ML20116L160: Difference between revisions

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#REDIRECT [[ST-HL-AE-4258, Special Rept:On 921007,SDG Tripped on Turbocharger Thrust Bearing Failure.Caused by Improper Installation of New Eutectic or Degradation of Turbocharger.Turbocharger Replaced.Vendor Manual,Drawings & Procedures Revised]]
| number = ML20116L160
| issue date = 11/13/1992
| title = Special Rept:On 921007,SDG Tripped on Turbocharger Thrust Bearing Failure.Caused by Improper Installation of New Eutectic or Degradation of Turbocharger.Turbocharger Replaced.Vendor Manual,Drawings & Procedures Revised
| author name = Jump W
| author affiliation = HOUSTON LIGHTING & POWER CO.
| addressee name =
| addressee affiliation = NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
| docket = 05000498
| license number =
| contact person =
| document report number = ST-HL-AE-4258, NUDOCS 9211180191
| document type = REPORTABLE OCCURRENCE REPORT (SEE ALSO AO LER), TEXT-SAFETY REPORT
| page count = 4
}}
 
=Text=
{{#Wiki_filter:.                                        .                                                    .              ____                                __
The Light
            ' cllouston o mp1.ighting a ny"""d''I""I''"I"'
a l'ower 33"""""'"aung Stadon                                                          l' a Uus W Kadsw o"EI'na* 77m Noveraber 12, 1992 ST-HL-AE-4258 File No.:      G02 10CFR50 U. S. Nuclear Regulhtory Commission Attention:        Document Control Desk Washington, DC            20555 South Texas Project Unit 1 Docket No. STN 50-498 Special Report Regarding A Non-Valid Failure qf Standby Diesel Generator #12 on October 16, 1992 r                      Pursuant      to  the          South      T(      '
                                                                                      .            Project                            (STP)  Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power (HL&P) submits the attached Special Report regarding a Standby Diesel Generator #12 non-valid failure which occurred on October 16, 1992.
If you should have any questions on this matter, please contact Mr. C. A.        Ayala at (512) 972-8626 rT me at (512) 972-~<205.
j                                                  nt.    .
William J. Jump General Manager, Nuclear Licensing MKJ/sr
 
==Attachment:==
: 1. Special Re port Regarding A Non-Valid Failure of SDG
                                      #12 on October 16, 1992 17~10G 1
i
                                                                                                                                                                  ,      9. t mm26,m A Subsidia)y of Ilouston lodustries incorporated                                                                        ~
e'        I 9211100191 921113                                                                                                                                    .
        . {DR ADOCK 05000498
              ~
PDR
 
9 11 utton L!ghting & Power Company                                                ST-HL-AE-4258 South Texas Project F.lectric Genciating Station                                File-No.t 002 Page 2 Cet Regional Administrator, Region IV                                      Rufus S. Scott Nuclear hogulatory Commission                                          Ase >ciato General Counsel 611 Ryan Plaza Drive, Suite 400                                        Houston Lighting & PoWor Company Arlington, TX 76011                                                    P. O. Box 61867                          i Houston, TX    77208 George Dick, Project Manager U.S. Nuclear Regulatory Commission                                    INPO Washington, DC 20555                                                  Records Centar 1100 circle 75 Parkway J.        I. Tapia                                                    Atlanta, GA- 39339-3064 Senior Resident Inspector                                                                                      j c/o U. S. Nuclear Regulatory                                          Dr. Joseph H. Hondric                    !
Commission                                                            50 bellport Lane P. O. Box 910                                                          Bollport, NY 11713 Bay City, TX            77414 D. K. Lacker                            l J. R. Newman, Esquire                                                  Bureau of Radiation Control              i
            ' Nowman & Holtzinger,                P.C.                              Texas Department of Health            -
1615 L Stroct, N.W.                                                    1100 West 49th Street              -1
          - Washington, DC              20036                                      Austin, TX 78756-3189 D. E. Ward /T. M. Puckett                                                                                      l Contral Power and Ljght Company                                                                                .
P. O. Box 2121 Corpus Christi, TX                78403 J.        C. Lanicr/M. B. Leo                                                                              '
City of ,,ustin Electr4c Utility Department P.O. Box 1088                                                                                              .;
Austin, TX 78767
(
K. J.            Fiodler/M. T. Hardt City Public Service Board P. O. Box 1771                                                                                                :
San Antonio, TX 78296 t
Povised- 10/11/91 L4/NRC/
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4 A*...chment                                        ;
ST-HL-AE-4258 page 1 of 2                                        l South Texas project                                                                              l Unit 1                                                                            ;
Docket No. STN 50-498                                                                            i Special Report Hegarding A Non-Valid                                                                            l Failure of Standby Diesel Gerlplator #12 on October 16< 1992 DMOHEHON OF EVENT:
l On October 7, 1992 at 0057 hours, Standby Diesel Generator (SDG)                                                                        ]
          /12 had been st- ed for a fivo hour maintenance run. The SDG was                                                                          l loaded incremently to 100 percent.                                The SDG tripped at 0456 hours                                        -
on a turbochargue thre.                        bearing failure.                      The actual thrust                                l clearance was verified und found to be acceptable                                          However, during troubleshooting the eutectic was found to be tripped and was subsequently replaced in accordance with procedural guidsnce.
On October 16, 1992, Unit 1 was in no modo during a refueling outage.          SDG #12 was started in the emergency mode at 0156 hours and loaded to perform the surveillance procedure for the 24 hour load test.          After being released from the emergency mode SDG #12 tripped at 0205 hours.                    The locsl annunciator indicated a failed                                                      >
turbocharger thrust bearing. The cutoctic was again identified as a problem. The instructions for catting the eutectic were modified to add a tolerance to the clearance by 1/8 turn with the on-site Cooper-Bessemer representative concurrence. The catectic was then i          replaced utilizing the modified clearance.                                                This event wan l          classified as a non-valid failure.
The turbo thrust bearing failure trip is actuated by a entectic installed in the turbocharger air inlet end bearir.g cap.                                                      If the turbo thruct bearing clearance is excessive, then the' impeller nut i
will induce friction on the end of the outectic, heating and l          melting the alloy.                  The molting alloy allows control air to be l          dumped from the uafety trip valve, tripping the engine thus providing protection for the turbocharger.
i On October 17, 1992, at 0420 hours SDG #12 was started in the non-l          emargency modo to verify proper function prior to'the 24 hour run.
i The SDG was taken to 110 percent full load for a load test on the turbo thrust bearing trip. At 0642 hours SDG #12 was placed in the cooldown cycle. Approximately two minutes into the cooldown cycle,
!          the SDG tripped on turbo thrust bearing failure.                                                'The ff-site Cooper-Bessemer factory expert was contacMd ann he d wied a request for any further increase in the outectic setting.                                              In order
          .to assure resolution of the ongoing problems with the turb> charger thrust bearing and to allow continued progress on the SDG work, a-management decision was made to replace the turbocharger.                                                              The l
turbocharger has been sent off-site for a failure analysis.
l sum 290s. cot l
L
            -                    ,n.- - .            ..,.,m.,  .
                                                                                  ,  . ~ . . ,        ,,%      .,-.r    m.., . , , - . .    ,
 
_ --                - . - . - - - - - - - . - - - _ - _ ~ ,
e Attachment                      )
ST-HL-AE-42Sd Page 2 of 2 Cit %E 0F.12L1L :
The cause of tuo trips that occurred on October                                7,    1992 and October 36, 1992, is suspected to be due tc improper installation of the new outectic or degradation in the turbocharger allowing the rotor to actuate the trip por design. The October 17, 1992, trip                                        l j
may be due to a defective eutectic.                              Inspection of the eatectic indicated a small pinhole leak. Since there is minimal thrust on-the turbocharger rotor during the cooldown cycle and the leak was so omall, a defective eutectic was suspected.                                Further failure analysis of the turbocharger will be conducted to determine if a-.
degradation of the turbocharger contributed to this event.
MMLYSIS.0F EVENT:
This incident is classified as a non-valid failure since the SDG operated satinf actorily in the emergency mode Lnd if challonged would have perf ormed its safety function. The turbo thrust bearing failure trip is bypassed in the emergency mode.
CQ@ECTIVE ACTIONS:
: 1.      The vendor manual, appropriate drawings and procedures will be revised to reflect tolerances associated with setting the outmtic clearance.                              Copper-Bessemer has agreed to allow P. toed tolarances for the eutectic setting. This will be r"  1a ted by December 15, 1992.
: 2.        'o? . owing the third trip on October li, the turbocharger was
                      ;Aace.d.                A failure analysis will be conducted on the turbocharger and will be completed by January 28,_1993.
ADDITIONAL INFORMATIOll:
Per STPEGS Technical Specificatica 4.8.1.1', there has been 1 valids                                  >
failure in the last 20 valid tests of SDG 12.- The number of valid.
failures:within the_last 100 valid tests.is less than or equal to                                      -
: 4. Therefore, the testing frequency for SDG 12 re.nains at once per 31 days.
SKEP\97-306,001
                                                                                              ,  .      . _ .}}

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