Part 21 Report - 1998-431

 
 

ACCESSION #: 9805260384



                      VALCOR [Registered Trademark]

                     VALCOR ENGINEERING CORPORATION



   2 Lawrence Road o Springfield, New Jersey 07081 USA o 973-467-8400

           Fax: 973-467-8382 o Internet: http://www.valcor.com



                                                              May 19,1998

Operations Center

Nuclear Regulatory Commission

Washington, D.C. 20555



Attn: Mr.  Bob Stranski

Fax: 301-816-5151



SUBJECT:  10CFR21 Reporting of Delay-In-Closing Problem of Valcor Valve,

          Part Number V70900-65-11.



Confirming our telephone conversation earlier this afternoon, Valcor is

submitting the attached report "Summary of V70900-65-11 Delay-In-Closing

Problem Due To Residual Magnetism" under the provision of 10 CFR Part 21.



The report contains all the elements required per 21.21.d.4 of the Part

21.  Please feel free to call me at 973-467-8400, extension 284 if you

need any additional information.



VALCOR ENGINEERING CORPORATION



Jimmy Shieh

Quality Assurance Director



cc:  H.  Loran

     D.  Shave

     B.  Matiez

     C.  DelPomo

     L.  Olsen, PP&L





                                            VALCOR [Registered Trademark]

May 19, 1998                               VALCOR ENGINEERING CORPORATION



Summary of V70900-65-11 Delay-In-Closing Problem Due To Residual

Magnetism



Following 6 to 18 months of continuously energized service, 3 units of

Valcor Model V70900-65-11 air pilot valves have reportedly failed to

stroke closed immediately upon de-energization when installed in their

respective systems.  Despite best efforts, the delays in closing have not

been able to be replicated outside of the plant system.  Delays in

closing have ranged from 1 to 5 minutes.



Upon investigation, a potential cause of the delayed closing is the

possible susceptibility of this particular model to the effects of

residual magnetism.  Delayed closing may occur when the air gap between

the plunger and the stop becomes too small or if the plunger makes

contact with the stop.  Extended periods of continuously energized

service, and subsequent compression setting of the O-ring seat, may

induce the small air gap condition.  As a result of the small air gap,

the valve may then be subject to residual magnetism forces, which tend to

prevent closure of the valve upon de-energization.  Opening operation of

the valve is not affected.



The V70900-65-11 is an AC-powered version and is the only version of the

V70900-65 air pilot series subject to this effect.



Only 46 units of this particular model have been delivered, all to PP&L's

Susquehanna Nuclear Power Plant.  All of these units have been, or are

scheduled to be, modified by Valcor to positively eliminate the potential

for residual magnetism effects.  The corrective action includes the

insertion of a non-magnetic residual washer between the plunger and the

stop, and also includes modification of the assembly procedure to

specifically measure and control the air gap.  This results in a higher

drop out voltage for the valve.  Other corrective action, which has

already been accomplished, includes the modification of the reference

design to add the residual washer to units built in the future.



The initial report of a potential problem with one valve was received by

Valcor in September of 1997.  Subsequent investigations by the utility

and by Valcor led Valcor to believe that a possible problem might exist,

and Valcor initiated a 10CFR21 evaluation in accordance with internal

procedures in late March, 1998.  Further plant testing in April and May

of 1998 identified 2 other valves which appeared to delay in closing.





GENERAL INFORMATION or OTHER                 EVENT NUMBER: 34262



LICENSEE: VALCOR ENGINEERING CORPORATION     NOTIFICATION DATE:

05/19/98

CITY: SPRINGFIELD             REGION: 1      NOTIFICATION TIME: 15:59[ET]

COUNTY:                        STATE: NJ     EVENT DATE:         05/19/98

LICENSE#:                  AGREEMENT: N      EVENT TIME:       00:00[EDT]

DOCKET:                                      LAST UPDATE DATE:   05/19/98



                                                  NOTIFICATIONS



                                             GENE KELLY     RDO



NRC NOTIFIED BY: JIMMY SHIEH                 VERN HODGE     NRR

HQ OPS OFFICER: BOB STRANSKY



EMERGENCY CLASS: NOT APPLICABLE

10 CFR SECTION:



CDEG 21.21(c)(3)(i) DEFECTS/NONCOMPLIANCE



                               EVENT TEXT

10 CFR PART 21 REPORT



FOLLOWING 6 TO 18 MONTHS OF CONTINUOUS ENERGIZED SERVICE, THREE

VALCOR

MODEL V70900-65-11 AIR PILOT VALVES FAILED TO STROKE CLOSED

IMMEDIATELY

UPON DEENERGIZATION WHEN INSTALLED IN THEIR RESPECTIVE SYSTEMS. 

DELAYS

IN CLOSING HAVE RANGED FROM ONE TO FIVE MINUTES.  DESPITE BEST

EFFORTS,

THE VENDOR REPORTED THAT CLOSING DELAYS HAVE NOT BEEN REPLICATED

OUTSIDE

OF THE PLANT SYSTEMS.



THE VENDOR REPORTED THAT A POTENTIAL CAUSE OF THE DELAYED CLOSING

IS THE

POSSIBLE SUSCEPTIBILITY OF THIS PARTICULAR MODEL TO THE EFFECTS OF

RESIDUAL MAGNETISM.  DELAYED CLOSING MAY OCCUR WHEN THE AIR GAP

BETWEEN

THE PLUNGER AND THE STOP BECOMES TOO SMALL OR IF THE PLUNGER MAKES

CONTACT WITH THE STOP.  EXTENDED PERIODS OF CONTINUOUSLY ENERGIZED

SERVICE AND SUBSEQUENT COMPRESSION SETTING OF THE O-RING SEAT MAY

INDUCE

THE SMALL AIR GAP CONDITION.  AS A RESULT OF THE SMALL AIR GAP, THE

VALVE

MAY THEN BE SUBJECT TO RESIDUAL MAGNETISM FORCES, WHICH TEND TO

PREVENT

CLOSURE OF THE VALVE UPON DEENERGIZATION.  OPENING OPERATION OF THE

VALVE

IS NOT AFFECTED.



THE V70900-65-11 IS AN AC POWERED VERSION AND IS THE ONLY VERSION OF

THE

V70900-65 AIR PILOT SERIES SUBJECT TO THIS EFFECT.  ONLY 46 UNITS OF THIS

PARTICULAR MODEL HAVE BEEN DELIVERED, ALL TO THE SUSQUEHANNA

STEAM

ELECTRIC STATION.  ALL OF THE UNIT HAVE BEEN, OR ARE SCHEDULED TO BE,

MODIFIED BY VALCOR TO ELIMINATE THE POTENTIAL FOR RESIDUAL

MAGNETISM

EFFECTS.





*** END OF DOCUMENT ***