Information Notice 1990-21, Potential Failure of Motor-Operated Butterfly Valves to Operate Because Valve Seat Friction was Underestimated

Potential Failure of Motor-Operated Butterfly Valves to Operate Because Valve Seat Friction was Underestimated

ML031210574
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	03/22/1990
Revision:	0
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-90-021, NUDOCS 9003160306
Download: ML031210574 (4)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555March 22, 1990NRC INFORMATION NOTICE NO. 90-21: POTENTIAL FAILURE OF MOTOR-OPERATEDBUTTERFLY VALVES TO OPERATE BECAUSEVALVE SEAT FRICTION WAS UNDERESTIMATED

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

This information notice is intended to alert addressees to the potential formotor-operated butterfly valves to fail to open on an electrical signal as aresult of friction forces exerted on the valve seats that exceed the valuesassumed when selecting the motor actuators and setting the torque switches.It is expected that recipients will review the information for applicabilityto their facilities and consider actions, as appropriate, to avoid similarproblems. However, suggestions contained in this information notice do notconstitute NRC requirements; therefore, no specific action or written responseis required.

Description of Circumstances

In October 1988, at Catawba Nuclear Station Unit 1, a motor-operated butter-fly valve in the service water system failed to open under high differentialpressure conditions. Following the valve failure, the licensee concluded thatthe valve manufacturer, BIF/General Signal Corporation, had underestimated thedegree to which the material used in the valve seat would harden with age (theresponsibility for these valves has been transferred to Paul-Munroe Enertech).This underestimation of the age hardening had led the manufacturer to assumevalve seat friction forces that were less than the actual friction forces inthe installed valve. To overcome the larger-than-anticipated friction forces,the licensee's engineering staff recommended the open torque switch for 56butterfly valves be reset to the maximum allowable value. These valves arerequired to open to satisfy their safety function and were supplied by thismanufacturer to Catawba Units 1 and 2. The systems in which these valves arelocated include the component cooling water system, service water system, andvarious ventilation systems.By July 26, 1989, the torque switch adjustments were completed at CatawbaUnits 1 and 2. After reviewing the final settings, the licensee's engineeringstaff determined that the actuators for three butterfly valves in the component9003160306 IN 90-21March 22, 1990 cooling water system might not be able to overcome the friction forces resultingfrom maximum seat hardening. On December 13, 1989, the licensee determinedthat the failure of these BIF/General Signal motor-operated valves (MOYs) couldcause a loss of cooling water to residual heat removal system heat exchangers.To resolve the concern regarding the operability of these BIF/General Signalvalves, a torque switch bypass was installed on two of the actuators to allowfull motor capability during opening. The third actuator was considered tobe operable because of a recent replacement of the seat material, but an opentorque switch bypass will be installed in that actuator at a later date. Thissituation is described in detail in Catawba Licensee Event Report 89-29, datedJanuary 15, 1990.Discussion:The underestimation of the friction forces that occur as a result of agehardening of the seat material could lead tp the common mode failure of alarge number of motor-operated butterfly valves to open on an electricalsignal. In the Catawba case, the licensee determined that the torqueswitches of 56 valve actuators in several important plant systems requiredadjustments. A database search shows 12 other reactor units having a combinedtotal of approximately 300 butterfly valves from this manufacturer. The af-fected valves are located in such plant systems as high pressure coolantinjection, service water, and standby gas treatment.In addition to the BIF/General Signal valves, motor-operated butterfly valvessupplied by other manufacturers might fail to operate properly if the manu-facturers underestimated friction forces during the selection of the motoractuators and the trip setpoints for the torque switches. For example, inInformation Notice 88-94, dated December 2, 1988, "Potentially UndersizedValve Actuators," the staff stated that past inaccuracies in the method usedto predict valve friction forces had led to the potential for undersizedactuators on certain motor-operated butterfly valves manufactured by FisherControls International. As a result, the concern with regard to the effectof various friction losses on the operability of motor-operated butterflyvalves is applicable to all such valves.On June 28, 1989, the NRC issued Generic Letter 89-10, "Safety-Related Motor-Operated Valve Testing and Surveillance," to all holders of nuclear power plantoperating licenses and construction permits. In the generic letter, the NRCstaff requested that the addressees establish a program to provide for thetesting, inspection, and maintenance of safety-related MOVs and certain otherMOVs in safety-related systems. The scope of Generic Letter 89-10 includesmotor-operated butterfly valves in safety-related systems. One of the factorscontributing to the need for the generic letter was the uncertainty in theanalytical techniques used by licensees and valve vendors in selecting motoractuators for valves and setting their torque switches. The potential failureof butterfly valves discussed in this information notice is evidence of thatuncertaint '-' _ IN 90-21March 22, 1990 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please call one ofthe technical contacts listed below or the appropriate NRR project manager.Division of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Thomas G. Scarbrough, NRR(301) 492-0916John W. Thompson, NRR(301) 492-1175

Attachment:

List of Recently Issued NRC Information Notices

/AttachmentIN 90-21March 22 199CPage I f ILIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESlaoratlon -* fNotici90-20P No.Sublecti-.- ,Issuanco---------Personnel Injuries Resulting 3/22/90from Improper Operation ofRadwaste Incinerators90-19 Potential Loss of EffectiveVolume for ContainmentRecirculation Spray atPWR Facilities90-18 Potential Problems withCrosby Safety Relief ValvesUsed on Diesel GeneratorAir Start Receiver Tanks90-17 Weight and Center ofGravity Discrepanciesfor Copes-Vulcan Valves89-59, Suppliers of PotentiallySupp. 2 Misrepresented Fasteners90-1690-15Compliance with NewDecoeuissioning RuleReciprocity: Notificationof Agreement State RadiationControl Directors BeforeBeginning Work in AgreementStates3/14/903/9/903/8/903/7/903/7/903/7/903/6/903/5/902/28/90Issued toAll NRC licenseeswho process orIncinerate radio-active waste.All holders of OLsor CPs for PIRs.All holders of OLEor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All materials licensees.All holders of NRCmaterials licenseswhich authorize useof radioactivematerial at temporaryJob sites.All U.S. NRC byproductmaterial licensees.AlI holders of- OLs-or CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.90-14 Accidental Disposal ofRadioactive materials90-13 Importance of Review andAnalysis of SafeguardsEvent Logs90-12 Monitoring or Interruptionof Plant ComueiicationsOL

• Operating LicenseCP

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