ML20087B663

Ro:On 710308,diesels Were Started for Weekly Periodic Test. Both Units Inoperative.Probably Caused by Cold Oil & Trapped Air in Copper Tubing from Diesel Oil Sys.Lines Replaced

ML20087B663
Person / Time
Site:	Robinson
Issue date:	04/07/1971
From:	Utley E CAROLINA POWER & LIGHT CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20087B667	List: ML20087B663 ML20087B678 ML20087B710
References
NUDOCS 8403090333
Download: ML20087B663 (2)

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U Carolina Power & Light Company Raleigh, North Carolina 27602 l April 7,1971 y ,\ 'O 4 j , c' ~ . q h O l. J b.l 1 -

Dr. Peter A. Morris [. APR 12197l# h Division of Reactor Licensing fh c.s.nert W M i U. S. Atomic Energy Commission $$ f Washington, D. C. 20545 h uvi sma

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'%/j# 3 FACILITY OPERATING LICENSE DPR-23 DOCKET NO.56-261

Dear Dr. Morris:

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In accordance with Technical Specifications, H. B. Robinson Unit No. 2, Carolina Power & Light Company reports the following difficulties with the lube oil system of the emergency diesel generators.

Because of a history of drif ting set points, on March 5,1971 the dicsc1 low lube oil pressure switches were replaced with switches that were considered more reliable. To reduce the possibility of these switches being affceted by vibration, they were mounted on the walls adjacent to the I Vp .,6 3 dicsci control panels instead of in the original location inside the con-trol pancis. After switch installation, each diesel was run satisfactor(ly. '

Altwa four separate times to ensure operability with the new pressure switches t--

installed. Reactor operation at power was begun the following afternoon, 3-#3 7 / March 6,1971.

Ort the 16-24 shift, March 8, at 11:00 p.m. , the diescis were started for a weekly periodic test. Both units started but proved inopera-tive when cach ran only about 15-20 seconds before shutting down on low lube

_ oil pressure (16 psig set point). The lube oil pressure gauges,.however, indicated normal starting oil pressure of about 45 psig on each diesel.

. The reactor plant had been operating approximately 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />. One hour later, the two low lube oil pressure switches were disconnected cicctrically to per- .

mit diesel operation entil permanent corrective action could be taken.

On the 08-16 shift, March 9, the pressure switch set points were checked and found to be correct. Some air was vented from the pressure switch oil lines, and the diescis were rctested. Both operated satisfactorily.

Cause of' Incident 5 [/ The lines from the diesel lube oil system to the low lube oil

[ pressure switches are very small diameter (1/4") copper tubing and are rela-tively long lines (approximately 15 feet). The oil in-these lines is cold-M 8403090333 710407 ~' '

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7 Dr. . Peter A. Morris - 2- April 7, 1971 s'

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. l and viscous, and there was some entrapped air. It is felt that these conditions inhibited transmission of oil pressure to the pressure switches quickly enough to prevent dicsci shutdown af ter the lo-oil-pressure-shutdown bypass TD relay (15 seconds) dropped out.

Corrective Action The pressure switch oil lines have been replaced with 3/8" tubing, and a venting connection has been installed near the pressure switches to permit the release of any entrapped air in the oil lines to the pressure switches.

Yours very truly,

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f:/ E.

. Uticy Manager Generation & System Operations EEU:litt e

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