Information Notice No. 84-10: Motor-Operated Valve Torque Switches Set Below the Manufacturer's Recommended Value
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
February 21, 1984
Information Notice No. 84-10: MOTOR-OPERATED VALVE TORQUE SWITCHES SET
BELOW THE MANUFACTURER'S RECOMMENDED
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
This information notice is provided as a notification of motor operated
valve torque switches being set below the manufacturer's recommended values.
No specification is required in response to this information notice, but it
is expected that recipients will review the information presented for
applicability to their facilities.
Description of Circumstances:
On January 5, 1984, the GPU Nuclear Corporation reported (LER 83-024) that a
review of records had revealed that a number of motor-operated valve torque
switches were set below the manufacturer's recommended values at the Oyster
Creek Nuclear Generating Station. Further investigation, by the utility,
revealed that the torque switch setpoints set during preoperational testing
were lower than the manufacturer's recommended values. In some cases, these
setpoints were later changed to values even lower than those used during
GPU was prompted to review the records by attendance of GPU representatives
at a recent INPO-sponsored "Valve and Valve Motor Operator Workshop" and
after reviewing of INPO Significant Operating Event Report No. 83-09, "Valve
Inoperability Caused by Motor Operator Failures" and INPO Report No. 83-037,
"Assessment of Motor Operated Valve Failures."
GPU attributes the apparent cause of the erroneous torque switch setpoints
to a lack of sufficient knowledge about setpoint design basis and how the
setpoints affect safety system functioning. It should be noted that during
the review, the utility discovered that no formal setpoint requirement or
documentation identifying the importance of torque switch settings existed.
February 21, 1984
Page 2 of 3
Preoperational testing and subsequent surveillance/maintenance testing was
apparently conducted under low differential pressure conditions. As a
result, the utility believes the torque switch settings were reduced to
prevent applying a force that would cause the valve to jam in the closed
position and possibly damage the motor operator or valve during periodic
surveillance. Because differential pressure is a contributor in determining
the amount of force necessary for full closure, the potential exists that
some of the valves may not fully close or open under design-basis accident
The actual design basis will vary with each valve operator in different
systems, and these bases are presently under investigation by GPU with
General Electric (the nuclear steam system supplier), the various valve
manufacturers, and the,valve operator manufacturer (Limitorque). At this
time, because various unspecified conservatism exist in establishing base
line setpoints, the utility has not been able to determine that any valve
would not have operated during accident conditions with setpoints lower than
GPU's immediate corrective action was to investigate the historical data on
isolation valves based on the Limitorque bill of material, preoperational
test data, and surveillance/maintenance records.
In addition, the following corrective actions on isolation and
safety-related valves will be initiated:
1. The actual design basis investigation will be completed.
2. The appropriate torque switch setpoints will be determined.
3. The torque switch setpoints will be reset on all applicable valves.
4. Administrative controls will be issued to eliminate recurrence of this
NRC has previously identified problems with torque and limit switch
setpoints in Bulletin No. 72-3, "Limitorque Valve Operator Failures";
Circular No. 77-01, "Malfunctions of Limitorque Valve Operators"; Circular
No. 81-13, "Torque Switch Electrical Bypass Circuit for Safeguard Service
Valve Motors"; and Information Notice No. 82-10, "Following Up Symptomatic
Repairs To Assure Resolution of the Problem." In addition, NRC is currently
investigating the need for changing the inservice testing and inspection
programs to ensure that safety-related valves have the torque and limit
switch settings that will ensure proper operation of the valves during
February 21, 1984
Page 3 of 3
No written response to this information notice is required. If you have any
questions regarding this matter, please contact the Regional Administrator
of the appropriate NRC Regional Office, or this office.
Edward L. Jordan, Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: R. J. Kiessel, IE
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