电耳说明书21.docx
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电耳说明书21
ELECTRICEAR
INSTALLATIONCOMMISSIONNING&MAINTENANCEMANUAL
SUMMARY
1-PURPOSE3
2-MILLLEVELMEASUREMENTPRINCIPLES4
2.1-Foreword4
2.2-Comparisonbetweenthedifferentlevelmethods5
2.3-Noisecharacteristicsofmills7
2.5- ApplicationoftheM.S.C.2000ontubemillsindirectfiring8
3-DESCRIPTIONOFTHEEOUIPMENT9
3.1-Generalpresentation9
3.2-Microphone11
3.3-Audiosignalconverter错误!
未定义书签。
3.4-Powersupply12
3.5-Display13
4-INSTALLATIONOFTHEEQUIPMENT13
4.1-Microphone13
4.2-Transmitter14
5-PRIMARYTESTSBEFORESTARTUP14
5.1-Installationcheck14
5.2-Audiosignalconverter15
6-STARTUPCALLBRATION15
6.1-Calibrationofthebooster15
6.2-Calibrationofthetransmitter15
7-NOISECORRECTIONMEASUREMENT16
8-SETTINGOFTHECONTROLLOOP17
9-PERFORMANCETESTS18
10-ANNEXESTOTHEMANUAL18
1-PURPOSE
Thepurposeofthispresentmanualistodescribetheequipment,Installationandcommissioningprocedureofthemillnoiselevelsystemcalled“ELECTRICEAR”.ThissystemcansubstituteothermilllevelequipmentssuchasdeeptubesPsystemormillmotorpowersystem.
2-MILLLEVELMEASUREMENTPRINCIPLES
2.1-Foreword
Aprerequisiteforthecorrectuseofhorizontalmills(tubemills),fordirectfiringofpulverizedcoal,isthattheamountofcoalinsidethemillmustbecontrolledtoa"constantlevel"inordertomaintaintheair/coalratioasconstantaspossibleandalsotobesurethatthegrindingisoptimum.
Fromthebeginingofuseofthiskindofmillseveralsystemshavebeenenvisaged(someofthem"accrobatic"),butinfactthreetypesofmeasurementaretodayundercompetition.
Theyare:
-themeasureofthemillmotorpowerconsumption
-theprobemethod(deeptubessystem)
-themeasureofthenoiseemittedbythemill.
Eachofthesemeasureshasitsownadvantagesanditisveryinterrestingtocomparethedifferentsolutionsinordertoadoptthebestone.Infinalwehavetokeepinmindthattheanswerwillbegivenbythemillgrindingbehaviour.
Justlookingfromthe"outside"wecanmakeafirstclassification:
-Thepowermeasurementisnotdirectlyincontactwiththeprocess,butafailureinthetransmitterneedsanywaytostopthemotor(thusthemill).Thepowerisinfactanindirectmeasuremethod.
-Theprobemethodistheonlydirectmethodofmeasurementofwhathappensinthemill;neverthelessthemeasureisdirectlyincontactwithanhostileprocess(coaldust,turbulentatmosphere,cascadingofsteelballs.probespluggingrisks...).
-Thenoisemeasuremethodisnotincontactatallwiththeprocessbutitisalso,likethepower,anindirectmethod.Itsqhallbenoticedthatistheonlymethodwherethemaintenanceisveryeasyanddoesnotrequirethegindingcircuittobeshutdown.
STEININDUSTRIEusingatfirsttheProbemethodhasnowdeveloppedasophisticatednoisemeasurementsystemandtheassociatedlevelcontrolbasedonthe"electricear",thegenerationofthiskingofequipmentiscalledtheM.S.C.2000(MillSoundComputer).Wewillseefurtherthatthismeasurementcanalsobeusedtoassesswhetheramillis"optimized"ornot.
2.2-Comparisonbetweenthedifferentlevelmethods
Tobetterevaluatetheadvantagesofthenoisemeasurementsystem,itiswelltounderstandhowthegrindingtakesplaceandtocomparetheevolutionofthedifferenttypesofmeasuresignalsaccordingtothedifferentphenomenawhichcanhappeninamill.
Startingfromanemptymillandfillingupprogressivelythethreesignalsofpower,noiseanddpgivenbytheprobeslevelsystemcanbeseeninthefigures3,4and5.
Figure3
Curvepowerversuscoalamount(L)
Figure4
Curvenoiseversuscoalamount(L)
Figure5
CurvedeltaPversuscoalamount(L)
Itispossibletoexplainthereasonoftheshapeofeachcurvegiveninthefigures3to5bylookingofwhathappensinsidethemillandmainlybetweentheballs.Thefigure6givesfourmajorstepsinthemillfillingup.
SETP1
Thereisnocoal.Ballsaregrindingbetween
eachother.Thereisaballexcessivewear.
Rawcoalisintroducedandbegingstofillthe
freespacebetweentheballs.Thedensityof
themixtureball+coalincreases(Power
SETP2
beginstoincreaseandnoisesmoothes).
Grindingisstillnotefficientandballwearis
important.
Thereisanoptimalcoalfillingandthe
grindingisgoodbyattrition.Coalactsasa
SETP3
lubricantbetweentheballssmoothes
significantlythenoise,powerbeginsto
decreaseasthegrindingmediumgravity
centregetsclosertotherotatingaxis.
Thereisnowtoomuchcoal,ballsarenow
SETP4
"floating"inthecoal.Attritionandgrinding
areverybad,ontheotherhandthewearof
ballsisverylow.
Figure6 - Phasesofmillfillingup
Figure7 - Evolutionofpower,noiseanddpaccordingtothestepsofmillfillingup
2.3-Noisecharacteristicsofmills
Thenoiseevolutioncurveinfigure4givesthenoiseemittedbythemillversusthecoalamountitcontains.Incomparisonwiththedeeptubesignalitcanbeseenthedifferenceofsensitivitybetweenthetwosignals.
Whenlookingtothenoisedetectedwhenthemillleveliscontrolledbyanothermeansi.e.thedeeptube,itcanbeseenthatthenoisechangeswhenload(milloutput)changes.
Thisisduetothefactthatthenoisedependsnotonlyofthecoalamountinthemillbutalsooftheaveragegranulometryinthemillwhichchangesaccordingtotheresidenttimeinthemill.
Thefigure9showsthatamillcanbeconsideredasavesselwitha
Figure9-Residenttimedemonstration
rawcoalinputandpulverizedcoaloutput.Forexampletakingamillofratedoutputof100t/hinwhichwehaveabout17tonsofcoaltheresidenttimeatfullload(fulloutput)is:
17/100=0.17hthatisabout10minutes
Athalfloadtheresidenttimeisthedouble,itmeansthatthecoalhasmoretimetobegrindedandthereforethegranulometryislowerthanathighload.
Thechangeofgranulometryhasaninfluenceonthenoiseandcanbesummarizedasfollows:
*whenathighloadstheparticulesofcoalarebiggerandthenoiseissmoothed,
*atlowloadthecoalparticulesaresmallerandtheshocksbetweentheballsgivemorenoise.
Thefigure10givesaroughideaoftheevolutionofthenoisewhenthemillloadchanges.
Figure10-Dependanceofnoiseversusmilloutput
Asademonstrationofthisinfluenceofthemilloutputonthenoisethefigure11herebelowgivesachartrecordshowingthisphenomenon.
Figure11-Recordingnoiseversusmilloutput
2.5- ApplicationoftheM.S.C.2000ontubemillsindirectfiring
Thecontrolofthe"level"onamillindirectfiringusingthenoiseemittedbythemillisveryinterestingasitisasolutiongivingmoreflexibilitythantheothermeanssuchasdporpower(seeparagraph2.2).
Assaidbeforethenoisesignalisrepresentativeofthecoalamountinthemillbutitisalsoinfluencedbythemilloutput.Thefigure13showsthefamilyofcurvesofthenoisesignalversusthecoalinthemilltheparameterbeingthemilloutput.
Figure13-Noisecharacteristiccurves
l
Inordertocontrolcorrectlythecoal1evelinthemillitisthennecessarytocompensatethenoiseinfonctionofthemillload.Forthispurposethegoodparametertobeusedistotaketheprimaryairflowthroughthemillwhichrepresentsthecoaloutput.
3-DESCRIPTIONOFTHEEOUIPMENT
3.1-Generalpresentation
Toobtainanaudiosignalwhichisrepresentativeofthecoalamountinthemillandwhichremainsreproducibleandaccurate,STEININDUSTRIEhasdeveloppedanaudiosignalconverterwhosebasicstructureisgiveninfigurel1.Theaudiosignalfromthemicrophoneisprocessedasfollows:
-Initialwideaudiobandwidthpreamplificationtobringthemillivoltscomingfromthemicrophoneintoanacceptableleveltooperatethefilter.
-Filtrationbyaswitched-capacitynumericalfilterwherecentralfrequencyandbandwidthareadjustable.Thesettingofthisfilterismadeinlaboratoryanddoesnotneedtobetouchedduringmillcommissioning.
-Finalamplificationandimpedanceadaptationbeforerectifying.
-RectifyingofthesignalfromACsoniccompoundsintoDCsmoothedsignaldb.
-Linearizationofthesignaltoincreasethesensitivityofthesignalintheoperatingcontrolarea.
-Apotentiometercanadjusttheoutputcurrentreading20mAwhenthereisnocoal.
-Adatasamplingcircuitcanbeusedformakinganalogysignaldigitalization.
-Amicroprocessorcananalyzeanddealwiththesoundsignal.
-Ancurrentsignalgeneratorof4–20mAcanbeusedfordisplayingthecoalamountofmill.
TheM.S.C.2000noisetransmitterispresentedinstandardracks19inches,includingthefollowingmodules:
-ApowersupplyacceptingACv01tages220V±20%(50or60Hz).
-Theaudiosignalconverter
-AnLCDdigitaldisplaygivingtheoutputsignalfromtheconverterortheisolatingmodulewithaswitchallowingadisplayeitherdirectlyinmAorinpercent.
Thefigure12herebelowgivesthepresentationoftherackfront.
Suchequipmentaspresenteddeliversasignalsuitableformanyapplicationssuchas:
-Themonitoringonly:
inthiscasethesignalisusedforrecording,forindicationandforalarmthresholdrelays(veryhighlevelorverylowlevel)
-Thecontrolofthelevelinaconstantflowmill:
thisisthecaseofapulverizingplantforindirectfiringorotherpurposes.Inthatcasethesignaldeliveredbythenoisetransmitterisuseddirectlyinaconventionnalcontroller
-Thecontrolofthelevelinatubemillindirectfiringbyusingthenoisesignalavailablefromth