre-treatmentwastewaterbeforeflowingitintothemunicipalwastewatertreatmentsystem.
Storagevesselsaretypicallybulkstorageofliquidchemicals,hydrochloricacid,orsulfuricacid.Storedinvesselstenmeters(33ft)orless,theypresentnochallengestotheultrasonicsystemotherthanrequiringthatthewettedmaterialofthetransducerhousingiscompatiblewiththematerialinthevessel.
Ultrasonicsisalsousedforinventorycontrolonfinishedgoodsstoragesilos.Apopularapplicationisthecontainmentofplasticpelletsinsilos.TheSITRANSLR560isalsoverysuitableforthisapplication.
Thesilosaretallandnarrowandthepelletsarepneumaticallyfed.Aimingisrequiredbecausethepelletshaveaslightangleofreposeandproperaimingincreasesthereceivedechostrengthandprovidesamorereliablesignal.
Applicationone:monitoringfluidlevelofdrillingmudpitsandtanksAsupplierofcontrolandinformationsystemsforhighqualityoilandgasdrillingequipmentwaslookingforatechnologytomonitorfluidlevelsindrillingrigmudpitsortanks.Drillingmudisanessentialcomponentindrilling,andprecisemonitoringofthetotalmudvolumeinarig’sdrillingfluidcirculatingsystemisessentialforsafe,efficientoperation.Varioustechnologies,includingmechanicalfloats,hadfailed.
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Drillingfluidor“mud”ispumpeddownthroughthedrillpipewhereitblowsoutthroughnozzlesinthedrillbit.Themudthenflowsbackuptheholetothesurface,clearingtheholebycarryingtheformationcuttingsalongwithit.Themudlubricatesthedrillpipeandcoolsthedrillbit.Theweightofthemudcolumnpreventsformationfluidsfromenteringthewellbore,preventinga“blowout.”Throughhydrostaticpressure,italsohelpspreventcaving.Anincreaseinfluidlevelsmayindicategas,oil,orotherfluidshaveenteredthewellbore.Ifdrillingfluidlevelsdecrease,circulationisbeinglosttotheformation.Leftunchecked,eithersituationcouldresultinablowout.
Conditions
Mudtanksaregenerallysquareorrectangularinterconnectedsteeltanksusedonoffshoreoilrigstocontainthelargevolumesofdrillingmudflowingthroughthedrillingfluidcirculatingsystem.Onlandrigs,thesetanksarecalledmudpits,athrowbacktothedayswhenearthenpitsweredugtocontaindrillingmud.
SolutionThecompanyinstalledSITRANSProbeLUs.Thenon-contactingultrasonictechnologydoesnotbecomefouledwithmaterialnoraretheremovingpartstowearout,makingitpracticallymaintenancefree.TheProbeLU’sadvancedechoprocessingignoresmovingagitatorbladesandlocksontothetargetedmateriallevelinsteadofobstructions.Withits2-inchNPTconnection,itissimpletomount.Itcanbeinstalledandcalibratedregardlessofmateriallevelswithinavessel.Oneunitworkswithallvesselsizes.Itsrangegoesfromlessthan30centimeters(oneft)tomorethanfivemeters(16ft).ThereisanIntrinsicallySafeversionavailableforFMClassI,Division1applications.
BenefitsThecompanynowhasareliablenon-contactlevelmeasurement,avoidingelectromechanicaldevicesthataresubjecttowearandtear.Thesavingsfromreducedmaintenanceorreplacementcostsaresignificant.
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Bothsafetyanddrillingefficiencyarealsoincreasedasthecompanyprovidesprecisemonitoringofacriticaldrillingvariable.
Applicationtwo:inventorycontrolOneofthelargestby-productsrecoveryfirmsinNorthAmericaneededtomeasurelevelintheirholdingtanks.Thetanks,indoorandoutdoor,holdavarietyofchemicalandoilwasteproductsreadyfortreatment.Governmentenvironmentalregulationsinsuchafacilityarenecessarilyverystringent.
BeforecontactingSiemens,thecompanyusedfloatswithexternalsightboardindicators.Thesemechanismsoftenstuckorfroze,andthemalfunctionsmademeasurementunreliable.Plantpersonnelhadtoconductfrequentvisualcheckstoverifythatthereadingswereaccurate,andtodetectandfixequipmentproblems.Unreliablereadingsalsomadeinventorymanagementproblematic.
Conditions
Outdoortanksfortreatingandstoringsolvents,wasteoils,andcausticsIndoortanksforhazardousprocesswaterMandatoryhigh-levelalarmstoguardagainstspills
SolutionSiemensinstalledacompleteultrasoniclevelmeasurementsystemthatoffersbothcontinuouslevelmonitoringaswellashigh-pointleveldetection.Eachofthe19tanksisequippedwithanEchomaxultrasonictransducer,connectedtooneofthreeSITRANSLU10transceivers.ThesystemusespatentedSonicIntelligencesoftwareforenhancedreliability.LeveldataisfedtoanHMI(Human-MachineInterface)locatedinsidethetestinglab.ASmartLinxinterfacecardconvertsthesignalstoModbusRTUprotocolusedbytheHMI.MaterialleveldataisroutedtothreeSAM-20devicesthatcontrolthehigh-levelalarmindicators,identifythetanks,andconnecttoaPLCthattriggersbothlightandsoundalarmsifhighlevelsoccur.
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BenefitsWithautomated,reliablelevelmeasurementinplace,personnelnolongerneedtowastetimewithfrequentmanualinspections.Non-contactingultrasonictechnologyrequiresalmostnomaintenanceand,withnomorefloatmechanicalproblems,thecompanyhasgreatlyreduceditsmaintenancecosts.
Tanklevelsaremonitoreddirectlyinrealtime.Withexactcontentandstoragedataalwaysavailableattheclickofabutton,thelabcanscheduledeliveriesknowingstoragespaceisavailable.Reliablecontinuousmonitoringallowsforeffectiveschedulingandaccurateinventorycontrol.Thehigh-pointlevelalarmseliminatetheriskofspillage,andhelpenhanceplantsafety.
Otherindustries
Applicationone:ultrasonicsystemforPeterboroughLiftLockThePeterboroughLiftLockNationalHistoricSiteofCanadaisoneof40locksontheTrent-SevernWaterway,anationalhistoriccanaloperatedbyParksCanada.
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Originallybuiltformarinecommerce,thewaterwaystretches386kmfromLakeOntario’sBayofQuintetoGeorgianBay.Today,itisaworld-famoustouristdestinationforrecreationalboatersandisregardedasoneofthefinestinterconnectedsystemsofnavigationintheworld.ThehistoriclockstationsoftheTrent-Severnarecentraltonumeroustownsandvillagesinthewaterwaycorridor.ThePeterboroughLiftLock(150kmnortheastofToronto,Canada)istheworld’shighesthydraulicliftlockandanengineeringmarvelthatattracts160,000visitorsannually.
ConditionsTheLiftLockisamassiveconcretestructuresupportingtwochamberswithramsconnectedinaclosedwaterhydraulicsystemwithacrossovervalve.Operatorsfloodtheupperchamberwithanextra30centimeters(12")ofwater,thenopenthecrossovervalvesothattheheavyupperchamberpushesdown,forcingthelowerchamberup.Boatsinthechambersareliftedorloweredabreathtaking19.8m(65ft)inonlyminutes.Smoothoperationdependsonensuringadifferentialof30centimetersofwater.Theweightdifferentialoftheextrawaterintheupperchamberdrivesthesystemthatraisesandlowersboats.
Throughoutitshistory,theLiftLockhasreliedonmanualwaterlevelmeasurementbut,whentheLiftLockcelebratedits100thanniversaryinJuly2004,itreceivedahightechbirthdaypresentfromSiemens
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Milltronicswhoprovidedanewultrasoniclevelmeasurementsystem.“ThelevelmeasurementsystemisourbirthdaypresenttotheLiftLockasitturns100andourgifttothecommunityasSiemensMilltronicscelebratesits50thanniversarythisyear,”saidDaveBignell,PresidentandCEOofSiemensMilltronicsin2004.“We’reproudtohaveourtechnologyinstalledinthislandmarkstructure.”
SolutionEchomaxXRS-5transducersarenowmountedupstreamanddownstreaminABStubesandenclosedinaluminumpipe.Thisprotectstheultrasonicdevicesfrombeingbumpedordamagedbyboatsinthelock.ThetransducersarewiredintoaMultiRangertransceiverlocatedinthecontroltoweranditprocessesthesignalsandprovidesadigitalreadoutofthewaterlevels.MultiRangerisknownforitsreliable,accuratecontinuouslevelmeasurement.It’salsocompact,whichisimportantinthetightquartersoftheLiftLock’ssmallcontroltower.
Benefits“Thenewsystemhelpsensureproperoperationofthelock,”saysBruceKitchen,WaterControlEngineerfortheTrent-SevernWaterway.“Theultrasoniclevelsystemenablesthelockmastertotellataglancetheelevationsofthewaterupstreamanddownstream.Accuratelymonitoringandcoordinatingtheselevelshelpourstaffachievetheoptimumelevationdifferentialfortheworkingofthisheritagemachine.”
1BillyJoel,“RunningonIce.”TheBridge,1986.2©Copyright2004SiemensMilltronicsProcessInstruments.EchomaxandSITRANSLUT400areregisteredtrademarksofSiemensMilltronicsProcessInstruments.
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ChapterSeven
Bestinclass–theultrasonicproductlineYou’resimplythebest,betterthanalltherest.1
TheSiemensMilltronicslineofsophisticatedultrasonicinstrumentsisdesignedtomeetlevelmeasurementchallengeswithaccuracy,reliability,andlongevity.Theinstrumentsrepresenttheexperiencegatheredfromanexcessofamillionapplications2andreflectthecollecteddedicationandinnovationofoverahalfacenturyofservicebyourenthusiasticandimaginativepeople.
Fromtransistorstochips,frommilliampstoPROFIBUS,frommetaltoPVDF,fromaconvertedgaragetoamultinationalcompany,SiemensMilltronicshaspushedtheboundariesofultrasonictechnologytotakealeadershiproleinthewater/wastewaterindustryonaglobalscale.
Ourultrasonicinstrumentsmeetthechallengeofmanytypesofapplications,andtheSiemensMilltronicscatalogcontainsinstrumentsforthemall.Inthefollowingpages,weofferbriefdescriptionsofbothourlatestandgreatest,aswellasthetriedandtrue.Combined,theyformagroupreadytotakeonthemeasurementchallenge,atanylevel.
SITRANSLUT400SITRANSLUT400isahighaccuracysystemthatexcelsatcontinuouslevelmonitoringandcontrolinliquid,solid,orslurryapplicationsinawiderangeofindustries.
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Threemodelsmakeuptheseries:
SITRANSLUT420LevelControllerSITRANSLUT430Level,Pump,andFlowControllerSITRANSLUT440HighAccuracyOpenChannelMonitor(OCM),whichalsoprovidesafullsuiteofadvancedlevel,volume,andpumpcontrols
Thesecontrollersareaflexiblesolutionforaworldofapplications:water/wastewatermonitoringandpumping,inventorymanagement,crushercontrol,truckload-outs,oranythinginbetween.
Thesystemiseffectiveinwetwells,weirs,andflumeswherebuildupandturbulencearetypicaloperatingconditions.Itcanbecustomizedtomeetyourspecificapplicationneeds—frommeasuringflowrateinanarrowflumetovolumeinaferricchloridestoragebank.
Inadditiontomonitoringflowrateinsewageworks,SITRANSLUT400canmonitorindustrialdischargeandproviderainfall/stormwaterstudies,inflow/infiltrationstudies,andsewersystemevaluations.Theprogrammableheadversusflowcurveaccuratelydefinesflowrateonuniqueornon-standardweirsandflumes.
TheLUT400hasdataloggingandisadjustable,rangingfromonceperminutetoonceadayasitrecordstheaverageflowrateforthattimeperiod.Dailyrecordingincludesmin/maxoftemperatureandflowrates,
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thetimetheyoccurred,andthedailytotal.Advancedfunctionsincludevariableratelogging.Itcanbepre-programmedtologatahigherratewhenneeded.
TheSITRANSLUT400featuresawall,pipe,orDINrailmountedenclosure,housingelectronicswithahermeticallysealed,corrosion-resistantEchomaxtransducer.Componentscanbeseparatedasfaras365meters(1200ft).
Keybenefitsindustry-leadingaccuracyof±1mm(0.04")givesyouconfidenceinyourmeasurementseasytouse–localuserinterfacewithfour-buttonprogramming,menu-drivenparameters,andWizardsupportforkeyapplicationsoptionalsubmergenceshieldstoprotectthetransducerduringflooding.Patenteddetectionsoftwarecandifferentiatebetweenasubmergedconditionandahighlevel.wall,pipe,andDINrailmountingconfigurationswith¼-turnfastenersforquickaccessandhassle-freewiringwithremovableterminalstripsoutputsforalarms,chartrecorders,controllers,andintegrationofexistingsystemsenergysavingfunctionswithbuilt-inreal-timeclockreal-timeclockcontrolallowspumpsetpointstoalteraccordingtothetimeofday.Inatypicalwetwellinstallation,thiscouldmeanpumpingoutthewellbeforepeakrateandthendeferringpumpingduringtheexpensiveperiod.Penaltiesimposedby‘triads’andsimilarelectriccompanyincentivescanbeavoidedautomaticallyinmostinstances.specialcontrolmodetoreducegreaseringsandotherdepositswithapumpvolumesystemusingpatentedalgorithms,theLUT400continuouslymonitorsinflowpriortoapumpstarting,thuscalculatinganaccurateandtimelyinflowrate.Wheneachpumpstarts,itscurrentcapacityiscalculatedandstored,givingaccuratecalculation
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ofpumpedvolumethroughput,unaffectedbyvariableinflow.Theunitdoesnotrequireanydiscreteinputsfromthepumps,oranyformofin-lineflowmonitoring.
Keyapplications
wetwells
flumes/weirs
chemicalstorage
liquidstorage
bulksolidsstorage(gravel,flourbins,grains,cereals)
plasticpellets
crushercontrol
SITRANSProbeLUSITRANSProbeLUisa2-wirelooppoweredultrasonictransmitterforlevel,volume,andflowmonitoringofliquidsinstoragevessels,simpleprocessvessels,andinopenchannels.SITRANSProbeLUisdesignedtomonitorlevelinthewaterandwastewaterindustryandinchemicalstoragevessels.
SITRANSProbeLUfeaturesfield-provenSonicIntelligencesignalprocessingthatincorporatesnewechoprocessingcapabilitiesandthelatestmicro-processorandcommunicationstechnology,providingacontinuouslevelmeasurementrangeofeithersixortwelvemeters(20or40feet),dependingonapplicationrequirements.
SITRANSProbeLUoccupiesauniqueplaceintheultrasoniclandscape.WithitsAutoFalse-EchoSuppression,iteffectivelyeliminatesvesselobstructions,negatinganyinterferencecausedbyextraneousvessel
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clutter.Furthermore,itsadvancedsignal-to-noiseratioallowsforclearechoesandamarket-leadingaccuracyfortransmittersof0.15%ofrange.
OtherapplicationconditionslikechemicalcontentsandprocesstemperaturevariationsareeasilydealtwithbecausethetransducerisavailableasETFE3orPVDF4,andaninternaltemperaturesensorcompensatesfortemperaturechanges.
Keybenefitseasyinstallationandsimplestartupprogrammableusinginfraredintrinsically-safehandheldprogrammer,SIMATICPDM,orHART®CommunicatorcommunicationusingHARTorPROFIBUSPApatentedSonicIntelligencesignalprocessingextremelyhighsignal-to-noiseratioAutoFalse-EchoSuppressionforfixedobstructionavoidance
Keyapplications
Storagevessels Waterindustry
acid
lubeoils
juices
vegetableoils
resins
cleanwatertowers
liquidsugars/cornsyrup
fueloils
charcoalfilters
flocculants
stormwaterholdingtanks
chlorinestorage
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Sulfuricacidstorage Waterstorage
TheProbeTheProbeisashort-rangeintegratedultrasonicleveltransmitter,idealforliquidsandslurriesinopenorclosedvessels.ThetransducerisavailableinPVDF,makingthedevicesuitableforuseinawidevarietyofapplicationsfromwater/wastewatertopizzasauce.Itisidealforthefoodandpharmaceuticalindustriesasitcanbequicklyremovedforcleaning.
TheProbeisaworkhorse,providingreliableleveldatabasedonSonicIntelligenceechoprocessingalgorithms.Ithasanonboardfilterthatdiscriminatesbetweentrueandfalseechoesfromacousticalorelectricalnoisesandagitatorbladesinmotion,aswellastemperaturecompensation.Italsoprovidesdistancereadingsconvertedfordisplay,analogoutput,andrelayactuation.
Keybenefitseasytoinstall,program,andmaintainaccurateandreliable
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transducersavailableinPVDFsanitarymodelavailablepatentedSonicIntelligence®echo-processingintegraltemperaturecompensationuptofivemeter(16.5ft)measurementrange
Keyapplications
chemicalstoragevessels
filterbeds
mudpits
liquidstoragevessels
MultiRanger100/200MultiRangerisaversatile,shorttomedium-rangeultrasonicsingleandmulti-vessellevelcontroller.MultiRangerofferstruedual-pointmonitoring,digitalcommunicationswithbuilt-inModbus®RTUviaRS-485,aswellascompatibilitywithSIMATICPDM,allowingPCconfigurationandsetup.MultiRangercontainsSonicIntelligenceadvancedecho-processingsoftwareforincreasedreadingreliability.
MultiRangerfeaturesthefollowing:
cost-effectivelevelalarming
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ON/OFFandalternatingpumpcontrolupto15meters(50ft)measuringrangemonitorsopenchannelflowconvertslevelreadingtovolumemeasuresdifferentialleveloverabarscreenadvancedrelayalarmingadvancedpumpcontrolfunctions
MultiRangeriscompatiblewithchemical-resistantEchomaxtransducersthatcanbeusedinhostileenvironmentsattemperaturesashighas145°C(293°F).
Keybenefitsdigitalinputforback-upleveloverridefrompointleveldevicecommunicationusingbuilt-inModbusRTUviaRS-485compatiblewithSmartLinxsystemandSIMATICPDMconfigurationsoftwaresingleordual-pointlevelmonitoringAutoFalse-EchoSuppressionforfixedobstructionavoidancedifferentialamplifiertransceiverforcommonmodenoisereductionandimprovedsignal-to-noiseratiowallandpanelmountingoptions
Keyapplications
water/wastewater
fueloil
municipalwaste
acids
woodchips
materialswithhighanglesofrepose
bulksolidsstorage
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MultiRangermonitoringandstoragevessel
TwoMultiRangersmeasuringammoniatanks
MultiRangermeasuringcanallevelsatPeterboroughLiftLock,Ontario,Canada
SITRANSLU10SITRANSLU10isalong-rangelevelmonitoringsystemforliquidsandsolids,offeringten-pointmonitoringinasingleunitforawiderangeofapplicationstoscanliquids,solids,oracombinationofbothcontainedinvesselsofdifferingsizes,shapes,andconfigurations.
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UsingthepatentedSonicIntelligenceecho-processingsoftwaretomeasurelevel,space,distance,volume,oraverage/differential,theLU10providessuperiorreliabilityandaccuratemeasurementinvesselsupto60metersinheight(200ft).Furthermore,transducerscanbemountedupto365meters(1200ft)fromthemonitor.Readingsaredisplayedinuser-selectablelinearengineeringunitsonthebacklitLCD.
KeybenefitsconnectiontoaDCSorPLCusingSiemensMilltronicsSmart-Linx®interfacemodulesforremotetwo-waycommunicationandfullparameteraccess5ten-point,long-rangelevelmonitoringautomaticlevel-to-volumeconversionforstandardorcustomtankshapesDolphinPluscompatibleeasytoinstall,easytoprogramwithremovableinfraredkeypadtenmAoutputsareavailablethroughexternalmoduleSITRANSLUAOtwentyrelaysforalarmsareavailablethroughexternalmoduleSITRANSLUSAM
Keyapplications
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chemicalstorage
liquidstorage
bulksolidsstorage(sugar,flourbins,grains,cereals)
plasticpellets
tankfarms
SITRANSLU10monitoringcoalbunkers
HydroRanger200HydroRanger200isalevelcontrollerforuptosixpumps,andprovidescontrol,differentialcontrol,andopenchannelflowmonitoring.
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Forwaterauthorities,municipalwater,andwastewaterplants,HydroRanger200isaneconomical,low-maintenancesolutiondeliveringcontrolefficiencyandproductivityneededtomeettoday’sexactingstandards.
HydroRanger200usesprovencontinuousultrasonicechorangingtechnologytomonitorwaterandwastewaterofanyconsistencyupto15meters(50ft)indepth.Achievableresolutionis0.1%withaccuracyto0.25%ofrange.Unlikecontactingdevices,HydroRanger200isimmunetoproblemscausedbysuspendedsolids,harshcorrosives,greaseorsiltintheeffluent,reducingdowntime.
Keybenefitssingleordual-pointmonitoringdigitalcommunicationswithbuilt-inModbusRTUviaRS-485SIMATICPDMcompatible,allowingforPCconfigurationandset-up.SonicIntelligenceadvancedecho-processingsoftwareprovidesincreasedreadingreliabilitywallorpanelmountingversions
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sixrelaysonboardasstandardmonitorswetwells,weirs,andflumescompatiblewithSmartLinxsystemanti-greaseringfunctiondifferentialamplifiertransceiverforcommonmodenoiserejectionandimprovedsignal-to-noiseratioMCERTSapprovedforopenchannelflow
Keyapplications
wetwells flumes/weirs barscreencontrol
EchomaxTransducersEchomaxtransducersfireultrasonicpulsesandmeasurethereturnechoestodeterminethedistancefromthetransducertothematerial,whetheritbeawiderangeofliquidsorbulksolidsapplications.Designsareavailablewithdifferentmeasuringranges,processconnections,andambienttemperaturespecifications.Thetransducersaresuitableforuseinmanyapplicationsfromthebenigncleanwaterfacilitiestotheaggressivechemicalplantsordustygrainapplications.
Toselectthepropertransducerfortheapplication,chooseaccordingtoapplicationrequirementsthatincludedistance,temperature,andvesselconfiguration.Thechartbelowindicateswhichtransducersaresuitablefortheapplications.
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XRS-5EchomaxXRS-5ultrasonictransducerprovidesreliable,continuousnon-contactinglevelmonitoringofliquidsandslurriesinnarrowliftstations/wetwells,flumes,weirs,andfilterbeds.Withabeamangleofjust10°andaCSMrubberface,ithasameasuringrangefrom0.3to8meters(1to26ft).Advancedechoprocessingensuresreliabledataeveninconditionswithobstructions,turbulence,andfoam.
Thepre-molded,hermeticallysealedrubberfaceandthePVDFenclosurearedesignedformaximumresistancetomethane,saltwater,caustics,andharshchemicalscommontowastewaterinstallations.With
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anIP68degreeofprotection,thisruggedsensorisfullysubmersibleintheeventoffloodconditions.Iffullsubmergenceispossibleintheapplication,useasubmergenceshieldtomaintainahighlevelreadingoutputduringsubmergedconditions.
Keybenefitsbasicsystemforhigh/lowalarmordualpumpcontrollow-costtransducercompatiblewithafullrangeofSiemensMilltronicstransceiversconnectstoadvancedcontrolsystemswithcommunications,telemetry,andSCADAintegrationcapabilitieschemicallyresistantPVDFcopolymerenclosureandCSMrubberfacemeasuringrange:eightmetersformeasurementofliquidsandslurriesfullysubmersible:IP68degreeofprotectioneasyinstallationwith1"NPTor1"BSPconnection
Monitoringlevelinsewagewetwell
XPS/XCTSeries
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EchomaxXPS/XCTtransducersmeasurelevelinawiderangeofliquidsandsolids.Thetransducerscanbefullyimmersed,areresistanttosteamandcorrosivechemicals,andcanbeinstalledwithoutflanges.
TheXPSseriesoffersversionsforvariousmeasuringrangesupto40meters(130ft),anduptoamaximumtemperatureof95°C(203°F).TwomodelshaveFMClass1,Div.1approvalsforapplicationswithameasuringrangeuptofifteenmeters(50ft).
TheXCTseriescanbeusedinapplicationsathighertemperaturestomeasureleveluptoadistanceoftwelvemeters(40ft)andatamaximumtemperatureof145°C(293°F).
Duringoperation,Echomaxtransducersemitacousticpulsesinanarrowbeam,sotheyareidealtransducersfordustyapplicationsandforthosewithalotofobstructions.
Keybenefitsintegraltemperaturecompensationlowringingeffectreducesblankingdistanceself-cleaningandlowmaintenanceconnectusingonlytwowires
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XPS-15measuringaggregate XPS-30smeasuringminingsilos
chemicallyresistantPVDFenclosureCSA,FM,ATEXandotherglobalapprovalshermeticallysealed
XLTSeriesEchomaxXLTtransducersoperateinawiderangeofbulksolids.UsingaSiemensMilltronicscontroller,theymeasurefrom0.9to60meters(1.8to200ft)inconditiontemperaturesupto150°C(300°F).Abeamangleofjust5°providesaccuratereadingsindeep,narrowtanks.
Withitshighlydevelopedsignalsensitivity,theXLTtransduceroperatesinavarietyofdifficultapplicationsincludinglimestone,cementclinker,andhotstone.Allmodelshaveasealedaluminumfacetowithstandharshestenvironments,andtemperaturevariationsareautomaticallycompensatedforbytheintegraltemperaturesensor.
Keybenefitssealedaluminumfaceintegraltemperaturesensorself-cleaningandlowmaintenancetwo-wireconnection
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easy-to-install1”threadedconnection
ST-HST-Htransducersmeasurelevelinchemicalstorageandliquidtanks.ThenarrowdesignoftheST-Hallowsthetransducertobemountedona2"standpipe.Whenmountedcorrectly,itiscompletelyprotectedfromtheprocess,andcanevenbeusedinharsh,corrosiveenvironments.
Keybenefitscanbemountedona2"standpipeimmunetocorrosiveandharshenvironmentseasytoinstallintegraltemperaturesensor
ST-Hmonitoringasmallammoniatank
Conclusion
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TheSiemensMilltronicsultrasonicinstrumentsoffercustomersathoroughlevelmeasurementsolution,regardlessofapplication.Fromsmallfoodtankstoten-storeysilos,ultrasonicmeasurementisreliableandcost-effective.Itremainsavibrantmeasurementpartner,alongwithagrowingnumberoftechnologiesofferedbySiemens.Oncethecenteroftheindustry,itisnowjoinedbyradar,frequencybasedcapacitance,andTDRtoofferafullcomplementoflevelapplicationsolutions.LevelmeasurementinturnisanintegralcomponentoftheSiemensTotallyIntegratedSolutionsapproachtocustomerrequirementsforprocessinstruments,promotingaunifiedinstrumentationstrategy.Flowmeters,valvepositioners,temperaturetransmitters,pressuretransmitters,andgasanalyzersopenuppossibilitiesforapplicationsolutionsotherthanthoserequiringultrasoniclevelmeasurement.
ThisfullarmamentofinstrumentsandtechnologiesisthestrengthofwhatSiemenscanofferitscustomers,andultrasonicsbeatsstronglyatitscore.Thetechnologyhasbeenhardatworkforseveraldecadesandshowslittlesignoflosingitspopularity.Industrialdevelopmentslikedigitalcommunications,trending,datalogging,andsoftwareconfigurationpackageskeepitcurrentandviable,alongsidethewholeoftheinstrumentationcatalog.
SiemensMilltronicsisdeterminedtodevelopultrasonictechnologytoitsutmostcapacity,andrecentproductsliketheSITRANSLUT400illustratethedeploymentofthetechnologytoitsmaximumbenefitbycombiningthebestoftheoldwiththebestofthenew.
ThesimplicityandprecisionoftheSITRANSLUT400exemplifieshowultrasonictechnologyisstillaviableandvibrantplayerinthelevelmeasurementfield.Whileothertechnologieslikeradar,capacitance,andTDRhavetheirplace,ultrasonicsremainsacost-effectiveworkhorsethatoffersreliableandlongtermservice.Whencoupledwiththelatestadvancesincommunicationsandsoftwareconfiguration,ultrasonicinstrumentationremainsmadeofsternerstuffandasignificantplayeronthelevelmeasurementstage.
1TinaTurner,SimplytheBest.1989(originallydonebyBonnieTyler,1988).
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2SiemensMilltronicshasinstalledoveramilliontotalapplications,combiningalltechnologies,includingultrasonics,radar,capacitance,andmechanicallevelmeasurement.Allofthisexpertiseisincorporatedineveryproductdesignedandproduced.3EthyleneTetrafluoroethylene4PolyvinylideneFlouride5Modulesforpopularindustrialbusescanbefactoryinstalledoraddedlatertomeetchangingneeds.Noexternalgatewayisrequired,reducinghardwareandcablingcosts.
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GlossaryEntriesinthisglossaryarefromtheOperationofMunicipalWastewaterTreatmentPlantstextbook,fromtheIEEEdefinitionbook,andfromthecontributionsprovidedbySiemensMilltronicsProcessInstrumentsproductandapplicationspecialists.
A
Accuracy Theabsolutenearnesstothetruth.Inphysicalmeasurements,itisthedegreeofagreementbetweenthequantitymeasuredandtheactualquantity.
Aeration 1)Thebringingaboutofintimatecontactbetweenairandaliquidbyoneormoreofthefollowingmethods:a)sprayingtheliquidintheairb)bubblingairthroughtheliquidc)agitatingtheliquidtopromotesurfaceabsorptionofair.
2)Thesupplyingoftheairtoconfinedspacesundernappes,downstreamfromgatesinconduits,andsoon,torelievelowpressuresandtoreplenishairentrainedandremovedfromsuchconfinedspacesbyflowingwater.
3)Reliefoftheeffectsofcavitationbyadmittingairtotheaffectedsection.
AerationTank Atankinwhichwastewaterorotherliquidisaerated.
AerobicDigestion
Thebreakdownofsuspendedanddissolvedorganicmatterinthepresenceofdissolvedoxygen.Anextensionoftheactivated-sludgeprocess,wastesludgeisstoredinanaeratedtankwhereaerobicmicro-organismsbreakdownthematerial.
Agitator Mechanicalapparatusformixingoraerating.Adeviceforcreatingturbulence.
Algorithm Aprescribedsetofwell-definedrulesorprocessesforthesolutionofaprobleminafinitenumberofsteps.
Allen-Bradley®RIOorAB®Rio
Allen-BradleyRIOprotocolisanoldprotocolforcommunicatingtoremoteI/O.ItisonlyusedbyAllen-BradleyPLCs.
Alum,Aluminum
Usedasacoagulantinfiltration.Dissolvedinwater,ithydrolysesintoAl(OH)2Sulfateandsulfuricacid(H2SO4).Toprecipitatethehydroxide,asneededfor[Al2(SO4)3•18H2O]coagulation,thewatermustbealkaline.
Ambient Generallyreferstotheprevailingdynamicenvironmentalconditionsinagivenarea.
AmbientTemperature
Thetemperatureofthesurroundingairthatcomesincontactwiththeequipment.
AnaerobicDigestion
Thedegradationofconcentratedwastewatersolids,duringwhichanaerobicbacteriabreakdowntheorganicmaterialintoinertsolids,water,carbondioxide,andmethane.
AnalogSignal Asignalwherethevaluecanbeinarangeofvalues(example:from4mAto20mA).
Antenna Anaerialwhichsendsoutandreceivesasignalinaspecificdirection.Therearefourbasictypesofantennainradarlevelmeasurement.SeeHorn,Parabolic,Rod,andWaveguide.
Attenuation Atermusedtodenoteadecreaseinsignalmagnitudeintransmissionfromonepointtoanother.Attenuationmaybeexpressedasascalarratiooftheinputmagnitudetotheoutputmagnitudeorindecibels.
AutoFalse-Echo
Suppression
AtechniqueusedtoadjustthelevelofaTVTcurvetoavoidthereadingoffalseechoes.(SeeTVT).
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AutoFalse-Echo
SuppressionDistance
DefinestheendpointoftheTVTdistance(SeeTVT).Thisisusedinconjunctionwithautofalse-echosuppression.
AutomaticSampling
Collectingofsamplesofprescribedvolumeoveradefinedtimeperiodbyanapparatusdesignedtooperateremotelywithoutdirectmanualcontrol.Seecompositesample.
AverageFlow Arithmeticaverageofflowsmeasuredatagivenpoint.
AverageVelocity
Theaveragevelocityofastreamflowinginachannelorconduitatagivencrosssectionorinagivenreach.Itisequaltothedischargedividedbythecross-sectionalareaofthesectionortheaveragecross-sectionalareaofthereach.Alsocalledmeanvelocity.
B
BarScreen Ascreencomposedofparallelbars,eitherverticalorinclined,placedinawaterwaytocatchdebris.Thescreeningsarerakedfromiteithermanuallyorautomatically.Alsocalledbarrack,rack.
BeamAngle Anglediametricallysubtendedbytheone-halfpowerlimits(-3dB)ofthesoundbeam.
BeamSpreading
Thedivergenceofabeamasittravelsthroughamedium.(http://www.ndt.net/article/az/ut_idx.htm)
Bias InSiemenslevelequipment,thereisaconfidencebiasvalueaddedindBtotheshortshotconfidencevalue.Thisisforcomparisononly.Itallowstheshortdistancetobechosenoverthelongshotdistancewiththesameconfidencevalue.PresetMilltronicsequipmentto20dB.
Biosolids Theorganicproductofmunicipalwastewatertreatmentthatcanbebeneficiallyused.
Blanking Zoneextendingdownwardfromthetransducerfaceinwhichitisreceived.
Bus Network.
BypassPipe Apipethatismountedperpendiculartoavesselwallandisopentothevesselatthetopandbottom.Thisistypicallyusedonvesselsthathavealotofturbulenceorfoam.Thebypasspipeprovidesacalmliquidsurfacelevelequaltothelevelinthevessel.
C
Cavitation 1)Theaction,resultingfromforcingaflowstreamtochangedirection,inwhichreducedinternalpressurecausesdissolvedgasestoexpand,creatingnegativepressure.Cavitationfrequentlycausespittingofthehydraulicstructureaffected.
2)Theformationofacavitybetweenthedownstreamsurfaceofamovingbody(forexample,thebladeofapropeller)andaliquidnormallyincontactwithit.
3)Describingtheactionofanoperatingcentrifugalpumpwhenitisattemptingtodischargemorewaterthansuctioncanprovide.
CentrifugalPump
Apumpconsistingofanimpellerfixedonarotatingshaftandenclosedinacasinghavinganinletandadischargeconnection.Therotatingimpellercreatespressureintheliquidbythevelocityderivedfromcentrifugalforce.
cfs(cuft./sec.) Therateofflowofamaterialincubicfeetpersecond;usedformeasurementofwater,wastewater,orgas;equals2.832x10-2m3/s.
Chlorination Theapplicationofchlorineorchlorinecompoundstowaterorwastewater,generallyforthepurposeofdisinfection,butfrequentlyforchemicaloxidationandodorcontrol.
Chlorinator Anymeteringdeviceusedtoaddchlorinetowaterorwastewater.
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ChlorineContact
Chamber
Adetentionbasinprovidedtodiffusechlorinethroughwaterorwastewaterandtoprovideadequatecontacttimefordisinfection.Alsocalledachlorinationchamberorchlorinationbasin.
Clarification Anyprocessorcombinationofprocesseswhoseprimarypurposeistoreducetheconcentrationofsuspendedmatterinaliquid;formerlyusedasasynonymforsettlingorsedimentation.Inrecentyears,thelattertermsarepreferablewhendescribingsettlingprocesses.
Clarifier Anylargecircularorrectangularsedimentationtankusedtoremovesettleablesolidsinwaterorwastewater.Aspecialtypeofclarifier,calledanupflowclarifier,usesflotationratherthansedimentationtoremovesolids.
CollectionSystem
Inwastewater,asystemofconduits,generallyundergroundpipes,thatreceivesandconveyssanitarywastewaterorstormwater;inwatersupply,asystemofconduitsorcanalsusedtocaptureawatersupplyandconveyittoacommonpoint.
CombinedSewer
Asewerintendedtoreceivebothwastewaterandstormorsurfacewater.
CONF. CONF.istheconfidenceofsignalvaluegeneratedbythecomputer.Itisbasedonalloftheechoprocessingalgorithms.ItcanbereadinRun(key#8)andprogrammodeP805.
Confidence Describesthequalityofanecho.Theechoconfidenceisbasedonhowwellthetransducerismountedandaimed,andthenoisefloorassociatedwiththeechoprofile.Transceiversdisplayboththeshortandlongechoconfidence.IfanechoisbelowaspecificconfidencethresholditisignoredbytheSonicIntelligence®softwareroutines.
ConfidenceThreshold
Thisistheminimumconfidencevalueofanechotoberecognizedasavalidecho(Parameter805).
D
DaisyChained Connectedinseries,oneaftertheother.Cableisconnectedtothefirstdevice,thencomesoutofthefirstdeviceandisconnectedtotheseconddeviceandsoon.
Damping Termappliedtotheperformanceofaninstrumenttodenotethemannerinwhichthemeasurementsettlestoitssteadyindicationafterachangeinthevalueofthelevel.
dB(decibel) Aunitusedtomeasurethelevelofsound.
Dechlorination Thepartialorcompletereductionofresidualchlorinebyanychemicalorphysicalprocess.Sulfurdioxideisfrequentlyusedforthispurpose.
Defoamer Amaterialhavinglowcompatibilitywithfoamandalowsurfacetension.Defoamersareusedtocontrol,prevent,ordestroyvarioustypesoffoam,themostwidelyusedbeingsiliconedefoamers.Adropletofsiliconedefoamercontactingabubbleoffoamwillcausethebubbletoundergoalocalanddrasticreductioninfilmstrength,therebybreakingthefilm.Unchanged,thedefoamercontinuestocontactotherbubbles,thusbreakingupthefoam.Avaluablepropertyofmostdefoamersistheireffectivenessinextremelylowconcentration.Inadditiontosilicones,defoamersforspecialpurposesarebasedonpolyamides,vegetableoils,andstearicacid.
DeviceDescription
AprogramfilewrittenintheHARTorPROFIBUSDeviceDescriptionLanguage
(DD) (DDL)thatcontainsanelectronicdescriptionofallofadevice’sparametersandfunctionsneededbyahostapplicationtocommunicatewiththedevice.
DeviceNetTM Aprotocoldevelopedbyagroupofcompaniesasanopenstandard,usedtoestablishmaster-slave/client-servercommunicationsbetweenintelligentdevices.ItisbasedontheCAN(ControlAreaNetwork)protocolandisdesignedforconnectingupintelligentdevicessuchaslimitswitchesandphoto-electricsensors.Seewww.odva.org.
Dewater Toextractaportionofthewaterpresentinasludgeorslurry.
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DifferentialFrequency
ThefrequencydeterminedbycalculatingthedifferencebetweenthetransmittedandreceivedfrequencyoftheFMCWradar.
DigestedSludge
Sludgedigestedundereitheraerobicoranaerobicconditionsuntilthevolatilecontenthasbeenreducedtothepointatwhichthesolidsarerelativelynonputrescibleandinoffensive.
Digester Atankorothervesselforthestorageandanaerobicoraerobicdecompositionoforganicmatterpresentinthesludge.SeealsoAerobicDigestion.
DigitalSignal Asignalwherethevaluecaneitherbealogical1oralogical0.
DissolvedOxygen(DO)
Theoxygendissolvedinliquid,usuallyexpressedinmilligramsperlitre(mg/L)orpercentsaturation.
DomesticWastewater
Wastewaterderivedprincipallyfromdwellings,businessbuildings,institutionsandthelink.Itmayormaynotcontaingroundwater,surfacewater,orstormwater.
DopplerBeatFrequency
Thefrequencydeterminedduringtheprocessofbouncingacontinuouswaveradarsignalfromamovingtarget.
“Dumb”AnalogInput/Output
Card
AninputoroutputcardthatdoesnothaveHARTcommunicationprotocolonit.
E
Echo Asignalthathasbeenreflectedwithsufficientmagnitudeanddelaytobeperceivedinsomemannerasasignaldistinctfromthatdirectlytransmitted.Echoesarefrequentlymeasuredindecibelsrelativetothedirectlytransmittedsignal.
EchoConfidence
Therecognitionofthevalidityoftheechoasindustrylevel.Ameasureofechoreliability.
EchoLockWindow
Awindowcenteredonanechoinordertolocateanddisplaytheecho’spositionandtruereading.
EchoMarker Amarkerthatpointstotheprocessedecho.
EchoProcessing
Theprocessbywhichtheradarunitdeterminestheecho.
EchoProfile Agraphicaldisplayofaprocessedecho.
EchoStrength DescribesthestrengthoftheselectedechoindBabove1mVrms.
ElectronicDevice
Description(EDD)
AnothernameforDeviceDescription(DD).SeedefinitionforDeviceDescription.
ElectronicDevice
DescriptorLanguage
(EDDL)
ThelanguagethattheDeviceDescription(DD)iswrittenin.
F
FalseEcho Anechocausedbytheinternalstructureofacontainer.Obstructionsandincorrectunitplacementwillreturnechoesthatdonotreflectlevel.
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FigureofMerit Aquantitycharacterizingperformanceofadevice,system,ormethodinrelationorcomparisontosimilaralternatives.Engineeringfrequentlydefinesfiguresofmeritformaterialsordevicestodeterminetheirrelativeutility.
FloatSwitch Anelectricalswitchoperatedbyafloatinatankorreservoirandusuallycontrollingthemotorofapump.
Flocculant Water-solubleorganicpolyelectrolytesthatareusedaloneorinconjunctionwithinorganiccoagulants,suchasaluminumorironsalts,toagglomeratethesolidspresenttoformlarge,denseflocparticlesthatsettlerapidly.
Flocculatingtank
Atankusedfortheformationofflocbythegentleagitationofliquidsuspensions,withorwithouttheaidofchemicals.
Flotation 1)Separationofsuspendedparticles,oroilandgrease,fromsolutionbynaturallyorartificiallyraisingthemtothesurface,usuallywithair.
2)Thickeningofwasteactivatedsludgebyinjectingairintoitandintroducingthemixtureintoatankwheretheairbuoysthesludgetothesurface.
Flow 1)Themovementofastreamofwaterorotherfluidfromplacetoplace;themovementofsilt,water,sand,orothermaterial.
2)Thefluidthatisinmotion.
3)Thequantityorrateofmovementofafluiddischarge;thetotalquantitycarriedbyastream.
4)Toensureforthordischarge.
5)Theliquidoramountofliquidperunittimepassingagivenpoint.
FlowRate Thevolumeormassofagas,liquid,orsolidsmaterialthatpassesthroughacrosssectionofconduitinagiventime;measuredinsuchunitsaskilogramsperhour(kg/h),cubicmetrespersecond(m3/s),litresperday(L/d),orgallonsperday(gpd).
Flume Aprimarymeasuringdeviceusedtomeasureliquidflow(Forexample,seeParshallflume).
FMCW(Frequencymodulatedcontinuous
wave)
Indirectradarlevelmeasurementtechniqueinwhichtheradardevicemodulatesthefrequencyofthetransmittedsignal.Levelismeasuredbycalculatingthedifferencebetweenthetransmittedsignalandthereturnsignal.
Frequency Thenumberofperiodsoccurringperunittime.Frequencymaybestatedincyclespersecond.
G
Gain Measuresoftheabilityofacircuittoincreasethepoweroramplitudeofasignalfromtheinputtotheoutput.
GritChamber Adetentionchamberoranenlargementofasewerdesignedtoreducethevelocityofflowoftheliquidtopermittheseparationofmineral(grit)fromorganicsolidsbydifferentialsedimentation.
H
HART® HighwayAddressableRemoteTransducer.Anopencommunicationprotocolusedtoaddressfieldinstruments.HARTisaregisteredtrademarkofHARTCommunicationFoundation.Seewww.hartcomm.orgformoredetails.
Head Theheightofthefreesurfaceoffluidaboveanypointinahydraulicsystem;ameasureofthepressureorforceexertedbythefluid.
HeadLevel Thetermusedforthelevelofwaterinaweir.
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I
IndustrialWastewater
Wastewaterderivedfromindustrialsourcesorprocesses.
Influent Water,wastewater,orotherliquidflowingintoareservoir,basin,treatmentplant,ortreatmentprocess
Inlet 1)Asurfaceconnectiontoadrainpipe.
2)Astructureathediversionendofaconduit.
3)Theupstreamendofanystructurethroughwhichwatermayflow.
4)Aformofconnectionbetweenthesurfaceofthegroundandadrainorsewerfortheadmissionofsurfaceorstormwater.
5)Anintake.
IntermediateFrequency
Afrequencytowhichasignalwaveisshiftedlocallyasanintermediatestepintransmissionorreception.
IntrinsicallySafe
IntrinsicSafetyisaprotectionmethod,usedforcertifyingelectricalequipmenttobeusedexplosiveatmospheres(flammablegasorcombustibledust),inwhichanysparkorthermaleffectproducedbytheequipmentisnotcapableofcausingignition.
J,K,L
LaminarFlow Non-turbulentflow.
LongShot Describesalengthofmeasurementbeyond1m(3ft.).
M
Manningformula
Aformulaforopen-channelflowpublishedbyRobertManningin1890.
Margin Thedifferencecalculatedbetweentheconfidenceandthethreshold.
MasterDevice Adeviceinamaster-slavesystemthatinitiatesalltransactionsandcommands(e.g.centralcontroller).
MasterSlaveProtocol
Communicationsysteminwhichalltransactionsareinitiatedbyamasterdeviceandarereceivedandrespondedtobyaslavedevice.
Measurement Eachtimeatransmitpulseorsetnumberofpulsesissenttothetransducer.
Microwaves Thetermfortheelectomagneticfrequenciesoccupyingtheportionoftheradiofrequencyspectrumabove1GHz.
MicrowaveFrequency
Microwaveradarbeamsrangeinfrequencybetween5.8GHzand26GHz.
Modbus® Aprotocolusedtoestablishmaster-slave/client-servercommunicationbetweenintelligentdevices.Itisatrulyopen,defactostandard,andthemostwidelyusednetworkprotocolintheindustrialmanufacturingenvironment.ModbusisaregisteredtrademarkofSchneiderElectric.Seewww.modbus.org.
Modem Adevicethattransmitsdataoveraphonelinebymodulatingthedigitalsignalsintoanalogsignalsatonesideandtransmittingthatanalogsignaloveraphoneline.Atthereceivingend,itdemodulatestheanalogsignalbackintoadigitalsignal.
MotorController
Aspecializedtypeofcontrollerwhosetypicalfunctionsperformedbyamotorcontrollerinclude:starting,accelerating,stopping,reversing,andprotectingmotors.
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Multi-master Morethanonemasterdeviceonthebus.
MultipleEchoes
Echoescausedbytheparaboliceffectofradartransmissioninsideadishedtopvesselorahorizontalcylindricaltank.Thesetypesofechoessurpassthereallevelwithinatank.
Multi-slave Morethanoneslavedeviceonthebus.
N
Nappe Thesheetorcurtainofwateroverflowingaweirordam.Whenfreelyoverflowinganygivenstructure,ithasawell-definedupperandlowersurface.
NearBlanking Ablindzonethatiscreatedinfrontofatransducerorantennatoblocktheunitfromreadingfalseechoes.
Nozzle Alengthofpipemountedontoavesselthatsupportstheflange.
O
OpenChannel Anynaturalorartificialwaterconduitinwhichwaterflowswithafreesurface.
OpenChannelFlow
Flowofafluidwithitssurfaceexposedtotheatmosphere.Theconduitmaybeanopenchanneloraclosedconduitflowingpartlyfull.
P
Parameters Inprogramming,variablesthataregivenconstantvaluesforspecificpurposesorprocesses.
ParshallFlume AcalibrateddevicedevelopedbyRalphParshallformeasuringtheflowofliquidinanopenconduitconsistingessentiallyofacontractinglength,athroat,andanexpandinglength.AtthethroatisasilloverwhichtheflowpassesatBelanger’scriticaldepth.Theupperandlowerheadsareeachmeasuredatadefinitedistancefromthesill.Thelowerheadneednotbemeasuredunlessthesillissubmergedmorethan67%.
Peer-to-PeerProtocol
Communicationsysteminwhichalltransactionscanbeinitiatedbyanydeviceonthenetworktoanyotherdeviceonthenetwork.
Primaryeffluent
Theliquidportionofwastewaterleavingtheprimarytreatmentprocess.
PrimarySedimentation
Tank
Thefirstsettlingtankfortheremovalofsettleablesolidsthroughwhichwastewaterispassedinatreatmentworks.Sometimescalledaprimaryclarifier.
PrimarySludge Sludgeobtainedfromaprimarysedimentationtank.
PrimaryTreatment
1)Thefirstmajortreatmentinawastewatertreatmentfacility,usedforthepurposeofsedimentation.
2)Theremovalofasubstantialamountofsuspendedmatter,butlittleornocolloidalanddissolvedmatter.
3)Wastewatertreatmentprocessesusuallyconsistingofclarificationwithorwithoutchemicaltreatmenttoaccomplishsolid-liquidseparation.
ProcessDeviceManager(PDM)
AprogrammadebySiemensthatisusedtoconfigure,maintain,andtrouble-shootfielddevicesonHARTandPROFIBUSnetworks.
ProcessTemperature
Thetemperatureofthegas,vapour,orairlocatedabovethematerialbeingprocessed.
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PROFIBUS Acommunicationprotocolusedtoaddressfieldinstruments.DifferenttypesincludeFMS(FieldbusMessagingSystem),DP(DecentralizedPeriphery),PA(ProcessAutomation).Seewww.profibus.comformoredetails.
Profile See“EchoProfile.”
ProgrammableLogic
Controller(PLC)
Anindustrialcomputerthatacceptsinputsfromtherealworld,runsaprogram,thengeneratesoutputstotherealworldthatisusedtocontrolprocesses.
Protocol Asetofrulesthatgoverntheexchangeofinformationbetweentwoormoredevices.
PumpingStation
1)Afacilityhousingrelativelylargepumpsandtheirappurtenances.Pumphousesistheusualtermforsheltersforsmallwaterpumps.
2)Afacilitycontainingliftpumpstofacilitatewastewatercollectionorreclaimedwaterdistribution.
PTFE AnacronymforPolytetrafluoroethylene.
Q,R
Radar RadarisanacronymforRAdioDetectionAndRanging.Adevicethatradiateselectromagneticwavesandusesthereflectionofsuchwavesfromdistantobjectstodeterminetheirexistenceorposition.
Range Distancebetweenatransmitterandatarget.
RangeExtension
Thedistancebelowthezeropercentoremptypointinavessel.
Relay Anelectricaldevicethatisdesignedtointerpretinputconditionsinaprescribedmannerandafteraspecifiedconditionsaremet,torespondtocauseelectricaloperationorsimilarabruptchangeinassociatedcontrolcircuits.Themostcommonformofrelayusesacoilandsetofcontacts.Whencurrentflowsinthecoil,contactsareopenedorclosed,dependingontheirarrangement.Relaysaresaidtobenormallyclosed.
Ringing Theinherentnatureofthetransducertocontinuevibratingafterthetransmitpulsehasceased.SeeBlanking.
S
Sampler Adeviceusedwithorwithoutflowmeasurementtoobtainaportionofliquidforanalyticalpurposes.Maybedesignedfortakingsinglesamples(grab),compositesamples,continuoussamples,orperiodicsamples.
Scum 1)Theextraneousorforeignmatterthatrisestothesurfaceofaliquidandformsalayerorfilmthere.
2)Aresiduedepositedonacontainerorchannelatthewatersurface.
3)Amassofsolidmatterthatfloatsonthesurface.
SecondaryEffluent
1)Theliquidportionofwastewaterleavingsecondarytreatment.
2)Aneffluentthat,withsomeexceptions,containsnotmorethan30mg/Leach(ona30-dayaveragebasis)ofBOD5andsuspendedsolids.
SecondarySedimentation
Tank
Asettlingtankfollowingsecondarytreatmentdesignedtoremovebygravitypartofthesuspendedmatter.Alsocalledasecondaryclarifier.
SecondaryTreatment
1)Generally,aleveloftreatmentthatproducessecondaryeffluent.
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2)Sometimesusedinterchangeablywiththeconceptofbiologicalwastewatertreatment,particularlytheactivated-sludgeprocess.Commonlyappliedtotreatmentthatconsistschieflyofclarificationfollowedbyabiologicalprocesswithseparatesludgecollectionandhandling.
Sedimentation 1)Theprocessofsubsidenceanddecompositionofsuspendedmatterorotherliquidsbygravity.Itisusuallyaccomplishedbyreducingthevelocityoftheliquidbelowthepointatwhichitcantransportthesuspendedmaterial.Alsocalledsettling.Itmaybeenhancedbycoagulationandflocculation.
2)Solid-liquidseparationresultingfromtheapplicationofanexternalforce,usuallysettlinginaclarifierundertheforceofgravity.Itcanbevariouslyclassedasdiscrete,flocculent,hindered,andzonesedimentation.
SedimentationTank
Abasinortankinwhichwastewatercontainingsettleablesolidsisretainedforremovalofthesuspendedmatterbygravity.Alsocalledasedimentationbasin,settlingbasin,settlingtank,orclarifier.
SettlingTank Atankorbasininwhichwater,wastewater,orotherliquidscontainingsettleablesolidsareretainedforasufficienttime,andinwhichthevelocityofflowissufficientlylowtoremovebygravityapartofthesuspendedmatter.
ShortShot Describesalengthofmeasurementwithin1m(3ft.).
Shot Onetransmitpulseormeasurement.
SlaveDevice Adevice(e.g.transmitterorvalve)inamaster-slavesystemthatreceivescommandsfromamasterdevice;aslavedevicecannotinitiateatransaction.
Sludge 1)Theaccumulatedsolidsseparatedfromliquidsduringthetreatmentprocessthathavenotundergoneastabilizationprocess.
2)Theremovedmaterialresultingfromchemicaltreatment,coagulation,flocculation,sedimentation,flotation,orbiologicaloxidationofwaterorwastewater.
3)Anysolidmaterialcontaininglargeamountsofentrainedwatercollectedduringwaterorwastewatertreatment.
SludgeBlanket Accumulationofsludgehydrodynamicallysuspendedwithinandenclosedbodyofwaterorwastewater.
Slurry Athickwaterymudoranysubstanceresemblingit,suchaslimeslurry.
SmartProcessInstrumentation
Microprocessor-basedinstrumentationthatcanbeprogrammed.Ithasmemory,andiscapableofperformingcalculationsandself-diagnosticsandreportingfaults,andcanbecommunicatedwithfromaremotelocation.
Stillpipe Apipethatismountedinsideavesselperpendiculartothevesselwall,andisopentothevesselatthebottom.Thisistypicallyusedonvesselsthathavealotofturbulenceorfoam.Thestillpipeprovidesacalmliquidsurfaceequaltothelevelinthevessel.
Submergence 1)Theconditionofaweirwhentheelevationofthewatersurfaceonthedownstreamsideisequaltoorhigherthanthatoftheweircrest.
2)Theratio,expressedasapercentage,oftheheightofthewatersurfacedownstreamfromaweirabovetheweircresttotheheightofthewatersurfaceupstreamabovetheweircrest.Thedistancesupstreamordownstreamfromthecrestatwhichsuchelevationsaremeasuredareimportant,buthavenotbeenstandardized.
3)Inwaterpowerengineering,theratiooftailwaterelevationtotheheadwaterelevationwhenbotharehigherthanthecrest.Theoverflowcrestofthestructureisthedatumofreference.Thedistancesupstreamordownstreamfromthecrestatwhichheadwaterandtailwaterelevationsaremeasuredareimportant,buthavenotbeenstandardized.
4)Thedepthoffloodingoverapumpsuctioninlet.
SuppressedWeir
Aweirwithoneorbothsidesflushwiththechannelapproach.Thispreventscontractionofthenappeadjacenttotheflushside.Thesuppressionmayoccurononeendorbothends.
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T
TimedRelay Arelaywhoseopeningorclosingisdelayedforaspecifiedamountoftimeaftertheoccurrenceofatriggerevent.
Totalizer Adeviceusedtocountpulses.Typicallyusedtocountthenumberofrelayclosures.
TotallyIntegrated
Automation(TIA)
ASiemensconceptforhavingallcomponentsofanautomationsystemtiedtogetherusingadvancedcommunicationprotocolsandtotallyintegratedtogether.
Turbidity 1)Aconditioninwaterorwastewatercausedbythepresenceofsuspendedmatterandresultinginthescatteringandabsorptionoflight.
2)Anysuspendedsolidsimpartingavisiblehazeorcloudinesstowaterthatcanberemovedbyfiltration.
3)Ananalyticalquantityusuallyreportedinturbidityunitsdeterminedbymeasurementsoflightscattering.
Turbulence 1)Thefluidpropertythatischaracterizedbyirregularvariationinthespeedanddirectionofmovementofindividualparticlesorelementsoftheflow.
2)Astateofflowofwaterinwhichthewaterisagitatedbycrosscurrentsandeddies,asopposedtolaminar,streamline,orviscousflow.
TVT(timevarying
threshold)
Atime-varyingcurvethatdeterminesthethresholdlevelatwhichtheechoisprocessed.
U,V,W,X,Y,Z
Ullage Amountofspaceleftinavesselinorderforittobefilled.Asopposedtothevolumeofmaterialinavessel.
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WorksCitedBoyes,Wait.“TheChangingStateoftheArtofLevelmeasurement,”FlowControlMagazine,February1999.
Carlson,Al.“OpenChannelFlowmetering,”June1998.
Carlson,Al.“TheRightTransducerfortheJob,”June1999.
Crabtree,Mick.PressureandLevel,CrownPublications(Pty)Ltd.,1998,pg39–48.
Duncan,Doug.“UltrasonicSensors:Nowanevenbetterchoiceforsolidmaterialleveldetection,”Instrumentation&ControlSystems.November1998.
Evans,Jack.“Ultrasonicscomesofageforsolidsandliquids,”inTech.April1997,pg39–42.
Felton,Bob.“Levelmeasurement:AncientChore,moderntools,”InTech,August2001.
Grant,DouglasM.andBrianD.Dawson.IscoOpenChannelFlowMeasurementHandbook.FifthEdition,ISCOInc.,1997.
Hughes,ThomasA.LevelMeasurementandControl,ISAPress,2002.
Li,Gordon.“AdvancedCircuitryImprovesSignal-to-NoiseRatio,”2003.
Massa,Frank.“Somepersonalrecollectionsofearlyexperiencesonthenewfrontierofelectroacousticsduringthelate1920sandearly1930s,”TheJournaloftheAcousticalSocietyofAmerica.April1985.pg1296–1302.
MassaProductsCorp.“FundamentalsofElectroacoustics,”
www.massa.com/fundamentals.htm
Milligan,Stephen.“HowtoInstallUltrasonicTransducers,”2003.
Sirlty,PaulA.“AnIntroductiontoUltrasonicSensing,”Sensors,Nov.1989.
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Copyright©SiemensMilltronicsProcessInstruments2012.
Allrightsreserved.
Noportionofthisbookmaybereproducedinanyformwithoutpermissioninwritingfromthepublisher.
FirstEdition,2006.SecondEdition,2008.ThirdEdition,2012
ISBN-10:ISBN0-9782495-0-X
ISBN-13:ISBN978-0-9782495-0-2
PrintedandboundinCanadaforSiemensMilltronicsProcessInstrumentsPeterborough,ONK9J7B2
www.siemens.com/processautomation
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