ML20091P578

Special Rept:On 911231,diesel Generator 2A Tripped 15 Seconds After Reaching 95% Speed Due to Low Lube Oil Pressure Indication During Routine Surveillance Test.Caused by Clogged Root Valve.Valve Cleaned

ML20091P578
Person / Time
Site:	Mcguire
Issue date:	01/30/1992
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9202030178
Download: ML20091P578 (2)

Text

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' January 30, 1992 U.S. Nuclear Regulatccy Commission Document Control Desk

. Washington,- D.C. 20555

Subject:

McGuire Nucle.ar Station Unit 2 Docket No. 50-370 Diesel Generator Special Report _

Gentlemen:

Pursuant to McGuire. Technical Specifications 4.8.1.1.3.c and 6.9.2, find attached a special report-concerning a valid failure of Diesel Generator 2A.

-Should there be any questions, please contact Terry Pedersen at (704)875-4487.

Ver/ truly yours, fYlitatlk T.C. McMeekin

-NGA/bcb

~

Attachment xc: Mr. S.D. Ebneter

~'

Administrator, Region II

'U.S. Nuclear Regulatory Commission 101_Mariette. St., NW, Suite 2900 Atlanta, GA 30323 INPO-Recorf.s Center Suite 1500 1100 Circle 75 Parkway Atlanta, GA. 30339 Mr.-Tim Reed U.S. Nuclear' Regulatory Commission Office of Nuclear Reactor Regulation Washington,.D.C. 20555 Mr. P.K. Van Doorn-NRC Resident Inspector McGuire Nuclear Station ,

I I

920203017e 920130 PDR ADOCK 05000370 3 S PDR '

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e DUKE POWER COMPANY McGUIRE NUCLEAR STATION Diesel Generator Special Report PIR 2-M91-0213 January 24, 1992 On December 31, 1991, at 0927, diesel generator (DG) 2A tripped 15

• econds after reaching 95% speed due to a " Low Lube Oil Pressure"

• ndication during a routine surveillance test (PT/2/A/4350/02A, Diesel Generator 2A Operability Test). Work Request 146375 was initiated and the start attempt (#856) was classified as a Valid Failure because the trip would not have been bypassed during an emergency start.

This wab the second Valid Failure in the last 20 Valid Tests and the fourth Valid Failure in the last 100 Valid Tests f or DG 2A. On a unit basis, this is the third Valid Failure in the last 100 Valid Tests of DGs 2A and 2B combined. Surveillance test frequency increases f rom monthly to weekly per Technical Specification Table 4.8-1 (Diesel Generator Test Schedule).

The trip was due to a slower than normal pressure buildup at the lube oil pressure switches (2LDPS5120 and 2LDPSS123). Fifteen seconds after 95% engine speed was reached, timing relay ARR timed out and t he trip occurred because the pressure switches had not yet cleared. The Operator also noted that the lube oil pressure rise was slower than normal as observed from the local control panel pressure gauge.

Investigation revealed that the root valve to the pressure switches was partially clogged with grit. This grit is residual from sand contamination of the lube oil system that was discovered in 1985.

The root valve and associated tubing were cleaned in 1985 but the grit has apparently since built up in the root valve. A -

modification was maoe to the lube oil system in 1990 to add a full-flow lube oil filter. Ttis filters all of the oil going to the engine and instrumentation to 5 microns. This should prevent future buildup of the grit. The pressure to the engine was normal throughout the event.

Immediate corrective acticn involved cleaning out the root valve (and tubing) and checking for leaks (none were found). Start #857 verified that the oil pressure rise was normal. Then start #858 was initiated (12/31/91 at 1532) to perform the operability run.

Work requests were written on all four DGs to blow out all of the lube oil and fuel oil tubing. Periodic maintenance activities will be setup on all DGs on a two year frequency to blow out the tubing and root valves.

A R.M. Roberts System Engineering

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