电耳说明书21.docx

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