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, 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, Crane
Issue date:	03/22/1990
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-90-021, NUDOCS 9003160306
Download: ML031210574 (4)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555

March 22, 1990

NRC INFORMATION NOTICE NO. 90-21:

POTENTIAL FAILURE OF MOTOR-OPERATED

BUTTERFLY VALVES TO OPERATE BECAUSE

VALVE SEAT FRICTION WAS UNDERESTIMATED

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is intended to alert addressees to the potential for

motor-operated butterfly valves to fail to open on an electrical signal as a

result of friction forces exerted on the valve seats that exceed the values

assumed when selecting the motor actuators and setting the torque switches.

It is expected that recipients will review the information for applicability

to their facilities and consider actions, as appropriate, to avoid similar

problems. However, suggestions contained in this information notice do not

constitute NRC requirements; therefore, no specific action or written response

is 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 differential

pressure conditions.

Following the valve failure, the licensee concluded that

the valve manufacturer, BIF/General Signal Corporation, had underestimated the

degree to which the material used in the valve seat would harden with age (the

responsibility for these valves has been transferred to Paul-Munroe Enertech).

This underestimation of the age hardening had led the manufacturer to assume

valve seat friction forces that were less than the actual friction forces in

the installed valve. To overcome the larger-than-anticipated friction forces, the licensee's engineering staff recommended the open torque switch for 56 butterfly valves be reset to the maximum allowable value. These valves are

required to open to satisfy their safety function and were supplied by this

manufacturer to Catawba Units 1 and 2. The systems in which these valves are

located include the component cooling water system, service water system, and

various ventilation systems.

By July 26, 1989, the torque switch adjustments were completed at Catawba

Units 1 and 2. After reviewing the final settings, the licensee's engineering

staff determined that the actuators for three butterfly valves in the component

9003160306

IN 90-21 March 22, 1990 cooling water system might not be able to overcome the friction forces resulting

from maximum seat hardening. On December 13, 1989, the licensee determined

that the failure of these BIF/General Signal motor-operated valves (MOYs) could

cause a loss of cooling water to residual heat removal system heat exchangers.

To resolve the concern regarding the operability of these BIF/General Signal

valves, a torque switch bypass was installed on two of the actuators to allow

full motor capability during opening.

The third actuator was considered to

be operable because of a recent replacement of the seat material, but an open

torque switch bypass will be installed in that actuator at a later date.

This

situation is described in detail in Catawba Licensee Event Report 89-29, dated

January 15, 1990.

Discussion:

The underestimation of the friction forces that occur as a result of age

hardening of the seat material could lead tp the common mode failure of a

large number of motor-operated butterfly valves to open on an electrical

signal. In the Catawba case, the licensee determined that the torque

switches of 56 valve actuators in several important plant systems required

adjustments. A database search shows 12 other reactor units having a combined

total of approximately 300 butterfly valves from this manufacturer. The af- fected valves are located in such plant systems as high pressure coolant

injection, service water, and standby gas treatment.

In addition to the BIF/General Signal valves, motor-operated butterfly valves

supplied by other manufacturers might fail to operate properly if the manu- facturers underestimated friction forces during the selection of the motor

actuators and the trip setpoints for the torque switches.

For example, in

Information Notice 88-94, dated December 2, 1988, "Potentially Undersized

Valve Actuators," the staff stated that past inaccuracies in the method used

to predict valve friction forces had led to the potential for undersized

actuators on certain motor-operated butterfly valves manufactured by Fisher

Controls International. As a result, the concern with regard to the effect

of various friction losses on the operability of motor-operated butterfly

valves 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 plant

operating licenses and construction permits.

In the generic letter, the NRC

staff requested that the addressees establish a program to provide for the

testing, inspection, and maintenance of safety-related MOVs and certain other

MOVs in safety-related systems.

The scope of Generic Letter 89-10 includes

motor-operated butterfly valves in safety-related systems. One of the factors

contributing to the need for the generic letter was the uncertainty in the

analytical techniques used by licensees and valve vendors in selecting motor

actuators for valves and setting their torque switches. The potential failure

of butterfly valves discussed in this information notice is evidence of that

uncertainty.

'-'

_

IN 90-21 March 22, 1990 This information notice requires no specific action or written response.

If

you have any questions about the information in this notice, please call one of

the technical contacts listed below or the appropriate NRR project manager.

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts:

Thomas G. Scarbrough, NRR

(301) 492-0916

John W. Thompson, NRR

(301) 492-1175 Attachment:

List of Recently Issued NRC Information Notices

/

Attachment

IN 90-21 March 22

199C

Page I

f I

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

laoratlon

-* f

Notici

90-20

P No.

Sublect

i-.-

,

Issuanco

- - -

- - - - - -

Personnel Injuries Resulting 3/22/90

from Improper Operation of

Radwaste Incinerators

90-19

Potential Loss of Effective

Volume for Containment

Recirculation Spray at

PWR Facilities

90-18

Potential Problems with

Crosby Safety Relief Valves

Used on Diesel Generator

Air Start Receiver Tanks

90-17

Weight and Center of

Gravity Discrepancies

for Copes-Vulcan Valves

89-59,

Suppliers of Potentially

Supp. 2

Misrepresented Fasteners

90-16

90-15

Compliance with New

Decoeuissioning Rule

Reciprocity:

Notification

of Agreement State Radiation

Control Directors Before

Beginning Work in Agreement

States

3/14/90

3/9/90

3/8/90

3/7/90

3/7/90

3/7/90

3/6/90

3/5/90

2/28/90

Issued to

All NRC licensees

who process or

Incinerate radio- active waste.

All holders of OLs

or CPs for PIRs.

All holders of OLE

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

All materials licensees.

All holders of NRC

materials licenses

which authorize use

of radioactive

material at temporary

Job sites.

All U.S. NRC byproduct

material licensees.

AlI holders of- OLs- or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

90-14

Accidental Disposal of

Radioactive materials

90-13

Importance of Review and

Analysis of Safeguards

Event Logs

90-12

Monitoring or Interruption

of Plant Comueiications

OL

• Operating License

CP

• Construction Permit

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, D.C. 20555

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, S300

FIRST CLASS MAIL

POSTAGE & FEES PAID

USNAC

PERMIT No. G097

120 5550

i -A1

,

ii~i

toltcyj

US NRC-OIRBCC

DIV OF INFO SUP SVCS

MrCROGRAPHICS SPECIALIST

RECORDS SERVICES BRANCH

W/FP-1-2 1 WdASHINGTON

DC

20555