Information Notice No. 84-10: Motor-Operated Valve Torque Switches Set Below the Manufacturer's Recommended Value
SSINS No.: 6835 IN 84-10 UNITED STATES 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 VALUE Addressees: All nuclear power reactor facilities holding an operating license (OL) or a construction permit (CP). Purpose: 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 preoperational testing. 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. 8401190062 . IN 84-10 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 conditions. 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 originally specified. 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 incident. 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 postaccident conditions. . IN 84-10 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 (301) 492-8119 Attachment: List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021