ML17054D020
| ML17054D020 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/17/1976 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML17054D021 | List: |
| References | |
| IEB-76-02, IEB-76-2, NUDOCS 7904200121 | |
| Download: ML17054D020 (8) | |
Text
Inspection and Enforcement Bulletin No. 76-02 March 17, 1976 RELAY COIL FAILURES GE TYPE HFA, HGA, HKA, HMA RELAYS DESCRIPTION OF CIRCUMSTANCES:
A failure of a General Electric (GE) Type 12HFA51A42H Relay occurred recently in a safety related circuit at the Turkey Point facility.
The relay failed during reactor safeguards systems testing., Earlier fail-ures of a similar nature involving GE type HGA relays were reported from Florida Power and Light Company in 1973.
The relay manufacturer has determined that open circuit coil failures of the relay windings had been caused by corrosion.
Halogens from a class of nylon coil spools (or bobbins) plus humid conditions were attributed as the fundamental causes of the corrosion and resulting coil failure.
The relays identified by the manufacturer which may have this nylon spool include HFA, HGA, HKA, HMA relay types, made by GE prior to 1969, and they may be identified by a white, nylon coil 'spool.
Portions of a GE service letter containing information about these relays are attached to this bulletin.
Further instructions regarding repair procedures can be obtained from the GE Service Engineering Department, Philadelphia.
ACTION TO BE TAKEN BY LICENSEES AN) PERMIT HOLDERS:
Licensees of power reactor facilities with an operating license or construction permit are'o take the following actions:
l.
If you have received the attached GE service letter, describe what action you have taken regarding replacement of the older style nylon coil bobbins with the recommended Lexan type bobbins in the types of relays identified in the enclosed GE letter.
2.
If you have not received the attached GE service letter, describe what action you plan to take if relays of the type and vintage described in the enclosed GE letter are in use or planned for use in safety related systems.
3.
For facilities with operating licenses, a report of the above descriptions and plans, including the date when the actions were or will be completed, should be submitted within 30 days after receipt of this bulletin.
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4.
For facilities with construction permits, a report of the above descriptions and plans, including the date when the actions were or will be 'completed, should be submitted within 60 days after receipt of this bulletin.
Reports should be submitted to the Director of the NRC Regional Office and a copy should be forwarded to the NRC Office of Inspection and Enforcement, Division of Reactor Inspection Programs, Washington, D. C.
20555.
Approval of NRC requirements for reports concerning possible generic problems has been obtained under 44 U.S.C.
3152 from the U. S. General Accounting Office.
(GAO Approval B-180255(R0072),
expires 7/31/77)
ATTACKKNT
'xtract from General Electric Service Letter:
HFA, HGA, HKA, HNA RELAYS NYLON COIL BOBBINS
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IE Bulletin Number 76-02 ATTACHMENT A EXTRACT FROM GENERAL ELECTRIC SERVICE LETTER HFA, HGA, HKA, HMA RELAYS NYLON COIL BOBBINS In 1954, a program was initiated to improve the mechanical and elec-trical properties of paper based spools used for HFA, HGA, HKA and HMA relay coils.
Heat stabilized nylon was selected for the spool material because its temperature characteristics made it well suited for Class A
- coils, and the, material provided the desired improvement in electrical and mechanical properties.
Manufacturing of HMA relays with the nylon spools started in 1955.
After three years of successful experience, the change to nylon spools wa implemented in HFA, HGA, and HKA relays in 1958.
In the mid 60's, a few failures of KfA coils utilizing the nylon spools for DC applications were reported.
As a result of these failures, an investigation was undertaken to determine the cause of the failures.
It was found from this investigation that the heat stabilizing element of the nylon coil spool contained halogen ions which could be released over a period of time.'hen combined with moisture, the halogen ions form hydrocloric acid and copper salts which could cause the eventual open circuit failure of the coils.
The most significant contributing factor in the reported failures is high humidity.
Other contributing factors are the small wire size used in HMA relays and in DC relays, and the release of halogen ions is accelerated by DC potential.
Relay coils which are continuously energized are not subject to this phenomenon because the coil temperature is maintained considerably above ambient, thus minimizing the probability of moisture getting into the coil.
After the spool material was changed to nylon in 1955-58, a new mate-rial, Lexan, became avaliable.
Lexan has the desired
- chemical, mech-anical and electrical characteristics for use in spools.
The change to the use of Lexan for spools was started in 1964 and completed in 1968.
The first relay changed was the HMA followed by the HGA and HFA.
Black was chosen for the. color of Lexan,spools to make them distinguishable from the nylon.
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Since the initial report of open cixcuited RfA co l,
ils the failures of limited.
However, recently one customer auxiliary relays has been very m
e reporte an accumu d
accumulation of open circuit failures of a signi ican number of HGA relays with nylon spools which were use circuits o rea ers.
f b k
As a result of this recent repoxt and in keeping ms we are bxing-rocedure of informing you of potential problems, we g
with our proce ure o
n u h the overall rate of ing this matter to your attention, even thoug failure continues to be extremely low.
s of HFA, HGA, HKA, and RfA relays in areas of Xf you have application high humidity, intermittent operation, DC power, an w t w i e
- spools, you may wis l,
wish to consider replacing the coils or relays.
1 OO I
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