View source for Information Notice 1986-93, Ieb 85-03 Evaluation of Motor-Operators Identifies Improper Torque Switch Settings

{{Adams
| number = ML031250142
| issue date = 11/03/1986
| title = Ieb 85-03 Evaluation of Motor-Operators Identifies Improper Torque Switch Settings
| author name = Jordan E
| author affiliation = NRC/IE
| addressee name = 
| addressee affiliation = 
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| license number = 
| contact person = 
| case reference number = BL-85-003
| document report number = IN-86-093, NUDOCS 8610310306
| document type = NRC Information Notice
| page count = 4
}}
{{#Wiki_filter:t -
                                                                 SSINS No.:  6835 IN 86-93 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, DC 20555 November 3, 1986 IE INFORMATION NOTICE NO. 86-93:   IEB 85-03 EVALUATION OF MOTOR-OPERATORS

IDENTIFIES IMPROPER TORQUE SWITCH SETTINGS

==Addressees==
:
    All nuclear power reactor facilities holding an operating license or a con- struction permit.

==Purpose==
:
    This notice is provided to alert recipients of a potentially significant safety

problem discovered while performing the evaluations requested by IE Bulletin

85-03, "Motor-Operated Valve Common Mode Failures During Plant Transients Due

to Improper Switch Settings," (IEB 85-03). It is expected that recipients will

review the information for applicability to their facilities and consider

actions, if appropriate, to preclude similar problems from occurring at. their

facilities. However, suggestions contained in this notice do not constitute

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

required.

==Description of Circumstances==
:
    As a result of followup on IEB 85-03, Duke Power Company (DPC) discovered

problems with valves operated by Rotork valve actuators at McGuire Nuclear

Station. Specifically, the problem involved valves for which the factory-set

torque switch settings had been previously changed at the plant site using a

generic correlation between actuator torque output and torque switch setting.

This could cause valve actuator motors to switch off before the valves complete

their travel. Arbitrarily raising the torque switch setting to its maximum may

result in damage to the valve and/or motor especially since thermal overload

protection has been eliminated in many applications. Based upon this

information, DPC has declared safety systems inoperable and shut down McGuire

Units 1 and 2.

Discussion:
     The vendor states that whenever the factory torque switch setting is changed in

the field, an individual calibration curve or a bench test is required to

accurately determine torque output.

8610310306

IN 86-93 November 3, 1986 According to information recently provided by the vendor, torque switch set- tings of 1, 2, 3, 4, and 5, do not always correspond to rated torque output

values between 40 and 100 percent as was used based on general information

available several years ago. Tests and analytical evaluations by the licensee

now confirm that the correlation used by the licensee was incorrect for some

actuators. For example, evaluation of several valve actuator certificates for

the same model revealed that the actual torque output with a switch setting of

"1" varied through a range of 11 to 55 percent of maximum actuator torque output.

The review did not indicate a variation in maximum output at the number 5 setting.

Analysis of two valves installed in the normal charging path, which would be

required to close during safety injection, indicated that they may not be able

to do so under differential pressure conditions which could exist following a

loss-of-coolant accident. Although the as-found switch setting agreed with the

design setting determined by DPC the application of output torque values being

linear between 40 and 100 percent was not correct for all actuators.

Preliminary data indicates that up to 41 nuclear units may have some Rotork

valve actuators. It is not known whether or not these are used in safety

related applications.

The above example specifically deals with improper setting of the torque

switches and illustrates the need for exercising extreme care in the setting of

motor-operator switches because all types of switches must be set properly to

ensure that the valves will function properly when needed. In fact, the

specific event that prompted the issuance of IEB 85-03 was caused by improperly

set torque bypass switches. Improperly set thermal overload switches

recently (October 22, 1986) rendered the high-pressure coolant injection system

inoperable at the Hope Creek Nuclear Station Unit 1. Both of these instances

involved actuators manufactured by a company other than Rotork.

In addition, care must be taken to insure that all of the ramifications of

changes to any of the motor-operator switches are fully understood. For

instance, IE Information Notice 86-29, "Effects of Changing Valve

Motor-Operator Switch Settings," describes how the changing of the limit

switches on certain motor-operated valves resulted in a control room indication

that the valves were closed when, in fact, they were partially open. This led

to an excessive cooldown rate in the reactor coolant system at San Onofre

Nuclear Generating Station Unit 3.

The information herein is being provided as an early notification of a possibly

significant matter that is still under consideration by the NRC staff. Recipi- ents should review the information for possible applicability to their facili- ties. If NRC evaluation so indicates, further licensee actions may be

requested.

IN 86-93 November 3, 1986 notice.

No specific action or written response is required by this information

If you have any questions about this matter, please contact   the Regional

Administrator of the appropriate regional office or this office.

dw

Divis

4   J

of

Director

Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Technical Contacts:   George Schnebli, RII

(404) 331-5582 Richard J. Kiessel, IE

(301) 492-8119 Attachment:  List of Recently Issued IE Information Notices

.           .. .. ---  - ---  - ..--            - -    - .     - T.- . -
                                                                                                 Attachment 1 IN 86-93 November 3, 1986 LIST OF RECENTLY ISSUED

IE INFORltATION NOTICES

InfTormation                                   Date of

Notice No.      Sub 1ect                       Issue    Issued to

86-82          Failures Of Scram Discharge     11/4/86  All power reactor

Rev. 1         Volume Vent And Orain Valves             facilities holding

an OL or CP

86-92          Pressurizer Safety Valve        11/4/86  All PWRfacilities

Reliability                              holding an OL or CP

86-91          Limiting Access                 11/3/86  All power reactor

Authorizations                           facilities holding

an OL or CP; fuel

fabrication and

processing facilities

86-90          Requests To Dispose Of Very     11/3/86  All power reactor

Low-Level Radioactive Waste              facilities holding

Pursuant to 10 CFR 20.302                an OL or CP

86-89          Uncontrolled Rod Withdrawal     10/16/86 All BWR facilities

Because Of A Single Failure              holding an OL or CP

86-05          Main Steam Safety Valve Test    10/16/86 All power reactor

Sup. I         Failures And Ring Setting                facilities holding

Adjustments                              an OL or CP

86-25          Traceability And Material       10/15/86 All power reactor

Sup. 1         Control of Material And                  facilities holding

Equipment, Particularly                  an OL or CP

Fasteners

86-88          Compensatory Measures For       10/15/86 All power reactor

Prolonged Periods Of Security            facilities holding

System Failures                          an OL or CP; fuel

fabrication and

processing facilities

86-87          Loss Of Offsite Power Upon An 10ilO/86   All power reactor

Automatic 3us Transfer                   facilities holding

an OL or CP

86-86          Clarification Of Requirements 10/10/86   All registered users

For Fabrication And Export Of            of NRCcertified

Certain Previously Approved              packages

Type 8 Packages

UNITED STATES

NUCLEAR REGULATORY COMMISSION            OL z Operating License                                                         FIRST-CLASS MAIL

CP= Construction Permit                                                       POSTAGE & FEES PAlO

WASHINGTON. D.C. 2E55 US. RAC

WASH 0 C

OfICIAL BUSINESS

PENALTY FOR PRIVATE USE. $3                                                                                         PERMIT No G4L}}

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