ML20099A986

Special Rept 92-004:on 920623,SDG 11 Tripped Due to High Vibration Signal.Caused by Loose Screw Due to Inadequate Procedure.Maint Procedure Governing Calibr of Vibration Sensors Will Be Revised

ML20099A986
Person / Time
Site:	Grand Gulf
Issue date:	07/23/1992
From:	Cottle W ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
92-004, 92-4, GNRO-92-00097, GNRO-92-97, NUDOCS 9207300082
Download: ML20099A986 (2)

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W. T. Cottie

-July 23, 1992 U.S. Nuclear Regulatory Commissira Mail Station F1-137 Washington, D.C. 20555 Attention: Document Control Desk --

Subject:

Grand Gulf Nuclear Station Unit 1 Docket No. 50-416

• License No. NPF-29 Special Report 92-004 Invalid Failure of Emergency Diesel Generator 11 Due to High Vibration Signe'.

GNRO-92/00097 Gentlemen On June 23, 1992, the Division I Diesel Generator (SDG 11) war started for the performance of the functional test in accordance with Technical Specification 4.8.1.2. ' Approximately one aninute following the start and prior to a.Ivad attempt, SDG 11 tripped on a high vibration signal. SDG 11

• was declared inoperable due to the conhtion. An investigation was ~

performed to determine the cause of the diesel failure.

The investigation revealed a screw which secures the control air conne.ction port and reset air connection port on vibration switch IP75N164A was loose.

No additional abnormal conditions were observed. A bench test revealed that, with the scres loose and some amount of vibration, the supply air leaks at a nte which results in an engine trip. The vi~ oration switch was replaced .id retested saulsfactorily.

The cause of the loose screw is attributed to an inadequate procedure. The procedure is deficient in that it does not identify the need to ensure the vibration switch securing screw is tightened following maintenance on these switches.

The maintenance procedure which governs the calibration of these vibration sensors will bc revised to address identified concerns with the vibration switch securing screw.

t 9207300002 920723 i PDR ADOCK 05000416 S PDR i SR92004/SNLICFLR I

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. buly 23, 1992 GNRO-92/00097 Page-2 of 3 The occurrence was caused by spurious operation of a trip that is bypassed during the emergency operating mode of the SDG. Therefote, this is considered an invalid failure of the SDG unit.

Yours truly, i / t

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WTC/RR/mtc ce: Mr. D. C. Hintz Mr. J. L. Mathis Mr. R. B. McGehee Mr. N. S. Reynolds Mr. H. L. Thomas Mr. Stewart D. Ebneter

-Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 Mr. P. W. O'Connor, Project Manager Office of Nuclear Peactor Regulation U.S. Nuclear Regulacory Commission Mail Stop 33H3 Washington D.C. 20555 oR92004/SNLICFLR

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