ML20106B102

Special Rept:On 920829,invalid Failure of DG 1B Occurred Due to Low Turbocharger Lube Oil Pressure Trip.Unit 2 Will Be Modified During 2EOC5 Refueling Outage to Install New Electronic non-emergency Trip Sys

ML20106B102
Person / Time
Site:	Catawba
Issue date:	09/24/1992
From:	Tuckman M DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9209300318
Download: ML20106B102 (3)

Text

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1 DUKEPOWER September 24,1992 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Catawba Nuclear Station, Unit 1 Docket No. 50 413 Specia! Report Invalid Failures of Diesel Generator IB Pursuant to Technical Specification 4.8.1.1.3 and 6.9.2, find attached a Special Report concerning the Unit 1 Diesel Generator B (DG 1B) invalid failure that occurred on August 29, 1992.

Very truly yours, N , 'f\ uck-M. S. Tuckman L

i CRIJSRDG1B92.492 Attachment I

xc: S. D. Ebneter Regional Administrator, Region II I

l W T. Orders l Senier Resident Inspector R. E. Martin, ONRR i

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i 9209300318 920924 I --

PDR ADOCK 05000413

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SPliCI AL Rl! PORT l CATAWilA NUCLliAR STATION DIESEL Gl!NIiRATOR 111 INVAl.lD FAILURii DUli TO LOW TURilOCil ARGliR LUllii OIL PRESSURii TRIP An invalid failure of Diesel Generator (DG) 111 occurred on August 29,1992 due to a low turbocharger lobe oil pressure trip. This failure occurred during Unit l's liiOC6 refueling outage while the t,ait veas in Mode 6. Operations was running the engine for Mechanical Maintcaance's break-in runs when the failure occurred. DG 111 was on a monthly test frequency prior to entering the outage. There have been 0 valid failures in the last 20 valid tests and 0 valid failures in the last 100 valid tests on DG IIL DG lil remains on a monthly operability test schedule in accordance with Technical Specification 4.8.1.1.2 _

Table 4.8-1 There is no unavailability time associated with this invalid failure since the =

Technical Specifications only require one DG during Mode 6. Since DG 1 A was operable, DG IB was not required. g Modi 0 cation CN-11149 was performed during i EOC6 outage to replace the non-emergency pneumatic trip instrumentation with electronic trip instrumentation. As part of this modification, the two Calcon turbocharger lube oil pressure sensors were replaced with Rosemount transmitters. These transmitters send signals to the new Rosemount 4001 alarm monitor, which provides a digital display and sends signals to trip the DG and alarm the annunciator panel when programmed setpoints are exceeded. The low turbocharger lobe oil pressure trips are part of the Group 2 tiip sensors, which meaas that they are locked out for 60 seconds on an engine start to allow time for engine pressures to build. If the turbocharger lube oil pressure is not greater than 20 psig after this 60 second period, the ,

engine will trip. Also, if pressure drops below 15 psig anytime after this 60 second period, the engine will trip. 20 psig has to be exceeded initially due to the 5 psig deadband programmed on the monitor for ihese channels. F On August 29,1992, tb DG lit break-in runs were begun. The 5 minute,15 minute, and 30 minute runs were completed without any problems. When tbc i hour breakir. nm was initiated, it was noticed that one of the cylinder pctcocks was open, so the engine was immediately shutdown. After this problem was corrected, the engine was restarted (start

1. 991). After running for 60 seconds, the engine tripped on low turbocharger lube ..il pressure. No one was observing the turbocharger lube oil pressure at the time of the trip i

to determine if the pressure was greater than 20 psig by the end of the Group 2 t meout ,

period. On several of the previous runs, terbocharger lube oil pressure was observed to increase satisfactorily. Personnel from the Instrumentation and Electrical Group and the ,

Component IIngineering Group investigated the newly installed alarm monitor and were unable to find any problems. The engine was once again started and no problems were observed. The 1 bour breakin run was completed. The engine was started for the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> breakin run and once more no problems were observed. The remainder of the DG runs were completed, which included numcious starts, ar.d no further problems occurred.

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No root cause could be determined for this trip. The two most likely reasons for the trip are: _ (1) turbocharger lube oil pressure not being high enough prior to the end of the 60 second lockout or (2) the relays for both the low turbocharget lobe oil pressure trip and :

annunciator on the Rosemount alarm monitor not clearing when pressure was increased.

As stated earlier, no problems were secn on previous runs or subsequent runs to indicate what might have caused the trip. The low turbocharger lube oil pressure trips are part of the non-emergency shutdown circuitry. On an emergency start signal due to a LOCA or a Blackout, this trip would be bypassed ad the engine would continue to run. The Unit 2 DGs will be modified during the 2EOC5 refueling outage to install the new electronic non-cmergency trip system.

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