United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-94: Potentially Undersized Valve Actuators

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION
                             WASHINGTON, D.C.  20555

                                December 2, 1988


Information Notice No. 88-94:  POTENTIALLY UNDERSIZED VALVE ACTUATORS 
                                   

Addressees:    

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose:

This information notice is being provided to alert addressees to potential 
problems concerning valves that may be equipped with undersized actuators 
incapable of providing sufficient thrust to seat, unseat or properly operate 
valves during some design conditions.  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 November 1987, the William B. McGuire Nuclear Station, Unit 1 (McGuire or 
licensee), experienced problems with feedwater bypass control valve 1CF-107 
for steam generator 1D.  During the startup of the unit, the level on steam 
generator 1D decreased to approximately 15 percent on the narrow range level 
instrumentation when flow through valve 1CF-107 failed to increase as demanded 
upon increase of reactor power to above 3 percent.  During the licensee's 
investi-gation, it was noticed that the valve was not responding as demanded 
and that in some cases the valve stroke time was slower than required for the 
control signal.  Valve 1CF-107 is a Fisher Controls (Fisher) valve, Model 
Number 667-ET, that was delivered to McGuire in 1975.

During subsequent investigations by the licensee and Fisher, it was determined 
by Fisher that the actuator for valve 1CF-107 had been sized using a calcula-
tion that did not explicitly account for any valve packing friction forces.  
The licensee identified additional valves supplied by Fisher and requested 
that Fisher recalculate the actuator sizes to include allowances for valve 
packing friction forces.  These evaluations showed that although some valve 
actuators were appropriately sized, some undersized actuators existed.

The licensee's immediate corrective actions for these undersized actuators 
included spring adjustments wherever possible.  In those cases in which com-
plete closure against design loads could not be assured, the valves were 



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declared inoperable and were deactivated in their safe positions.  Permanent 
corrective actions being considered by the licensee include changing control 
air operating limits, installing different springs, and installing larger 
actuators.  The licensee is also considering methods that could be used to 
measure actual packing frictional forces for use during actuator resizing 
calculations. 

Discussion:

Fisher Controls contacted the NRC regarding the potential undersized actuator 
issue, and an NRC inspection was subsequently conducted at Fisher to determine 
the extent of the problem.  On the basis of a review of Fisher documents and 
discussions with Fisher personnel, the NRC determined that actuators for 
valves supplied by Fisher may be undersized and incapable of seating, 
unseating or properly operating their valves during some design conditions.

Fisher indicated that until the mid-1970s it had supplied sliding stem valves 
with Fisher's standard single arrangement teflon packing, as its actuator 
sizing technology was principally based on teflon packing.  During the sizing 
of actuators for teflon-packed valves, Fisher did not account for the teflon 
packing friction forces as, based on their experience, the friction forces 
were calculated to be small compared to the actuator air pressure forces, 
actuator spring forces, valve differential pressure forces, and valve seating 
forces.  Around 1975, Fisher began supplying a number of valves with graphite 
laminate packing as a result of nuclear power industry requests to eliminate 
teflon material from radiation environments and general personal health and 
safety concerns resulting in the replacement of asbestos packing material.  In 
April 1976, Fisher began to explicitly account for packing friction forces in 
sizing all valve actuators when it became apparent that graphite packing 
friction forces and other non-teflon packing materials contributed 
significantly to the overall friction forces. The change was fully implemented 
for all Fisher orders shipped after January 1, 1977.

During the NRC inspection, Fisher also stated that some nuclear power plant 
licensees may have installed packing different from that provided in the 
original valve.  Such a change would be of concern if the new packing creates 
higher friction forces than the original packing.  For example, data provided 
by Fisher indicates that increased friction forces can result if teflon 
packing is replaced with graphite packing or graphite laminate packing is 
replaced with graphite ribbon packing.  If the size of the installed actuator 
cannot overcome the increased friction forces associated with the packing 
change, then the valve may be incapable of performing some of its intended 
functions. 

In addition, Fisher informed the NRC of the potential for undersized actuators 
on Fisher 9200 series butterfly valves.  These particular valves employ rotary 
shafts rather than sliding stems and are not subject to the same packing 
friction concerns previously discussed; however, some of these butterfly 
valves may be equipped with undersized actuators for a different reason.  
Fisher sized butterfly valve actuators ordered before March 1, 1982, using a 
method that under some circumstances underestimated the torque required to 
seat or unseat the butterfly disk in the 9200 series valves.  Butterfly valves 
ordered after 
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March 1, 1982, are not subject to this concern because they are equipped with 
actuators sized by the current Fisher method that more accurately predicts 
valve seat/disk frictional forces.

Conclusion:

The NRC has determined, on the basis of the McGuire event and the inspection 
at Fisher Controls, that the following types of valves may be equipped with 
undersized actuators that may not provide sufficient thrust to seat, unseat or 
properly operate their valves during some design conditions:

1.   Sliding stem valves supplied by any manufacturer that were repacked using 
     materials or procedures that increased the packing friction forces beyond 
     those accounted for in sizing the actuators.

2.   Fisher Controls sliding stem valves shipped before January 1, 1977, 
     supplied with graphite and other non-teflon packing.  The actuators for 
     these valves were sized by Fisher without accounting for packing friction 
     forces.  Actuators for sliding stem valves supplied by other 
     manufacturers may also be undersized, depending on the actuator sizing 
     methods used by these manufacturers. 
     
3.   Fisher Controls 9200 series butterfly valves ordered before March 1, 
     1982.  The method used to size the actuators for these valves may have 
     underestimated the torque needed to seat or unseat the butterfly disk.

Licensees who identify valves with potentially undersized actuators may wish 
to contact the appropriate valve manufacturer to obtain additional 
information. 

No specific action or written response is required by this information notice.  
If you have any questions regarding this matter, please contact one of the 
technical contacts listed below or the Regional Administrator of the appropri-
ate regional office.




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

Technical Contacts:  Joseph J. Petrosino, NRR
                     (301) 492-0979

                     Jaime Guillen, NRR
                     (301) 492-1170
                     
Attachment:  List of Recently Issued NRC Information Notices 
.                                                            Attachment 
                                                            IN 88-94 
                                                            December 2, 1988 
                                                            Page 1 of 1

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

88-93          Teletherapy Events            12/2/88        All NRC medical 
                                                            licensees. 

88-92          Potential for Spent Fuel      11/22/88       All holders of OLs
               Pool Draindown                               or CPs for nuclear
                                                            power reactors. 

88-91          Improper Administration       11/22/88       All holders of OLs
               and Control of                               or CPs for nuclear
               Psychological Tests                          power reactors and
                                                            all fuel cycle 
                                                            facility licensees 
                                                            who possess, use, 
                                                            import, export, or 
                                                            transport formula 
                                                            quantities of 
                                                            strategic special 
                                                            nuclear material. 

88-90          Unauthorized Removal of       11/22/88       All NRC licensees 
               Industrial Nuclear Gauges                    authorized to 
                                                            possess, use, 
                                                            manufacture, or 
                                                            distribute 
                                                            industrial nuclear 
                                                            gauges. 

88-89          Degradation of Kapton         11/21/88       All holders of OLs 
               Electrical Insulation                        or CPs for nuclear
                                                            power reactors. 

88-88          Degradation of Westinghouse   11/16/88       All holders of OLs
               ARD Relays                                   or CPs for nuclear
                                                            power reactors. 

88-87          Pump Wear and Foreign         11/16/88       All holders of OLs
               Objects in Plant Piping                      or CPs for nuclear
               Systems                                      power reactors. 

86-106,        Feedwater Line Break          11/10/88       All holders of OLs
Supp. 3                                                     or CPs for nuclear
                                                            power reactors. 
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Tuesday, November 12, 2013