ML20141M313

Special Rept:On 920708,SDG 13 Tripped on Low Turbocharger Lube Oil & Inlet Pressure.Caused by Presence of Water in Valve Cover Which Led to Corrosion.Design Changes to Provide Drainage to Valves Will Be Evaluated

ML20141M313
Person / Time
Site:	South Texas
Issue date:	08/07/1992
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-4172, NUDOCS 9208110281
Download: ML20141M313 (5)

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.ff.'"I'*f.".L.!".$'"_.[f_S:.nonyy{ yaderth, Temai 7tas August 7, 1992 ST-HL-AE-4172 File No.: G02 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Unit 1 Docket No. STN 50-498 Special Report Regarding a Nonvalid Failure of Standby Diesel Generator 13 on Julv 8. 1992 Pursuant to the South Texas Project Elcctric Generating Station (STPEGS) T.7hnical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power subr.its the attached Special Report regarling a nonvalid failure of Standby Diesel Generator 13'which occurred on July 8, 1992.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972-8628 or me at (512) 972-7205.

r William J. Jum Gcneral Manager,  !

Nuclear Licensing ]

JMP/ag

Attachment:

Special Report Regarding a Nonvalid Failure of SDG 13 on July 8, 1992 l

l 110039 SREP\92 209.001 A $ absidiray of Houston Industries incorporated 9208110281 920807- e i

PDR ADOCK 05000498 PDR- -

flouston Lighting & Power Company ST-HL-AE-4172 South Texas Project Electric Generating Station File No.t G02 Page 2 ces Regional Administrator, Region IV Rufus'S. Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 400 Houston Lighting & Power Company 2 Arlington, TX 76011 P. O. Box 61867 Houston, TX -77208 .

George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Record 1 Center 1100 circle 75 Parkway J. I. Tapia Atlanta, CA 30339-3064 Senior Resident Inspector '

c/w U..S. Nucleer Regulatory Dr.-Joseph M. Hendrie .

Commission 50 Bellport Lane- -

P. O. Box 910 Bellport, NY- 11713 /

Bay City, TX 77414 D. K. Lacker J. R. Newman, Esquire Bureau of Radiation Contr:1 Newman & Holtzinger, P.C. Texas Department of Health 1615 L Street, N.W. 1100 hest-49th Street Washington, DC 20036 Austin, TX 78756 1189 D. E. Ward /T. M. Puckett Central Power and Light Company 4 P. O. Box 2121 i Corpus Christi, TX 78403 J. C. Lanier/M. B. . Lee City of Austin Electric Utility Department P.O. Box 1088 Austin,'TX 78767 K. J.-Fiedler/M. T. Hardt City Public Service Board P. O. Box 3771 San Antonio, TX 78296 t

Revisee2 10/11/91 L4/NRC/

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Attachment ST-HL-AE-4172 Page 1 of 3 South Texas Project Unit 1 Docket No. STN 50-498 Special Report Regard.ing a Nonvalid Failure of Standby Diesel Generator 13 on Julv 8, 1992 DESCRIPTION OF EVENT:

On July 8, 1992, Unit I was in Modo 1 at 100% power. During the performance of Standby Diesel Generator (SDG) /13 Operability Test, SDG #13 tripped on low turbocharger lube oil inlet pressure as indicated by the local control board annunciator, The local turbocharger lube oil inlet pressure was verified to be adequatu.

A Service Request was initiated after the event to investigate the low turbocharger lube oil alarm condition. The turbocharger oil pressure alarm switch was replaced and calibrated. SDG #13 wa.:

then started and again the diesol' tripped with the same indication.

The valve which interfaces the lube oil system to the pneumatic trip header, PV-5699, was not operating properly as evidenced by a continuous air discharge. Wnen the cover for the valve was removed to provide access to the mounting bolts, water was observed in the valve. A replacement valve was installed and the old valve -

was retained for further evaluation. After an engineering evaluation, it was determined that the presence of water led to corrosion within the valve cover which prevonted proper operation of the valve. /

There are two potential sources for water er.try into this valve:

One source is from an accumulation of water in the pneumatic inlet supply to the valve which may have leaked by the pneumatic valve seat, This water may have' initiated corrosion which could prevent the linkage between the oil and pneumatic side of the valve from operating properly. The turbocharger oil pressure trip valve is located at the low point of the

. pneumatic system.

O Another source of water intrusion into the valve might be from the periodic cleaning of the diesel-engines. Water may' enter the valve cover through holes drilled in the back cover that mounts the valve to the side of the engine. When the engine is cleaned, water and oil may intrude into the valve.

Protective measures prior to the engine .. cleaning -included taping electrical components, but not the pneumatic components.

'SREP\92-209.001

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, Attachment ST-HL-AE-4172 Page 2 of 3 The valve is equipped with a vent connection on the valve body which is not used. As indicated in the vendor manual, the valve is normally installed with this vent connection on the bottom.

4 The vendor manual also shows tubing coming from this connection running into a sump. This indicates that this port is used as a drain. At the South Texas Project, tne valve is installed with this vent connection on the side of the valve. PV-5699 currently I has a plastic plug in this port. However, similar valves on SDG

1. 11 have the plastic plug removed.

CAUSE OF EVENT:

The cause of this event is apparently due to the presence of water in the valve cover which led to corrosion. This corrosion

within the valve cover prevented proper operation of the valve.

1 ANALYSIS OF EVENT:

4 This test was classified as a nonvalid failure since the failure can be identified as a spurious operation'of a protection feature that is bypassed in the emergency operation mode. The SDG would have been able to perform its safety function if challenged.

i 4

CORRECTIVE ACTIONS:

1. HL&P will inspect for moisture accumulations on the j turbocharger lube oil inlet pressure trip valve and the engine oil header _ pressure trip valve on the other engines _in both units. These inspections will be cor.pleted by March 23, 1993.

2. HL&P will determine whether Preventiva Maintenance activities, should be developed for inspecting for moisture acumulations and replacing the valve seat or diaphragm, and lubricating the valve internals for the turbo charger lube oil-inlet pressure

] trip valves and the engine oil haader pressure trip . valve.

This evaluation will be completed _ by_ September _3, 1992.

, Additional corrective actions will be developed as hacessary, i 3. Design changes will be evaluated to provide drainage of the valves. These design changes,. if warranted, will be installed -

1 by the end of the third refueling outage in Unit 2 and.the end of the fifth reiueling outage in Unit 1.

4. An evaluation will be performed t'o. determine necessary controls that are needed for SDG- equipment- component protection during area and equipment cleaning. This evaluation will be completed by September 10, 1992.

SREP\92 209.001

Attachment ST-HL-AE-4172 Page 3 of 3 ADDITIONAL INFORMATION:

At the time of this event, there were no valid failures in the last 20 valid tests and less than 4 valid failures in the last 100 teats for SDG #13. Therefore, the testing frequency will remain at once per 31 days.

There have been 'no similar events identified regarding a nonvalid f ailure of a SDG due to the presence of water in this- type of valve.

PV-5699 is manufactured by Amot Controls as model 1072L.

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SREP\92 209.001 i

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