ST-HL-AE-4142, Special Rept:On 920610,SDG 22 Tripped When Released from Emergency Mode.Caused by Regulator Valve Not Providing Sufficient Air Pressure.Troubleshooting & Repair on Annunciator Alarm Panel Performed

Special Rept:On 920610,SDG 22 Tripped When Released from Emergency Mode.Caused by Regulator Valve Not Providing Sufficient Air Pressure.Troubleshooting & Repair on Annunciator Alarm Panel Performed

ML20101Q329
Person / Time
Site:	South Texas
Issue date:	07/09/1992
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-4142, NUDOCS 9207140242
Download: ML20101Q329 (4)

Text

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The Light c o mp a ny S uth Tenn Project Electric Generating P. O.Station Box 789 Wadsworth. Teman 77483 Ho tosi1.i@ ig A Po m July 09, 1992 ST-IIL-AE-414 2 Filo No. G02 10CFR50 i

U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Unit 2 Docket No. STN 50-499 Special Report Regarding a Nonvalid Failure of Standbv Diesel Generator 22 on June 10. 1992 Pursuant to the South Texas Project Electric Generating Station (STPEGS) Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power submits the attached Special Report regarding a nonvalid failure of Standby Diesel Generator 22 which occurred on June 10, 1992.

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

a William J. Jum Manager, Nuclear Licensing JMP/ag Attachme.nt: Special Report Regarding a Nonvalid Failure of SDG 22 on June 10, 1992 id0dCU "p '

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A Subsidiary of 11ouston industries incorpcrated -

f8 i 9207140242 920709 PDR ADOCK 05000a99-S .

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Houston Lighting & Power Company South Texas Project Electric Gencrating Station ST-HL-AE-4142 Tile No,t G02 Page 2 cc!

l Regional Administrator, Region IV Rufus S. Scott

. Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 400 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 61867

Houston, TX 77208 1

George Dick, Project Manager d

U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center 1100 Circle 75 Parkway.

1 J. I. Tapia _ Atlanta, GA 30339-3064 i Senior Resident Inspector c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie

. Commission 50 Bellport Llane l

P. O. . Box 910 .Bellport, NY 11713 Bay City, TX 77414

" . K. Lacker J. R. Newman, Esquire Burert of Radiat13n Control Newnan & Holtzinger, P.C. Texat Department cf Health 1615 L Street, N.W. 1100 West 49th Street l Washington, DC 20036 Austin, TX 78756-3189 D. E. Ward /T. H. Puckett Central Power and Light Company

. P. O. Box 2121 i Corpus Christ., TX 78403 9

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 Sanknoio TX 78296 1

4 Revised 10/11/91 L4/NRC/

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Attachment

, ST-HL-AE-4142

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l South Texas Project

Unit 2 l Docket No. STN 50-499 Special Report Rega;-ding a Nonvalid Failure of S_tandby Diesel Generator 22 on June 10, 1992 F4QRIPTION OF EVENT:

On June 10, 1992, Unit 2 was in Mode 1 at 100% power. At 0130

hours, during a scheduled performance of 2 PSP 03-DG-0002, Standby Diesel 22 Operability Test, Standby Diesel Generator (SDG) 22 tripped when it was released from the em9rgency mode._ No alarms

. worn observed on the annunciator alarm panel. However, a green i

light had illuminated for the Master Trip Circuit when the engine was started. -The green- light signifies the presence- .of a nonemergency engine trip. Plant operators tested the annunciator lights and all were functional but when an auxiliary switch was transferred from automatic, no alarm was received although one was expected. This was an indication that the annunciator was not working although the lights were functional.

At 0221 hours0.00256 days <br />0.0614 hours <br />3.654101e-4 weeks <br />8.40905e-5 months <br />, plant operators suspected the trip was related to an annunciation problem and reset all the nonemergency trips on

SDG 22 for an engine start. When the engine was started, the amber light (signifies reset) doenergized and the green light energized indicating a nonemergency trip. Attempts to reset the Master Trip

, Relay were unsuccessful and the engine was subsequently shut down.

Troubleshooting on June 11, 1992 found a bad logic card at the i annunciator alarm panel. The logic card was replaced and ' the j annunciator appeared to be functioning satisfactorily.

Trouble:: hooting continued on SDG 22 and included verifying tightness of terminations for circuits associated with tho 865

, relay. Any nonemergency trip which occurs will deenergize the 86S relay. . Resistance acroas the contacts at the 86S' relay was also-

verified. Voltage measurements were performed on electrical

, circuits ' associated with the nonemergency trip' system with the l engine running. All circuits were found satisfactory. The SDG 22' was released from the emergency modo and subsequently tripped. All i trip hlarms were observed on the annunciator which indicated a problem vith the shutdown air supply. The shutdown air system provides air prensure to reset all trip alarms and provides a permissive for starting air pressure when the engine is in~ the test ~

node.

SREPiB2-175,001

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i Attachment 4 ST-HL-AE-4142 Page 2 of 2 4

D.ESCRIPTION OF EVENT: (Con't)

Troubleshooting on the pneumatic shutdown system found that the reset air regulator valve would not regulate air pressure to greater than 10 psig when starting the engine. Normal shutdown air pressure is 30 psig. The reset air regulator was repir.ced. On June 32, 1992, at 0123 hours0.00142 days <br />0.0342 hours <br />2.03373e-4 weeks <br />4.68015e-5 months <br />, post ma'ntenance testing was completed and SDG 22 was subsequently returned to service.

CAUSE OF EVENT:

The cause of this event was a reset air regulator valve not providing sufficient air pressure to reset the SDG 22 nonemergency trip alarms.

ANALYSIS OF EVENT:

In the subject failure, SDG 22 was started in the amergency mode and accelerated to rated speed, voltage, and frequency within the required ten seconda. 'rta SDG 22 tripped when it was rel2ased from the emergency mode. This indicates that the cause of the trip is in a no teme.rgency component and/or circuit. SDG 22 operated satisfactorily in the emergency mode and, if challenged, would have performed its design function. This event was classified as a nonvalid failure.

CORRECTIVE.ACT19ES:

1. Troubleshooting and repair on the annunciator alarm panel was performed.

2. Troubleshooting on SDG 22 consirted of verifying tightness of electrical connections, verifying contact resistance on the.

86S relay, obtaining voltage measurements, and-replacing an .

air regulator.

3. A design change will be evaluated for all SDGs to improve the reliability / performance of the reset air regulator valve and provide additional instre. mentation to allow monitoring air pressure. This evaluation will be completed by July 30,.1992.

Additional corrective actions will be determined as necessary.

ADDITIONAL INFORMATION:

There have been no valid failures in the last 20 valid tests-of SDG 22. The number of valid failures in the last 100 valid tests is less than four. Therefore, the testing frequency for SDG'  !

22 remains at once. Mr 21 days. l The regislator that failed is a Parker Model 07R Valve.

332P)92-178. 001 l

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