ML17216A555

Special Rept:On 860312,alarm Received Indicating That Diesel Engine Failed to Start.Caused by Insufficient Torqued Nut. on 860326,diesel Generator Tripped on High Crankcase Pressure.Caused by Oil Splashing on Pressure Switch

ML17216A555
Person / Time
Site:	Saint Lucie
Issue date:	05/07/1986
From:	Woody C FLORIDA POWER & LIGHT CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
L-86-192, NUDOCS 8605220269
Download: ML17216A555 (6)

Text

PLORIOA POWER & LIGHT COMPANY gg 7 1988 L-86-192 Dr. 3. Nelson Grace Regional Administrator, Region II U. S. Nuclear Regulatory Commission Suite 2900

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101 Marietta Street, N.W.

Atlanta, Georgia 30323

Dear Dr. Grace:

Re: St. Lucie Unit 2

'Docket No. 50-389 S ecial Re ort on Diesel Generator Failures The attached Special Report is being submitted as required per our Technical Specif ica tions.

Very truly yours, C. O. Woody Group Vic resident Nuclear Energy COW/SAV:de Attachmen t cc: Document Control Desk, USNRC, Washington, D.C.

Harold F. Reis, Esquire PNS-LI-86-105 sAr

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I Ll:1 PEOPLE... SERVING PEOPLE

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Re: St. Lucie Unit 2 Docket No. 50-389 L-86-192 SPECIAL REPORT DIESEL GERHERATOR FAILURES At 12:10 P.M., on March 12, 1986, the 2A Diesel Generator (D/G) was started for a required operability check as the 2B D/G was out of service.due to maintenance.

An alarm was received which indicated that one of the engines in the 2A D/G set had failed to start. The two D/G sets installed in Unit 2 are General Motors-EMD 605-EO units, each consisting of a 16 cylinder and a 12-cylinder engine mounted in tandem and driving a single generator. Local observations indicated that the 12-cylinder engine was receiving insufficient fuel flow and the 16-cylinder engine was attempting to carry the electrical load alone. The 2A D/G was removed from service for repair at 12:22 P.M.

Troubleshooting resulted in the discovery of an insufficiently torqued nut in a friction clutch used to operate the mechanical engine governor during startup. The locknut allowed excessive slippage and prevented the speed setting motor from driving the governor to its mechanical upper limit as required. As a result, the 12-cylinder engine would not assume any load and thereby constituted a valid diesel failure. This was the second failure of a Unit 2 diesel within the last 100 vali'd starts. The surveillance frequency for the diesels was once every 10 days, which is in accordance with Regulatory Position C.2.d. of Reg. Guide 1.108.

The friction clutch for the engine governor was replaced and the 2A D/G was returned to service at 0:38 A.M. on March 13. Discussion with a service representative of Woodward Governor has indicated that this is the first known failure of this type. The friction clutches are supplied as assembled units and are not required to be disassembled and inspected as part of the vendor's recommended preventative maintenance program. The governor in question is a Woodward model EGP-B13P. Unit 2 remained at full power during the 16.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> the 2A D/G was out of service. A Plant Work Order was written at this time to check all other governors for similar problems. The work, for Unit 2, will be done during the current refueling outage.

On March 26, 1986, with Unit 2 at full power, the 2B D/G was run for an operability check prior to placing the 2A D/G out of service for maintenance. At 2:17 P.M., the 2B D/G tripped on high crankcase pressure. The trip was believed to be spurious, probably caused by oil splashing on the pressure switch diaphram due to a slightly higher than normal oil level. Since this diesel trip is bypassed on an emergency start,.this is not considered a valid failure as described in Reg. Guide 1.108. The corrective action taken was'to reduce the oil level.

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At approximately 6:30 P.M. the 2B D/G was restarted locally to verify resolution of the problem. An engine fail-to-start alarm was received which indicated the 12-cylinder engine had not started. Investigation revealed an insufficiently torqued nut in the friction clutch similar to the failure observed previously in the 2A D/G.

This failure constituted the third failure in the last 100 valid tests, changing the surveillance frequency for the Unit 2 diesels to once every seven (7) days. The friction clutch was repaired and the 2B D/G was successfully returned to service at Il:00.P.M. on March 26. The 2B D/C was out of service for approximately 9.3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />'.

As previously stated, the 16-cylinder engine governor 'on the Unit 2 diesels will be inspected'for this failure during the current refueling outage. In addition, the governors on the Unit 1 diesels will be inspected as soon as possible. At present, the friction clutch failures are not believed to be indi'cative of a generic problem with the =IVoodward governors. The Unit 1 diesels have, similar engine governors which have not experienced this problem in their 10 years of service life. If the inspections of the remaining governors reveal further failure, which may be; indicative of a generic problem, a report will be submitted under 10 CFR 50.73(A)(2)(v).

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