ML20059B230

Informs of NRC Plans to Issue Info Notice Discussing Inoperability of Fairbanks Morse Diesel Generator.If No Comments Received by 931104,NRC Will Assume That Technical Info in Notice Correct

ML20059B230
Person / Time
Site:	Robinson
Issue date:	10/21/1993
From:	Marcus G Office of Nuclear Reactor Regulation
To:	Horinka M COLTEC INDUSTRIES, INC.
References
NUDOCS 9310280097
Download: ML20059B230 (4)

Text

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O October 21, 1993 I Mr. Michael Horinka Quality Assurance Manager Coltec Industries Fairbanks Morse Engine Division 701 Lawton Avenue Beloit, WI 53511-5492

Dear Mr. Horinka:

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SUBJECT:

INFORMATION NOTICE REGARDING FAIRBANKS MORSE DIESEL GENERATOR The U.S. Nuclear Regulatory Commission is planning to issue an information notice (IN) discussing the inoperability of Fairbanks Morse diesel generator which occurred at the H.B. Robinson plant and Duane Arnold Energy Center.

Walter Haass of Vendor Inspection Branch has discussed the technical issue l

regarding these events with you. Please review the draft IN to ensure that i

the technical information is correct and return any comments you may have as soon as possible.

Your cooperation is appreciated. If no comments are received by November 4, 1993, we will assume the technical information in the notice is correct. If you have any questions regarding this issue, please phone Peter Wen of my )

staff at (301) 504-2832.  !

l Original signed by Tae J. YdJn for I

Gail H. Marcus, Chief Generic Communications Branch Division of Operating Reactor Support Office of Nuclear Reactor Regulation

Enclosure:

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UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF NUCLEAR REACTOR REGULATION MSA WDM WASHINGTON, D.C. 20555 October XX, 1993 NRC INFORMATION NOTICE 93-XX: FAILURE OF EMERGENCY DIESEL GENERATORS TO START Addressees All holders of operating licenses or construction permits for nuclear power reactors.

Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this notice to alert addressees to the potential for causing an emergency diesel generator (EDG) failure to start on demand or to trip during operation due to an inadvertent improper execution of the reset operation at the conclusion of the previous run. It is expected that recipients will review the information for applicability to their facilities and consider actions as appropriate to avoid similar problems. However, suggestions contained in this notice are not NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances H.B. Robinson l

In August of 1987 at the H.B. Robinson plant, startup trips occurred on the "A" EDG. With the assistance of a vendor representative, several steps were ]

taken in an effort to preclude such trips, including replacement of the i governor, replacement of the governor oil, replacement of sticky fuel injection pumps, checking of injection pump timing, and rebalancing fuel rack l settings. In February of 1988, startup trips were again experienced. It was j finally concluded, after detailed inspection of the latch mechanism parts, that there was a possibility of wear on the tip of the latch, which may have been a contributing factor to the trips. These parts were replaced with new parts.

On June 3, 1992, during the performance of a test activity, the "A" EDG tripped at least twice on mechanical overspeed after the engine had been operating approximately one half hour. After detailed consideration of all possible scenarios for the trips and considering prior actions taken, it was determined that the most probable cause was a failure to properly reset the trip mechanism after the previous run. It was concluded that operations personnel apparently were unaware of the importance of moving the reset lever through its full travel. In addition, resetting was difficult for some individuals due to the location of the reset lever (i.e., shorter individuals may just barely reach the lever which is positioned over the exhaust manifold that is also generally hot at the time of the reset). Operations personnel  ;

were subsequently trained on the proper method for actuating the reset lever.

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4 to er xx, 1993 Page 2 of 3 Also, a step was provided to permit easier access to the lever for shorter operators.

Duane Arnold On June 11, 1993, while the Duane Arnold plant was operating at 85 percent of full power, the "A" EDG tripped approximately 3 seconds after the initial start signal during an operability surveillance test. A thorough analysis and evaluation of all the possible causes of the EDG trip was conducted by the licensee including occurrence of an actual overspeed condition, failure of the overspeed mechanism, actuation of the emergency stop pushbutton, failure of the emergency stop pushbutton, latch assembly not fully latched, latch assembly failure, mechanical trip mechanism failure, and annunciator circuit or trip lever microswitch failure. It was concluded that the most probable cause of the trip was that the latch assembly was not fully engaged from the previous reset operation and engine startup vibration unlatched the trip mechanism. Less than complete engagement of the latch assembly could be caused by an inadequate reset operation or by interference of the emergency stop pushbutton mechanism. Primary corrective actions adopted by the licensee included procedure revisions to ensure a more positive latching operation, improved physical access to the reset lever, and operator training.

The procedure revision directs operators to perform the reset operation a second time following the initial resetting of the trip. The second reset is somewhat easier to perform and should ensure that the latch is fully engaged in the event that the initial latching sequence resulted in a partially latched condition. Verification that the latch is fully seated is accomplished by checking that the reset lever now moves freely.

Discussion The diesel manufacturer for both plants, Coltec/Fairbanks Morse Engine Division, had previously issued a service information letter (SIL, Volume A, Issue 25, dated August 1, 1991) addressing a revised overspeed trip adjustment. The SIL recommends that the overspeed trip setting be raised from the range of 112 to 115 percent to the range of 115 to 117 percent. This is believed to be particularly necessary for engines required to make a " fast start" where there is a greater possibility of exceeding rated speed during '

startup. In light of events that occurred at H.R. Robinson and Duane Arnold, the manufacturer advised that proper resetting of the trip mechanism, by slowly moving the reset lever fully to the reset position and back, twice, would help ensure reliable overspeed mechanism operation. The inadvertent partial reset latching operations described above may also occur on other '

units having similar mechanical trip mechanisms.

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IN 93-XX October xx, 1993 .

DRAM- e 9e a er a  !

This notice requires no specific action or written response. If you have any  :

questions about the information in this notice, please contact one of the  ;

technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

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Brian K. Grimes, Director Division of Operating Reactor Support Office of Nuclear Reactor Regulation Technical contacts: Larry Garner, RIl (404) 331-4663 Chris G. Miller, Rlli (319) 851-5111 Walter P. Haass, NRR (301) 504-3219

Attachment:

1. List of Recently Issued Information Notices t

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