ML20086M373

Special Rept:On 911107,two Invalid Failures of Diesel Generator a Occurred.Caused by Failure of Turbo Lube Oil Pressure Sensor.Entire Pneumatic Control Sys Will Be Replaced W/Electronic Control Sys

ML20086M373
Person / Time
Site:	Catawba
Issue date:	12/06/1991
From:	Tuckman M DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9112170382
Download: ML20086M373 (3)

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DUKE POWER December 6,1991 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Catawba Nuclear Station, Unit 2 Docket No 50-414 Special Report Invalid Failure of Liesel Generator 2A Pursuant to Technical Specification 4.8.1.1.3 and 6.9.2, find attached a Special Report concerning the two Unit 1 Diesel Generator A (D/G 2A) invalid failures that occurred on November 7,1991.

Very truly yours, M.h-M. S. Tuckman CRUDG2Al26,91

. nu .iment xc: S. D. Ebne:er Regional Administrator, Region II W. T. Orders Senior Resident Inspector R. E. Martin, UNRR r

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CATMVBA NUCLEArlTAILQE DIESEL GENERATOR 2DVAI.lD FAILURE DUE TO TUPDO LUBE O't SENSOR FAILURE Two invalid failures of Diesel Generator (D/G) 2A cc:urred on November 7,1991 due to a failure of a turbo lube oil pressure sensor. These failures occurred during Unit 2's 2EOC4 refueling outage while the unit svas in "No mode". The initial failure occurred during D/G 2A's 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> run, and a subsequent failure occurred du.-ing troubleshooting.

D/G 2A was on a weekly testing frequency at the time of these failures. There have been 2 valid failures in the last 20 valid tests and 4 valid failures in the last 100 valid tests.

There is no unavailability time associated with these failures since rechnical Specincations only requires one operable D/G during "No mode" conditions. Since D/G 2B was operable, the 2A D/G was not required. D/C 2A remains on a weekly test frequency in accordance with Technical Speci6 cation 4.8.1.1.2 Table 4.0-1.

At approximately 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on November 7,1991, D/G 2A was 57 minutes into its Technical Specincation required 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> run (Start # 704) when the engine tripped on Lo Turbo Lube Oil Pressure. Operators in the room were watching the Turbo Oil Pressure

, Gage at the time of the trip and pressures were normal for the conditica of the engine.

Operations (OPS) initiated work request 495340PS for the Instrumentation and Electrical Section (IAE) to investigate and repair the problem. IAE requested that OPS run the engine in order to observe certain pressures in the pnemratic coctrol system to pinpoint the problem. At approximately 1830 hours0.0212 days <br />0.508 hours <br />0.00303 weeks <br />6.96315e-4 months <br />, OPS restarted the engine (start # 705) and the engine came up to speed and ran with no problems seen. No leaks were observed in the pneumatic control system and Turbo Lube oil pressure indicated - 28 Psig. At this point the engine had been rtmning for - 15 minutes. IAE requested the operator to load the engine to 5750 kW to see if this would have any effect. This was performed and after ~ 2 minutes, the engine tripped and the annunciator for TRIP LOW PRESSURE TURBO OIL was received. At the time of the trip, there was a technician stationed at the Right Bank Turbochirger Oil Sensor who observed this sensor vent at the same time the trip ocentred Turbo Oil Pressure on the gage on the control panelindicated -21 Psig, which was normal for the load on the generator, when the trip signal was received. IAE replaced this sensor and the engine was restarted and ran with no other problems seen. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> run was then completed.

The design setpoint of the Turbo Lube Oil Sensors is 15 Psig decreasing. When IAE checked the calibration on the right bank sensor that was removed, it was found to be hi<;h and not repeatable. Apparently, after the engine was loaded and the turbo oil pressure decreand to 21 Psig, the sensor tripped due 3 the elevated setpoint and instability of the sensor. This particular sensor is a Calcon Model #B4400B. There have been numerous failt.res of this part r. umber and other Calcon parts. This sensor is part of the non-emergency trip system and would not have tripped the engine had it been called upon in an emergency situation. None of these model number sensors are utilized in the emergency portion of the D/G control systems. During IEOC6 and 2EOC5 outages, the entire 1

pneumatic control system will be replaced with an electronic control system per NSMs CN-11149 (Unit 1) and CN-20528 (Unit 2). The deletion and replacement of all tbc Calcon instrumentation will be included as part of these modifications.

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