United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9907150121

Foxboro
The Foxboro Company
Foxboro, MA 02035-2099
United States of America
Telephone +1 508 543 8750
Facsimile +1 508 549 6750
Internet http://iom.invensys.com/UK/Pages/Foxboro.aspx/

July 9, 1999

Mr. Bob Stransky
United States Nuclear Regulatory Commission
Event Assessment
1155 Rockville Heights
Rockville, MD 02852

SUBJECT: Our notification to you at 10:00 AM July 9, 1999

Dear Mr. Stransky,

In accordance with 10CFR21 this letter is to inform you that Foxboro Co. has identified a potential defect with N-2A0-L2C-R or N-2A0-L2C-R with ECEP 10273, Contact Output Isolator cards that may contain specific N0152CK or C0147SS relays. These relays, supplied by Potter & Brumfield, were manufactured utilizing pure tin plated contact support arms. As a result, in low voltage, low current applications, the growth of tin whiskers between adjacent metallic surfaces of the contact support arms can lead to the establishment of a resistive shunt path. This shunt path would prevent the relay from functioning as designed. This potential defect is limited to only those relays supplied by Potter & Brumfield manufactured from 1 December 1981 to 31 December 1993.

Foxboro is taking immediate corrective action to rectify the situation and will notify all Nuclear Utilities that have purchased this product from Foxboro during the time period affected and provide replacement relays.

Sincerely,
The Foxboro Company

George Robert Johnson
Director, Corporate Quality Assurance and Product Safety

SIEBE

A Siebe Group Company


07/09/1999 U.S. Nuclear Regulatory Commission Operations Center Event Report Page 1
General Information or Other (PAR) Event # 35906
Rep Org: FOXBORO COMPANY Notification Date / Time: 07/09/1999
10:35 (EDT)
Supplier: FOXBORO COMPANY Event Date / Time: 07/09/1999 (EDT)
Last Modification: 07/09/1999
Region: 1 Docket #:
City: FOXBORO Agreement State: Yes
County: License #:
State: MA
NRC Notified by: G. ROBERT JOHNSON Notifications: VERN HODGE NRR
HQ Ops Officer: BOB STRANSKY
Emergency Class: NON EMERGENCY
10 CFR Section: 21.21 UNSPECIFIED PARAGRAPH
DEFECTIVE RELAYS PROVIDED TO FOXBORO BY VENDOR

"Foxboro Co. has identified a potential defect with N-2A0-L2C-R or N-2A0-L2C-R with ECEP 10273, Contact Output Isolator cards that may contain specific NO152CK or CO147SS relays. These relays, supplied by Potter & Brumfield, were manufactured utilizing pure tin plated contact support arms. As a result, in low voltage, low current applications, the growth of tin whiskers between adjacent metallic surfaces of the contact support arms can lead to the establishment of a resistive shunt path. This shunt path would prevent the relay from functioning as designed. This potential defect is limited to only those relays supplied by Potter & Brumfield manufactured from 1 December 1981 to 31 December 1993.

"Foxboro is taking immediate corrective action to rectify the situation and will notify all Nuclear Utilities that have purchased this product from Foxboro during the time period affected and provide replacement relays."

The representative reported that two failed relays were identified after being returned by a foreign reactor facility.


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