DCL-84-086, Final Deficiency Rept Re Malfunction of Valve Operator Mfg by Limitorque.Initially Reported on 830627.Existing Screws Will Be Replaced on Affected Valves Prior to Fuel Load.Maint Procedures Modified

Final Deficiency Rept Re Malfunction of Valve Operator Mfg by Limitorque.Initially Reported on 830627.Existing Screws Will Be Replaced on Affected Valves Prior to Fuel Load.Maint Procedures Modified

ML20081C856
Person / Time
Site:	Diablo Canyon
Issue date:	03/01/1984
From:	Schuyler J PACIFIC GAS & ELECTRIC CO.
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
DCL-84-086, DCL-84-86, NUDOCS 8403150048
Download: ML20081C856 (1)

Text

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G PACIFIC AND E LE C T RIC C O M PANY G-AS,LM!!aR -o ~

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asuCLE AR Nata GE%ER ATIO's March 1,1984 PGandE Letter No.: DCL-84-066 Mr. John B. Martin, Regional Administrator U. S. Nuclear Regulatory Commission, Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368 Re: Docket No. 50-323 Diablo Canyon Unit 2 10 CFR 50.55(e) Report - Malfunction of Limitorque Valve Operator

Dear Mr. Martin:

On June 27, 1983, PGandE submitted information related to the binding of a torque switch on an operator manufactured by Limitorque. This is the final report on the subject.

Binding occurred between the manual torque arm and mounting screws on the torque switch assembly when a Unit 1 valve was manually closed and overtorqued. In this condition, the valve can be opened electrically but cannot be closed electrically.

Investigation into the cause of the binding showed that it was[d_ue to excessive height of the mounting screws) which interfered with free movement of the torque switch arm on some valves. The existing mounting screws (her socket heacs) had b?en installed as a precaution after the original mounting screws were found to be loose after severe seismic testing. Since the acceleration during the test exceeded requirements for seismic qualification and the original screws had been qualified to Diablo Canyon requirements by the vendor, the precaution was uonecessary. (Replacement of the existing screws with the original type on the affected valves will eliminate the binding problem.

Unit 2 motor-operated valves will be reviewed during normal construction and maintenance activities. Replacement of the screws will be completed prior to Unit 2 fuel load.

Since PGandE's investigation indicated that the binding was caused by the replacement screws, no generic implications exist for the vendor-supplied equipment. (haintenance procedures are being modifies /to require use of the screw type supplied by the manufacturer on mounting torque switches.

Sincerely, e403150048 840301 DRADOCK05000g cc: Service List .

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