United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 89-61: Failure of Borg-Warner Gate Valves to Close Against Differential Pressure

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             WASHINGTON, D.C.  20555

                                 August 30, 1989

Information Notice No. 89-61:  FAILURE OF BORG-WARNER GATE VALVES TO 
                                   CLOSE AGAINST DIFFERENTIAL PRESSURE


All holders of operating licenses or construction permits for nuclear power 


This information notice is intended to alert addressees to potential problems 
resulting from Borg-Warner gate valves with air or motor actuators failing to 
close against differential pressures.  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:

On March 14, 1988, a motor-driven auxiliary feedwater (AFW) pump discharge 
isolation motor-operated valve (MOV) failed to fully close against a differen-
tial pressure of 1800 psi at Catawba Nuclear Power Plant, Unit 2.  The valve 
failed while an AFW piping flush was being performed.  At the time of the 
failure, the reactor was shut down and the steam generators were in hot 
standby.  The failure of the MOV to fully close was a contributing factor that 
led to overfilling steam generator 2A and resulted in an automatic feedwater 
isolation.  The licensee, Duke Power Company, investigated the failure and 
reported (Licensee Event Report No. 414/89-10) the cause to be a higher valve 
factor than originally specified by the valve manufacturer, Borg-Warner, for 
sizing valve actuators.  The valve factor is the term which is multiplied by 
the valve seat area and the differential pressure across the valve to 
calculate one of the parameters used in the standard valve thrust formula.  If 
a low valve factor is used when sizing the valve air or motor actuator, the 
calculated required valve thrust will also be low.  This results in low torque 
switch settings being specified and, in some cases, can result in undersized 
air or motor actuators. 


The AFW MOV that failed to close against 1800 psi, 2CA62A, was a Borg-Warner 
4-inch, 1500-psi, flexible wedge, carbon steel gate valve with a pinned body 

.                                                            IN 89-61
                                                            August 30, 1989
                                                            Page 2 of 3

guide insert ring disk guide.  Actuation of the torque switch stops the motor 
when the valve is closed and fully seated.  The torque switch was not bypassed 
in the closing direction.  Following the March 14, 1988, failure to close, the 
valve was diagnostically tested and the switch settings were found to be 
within specified tolerances.  Since no problems were found with the torque 
switch settings, the valve was retested at 1800 psi differential pressure and 
again failed to fully close.  In order to get the valve to fully close at 1800 
psi differential pressure, the closed torque switch setting had to be 
increased to the maximum allowed by the manufacturer's design calculations.  
During the subsequent refueling outage, the valve was disassembled and 
inspected by the licensee in order to determine what was creating the 
excessive friction between the disk and seat rings.  The inspection did not 
reveal any damage or conditions that would have caused excessive friction.

In November 1988, Duke Power Company performed differential pressure testing 
on an MOV identical in design to 2CA62A.  This testing was performed on a test 
loop at the Riverbend Steam Station.  During the testing, valve signature 
analysis was obtained. This testing resulted in higher than anticipated 
seating loads at high differential pressure conditions, and the valve failed 
to close on two of the tests completed with differential pressures greater 
than 1500 psi.

In November 1988, four Catawba Nuclear Power Plant Unit 1 AFW MOVs, identical 
in design and size to 2CA62A, were differential pressure tested at 1800 psi.  
All four valves indicated intermediate position after being closed during the 
test and were 1/8 inch to 1/2 inch from the fully closed position.  The test 
results identified that all four valves failed to wedge completely shut.  One 
valve did not close enough to shut off flow.

In March 1989, valve 2CA62A and three identical Unit 2 AFW MOVs were differen-
tial pressure tested at 1800 psi.  During the test, the three Unit 2 identical 
valves failed to completely close and isolate flow.  All four valves failed to 
wedge completely shut.  Valve signature analysis test data obtained during 
this testing yielded closing valve factors ranging from 0.38 to 0.74 and were 
different for each valve tested.  These were higher than the 0.3 valve factor 
utilized by the valve manufacturer to size the actuators.

Testing performed by Duke Power Company on carbon steel valves similar in 
design to 2CA62A has yielded opening valve factors ranging from 0.48 to 0.67.  
Testing performed by Duke Power Company on stainless steel valves similar to 
2CA62A has yielded valve factors ranging from slightly higher than 0.3 to 0.5.

Based on Duke Power Company testing, the valve factor of 0.3 originally uti-
lized for Borg-Warner flexible wedge carbon steel or stainless steel gate 
valves with pinned body guide insert rings when sizing air or motor actuators 
was not correct.  The actual valve factors, as measured by Duke Power Company, 
vary from valve to valve but are consistently above 0.3.  This results in the 
potential that air- or motor-actuated valves will not operate against a 
differential pressure when called upon to do so because of inadequate torque 
switch settings or undersized actuators.
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                                                            August 30, 1989
                                                            Page 3 of 3

Related Generic Communications: 

The general concern of the ability of motor-operated valves to function 
properly when subjected to the design basis loadings has been previously 
addressed in NRC Bulletins 81-02, "Failure of Gate Type Valves to Close 
Against Differential Pressure," and 85-03, "Motor-Operated Valve Common Mode 
Failures During Plant Transients Due to Improper Switch Settings;" Circular 
77-01, "Malfunctions of Limitorque Valve Operators;" Information Notices 
81-31, "Failure of Safety Injection Valves to Operate Against Differential 
Pressure," and 85-50, "Complete Loss of Main and Auxiliary Feedwater at a PWR 
Designed by Babcock & Wilcox;" and Generic Letter 89-10, "Safety-Related 
Motor-Operated Valve Testing and Surveillance." 

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
the technical contact listed below or the appropriate NRR project manager.

                              Charles E. Rossi, Director
                              Division of Operational Events Assessment
                              Office of Nuclear Reactor Regulation

Technical Contact:  S. Tingen, RII
                    (404) 331-2603

Attachment:  List of Recently Issued NRC Information Notices

.                                                            Attachment 
                                                            IN 89-61 
                                                            August 30, 1989 
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                             NRC INFORMATION NOTICES
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to_________

88-48,         Licensee Report of Defective  8/22/89        All holders of OLs
Supp. 2        Refurbished Valves                           or CPs for nuclear
                                                            power reactors. 

89-60          Maintenance of Teletherapy    8/18/89        All NRC Medical 
               Units                                        Teletherapy 

89-59          Suppliers of Potentially      8/16/89        All holders of OLs
               Misrepresented Fasteners                     or CPs for nuclear
                                                            power reactors. 

89-58          Disablement of Turbine-Driven 8/3/89         All holders of OLs
               Auxiliary Feedwater Pump Due                 or CPs for PWRs. 
               to Closure of One of the 
               Parallel Steam Supply Valves 

89-57          Unqualified Electrical        7/26/89        All holders of OLs
               Splices in Vendor-Supplied                   or CPs for nuclear
               Environmentally Qualified                    power reactors. 

89-56          Questionable Certification    7/20/89        All holders of OLs
               of Material Supplied to the                  or CPs for nuclear
               Defense Department by Nuclear                power reactors. 

89-45,         Metalclad, Low-Voltage        7/6/89         All holders of OLs
Supp. 1        Power Circuit Breakers                       or CPs for nuclear 
               Refurbished With Substandard                 power reactors. 

89-55          Degradation of Containment    6/30/89        All holders of OLs
               Isolation Capability by a                    or CPs for nuclear
               High-Energy Line Break                       power reactors. 

89-54          Potential Overpressurization  6/23/89        All holders of OLs
               of the Component Cooling                     or CPs for nuclear
               Water System                                 power reactors. 

89-53          Rupture of Extraction         6/13/89        All holders of OLs 
               Steam Line on High                           or CPs for nuclear 
               Pressure Turbine                             power reactors. 
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Friday, May 22, 2015