United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #:  9412010115

COPES-VULCAN, INC,

PO BOX 577 o LAKE CITY, PENNSYLVANIA 16423-0577 o PHONE (814) 774-1500 o
FAX (814) 774-1682

                                        November 21, 1994

Document Control Desk
U.S. Nuclear Regulatory Commission
Washington, DC 20555

SUBJECT:  Defective Yokes, P/N 342849 manufactured by Copes-Vulcan, Inc.,
          Lake City, PA

REF:      FAX message to NRC Op Center dated Nov. 3, 1994

          Copes-Vulcan has been informed by Tennessee Valley Authority
(TVA) that yokes, P/N 342849, supplied for the upgrade of existing air
operated actuators at the Sequoyah Nuclear Plant do not have an
acceptable thread form for the 1/2"-13 UNC-2B tapped holes.  On November
3, 1994, Copes-Vulcan subsequently notified three (3) utilities of this
defect.  This problem was discovered during the assembly process while
attempting to secure the mating component to the yoke.  Application of
specified assembly torque could not be achieved as the mating component
would lose engagement with the 1/2"-13 UNC-2B thread in the yoke before
the required torque was applied.

          The source of the problem has been traced to a manufacturing
operation which was configured to use a roll tap to form the 1/2"-13 UNC-
2B threads.  For the subject yokes, a cutting tap was incorrectly used
for the threading operation.  This caused the minor diameter of the
thread to be oversize as the base material was cut, rather than formed
(mechanically displaced) to create the thread.

          An investigation into the affected yokes has limited the usage
to nine (9) yokes at TVA, one (1) yoke at Wisconsin Power and one (1)
yoke at Farley Southern Company.  The TVA yokes have not been installed
at this time and the Wisconsin Power, Point Beach, actuator which may
contain a defective yoke, would perform its fail safe mode as delivered
as would the valve at Farley.  All eleven (11) yokes will be replaced.

          Copes-Vulcan re-inspected all yokes in inventory and their
acceptability.

                                             Cordially,


                                             J. R. Scarpelli
                                             Director Quality Assurance
JRS/pjg
Attachment



                          COPES - VULCAN, INC.

                          MARTIN & RICE AVENUES
                           LAKE CITY, PA 16423
                                   USA

PHONE:         814-774-1708
FAX:           814-774-1682

DATE:          November 3, 1994         NO. OF PAGES SENT   1

FROM:          J. R. Scarpelli
               QUALITY ASSURANCE DEPARTMENT

TO:            COMPANY   TVA - Sequoyah

               ATTENTION    Steve Gilley

               FAX NO.  615-843-8750

          Copes-Vulcan, Lake City, Pennsylvania, has been informed by
Tennessee Valley Authority, Sequoyah, that nine (9) yokes, P/N 342849,
supplied to them as part of an upgrade program, have discrepant 1/2-13UNC
taped holes which could impact the ability to operate if installed.

          Copes-Vulcan has traced the problem to a manufacturing
operation which drills the holes oversize and then uses a roll tap to re-
form the threads.  If a roll tap is not used, the thread minor diameter
is oversize to the point of weakening the thread.  This is what happened
in this instance.

          An investigation into the affected yokes has limited the usage
to nine (9) yokes at TVA, one (1) yoke at Wisconsin Power and one (1)
yoke at Farley Southern Company.  The TVA yokes have not been installed
at this time and the Wisconsin Power, Point Beach, actuator which may
contain a defective yoke, would perform its fail safe mode as delivered
as would the valve at Farley.

          The affected utilities have been notified as of November 3,
1994.

          A written report as required by 10CFR21 will be issued.

                                        J. R. Scarpelli
                                        Director Quality Assurance
JRS/pjg


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