ML20070N345

Part 21 Rept Re Failures of Limit Switch Series EA740-86700 Mfg by Namco Controls Co Due to Excessive Amount of Grease on Contact Block & Contact Carrier & Wrong Matl of O-ring. Series EA740-86700 Switches Replaced w/EA740-50100 Switches

ML20070N345
Person / Time
Site:	LaSalle
Issue date:	05/02/1994
From:	Johnson I COMMONWEALTH EDISON CO.
To:	Russell W NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
REF-PT21-94 NUDOCS 9405060006
Download: ML20070N345 (7)

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, Commerize:lth Edistn 1 O ) 1400 Cpus Place Downers Grov2, Illinois 60515 C

M:y 2,1994 l i

l l s.. M't. William T. Russell, Director  !

Office of Nuclear Reactor Regulation l

j U.S. Nuclear Regulatory Commission Washington D.C. 20555 4

Attn: Document Control Desk 1

Subject:

Commonwealth Edison Company l [

' 10 CFR Part 21 Final Report (File 94-05) l Deficiency of I.imit Switch Series EA740-86700 Manufactured by Namco Comrol

Dear Mr. Runell:

1 The purpus of this letter is to notify the NRC Staff of concerns by Commonwealth Edison 4 Company (Ceco) toward the failures of Limit Switch Series EA740-86700 manufactured by Namco Control Co. 'The affected Limit Switches are oxd on Main Sicam Isolation Valves (MSIV) to provide j the MSIV position indication en Cnntml Room and an sutnmatic trip signal to the Reactor Protection i System (RPS).

A root cause investigation concluded that the frature of the switch to return the operating lever immediaccly to the neutnd position was due to one or all of the following; j - excessive amount of grease on the contas t block and contact carrier.

i wrong material of the O-ring, and

- a weak torsion spring.

4 "Ihc corrective action is replacement of the wrics EA740-il6700 switches with series EA740-50100 Namco limit switches that have mueb stronger torsion spring.

Provided as an attaclunent to thin letter is CECO's notification in accordance with the requirements 4

of 10 C1'R Part 21.

As stated in the nuached report. the defective component was identified only at Commonwealth

Edison LaSalle County Station. If there are any questions regarding this notification, plea.sc direct them to I. uke D. Kim ut (70li) 663 7457.

Respectfully, G/SMv' l [<A Trene . . Johnmon Licensing Operations Director

Attachment:

10 CFR Part 21 Final Report cc: J. B. Martin, Repmal Administrator R111 D. I!. llill.t. Sr. nim Assident inspector LSCS 1 1. E. Dyer, Director u I11-2 Director, NRR A. T. Gody Jr., LaS.'t Project Manager. NRR Office of Nuclear Facilhy Safety . IDNS 9405060006 940502 a g PDR PT21 EUTCEIL {t/j 94 PDR j

o- 2-:n ; o.44.u , 4 ooout, .vio,,, o, ,

.iENT BY:

l Attachment

! 10 CFR Part 21 Notification Deficiency of Limit Switch Series EA740-86700 l Manufactured by Namco Control Corporation and used at LaSalle County Station.  !

Part 21 File # 9405 l This notification is submitted according to requirements of 10 CFR Part 21, Section 21.1(b).

l Identification of Facility and Component-The defective component was identified only at Commonwealth l j

Edison's LaSalle County Station. The effected Limit Switches are used on Main Steam Isolation Valves (MSIV) 2B21-F022A/B/C/D and 2B21-F028A/B/C/D to provide the MSIV position indication to the l 4

Control Room and an automatic trip signal to the Reactor l Protection System (RPS).

component Manufacturer l The series EA740-86700 limit swilebes are manufactured by Namco Controls Corporation.

Nature of Defect i l The EA740-86700 is a ' maintained contacts, operating lever I i returned" switch, which means that contacts are maintained in the  ;

trippaa position, and a torsion spring will return the lever to .

the initial (neutral) position when released. The switches I

i displayed an apparent inability to fully return the lever toi.e., the initial position after being actuated in either direction, I clockwise or counterclockwise. A root cause investigation concluded that the failure of the switch to return the operating lever immediately to the neutral position was due to one or all of the following:

- excessive amount of grease on the contact block and contact carrier,

- wrong material of the 0-ring, and

- a weak torsion spring.

Safety Significance .

The safety tunction of the MSIV limit switches is to provide an automatic trip signal to the Reactor Protection System to initiate an automatic scram when closure of the MSIV's is detected during power operation, to protect the reactor when its link to the heat sink (turbine or condenser) is in the process of being removed. The MSIV closure scram anticipates the pressure and flux transients that occur during MSIV closure and by that protects reactor vessel pressure and fuel thermal / hydraulic Safety Limits. RPS logic for full scram actuation requires MSIV

3ENT BY: 5- 2-94 ; 8:42AM ; -.

913014928187;* 4/ 4 l

1. closed' indication on 3 of the 4 MSIV's - (inboard or outboard) .

f This logic provides redundancy and allows MSIV's to be functionally tested during power operation. The MS1V limit switches also provide Control Room indication of the MSIV position to the operator.

Failure of the MSIV limit switch to reposition during valve closure (limit switches at full closed position) could result in incorrect position indication of the MSIV to either the Control Room position indicating lights or to the process computer.

Failure of the MSIV limit switch to reposition during valve opening (limit switch at full open position) could result in failure of the MSIV limit switch to actuate for the RPS scram function for MSIV not fully open or could result in incorrect valve position indication.

Discovery Date March 1, 1994 l

Corrective Action The corrective action is replacement of the series EA740-86700 switches with series EA740-50100 Namco limit switches that have l

l much stronger torsion spring. The Station will replace the HSIV limit switches on Unit 2 in June, 1994 and on Unit 1 at the next refueling outage during the fall of 1995. LaSalle Site Engineering & Construction is responsible for these actions.

Number and Location of All Defective components The defective Namco limit switches series EA740-86700 were found on the LaSalle County Station Unit 2 Main Steam Isolation Valves.

There are eight MSIVs per Unit (four outboard and four inboard),

with four limit switches installed on each MSIV.

The same model of limit switches is installed on Unit 1 MSIV's, but no defective switches were found.

Contacta Questions pertaining to this notification should be addressed to:

Luke Kim Regulatory Assurance Commonwealth Edison Company 1400 Opus Place, Suite 400 Downers Grove, IL 60515 (708) 663-7457

l POWER REACTOR EVENT NUMBER: 27200

! FACILITY: LASALLE REGION: 3 NOT1FICATION DATE: 05/02/94

! UNIT: () (2) ( ) STATE: IL NOTIJICATION TIME: 08:41 (ET]

l RX TYPE: [1] GE-5,[2] GE-5 EVENT DATE: 05/02/94

! EVENT TIME: 00:00(CDT) l NRC NOTIFIED BY: IRENE M. JOHNSON LAST UPDATE DATE: 05/02/94 t

HQ OPS OFFICER: CHAUNCEY GOULD NOTIFICATIONS EMERGENCY CLASS: NOT APPLICABLE 10 CFR SECTION:

CCCC 21.21 UNSPECIFIED PARAGRAPH I

UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE CURR PWR CURR RX MODE 1

2 N Y 100 POWER OPERATION 100 POWER OPERATION 1

EVENT TEXT l LICENSEE IS MAKING A PART 21 NOTIFICATION OF DEFECTIVE NAMCO CONTROLS CORPORATION LIMIT SWITCHES SERIES "EA740-86700" INSTALLED ON MAIN STEAM ISOLATION VALVES (MSIV) "2B1-F022A/B/C/D" and "2B21-F028A/B/C/D" TO PROVIDE THE MSIV POSITION INDICATION TO THE CONTROL ROOM AND AN AUTOMATIC TRIP SIGNAL TO THE REACTOR PROTECTION SYSTEM (RPS).

FAILURE OF THE SWITCHES TO RETURN THE OPERATING LEVER IMMEDIATELY TO THE NEUTRAL POSITION WAS DUE TO ONE OR ALL OF THE FOLLOWING:

-EXCESSIVE AMOUNT OF GREASE ON THE CONTACT BLOCK AND CONTACT CARRIER,

-WRONG MATERIAL OF THE O-RING, AND

-A WEAK TORSION SPRING.

CORRECTIVE ACTIONS INCLUDE REPLACEMENT OF UNIT 2 DEFECTIVE LIMIT SWITCHES (TOTAL OF 8) IN JUNE 1994 AND REPLACEMENT OF UNIT 1 (NO DEFECTS FOUND)

LIMIT SWITCHES DURING THE FALL OF 1995.

HOONOTE: SEE EVENT #26728 AND #26866 FOR ADDITIONAL INFORMATION.

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l GENERAL INFORMATION or OTHER EVENT NUMBER: 26728 i

I LICENSEE: NOTIFICATION DATE: 02/02/94

. CITY: MENTOR REGION: 3 NOTIFICATION TIME: 12:50 (ET]

COUNTY: STATE: OH EVENT DATE: 02/02/94 i

LICENSE #: AGREEMENT: N EVENT TIME: 00 : 00 [EST)

DOCKET: LAST UPDATE DATE: 02/02/94 NOTIFICATIONS NRC NOTIFIED BY: SLAYBAUGH HQ OPS OFFICER: GREG SCARFO i EMERGENCY CLASS: NOT APPLICABLE i

10 CFR SECTION:

j CDEG 21.21(c) (3) (i) DEFECTS / NONCOMPLIANCE 1

a EVENT TEXT

NAMCO CONTROL OF MENTOR, OHIO, REPORTED FAULTY OPERATING LEVERS ON A LINE OF LIMIT SWITCHES.

NAMCO CONTROL OF MENTOR, OHIO, REPORTED THAT DURING OPERATION OF MSIVs AT LASALLE STATION, NAMCO CONTROLS EA740-86700 LIMIT SWITCH OPERATING LEVERS i WOULD NOT RETURN TO THE INITIAL POSITION AFTER ACTUATING THE SWITCHES. AN l

INVESTIGATION IS IN PROGRESS TO DETERMINE THE ROOT CAUSE.

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OTHER NUCLEAR MATERIAL EVENT NUMBER: 26866 LICENSEE: NAMCO CONTROLS NOTIFICATION DATE: 03/02/94 CITY: MENTOR REGION: 3 NOTIFICATION TIME: 14:30 (ET]

COUNTY: STATE: OH EVENT DATE: 03/02/94 LICENSE #: AGREEMENT: N EVENT TIME: 00:00[EST)

DOCKET: LAST UPDATE DATE: 03/31/94 NOTIFICATIONS NRC NOTIFIED BY: HAROLD EVERSON j HQ OPS OFFICER: RUDY KARSCH EMERGENCY CLASS: NOT APPLICABLE l 10 CFR SECTION:  ;

CCCC 21.21 UNSPECIFIED PARAGRAPH l l

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EVENT TEXT '

NAMCO CONTROLS; A FOLLOW UP TO A PREVIOUS NOTIFICATION ON 2/2/94 (# 26728).

COMMONWEALTH EDISON REPORTED THAT OPERATING LEVERS ON EA740-86700 LIMIT SWITCHES WOULD NOT ALWAYS RETURN TO THEIR INITIAL POSITION. NAMCO LOCATED j IN MENTOR, OHIO HAS BEEN ABLE TO VERIFY THIS CONDITION IN ONLY ONE OF THE 1

RETURNED UNITS. NAMCO HAS DETERMINED THE ROOT CAUSE TO BE A REACTION BETWEEN THE OIL USED TO LUBRICATE THE SHAFT OF THE O-RING. THE O-RING IS USED TO SEAL THE SHAFT CONNECTED TO THE OPERATING LEVER. THIS REACTION RESULTED IN THE ENLARGEMENT OF THE O-RING WHICH PLACED ADDITIONAL FRICTION IN THE AREA OF THE SHAFT AND THE BUSHING THAT THE SHAFT ROTATES IN. NAMCO HAS FURTHER DETERMINED, WITH THE HELP OF TWO TEST LABS, THAT THE O-RING WAS i NOT MADE OUT OF THE MATERIAL SPECIFIED BY NAMCO. A SECOND O-RING FROM THIS l LOT WAS ALSO TESTED AND FOUND TO BE OF THE CORRECT FAMILY OF MATERIAL.

ADDITIONAL TESTING IS BEING PERFORMED, WITH RESULTS EXPECTED BY MARCH 7, 1994. AT THIS TIME NAMCO HAS NO EVIDENCE OF ANY OTHER OCCURRENCE OF THIS PROBLEM. THE O-RING MANUFACTURER. INFORMED NAMCO THAT THE REACTION BETWEEN  ;

THE INCORRECT O-RING MATERIAL AND THE OIL ON THE SHAFT WOULD TAKE NO LONGER {

THAN 21 DAYS, MAMCO BELIEVES THIS IS AN ISOLATED OCCURRENCE.

co* UPDATE 3/18/94 e 08:13 FROM SLAYBAUGH TO GOULD VIA FAX *** THE LICENSEE BELIEVES, BASED ON THEIR REVIEW, THAT THE SITUATION MAY BE AN ISOLATED SITUATION. THIS IS BASED ON THE "O" RING USED ON THE SHAFT BEING MADE FROM THE WRONG MATERIAL. THEY ARE CONTINUING TO INVESTIGATE THIS CONDITION.

• UPDATE 3/31/94 e 09:20 FROM SLAYBAUGH TO SEBROSKY VIA FAX * *

• ALTHOUGH NAMCO BELIEVES THAT THEY HAVE DETERMINED THE ROOT CAUSE OF THE PROBLEM INITIALLY REPORTED TO THEM BY THE CUSTOMER AND THAT THE PROBLEM IS (Continued on next page)

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. l LICENSEE: NAMCO CONTROLS PAGE # 2 OF EVENT NUMBER: 26866 ISOLATED, NAMCO'S ANALYSIS LEAD TO ANOTHER ISSUE CONCERNING THE ACTUAL O-RING' MATERIAL SUPPLIED TO NAMCO BY ONE OF ITS VENDORS.

ALL O-RINGS USED IN NUCLEAR QUALIFIED LIMIT SWITCHES, FOR THE PURPOSE OF THE SHAFT SEAL MENTIONED ABOVE WERE SPECIFIED TO BE MANUFACTURED BY PARKER HANNIFIN CORPORATION. AS PART OF THIS REVIEW, NAMCO ASKED PARKER HANNIFIN TO ANALYZE O-RING MATERIAL FROM FOUR BATCHES OF MATERIAL THAT WERE SUPPLIED TO NAMCO WITH THE REQUIRED CERTIFICATIONS FROM PARKER HANNIFIN AND PURCHASED FROM VARIOUS PARKER HANNIFIN DISTRIBUTORS. PARKER HANNINFIN'S RESULTS WERE INCONCLUSIVE. 1 1

NAMCO CONTRACTED TWO INDEPENDENT LABORATORIES TO ANALYZE THE MATERIAL IN QUESTION. THEY CONCLUDED THAT ALL SAMPLES WERE OF ETHYLENE-PROPOYLENE l RUBBER AND THAT SIMILAR PERFORMANCE WOULD BE EXPECTED AMONG THE TESTED O-RING SAMPLES.

BASED ON THESE RESULTS, NAMCO HAS RELEASED THE HOLD ON SHIPMENTS.

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