ML17223B320

Special Rept:On 911021 & 22,1B EDG Failed During 24 Hr Surveillance Runs.First Failure Caused by Broken Shaft Due to Fatigue at High Stress Location.New Shaft,Of Modified Design,Installed.Run Performed Satisfactorily on 911027

ML17223B320
Person / Time
Site:	Saint Lucie
Issue date:	11/13/1991
From:	SAGER D A FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-310, NUDOCS 9111200215
Download: ML17223B320 (5)

Text

REGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9111200215DOC.DATE:91/11/13NOTARIZED:NOFACIL:50-335St.LuciePlant,Unit1,FloridaPower6LightCo.AUTH.NAMEAUTHORAFFILIATIONSAGER,D.A.FloridaPower&LightCo.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)

SUBJECT:

Specialrept:on911021622,1BEDGfailedduring24hrsurveillanceruns.Firstfailurecausedbybrokenshaftduetofatigueathighstresslocation.Newshaft,ofmodifieddesign,installed.24hrrunperformedsatisfactorily911027.D*s>>@~~*a~<<D~:p2>>C>>*~a~<<~>>~D:>>~I~~~L~TITLE:50.73/50.9LicenseeEventReport(LER),IncidentRpt,etc.NOTES:DOCKET05000335RECIPIENTIDCODE/NAMEPD2-2LANORRIS,JINTERNAL:ACNWAEOD/DOAAEOD/ROAB/DSPNRR/DET/EMEB7ENRR/DLPQ/LPEB10NRR/DREP/PRPB11NRR/DST/SICBSH3NRR/DST/SRXBSERES/DSIR/EIBEXTERNAL:EGGGBRYCE,J.HNRCPDRNSICPOORE,W.COPIESLTTRENCL1111221122111122111111331111RECIPIENTIDCODE/NAMEPD2-2PDACRSAEOD/DSP/TPABNRR/DET/ECMB9HNRR/DLPQ/LHFB10NRR/DOEA/OEABNRR/DST/SELBSDPLBSD102RGN2FILE01LSTLOBBYWARDNSICMURPHY,G.ANUDOCSFULLTXTCOPIESLTTRENCL11221111111111111111111111DNOTETOALL"RIDS"RECIPIENTS:DDPLEASEHELPUSTOREDUCEWASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMPl-37(EXT.20079)TOELIMINATEYOURNAMEFROMDISTRIBUTIONLISTSFORDOCUMENTSYOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:LTTR33ENCL33 P.O.Box128,Ft.Pierce,FL34S54-0128oVfgpgL-91-31010CFR50.36U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,DC20555Gentlemen:Re:St.LucieUnit1DocketNo.50-335SpecialReportDateofEvents:October21and22,1991EmerencDieselGeneratorFailuresTheattachedSpecialReportisbeingtransmittedpursuanttotherequirementofSt.LucieUnit1TechnicalSpecifications4.8.1.2.2and6.9.2.Thisreportprovidesnotificationoftwofailuresassociatedwiththe1BEmergencyDieselGeneratorduringthe24hoursurveillanceruns.Shouldtherebeanyquestionsonthisinformation,pleasecontactus~Verytrulyyours,D.A.SagerPlantVicePresidentDAS/JWH/kwAttachmentcc:StewartD.Ebneter,RegionalAdministrator,RegionII,USNRCSeniorResidentInspector,USNRC,St.LuciePlantDAS/PSL4550-91gpZPlii2002l55'il.ij.=.r"DR(ADOCki05000='35PDRc(-~!pranFPLGroupcompany

~Fir~Fjiilir",SpecialReport18EmergencyDieselGeneratorFailuresSt.LucieUnit1wasinMode5andbeginningarefuelingoutage.At0357onOctober21,1991,the1BEmergencyDieselGenerator(EDG)wasstartedforits24hoursurveillancerun.TheEDGautomaticallytrippedat0928onhighdischargewatertemperature.Theradiatorfanidlerpulleyshaftwasfoundtobesheared.Analysisshowedthatthebrokenshaftwascausedbyfatigueatahighstresslocation.Anewshaft,ofamodifieddesign,wasinstalled.Thenewshaftismadeofadifferentmaterialandhasreducedstressrisersattheshaftdiameterstepstoincreaseshaftfatigueresistance.Thissurveillancerunwasafailureofavalidtest.RG1.108$2.a.3requiresatesttobeperformedatleastoncepereighteenmonthstodemonstratefull-load-carryingcapacityforanintervalofnotlessthan24hours.TheEDGranfiveandone-halfhoursbeforetripping.nF,ilrThe1BEDGwasrestartedat2035onOctober22,1991.Theradiatorfanbeltswerefoundtobeflappingexcessively.PlantmanagementdecidedtoshutdowntheEDGtodeterminethecauseoftheexcessiveflapping.TheEDGwasstoppedat0931onOctober23.Crackswerefoundonthefandrivebeltbearingsupportframe.EvaluationofthestructurerevealedanaturalfrequencyatthethirdharmonicoftheEDGrotationalspeed.Thepresenceofexcitationforcesnearthenaturalfrequencyofthestructureexplainsthereducedlifeoftheidlershaftandsupportingframe.Theexcitationisproducedbythetorsionaloscillationfromthe12cylinderEDG.Toincreasetheservicelifeofthefancomponentsandassociatedsupportstructure,thecrackswererepairedandstiffenerplateswereinstalled.Theseactionswereperformedonboththe1Aand1BEDGs.Futureplansaretoinstallvibrationisolatorsonthe1Aand1BEDGpowertakeoffshafts.TheseisolatorsgreatlyreducetheamplitudeoftorsionalvibrationsbeingtransmittedtothefanassemblyframeandhaveproventobebeneficialonSt.LucieUnit2EDGs.Thislong-termcorrectiveactionwillbeevaluatedforimplementationduringthenextrefuelingoutage.ThesurveillancerunstartedonOctober22wasalsoafailureofavalidtest.RG1.108g2.e.7statesthattestsperformedtoverifycorrectionoftheproblemshouldbeconsideredvalidtestsandsuccessesorfailures,asappropriate.Filure,immThesefailureswerethefirstandsecondfailuresofthe1BEDGsinceimplementationoftheRG1.108-basedTechnicalSpecifications.Todate,twentyvalidtestshavebeenperformed.ThecurrentsurveillanceintervalisoncepersevendaysperTechnicalSpecification4.8.1.1.The24hourrunwasperformedsatisfactorilyfrom2001onOctober27to2011October28,1991.