United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-35: Failure of Air Check Valves to Seat

                                                         SSINS No.: 6835  
                                                          IN 85-35         

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                               April 30, 1985 

Information Notice No. 85-35:   FAILURE OF AIR CHECK VALVES TO SEAT 

Addressees 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 

Purpose: 

This information notice is being provided as a notification of a potentially
significant problem pertaining to Parker-Hannifin Corporation check valves, 
supplied by Anchor/Darling Valve Company, that may degrade the capability 
for closing main steam isolation valves (MSIVs) or feed water isolation 
valves (FWIVs) or may inhibit other safety functions. It is expected that 
recipients will review the information for applicability to their facilities 
and consider actions, if appropriate, to preclude a similar problem 
occurring at their facilities. 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, 1985, at Byron Unit 1, two MSIVS failed to close on a main 
steam line isolation signal as required. The cause was determined to be 
failure of instrument air check valves to seat in response to gradually 
decreasing air pressure. 

At the time of the isolation signal, the unit was cooling down following the
startup test for loss of offsite power. The removal of offsite power had 
deenergized the station air compressors, allowing the instrument air 
pressure to decrease. The leaking instrument air check valves had allowed 
air accumulators to bleed down, removing the air pressure needed to shift 
hydraulic spool valves so that the hydraulic circuits could close the MSIV 
(see Figure 1). As a result, one of the four MSIVs did not close and one 
MSIV only partially closed. 

In subsequent bench testing, 7 of 8 check valves removed from Unit 1 failed 
to seat, as did 4 of 11 replacement valves, when gradual loss of instrument 
air pressure was simulated. All valves seated when the supply pressure was 
rapidly decreased. Preoperational testing using rapid depressurization was 
satisfactory; however, preoperational testing did not require slow 
depressurization. Subsequent retesting has indicated continuing problems. 
The licensee has decided to replace all these Parker-Hannifin check valves 
with Parker-Hannifin check valves of modified design. 

8504250455  
.

                                                           IN 85-35        
                                                           April 30, 1985  
                                                           Page 2 of 2     

The valves that leaked are identified in Parker-Hannifin literature as 
"Barstock Inline Check Valves, C Series, Catalog 2502."  They were 
manufactured by Parker-Hannifin and supplied by Anchor/Darling Valve Company
(Part No. W30261). The replacement valves are described as Viton Seat Body 
Brass Check Valves with order number 8F-CAL-10-B. Anchor/Darling has 
notified the NRC that the same check valves have been supplied to the plants 
listed in Attachment 1 for use in instrument air supply lines to MSIV 
actuators or to FWIV actuators. It should also be noted that the valves may 
be in use in other applications and/or other facilities. 

A previous Information Notice, 82-25, described a related event with 
different equipment. Valves equipped with Ralph A. Hiller Co. actuators were
capable of achieving their fail-safe position when the instrument air header
was suddenly depressurized, but would not do so with a slow 
depressurization. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 


                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Vern Hodge, IE 
                    301-492-7275 

Attachments: 
1.   Figure 1 MSIV Control System 
2.   List of Known Applications 
3.   List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Tuesday, November 12, 2013