servo valve calibration.docx

servo valve calibration.docx

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servovalvecalibration

servovalvecalibration

Postedby ESKAY

 on19May,2013-4:

16pm

DearCSAandAll,

Iwouldliketocalibratethedistillatefuel65FPservo,throthe"calibrate"modefacilityinMk6system.[GEFr5Mk6control].Unlike,theGasservovalvecalibration,wherewesettheservovalveoutputvaluesthro"manual"setpointandthencomparetheerrorwiththeLVDTfeedback.Howcanwemakeuseofthisprocedureforthe65FPservo,wherewehaveNOLVDTforthefeedbackandthereisNOstem（scalemarking）onthe65FPservotoseethemovementoftheservo?

WehaveonlyFlowdividerasthefeedbackandourturbinedon'thavetheauxiliarypumpandneedtoruntheturbinein"crank"modeforthecalibrationwithinlimitedtime.Pleaseguidemefortheproperandeffectivecalibrationofthedist.fuelsystem.

Thanks..

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PostedbyBobJohnstonon19May,2013-7:

09pm

It'sdifficultIknow,reallytheonlywaytocheckisdoa"dummyfire"withnosparkplugsandquicklycheckthefuelflowatacoupleofManualFSRpoints.Runatrendofthemajorcriteriaatthesametimeandyoucanthenreview.

GivethemachineabitofaCrankaftertestingandbeforefiringtogetridoftheexcessfuel.

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Postedby CSA

 on20May,2013-6:

23am

ESKAY,

Thisideaof"calibratingservo-operateddevices"onGE-designheavydutygasturbinesisa HUGE myth.It'ssimply notpossible tocalibrateanythingotherthanLVDTfeedback.EvenwhenGEfieldpersonnelsaytheyare"calibrating"theSRVortheGCVortheIGVsortheLFBV（LiquidFuelBypassValvetheyare NOT. TheyareonlycalibratingtheLVDTfeedbackfromthosedevices.Thereiszero effectontheservoortheservo-valveoutputstabilityafter"calibration";theonlythingthatchangesistheLVDTfeedbackcalibration.

Fullstop.

Period.

It'ssimplyimpossibletosendapositionreferencetoadevicethathasnopositionfeedbackandexpectthatdevicetogotosomeposition,orwhattheSpeedtronicbelievesthatpositiontobeifthereisnopositionfeedback.

So,don'tbelieveeverythingyouhearpeoplesaywhoseemtobeknowledgeableaboutGESpeedtroniccontrolsystems,becausetheyquiteoftendon'tsaywhattheymean,andtheyquiteoftendon'tknowwhattheyaresaying.Especiallywhentheyaretalkingaboutelectro-hydraulicservo-valves.

Ifyouarehavingproblem（s）withcontrolofliquidfuel,telluswhattheproblem（s）are,whatyouhavedonetotroubleshoottheproblem,andwhattheresultsofyourtroubleshootingwere.Thenwecantrytohelpyouwithresolvingyourproblem,orwithunderstandingtheliquidfuelsystemanditscomponents.

AsBobJohnstonsays,ifyoudon'thaveanACmotor-drivenAuxiliaryHydraulicPumpthenyouaregoingtohavetocranktheunittoestablishhydraulicpressure--justaswithanyotherhydraulically-operateddevice.

TherehavebeensomeverycreativepeoplewhohaveusedtheDCmotor-drivenHydraulicRatchetPumptoprovidehydraulicpressuretothehydraulicsystem,butittakessometemporarytubingre-work.AndIdon'tbelievetheHydraulicRatchetPumpoutputisfilteredverywellsotherecanbecontaminationofservosand/orservofiltersifthat'susedforthatpurposewithoutproperfiltration.Also,thepressureoftheHydraulicRatchetPumpisnotadjustableandislikelynotthesameastheMainHydraulicPump,noristheflow-rateoutputoftheHydraulicRatchetPumpanywherenearthatoftheMainHydraulicPump.Itworksforacrudecheckofsystemoperation,butforanythingmorethanthatitisnecessarytocranktheunittogetpressurefromtheAccessoryGear-drivenMainHydraulicPumpifthereisnoACmotor-drivenAuxiliaryHydraulicPump.

TheliquidfuelcontrolvalvesofmostGE-designheavydutygasturbinesaredesignedtocontrolflow-rateusingfeedbackfromtheliquidfuelflowdivider.Theflowcontrolvalveispositionedatwhateveropening/closingitneedstobeatinordertomakethescaledfeedbackfromthespeedpick-upsontheliquidfuelflowdividerequaltotheliquidfuelflow-ratereference（foraMarkVI,thatsignalnameisusuallyFQR,andtheflow-ratefeedbackisusuallyFQLorFQLMorFQLM1）.

EvenforLFBVswithLVDTs,theLVDTsarejusttherefor"stability";themaincontrol"loop"fortheliquidfuelsystemisflow-rateusingtheliquidfuelflowdividerfeedback.

ToproperlycalibrateLVDTfeedbackitisnecessarytophysicallymeasurethepositionofthedevicewiththeLVDTs--somethingmostpeopleneverdoonGE-designheavydutygasturbineswhen"calibrating"LVDTfeedback.MostoftheLFBVsonnewerGEFrame5sdonothavevalvestemsorplugsthatarevisiblesoit'snotevenpossibletoverifythepositionofthevalveplug.

Again,ifyouarehavingproblemswithliquidfueltelluswhattheyare,whatyou'vedone,andwhattheresultsofwhatyou'vedonewere.Ifyouonlyrunliquidfueloccasionallyandyouhavetroublestransferringfromgasfueltoliquidfuel,ortroublestartingonliquidfuelthentheLFBVisnottheproblem--norwouldthe"calibration"oftheLVDTsontheLFBVbetheproblem.

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Postedby CSA

 on20May,2013-1:

41pm

ESKAY,

Ithoughtwe'dbeenoverthisbefore....

Nothinghaschangedsincethen.

Nothing.

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Postedby ESKAY

 on21May,2013-1:

33pm

DearCSA,

Thanksfordirectingmetotheoldthread,forthesameissueofcalibratingthe65FPservovALVE.

AsyouhavefurtherclarifiedthatthereisNOwaytocalibratethefunctionalityof65FPservo,otherthanrunningtheturbineindistillatemodeandandviewthetrendandvarioussignalsinsertedintothewatchwindowtoanalysetheproblem,ifany.Assuch,wehaveNOprobleminthedistillatefuelmodeoperation.Iwouldliketogettheknowledgeaboutcalibratingthedist.fuelservo,incase,ifitisrequired.Thanksfortheadviceandyouracknowledgement/quickresponse.

Wishingyou..Regards..

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Postedby ESKAY

 on22May,2013-12:

21pm

DearCSAsir,

Icouldnotfindtheanswerthrothe"search"facilityORearlierthreadsregardingmyclarificationonMk4servocalibration,whichwasrejectedbyoneofyourmoderator.

*******************************************************************

Moderator'snote:

ThemoderatorsforCarenot

employedbyCSA.ThemoderatorsworkforC.CSAisoneof

themanyreadersofthisforumwhofreelygiveshisadvicetoothers.

Heandthenumerousotherforumreadersandparticipantsarewhoand

whatmakesthisforumpossible.

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IFOLLOWEDTHEPROCEDUREGIVENINTHEMANUAL,butIhavecertainissues.OnthecalibrationdisplayforSRVANDGCV,whileGDAJisvaried,withL4X1-L4X-L3adj-L20FGX1-L3GCV（forGCV）-L3GRV（fortheSRV）-forcedto"1",withAUX.HydraulicoilpumpswitchedON.IfindtheSRVservovalvestrokingfromitsdatum（closed）positiontoitsfullopenpositionwithGDAJsetat-0.30andaboveandviceversa.WhereasforGCV,theSERVOdoesnotliftatall.IsittheJDAJhexa-decimalvalue,automaticallychangestoeither13OR12withtheFORCEENTERisactivatedORJDAJvaluechangeisNOTrequired.WhatmustbethevalueforLOCATELOWandLOCATEHIGH,normallysetfortheservo?

（forGCV/SRV）.WhyitisNOTpossibletoholdtheSRVatanyfixedvalueofGDAJ?

WhereamIwrong?

Pleasehelpsolvetheprobleminservocalibration.

Iseekyourkindhelp/adviceatyourearliest,sir.

Thanks..Withregards..

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Postedby CSA

 on22May,2013-2:

28pm

ESKAY,

Isenseyourfrustration.I,too,foracoupleofyearsasanewGEemployeewasunderthemistakenbeliefthatliquidfuelbypassvalves--indeed,anyservo-operateddeviceonaGE-designheavydutygasturbine--required"calibration."Itwasn'tuntilIreallythoughtaboutandunderstoodwhatcalibrationis,inageneralsense,andwhatis--orcanbe--calibratedonaGE-designheavydutygasturbinewithservo-operateddevicesthatitreallybecamecleartome.

Iwasonlyreferringyoutoapreviouspostinwhichyouasked,essentially,thesamequestion:

Howto"calibrate"aservo,specificallyaservo-operatedliquidfuelbypassvalvewhichdoesNOThaveLVDTsforpositionfeedback.

Whenusingthe"Calibrate"featureofaSpeedtronicturbinecontrolsystemonaservo-operateddevice,the>>ONLY<<"thing"thatiscalibratedisLVDT （position） feedback.IFTHEREARENOLVDTs,THEN>>NOTHING<

Theservoisnot"calibrated."

Thevalve（orIGVs）arenot"calibrated."

OnlyLVDTfeedbackfromadevicewithanelectro-hydraulicservo-valveiscalibratedusingthe"Calibrate"featureofaSpeedtronicturbinecontrolsystem.

RegardlessiftheSpeedtronicisaMarkIV,MarkV,MarkVI,orMarkVIe. IftherearenoLVDTsontheservo-operateddevicethennothingcanbecalibrated.

"Calibration"ofaservo-operateddevicewithLVDTsforpositionfeedbackistheprocessofconvertingthevoltagefeedbackfromtheLVDT（s）toposition,inpercentofratedstroke（travel）ofthedevice（or,inthecaseofIGVs,degreeofangleofopening）.

Ifthe0%strokeoccursat0.700VACRMSvoltagefeedback,andthe100%strokeoccursat3.500VACRMS（thevaluesareforexemplarypurposes ONLY）,thentheoffset（or"zero"）forthefeedbackvoltageis0.700VACRMS,andthegain（or"span"）forthefeedbackis0.028VACRMSperpercentstroke.TheSpeedtroniccalculatestheoffsetandgaininternallyafterdeterminingthevaluesduringacalibration;thereisnooperatorortechnicianactionrequir