ML20126F971

Special Rept:On 921127,HPCS DG 2B Received Low Lube Oil Pressure Signal,Causing DG to Trip.Caused by Replacement of Tubing W/Smaller Internal Diameter,Restricting Lube Oil Flow.Work Request Written to Replace Pressure Switch Tubing

ML20126F971
Person / Time
Site:	LaSalle
Issue date:	12/24/1992
From:	Diederich G COMMONWEALTH EDISON CO.
To:	Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 9301040002
Download: ML20126F971 (2)

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Commonwealth Edirn LaSalle County Nuclear Station 2001 N. 21st. Rd.

Marseilles, Illinois 61341 Telephone 815/357 6761 December 24, 1992 i . 1 l gy ;

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Mr. A. B. Davis >

Region III Administrator h~ biYtA1]

1 U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Dear Sir This Special Report is submitted in accordance with LaSalle Unit 2 Operating Licenses NPF-18, Technical Specification 4.8.1.1.3 and 6.6.C regarding Unit 2 Diesel Generator (E22, 2E22-S001).

On November 27, 1992, with LaSalle Unit 2 at 100% power, the Unit 2 High Pressure Core Spray (HPCS) Diesel Generator (DG) was started in accordance with LaSalle Operating Surveillance LOS-DG-M3, "2B DG Operability Run". Approximately 50 seconds later, the 2B DG received a low lube oil pressure trip signal, causing the 2B DG to trip. This failure was not a valid failure in accordance with Hegulatory Guide 1.108 and Technical Specification 4.8.1.1.3.

The cause of the low oil pressure trip signal was apparently due to a design error. The tubing which connects the pressure switch to the engine was replaced during the Unit 2 fourth refuel outage, L2R04. The original tubing that was replaced was 1/4 inch copper tubing with .049 inch wall thickness. This tubing was replaced with 1/4 inch stainless steel tubing with .005 inch wall thickness. This smaller internal diameter apparently restricted the lube oil flow long enough to trip the 2B DG on low lube oil pressure. The designed low lube oil pressure cirt.iitry contains a 50 second time delay that allows the lube oil-pressure to reach ratud pressure (20 psi) when the engine is started.

Therefore, 50 seconds after the start initiation signal was received, the 2B DG tripped on low lube oil pressure.

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Work request L19157 was written to replace the low labe oil pressure switch tubing with 1/4 inch .049 inch wall stainless steel tubing. The tubing will be replaced during the Unit 2 Division 3 work week beginning December 21, 1992. Action Itein Record 374-200-92-08501 has been initiated to track the completion of the root cause analysis of this situation.

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G.lJ.Diederich!

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Station Manager

LaSalle County Station GJD/TK/mk1 cca Nuclear Licensing Administrator NRC Realdent Inspector NRC Document Control Desk INPO - Records Center IDNS Resident Inspector i

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