Information Notice 1994-54, Failures of General Electric Magne-Blast Circuit Breakers to Latch Closed: Difference between revisions
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| issue date = 08/01/1994 | | issue date = 08/01/1994 | ||
| title = Failures of General Electric Magne-Blast Circuit Breakers to Latch Closed | | title = Failures of General Electric Magne-Blast Circuit Breakers to Latch Closed | ||
| author name = Grimes B | | author name = Grimes B | ||
| author affiliation = NRC/NRR | | author affiliation = NRC/NRR | ||
| addressee name = | | addressee name = | ||
Line 14: | Line 14: | ||
| page count = 15 | | page count = 15 | ||
}} | }} | ||
{{#Wiki_filter:UNITED | {{#Wiki_filter:UNITED STATES | ||
NUCLEAR REGULATORY COMMISSION | |||
OFFICE OF NUCLEAR REACTOR REGULATION | |||
WASHINGTON, D.C. 20555 August 1, 1994 NRC INFORMATION NOTICE 94-54: FAILURES OF GENERAL ELECTRIC MAGNE-BLAST | |||
CIRCUIT BREAKERS TO LATCH CLOSED | |||
==Addressees== | ==Addressees== | ||
All holders of operating licenses or construction permits for nuclear | All holders of operating licenses or construction permits for nuclear power | ||
reactors. | |||
PurDose | |||
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information | |||
notice to alert addressees to a condition in which certain General Electric | |||
(GE) medium-voltage Magne-Blast circuit breakers may begin to randomly fail to | |||
latch closed. It is expected that recipients will review the information for | |||
applicability to their facilities and consider actions, as appropriate, to | |||
avoid similar problems. However, suggestions contained in this information | |||
notice are not NRC requirements; therefore, no specific action or written | |||
response is required. | |||
==Description of Circumstances== | ==Description of Circumstances== | ||
The Maine Yankee Atomic Power Station (Maine Yankee) and the Millstone | The Maine Yankee Atomic Power Station (Maine Yankee) and the Millstone Nuclear | ||
IN 94-54-August 1, 1994 | |||
Power Station (Millstone) have recently experienced failures of safety-related | |||
GE Magne-Blast 4160-Vac circuit breakers to latch closed (also called "going | |||
trip-free"). Failures occurred during post-overhaul, preoperational, and | |||
in-service surveillance testing. At Maine Yankee, failures occurred shortly | |||
after an overhaul of the breakers, during troubleshooting of an indirectly | |||
related problem with limit switches. The affected breakers have failed to | |||
latch on a random basis during up to about two-thirds of attempted closures, both electrically and manually. At both plants, the affected breakers were | |||
among those recently overhauled by the GE Apparatus Service Division of | |||
Philadelphia, with quality assurance coverage provided by GE Nuclear Energy | |||
(NE) Power Delivery Services (PDS) of King of Prussia, Pennsylvania. Failure | |||
analysis, inspection, and testing of one of the affected breakers from Maine | |||
Yankee were performed at the GE Apparatus Service Division under the direction | |||
of GE NE PDS and the design engineer from the breaker manufacturer, GE | |||
Specialty Breaker Plant. The results were consistent with onsite testing at | |||
both Millstone and Maine Yankee. The failure analysis activities, observed by | |||
NRC and licensee representatives, identified the primary failure mode, apparent principal root causes, and the most effective remedies. | |||
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up&LB} b v\ gl~lIX | |||
IN 94-54 | |||
- August 1, 1994 Discussion | |||
The breaker models considered to be potentially affected at the present time | |||
include (1) Type AM-4.16-350-1H and (2) Type AM-4.16-250-6, -7, -8, or -9HB. | |||
GE is currently evaluating other Magne-Blast models for potential | |||
susceptibility. Among these models, only breakers equipped with one prop | |||
reset spring (prop spring), and in which all "Tuf-Loc" (Teflon-coated | |||
fiberglass) bushings (especially the prop bushings) have been replaced with | |||
aluminum-bronze bushings, have recently experienced unreliable latching. | |||
However, it should be noted that this failure ultimately results from a | |||
combination of contributing factors and not all breakers of the potentially | |||
affected type and configuration are prone to failure. In addition, there have | |||
been a few instances (although not recently) of one-prop spring breakers with | |||
Tuf-Loc prop bushings that have failed to latch due to other unsatisfactory | |||
conditions within the breaker such as excessive wear, hardened or insufficient | |||
lubrication, and/or being severely out of adjustment. No failures are known | |||
to GE or the NRC to occur in breakers equipped with two prop springs (included | |||
as original equipment since 1968, or added during maintenance or repair). The | |||
failure analysis testing appeared to confirm the GE position that breakers | |||
with two prop springs should not experience this problem. The details of the | |||
failure mode are discussed in Attachment 1 to this information notice. | |||
Attachment 2 shows the prop springs. | |||
It should be noted that, depending on the severity of the various contributing | |||
conditions, the onset of failure to latch reliably in these breakers may vary, and a breaker that has successfully passed rigorous post-maintenance testing | |||
and further receipt inspection and preoperational testing may subsequently | |||
start failing to latch reliably in service. In recent instances, failures to | |||
latch have begun to occur after about 35-50 operations (cycles) following | |||
overhaul or repair of the operating mechanism. Once started, the failure | |||
frequency has been observed during testing, to vary from 1 failure to latch in | |||
as many as 50 consecutive operations to 16 failures in 24 attempts. The | |||
operating characteristics of a given breaker (in particular, adequacy and | |||
consistency of prop action as explained in Attachment 1) can indicate the | |||
likelihood of unreliable latching. According to GE, the desired prop action | |||
positions the prop fully forward against its stop, thus providing maximum | |||
engagement under the prop pin (called prop wipe). However, affected breakers | |||
that start (or are likely to start) failing to latch reliably typically | |||
exhibit inconsistent (and often less than the design minimum) prop wipe even | |||
when they do latch. | |||
The NRC and licensees have expressed concerns regarding increased suscepti- bility to unwanted tripping with less than minimum design prop wipe caused by | |||
vibration or shock (e.g., during a seismic event). The Magne-Blast design | |||
engineer has stated that because of the geometry and magnitude of forces | |||
acting on the prop, once the mechanism has successfully latched (even if only | |||
barely), it would be extremely unlikely for the shocks or vibration associated | |||
with seismic events to cause the prop to move backwards and olut from under the | |||
prop pin. Nevertheless, a breaker that is latched, but with less than the | |||
design minimum prop wipe, is not in a condition for which it was analyzed or | |||
in which it was tested during seismic qualification. | |||
IN 94-54 August 1, 1994 Normal prop wipe can be confirmed with the breaker in its cubicle and closed | |||
(in test position if necessary) in most installations by visual inspection | |||
(using an inspection mirror and light) without having to get too close to | |||
energized components or hazardous mechanism parts if the switchgear cabinet | |||
door can be opened with appropriate safety precautions. Pending issuance of a | |||
service advice letter (SAL) by the manufacturer on this problem or a safety | |||
communication by GE NE, Attachment 2 illustrates an inspection hole in the | |||
right side of the mechanism frame through which the prop and prop pin position | |||
may be viewed. While the fully forward prop position (to the stop) is the | |||
desired condition (maximum wipe), the absence of failures to latch along with | |||
consistent and greater than minimum allowed prop wipe is, according to GE, | |||
indicative of continued reliable latching. However, because minimum prop wipe | |||
is not a published design specification, and because certain other factors | |||
(e.g., opening spring adjustment) may influence latching reliability, GE has | |||
requested that any licensee experiencing Magne-Blast breaker latching problems | |||
or noticing changed, inconsistent or apparently abnormally low prop wipe, particularly following overhaul or repair including prop bushing replacement, contact GE NE PDS at (610) 992-6049. | |||
Pending installation of a second prop spring in affected breakers, Maine | |||
Yankee has shifted, to the extent possible, its available dual prop spring | |||
breakers to locations where operability requires assured latching reliability | |||
for closure or reclosure during a design-basis event. For the remaining | |||
potentially affected breakers, Maine Yankee is planning expedited inspections | |||
with the assistance of GE NE PDS to aid in its operability determinations. | |||
===Related Generic Communications=== | |||
Information Notice 84-29, "General Electric Magne-Blast Circuit Breaker | |||
Problems," dated April 29, 1984. | |||
Information Notice 90-41, "Potential Failure of General Electric Magne-Blast | |||
Circuit Breakers and AK Circuit Breakers," dated June 12, 1990. | |||
Information Notice 93-91, "Misadjustment Between General Electric 4.16-KY | |||
Circuit Breakers and Their Associated Cubicles," dated December 3, 1993. | |||
Information Notice 94-02, "Inoperability of General Electric Magne-Blast | |||
Breaker Because of Misalignment of Close-Latch Spring," dated January 7, 1994. | |||
IN 94-54 | |||
: August 1, 1994 This information notice requires no specific action or written response. If | |||
you have any questions about the information in this notice, please contact | |||
one of the technical contacts listed below or the appropriate Office of | |||
Nuclear Reactor Regulation (NRR) project manager. | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR | |||
(301) 504-2995 Kamalakar Naidu, NRR Sikindra Mitra, NRR | |||
(301) 504-2980 (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices | |||
47 g AnJ-L | |||
^d | |||
Attachment 1 IN 94-54 August 1, 1994 DETAILS OF THE FAILURE MODE AND CONTRIBUTING FACTORS | |||
The cause of the failures to latch cited in the body of the Information Notice | |||
is related to a component of the Type ML-13 breaker operating mechanism called | |||
the prop (see Attachment 2). The breaker will fail to latch closed when the | |||
prop does not travel forward fast enough (relative to the motion of the | |||
closing linkage) to be in the proper position under the prop pin of the | |||
closing linkage as it rises above then descends onto the prop during the | |||
closing cycle (whether manually or electrically initiated). Absent a trip | |||
condition upon closing, the prop is permitted (by the rotation of the main | |||
cam) to be pulled forward under the prop pin by the prop reset spring (or | |||
springs when two are fitted). If the slower speed of the prop relative to the | |||
pin is such that the pin passes down in front of the prop instead of landing | |||
on top of it (called latching) as it is supposed to, the linkage will | |||
"collapse" causing the moving contact arms to immediately drop down to the | |||
open position. This condition or action is also called the trip-free | |||
condition because it occurs in the same manner as if a trip signal were | |||
present at the breaker tripping mechanism when the breaker attempts to close, thus preventing the prop from moving forward and latching. | |||
According to GE, and as apparently confirmed by testing, several conditions | |||
must be present to render a given breaker susceptible to this failure mode. | |||
Most fundamental are the individual breaker model and configuration, mechanism | |||
type, and vintage. Within these constraints, certain modifications or | |||
upgrades that have (or have not) been performed on a given breaker influence | |||
its susceptibility. Finally, the condition of the breaker mechanism in terms | |||
of age and type of moving parts, wear, lubrication, and adjustment can | |||
ultimately be the determining factor with regard to latching reliability. | |||
Due to their particular combination of operating (opening and closing) spring | |||
configurations, all 4.16-kilovolt (Kv)-rated, vertical-lift, air-magnetic | |||
(Magne-Blast) breakers of 350-million volt-ampere (MVA) interrupting rating | |||
(Type AM-4.16-350-1H) that are fitted with only one prop spring are considered | |||
by GE to be potentially affected. Also potentially affected, owing also to | |||
their particular operating spring configurations, are those 4.16-Kv, 250-MVA- | |||
rated Magne-Blast breakers with one prop spring that have a 78-kilo-ampere | |||
(kA) close-latch rating (called a "high momentary" rating), which includes | |||
Models AM-4.16-250-6, -7, -8, or -9HB (the "H" suffix indicates the ML-13 type | |||
mechanism and the "B" indicates the high momentary rating). | |||
Within this population, the major factor determining susceptibility is the | |||
number of prop springs installed. With one anomalous exception (a breaker | |||
suspected of being grossly out of adjustment), only breakers with one prop | |||
spring have thus far been reported to experience unreliable latching. | |||
Breakers of these models built before about 1968 were originally fitted at the | |||
factory with a single prop spring. After this time, breakers with close and | |||
latch ratings of 77 Ka or 78 Ka were factory fitted with two prop springs, in | |||
order, according to GE, to make the breakers less sensitive to fit and | |||
adjustment tolerances and to facilitate factory setup. The failure analysis | |||
testing indicated that breakers built with or modified subsequently to add a | |||
second (upper) prop spring, and that are not otherwise in severely out of | |||
tolerance condition, should not be susceptible to this failure mode. | |||
Attachment 1 | |||
: IN 94-54 August 1, 1994 The breaker manufacturer, in GE Service Advice Letter (SAL) No. 073-348.1, issued in December 1990, recommended replacement of the main (lower) prop the | |||
spring with an improved spring (called the "gold" prop spring because of | |||
color of its cadmium plating). NRC Information Notice 90-41, "Potential | |||
Failure of General Electric Magne-Blast Circuit Breakers and AK Circuit fitted | |||
Breakers," also addressed this problem. The gold prop spring has been original | |||
in breakers built since 1971, due to fatigue failures reported in the | |||
spring. Although SAL 073-348.1 did describe the dual prop spring | |||
configuration, it did not address the addition of a second prop spring. See | |||
Attachment 2. | |||
Recent breaker overhauls/repairs that included replacement of the Tuf-Loc | |||
(Teflon-coated fiberglass) prop bushings with aluminum-bronze prop bushings, in conjunction with cleaning and relubrication of the closing linkage and | |||
renewal of worn parts have not been demonstrated conclusively to be the sole | |||
cause of the recently reported failures to latch. However, they appear to | |||
have been the common precipitating events. In breakers of the affected models | |||
with one prop spring that have had all the Tuf-Loc bushings (except for the | |||
prop bushings) replaced with aluminum-bronze, the recently reported failures | |||
to latch have begun to occur after about 35-50 operations (cycles) after prop | |||
completion of overhaul or repair that included replacement of the Tuf-Loc | |||
bushings with aluminum-bronze. Since 1975, these breakers have been fitted | |||
with aluminum-bronze sleeve bearings or bushings in their mechanisms (except | |||
for the prop bushings) for improved wear characteristics. Many of the older in | |||
Magne-Blast breakers, in accordance with GE SAL 073-318.1 (and .1A), issued | |||
1977, and 318.2, issued in 1979, have had their original Tuf-Loc bushings "GE | |||
replaced with the aluminum-bronze bushings. IE Information Notice 84-29, Magne-Blast Circuit Breaker Problems," also addressed this issue. The factory | |||
bushing replacement kits, supplied under catalog no. 0156C9403G001, did not | |||
include replacement bushings for the prop. Hence, most prop bushing | |||
replacements have been performed only recently. | |||
When other conditions in a breaker are conducive to marginal latching, it | |||
appears that the new bushings, in conjunction with reduced friction in the | |||
closing linkage from the overhaul, cleaning and new lubricant, may shift the | |||
force and speed balance in the mechanism. The shift can be sufficient to | |||
speed up the motion of the closing linkage and prop pin relative to the prop | |||
(which also may actually be slightly retarded) beyond design margins. Under | |||
these conditions, a single prop spring can no longer move the prop forward | |||
fast enough to latch reliably, or if it does latch, to ensure the desired prop | |||
wipe. Where the second prop spring has been installed in conjunction with the | |||
mechanism overhaul, failure to latch reliably in the manner described hereinnot | |||
has not been reported, and according to GE, as confirmed by testing, would | |||
be expected to occur. Disassembly and detailed inspection of the Maine Yankee | |||
breaker operating mechanism after testing revealed no additional significant | |||
factors contributing to the failures to latch experienced by the test breaker. | |||
Therefore, the test results appear to have confirmed the factors to which | |||
close-latch reliability is most sensitive. | |||
Attachment 2 | |||
1, IN 94-54 August 1, 1994 Page 1 of I | |||
MAGNE-BLAST OPERATING MECHANISM PROP DIAGRAMS | |||
1. Handle | |||
2. Trip Coil Support | |||
3. Trip Coil | |||
4. Trip Armature | |||
5. PROP SPRING | |||
5A. SECOND PROP SPRING | |||
(if fitted) | |||
6. Cam Follower Roller | |||
7. Trip Shaft | |||
8. Trip Latch | |||
9. Trip Latch Roller | |||
10. Roller Support | |||
11. Crank Shaft | |||
12. Cranks | |||
13. PROP PIN | |||
14. PROP | |||
15. Drive Shaft | |||
16. Cam | |||
17. PROP BUSHING | |||
FRONT OF BREAKER | |||
Figure 1 (Adapted From Figure 7 of GE Instruction Book GEI-88761) | |||
Figure 2: Right Side View of ML-13 Operating Mechanism | |||
(From Figure 4 of GE Instruction Book GEI-88761) | |||
Attachment 3 | |||
' IN 94-54 August 1, 1994 LIST OF RECENTLY ISSUED | |||
NRC INFORMATION NOTICES | |||
Information Date of | |||
Notice No. Subject Issuance Issued to | |||
91-45, Possible Malfunction of 07/29/94 All holders of OLs or CPs | |||
Supp. 1 Westinghouse ARD, BFD, for nuclear power reactors. | |||
and NBFD Relays, and | |||
A200 DC and DPC 250 | |||
Magnetic Contactors | |||
94-42, Cracking in the Lower 07/19/94 All holders of OLs or CPs | |||
Supp. 1 Region of the Core Shroud for boiling water reactors | |||
in Boiling-Water Reactors (BWRs). | |||
94-53 Hydrogen Gas Burn Inside 07/18/94 All holders of OLs or CPs | |||
Pressurizer During Welding for nuclear power reactors. | |||
94-52 Inadvertent Containment 07/15/94 All holders of OLs or CPs | |||
Spray and Reactor Vessel for nuclear power reactors. | |||
Draindown at Millstone | |||
Unit 1 | |||
94-51 Inappropriate Greasing 07/15/94 All holders of OLs or CPs | |||
of Double Shielded Motor for nuclear power reactors. | |||
Bearings | |||
94-50 Failure of General 07/14/94 All holders of OLs or CPs | |||
Electric Contactors for nuclear power reactors. | |||
to Pull in at the | |||
Required Voltage | |||
94-49 Failure of Torque 07/06/94 All holders of OLs or CPs | |||
Switch Roll Pins for nuclear power reactors. | |||
94-48 Snubber Lubricant 06/30/94 All holders of OLs or CPs | |||
Degradation in High- for nuclear power reactors. | |||
Temperature Environments | |||
94-13, Unanticipated and Unin- 06/28/94 All holders of OLs or CPs | |||
Supp. 1 tended Movement of Fuel for nuclear power reactors. | |||
Assemblies and other | |||
Components due to Improper | |||
Operation of Refueling | |||
Equipment | |||
OL = Operating License | |||
CP = Construction Permit | |||
IN 94-54 August 1, 1994 This information notice requires no specific action or written response. If | |||
you have any questions about the information in this notice, please contact | |||
one of the technical contacts listed below or the appropriate Office of | |||
Nuclear Reactor Regulation (NRR) project manager. | |||
orig /s/'d by CIGrimes/for | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR | |||
(301) 504-2995 Kamalakar Naidu, NRR Sikindra Mitra, NRR | |||
(301) 504-2980 (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices | |||
*SEE PREVIOUS CONCURRENCE | |||
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED | |||
SAlexander* KNaidu* GCwal ina* MMejac* | |||
05/19/94 04/14/94 05/19/94 04/18/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR | |||
LNorrholm* CERossi* SMitra* CBerlinger* | |||
05/24/94 05/27/94 07/06/94 07/11/94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR | |||
PWen* ELDoolittle* BKGrimes(Y- | |||
07/13/94 07/14/94 OT/94 | |||
07D NAM 1 OFFICIAL RECORD COPY DOCUMENT NAME: 94-54. IN | |||
NOTE: The PMs for Maine Yankee (E. Trottier) and Millstone-1 (J. Andersen) | |||
have been informed of the development of this information notice, and | |||
their comments have been incorporated. | |||
Steve Alexander of the Vender Inspection Branch has consulted with GE on | |||
the technical accuracy of this information notice. GE's comments have | |||
been incorporated. | |||
Peter Wen, 7/13/94 | |||
IN 94-XX | |||
July XX, 1994 This information notice requires no specific action or written response. If | |||
you have any questions about the information in this notice, please contact | |||
one of the technical contacts listed below or the appropriate Office of | |||
Nuclear Reactor Regulation (NRR) project manager. | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR | |||
(301) 504-2995 Kamalakar Naidu, NRR Sikindra Mitra, NRR | |||
(301) 504-2980 (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices | |||
*SEE PREVIOUS CONCURRENCE | |||
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED | |||
SAlexander* KNaidu* GCwal ina* MMejac* | |||
05/19/94 04/14/94 05/19/94 04/18/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR | |||
LNorrholm* CERossi* SMitra* CBerlinger* | |||
05/24/94 05/27/94 07/06/94 07/11/94 OGCB: QRS:NRR AO/ :DORS:NRR D/:DORS:NRR | |||
PWen tV\1 E 4ff^1ttl e BKGrimes | |||
07/13 /94 07/" /4 07/ /94 4 OFFICIAL RECORD COPY DOCUMENT NAME: GEMAGNET.IN | |||
NOTE: The PMs for Maine Yankee (E. Trottier) and Millstone-I (J. Andersen) | |||
have been informed of the development of this information notice, and | |||
their comments have been incorporated. | |||
Steve Alexander of the Vender Inspection Branch has consulted with GE on | |||
the technical accuracy of this information notice. GE's comments have | |||
been incorporated. | |||
Peter Wen, 7/13/94 | |||
IN 94-XX | |||
July XX, 1994 Normal prop wipe can be confirmed with the breaker in its cubicle and closed | |||
(in test position if necessary) in most installations by visual inspection | |||
(using an inspection mirror and light) without having to get too close to | |||
energized components or hazardous mechanism parts if the switchgear cabinet | |||
door can be opened with appropriate safety precautions. Pending issuance of a | |||
service advice letter (SAL) by the manufacturer on this problem or a safety | |||
communication by GE NE, Attachment 2 illustrates an inspection hole in the | |||
right side of the mechanism frame through which the prop and prop pin position | |||
may be viewed. While the fully forward prop position (to the stop) is the | |||
desired condition (maximum wipe), the absence of failures to latch along with | |||
consistent and greater than minimum allowed prop wipe is, according to GE, | |||
indicative of continued reliable latching. However, because minimum prop wipe | |||
is not a published design specification, and because certain other factors | |||
(e.g., opening spring adjustment) may influence latching reliability, GE has | |||
requested that any licensee experiencing Magne-Blast breaker latching problems | |||
or noticing changed, inconsistent or apparently abnormally low prop wipe, particularly following overhaul or repair including prop bushing replacement, contact GE NE PDS at 610-992-6049. | |||
Pending installation of a second prop spring in affected breakers, Maine | |||
Yankee has shifted, to the extent possible, its available dual prop spring | |||
breakers to locations where operability requires assured latching reliability | |||
for closure or reclosure during a design-basis event. For the remaining | |||
potentially affected breakers, Maine Yankee is planning expedited inspections | |||
with the assistance of GE NE PDS to aid in its operability determinations. | |||
NRC Information Notice 94-XX, issued May XX, 1994, discusses other recently | |||
identified problems impacting Magne-Blast operability, related to defective | |||
and improperly installed GE CR2940 limit switches. | |||
This information notice requires no specific action or written response. | |||
If you have any questions about the information in this notice, please contact | |||
one of the technical contacts listed below or the appropriate Office of | |||
Nuclear Reactor Regulation (NRR) project manager. | |||
ORIG /S/'D BY BKGRIMES | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR Kamalakar Naidu, NRR | |||
(301) 504-2995 (301) 504-2980 | |||
Sikindra Mitra, NRR (301) 504-2783 Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices *See previous concurrence | |||
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED | |||
SAlexander* KNaidu* GCwalina* MMejac* | |||
05/19/94 04/14/94 05/19/94 04/18/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE(PR, 1 C/EELB:DE:N f ) | |||
LNorrholm* CERossi* Smityaafb' Cjerlinger | |||
05/24/94 05/27/94 cuff/94 OV/tt/94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D7:DORS:NRR | |||
===PWen BKGrimes=== | |||
07/ /94 07/ /94 07/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I MAGNE3AT.GE | |||
IN 94-XX | |||
May XX, 1994 Normal prop wi can be confirmed with the breaker in its cubicle and closed | |||
(in test position if necessary) in most installations by visual inspection | |||
(using an inspectio mirror and light) without having to get too close to | |||
energized components r hazardous mechanism parts if the switchgear cabinet | |||
door can be opened wit appropriate safety precautions. Pending issuance of a | |||
service advice letter (SAL) by the manufacturer on this problem or a safety | |||
communication by GE NE, Attchment 2 illustrates an inspection hole in the | |||
right side of the mechanism ame through which the prop and prop pin position | |||
may be viewed. While the fully forward prop position (to the stop) is the | |||
desired condition (maximum wipe), the absence of failures to latch along with | |||
consistent and greater than minim allowed prop wipe is, according to GE, | |||
indicative of continued reliable la thing. However, because minimum prop wipe | |||
is not a published design specificatio, and because certain other factors | |||
(e.g., opening spring adjustment) may i'hluence latching reliability, GE has | |||
requested that any licensee experiencing 14 gne-Blast breaker latching problems | |||
or noticing changed, inconsistent or appare tly abnormally low prop wipe, particularly following overhaul or repair in uding prop bushing replacement, contact GE NE PDS at 610-992-6049. | |||
Pending installation of a second prop sprin in affected breakers, Maine | |||
Yankee has shifted, to the extent possible, its aailable dual prop spring | |||
breakers to locations where operability requires assured latching reliability | |||
for closure or reclosure during a design-basis event. For the remaining | |||
potentially affected breakers, Maine Yankee is plannin expedited inspections | |||
with the assistance of GE NE PDS to aid in its operabilMty determinations. | |||
NRC Information Notice 94-XX, issued May XX, 1994, discusles other recently | |||
identified problems impacting Magne-Blast operability, rela ed to defective | |||
and improperly installed GE CR2940 limit switches. | |||
This information notice requires no specific action or w *tten response. | |||
If you have any questions about the information in this notice, lease contact | |||
one of the technical contacts listed below or the appropriate Of ce of | |||
Nuclear Reactor Regulation (NRR) project manager. | |||
ORIG /S/'D BY BKGRIMES | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR Kamalakar Naidu, NRR | |||
(301) 504-2995 (301) 504-2980 | |||
Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices *See previous concurrence | |||
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED | |||
SAlexander* KNaidu* GCwalina* MMeJac* | |||
05/19/94 04/14/94 05/19/94 04/18/94 C/VI BDRIL:NRR D/D I *N ChftA EELB:DE:NRR C/EELB:DE:NRF | |||
LN I film SMitra CBerlinger | |||
'05JK1 /94 05/17g 4\ 05/ /94 05/ /94 OGCB:DORS:NRR AC/OGCB:DORS :NRR D/:DORS:NRR | |||
PWen AJKugler BKGrimes | |||
05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I MAGNE3AT.GE | |||
IN 94-XX | |||
May XX, 1994 Normal prop wipe can be confirmed with the breaker in its cubicle and closed | |||
(in test position if necessary) in most installations by visual inspection | |||
(using an inspection mirror and light) without having to get too close to | |||
energized components or hazardous mechanism parts if the switchgear cabinet | |||
can be opened with appropriate safety precautions. Pending issuance of a | |||
serv' advice letter (SAL) by the manufacturer on this problem or a safety | |||
communic ion by GE NE, Attachment 2 illustrates an inspection hole in the | |||
right side the mechanism frame through which the prop and prop pin position | |||
may be viewed. hile the fully forward prop position (to the stop) is the | |||
desired condition aximum wipe), the absence of failures to latch along with | |||
consistent and grea than minimum allowed prop wipe is, according to GE, | |||
indicative of continue reliable latching. However, because minimum prop wipe | |||
is not a published desig specification, and because certain other factors | |||
(e.g., opening spring adjus ent) may influence latching reliability, GE has | |||
requested that any licensee e eriencing Magne-Blast breaker latching problems | |||
or noticing changed, inconsiste or apparently abnormally low prop wipe, particularly following overhaul o repair including prop bushing replacement, contact GE NE PDS at 215-992-6049. | |||
Pending installation of a secon rop spring in affected breakers, Maine | |||
Yankee has shifted to the extent possibe, its available dual prop spring | |||
breakers to locations where operability quires assured latching reliability | |||
for closure or reclosure during a design-b is event. For the remaining | |||
potentially affected breakers, Maine Yankee planning expedited inspections | |||
with the assistance of GE NE PDS to aid in it operability determinations. | |||
NRC Information Notice 94-XX, issued May XX, 19 , discusses other recently | |||
identified problems impacting Magne-Blast operab ity, related to defective | |||
and improperly installed GE CR2940 limit switches. | |||
This information notice requires no specific ac ion or written response. | |||
If you have any questions about the information in th notice, please contact | |||
one of the technical contacts listed below or the appro late Office of | |||
Nuclear Reactor Regulation (NRR) project manager. | |||
ORIG /S/'D BY BKGRIMES | |||
Brian K. Grimes, Directo | |||
Division of Operating Reac or Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR Kamalakar Naidu, NRR | |||
(301) 504-2995 (301) 504-2980 | |||
Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices | |||
VIB:DRIL VIB:DRIL SC V :DRIL TECHED | |||
S~lexanderl'J K &aicu, G& S1na MMejac* | |||
05/(9/94 04/ W 94* O'5/94 04/18/94 C VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR CIEELB:DE:NRR | |||
Lgrrholm CERossi SMitra Caerlinger | |||
05/ /94 05/ /94 05/ /94 05/ /94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR | |||
PWen AJKugler BKGrimes | |||
05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNE3AT.GE | |||
<&c rfmtC'al Cak"vyc.t | |||
IN 94-XX | |||
April XX, 1994 Prop wipe can be etermined in most installations by visual inspection without | |||
having to get too lose to hazardous mechanism parts if the switchgear cabinet | |||
door can be opened fely. Pending issuance of a SAL by the manufacturer on | |||
this problem (and/or Service Information Letter by GE NE), Attachment 2 illustrates one locatlo where the prop position may be seen. While fully | |||
forward prop position (t the stop) is the desired condition (maximum wipe), | |||
the absence of failures to latch along with consistent and greater than | |||
minimum allowed prop wipe is according to GE, indicative of continued | |||
reliable latching. However, cause minimum prop wipe is not a published | |||
design specification, and becau certain other factors (e.g. opening spring | |||
adjustment) may influence latchin reliability, GE has requested that any | |||
licensee experiencing Magne-Blast eaker latching problems or noticing | |||
changed, inconsistent or what appear to be abnormally low prop wipe, parti- cularly following prop bushing replacemnt, contact GE NE PDS at 215-992-6049. | |||
In the meantime, pending installat n of a second prop spring in its | |||
affected breakers, Maine Yankee has shift to the extent possible, its | |||
available dual prop spring breakers to loca Ions where operability requires | |||
assured latching reliability for closure or closure during a design basis | |||
event. For the remaining suspect breakers, Mane Yankee has undertaken | |||
expedited inspections with the assistance of G E PDS to aid in its operabil- ity determinations. NRC Information Notice 94-X issued April XX, 1994, dis- cusses other recently identified problems impactin Magne-Blast operability, related to defective and improperly installed GE CR 940 limit switches. | |||
This information notice requires no specific ac on or written response. | |||
If you have any questions about the information in thi notice, please contact | |||
the technical contacts listed below or the appropriate ffice of Nuclear | |||
Reactor Regulation (NRR) project manager. | |||
ORIG /S/'D BY BKGRIMES | |||
Brian K. Grimes, Directo | |||
Division of Operating Reac or Support | |||
Office of Nuclear Reactor R ulation | |||
Technical contacts: Stephen Alexander, NRR | |||
(301) 504-2995 Kamalakar Naidu, NRR | |||
(301) 504-2980 | |||
Attachments: | |||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued NRC Information Notices | |||
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED | |||
Salexander Knaidu Gcwalina 41./V (,AA- | |||
04/ /94 04/ /94 04/ /94 04/AR/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR | |||
Lnorrholm CERossi SMitra Cberlinger | |||
04/ /94 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR | |||
PWen AJKugler BKGrimes | |||
04/ /94 04/ /94 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN | |||
IN 94-XX | |||
April XX, 1994 Prop wipe can be termined in most installations by visual inspection without | |||
having to get too c eto hazardous mechanism parts if the switchgear cabinet | |||
door can be opened sa ly. Pending issuance of a SAL by the manufacturer on | |||
this problem (and/or a rvice Information Letter by GE NE), Attachment 2 illustrates one location ere the prop position may be seen. While fully | |||
forward prop position (to t stop) is the desired condition (maximum wipe), | |||
the absence of failures to lat h along with consistent and greater than | |||
minimum allowed prop wipe is, a cording to GE, indicative of continued | |||
reliable latching. However, bec se minimum prop wipe is not a published | |||
design specification, and because ertain other factors (e.g. opening spring | |||
adjustment) may influence latching eliability, GE has requested that any | |||
licensee experiencing Magne-Blast breker latching problems or noticing | |||
changed, inconsistent or what appears o be abnormally low prop wipe, parti- cularly following prop bushing replacem t, contact GE NE PDS at 215-992-6049. | |||
In the meantime, pending installatlo of a second prop spring in its | |||
affected breakers, Maine Yankee has shifte to the extent possible, its | |||
available dual prop spring breakers to loca ions where operability requires | |||
assured latching reliability for closure or eclosure during a design basis | |||
event. For the remaining suspect breakers, M ne Yankee has undertaken | |||
expedited inspections with the assistance of G NE PDS to aid in its operabil- ity determinations. NRC Information Notice 94- , issued April XX, 1994, dis- cusses other recently identified problems impact g Magne-Blast operability, related to defective and improperly installed GE R2940 limit switches. | |||
This information notice requires no specific ction or written response. | |||
If you have any questions about the information in \this notice, please contact | |||
the technical contacts listed below or the appropri te Office of Nuclear | |||
Reactor Regulation (NRR) project manager. | |||
ORIG /S/'D BY BKG IMES | |||
Brian K. Grimes, irector | |||
Division of Operat ng Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Stephen Alexander, NRR | |||
(301) 504-2995 Kamalakar Naidu, NRR | |||
(301) 504-2980 | |||
1. Details of Failure Mode and Contributing | Attachments: | ||
1. Details of Failure Mode and Contributing Factors | |||
2. Magne-Blast Prop Mechanism Diagram | |||
3. List of Recently Issued_ RC Information Notices | |||
VIB:DRIL VIB:DRI SC/VIB:DRIL TECHED | |||
=== | ===Salexand9k Knaidu Gcwalina=== | ||
04//5'/94 04/14/94 s '4, 04/ /94 04/ /94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR | |||
Lnorrholm CERossi SMitra Cberlinger | |||
04/ /94 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR | |||
=== | ===PWen AJKugler BKGrimes=== | ||
04/ /94 04/ /94 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN}} | |||
{{Information notice-Nav}} | {{Information notice-Nav}} |
Latest revision as of 04:27, 24 November 2019
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 August 1, 1994 NRC INFORMATION NOTICE 94-54: FAILURES OF GENERAL ELECTRIC MAGNE-BLAST
CIRCUIT BREAKERS TO LATCH CLOSED
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
PurDose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to a condition in which certain General Electric
(GE) medium-voltage Magne-Blast circuit breakers may begin to randomly fail to
latch closed. It is expected that recipients will review the information for
applicability to their facilities and consider actions, as appropriate, to
avoid similar problems. However, suggestions contained in this information
notice are not NRC requirements; therefore, no specific action or written
response is required.
Description of Circumstances
The Maine Yankee Atomic Power Station (Maine Yankee) and the Millstone Nuclear
Power Station (Millstone) have recently experienced failures of safety-related
GE Magne-Blast 4160-Vac circuit breakers to latch closed (also called "going
trip-free"). Failures occurred during post-overhaul, preoperational, and
in-service surveillance testing. At Maine Yankee, failures occurred shortly
after an overhaul of the breakers, during troubleshooting of an indirectly
related problem with limit switches. The affected breakers have failed to
latch on a random basis during up to about two-thirds of attempted closures, both electrically and manually. At both plants, the affected breakers were
among those recently overhauled by the GE Apparatus Service Division of
Philadelphia, with quality assurance coverage provided by GE Nuclear Energy
(NE) Power Delivery Services (PDS) of King of Prussia, Pennsylvania. Failure
analysis, inspection, and testing of one of the affected breakers from Maine
Yankee were performed at the GE Apparatus Service Division under the direction
of GE NE PDS and the design engineer from the breaker manufacturer, GE
Specialty Breaker Plant. The results were consistent with onsite testing at
both Millstone and Maine Yankee. The failure analysis activities, observed by
NRC and licensee representatives, identified the primary failure mode, apparent principal root causes, and the most effective remedies.
9407270127 PmR 2 -O5M qq9o(
up&LB} b v\ gl~lIX
- August 1, 1994 Discussion
The breaker models considered to be potentially affected at the present time
include (1) Type AM-4.16-350-1H and (2) Type AM-4.16-250-6, -7, -8, or -9HB.
GE is currently evaluating other Magne-Blast models for potential
susceptibility. Among these models, only breakers equipped with one prop
reset spring (prop spring), and in which all "Tuf-Loc" (Teflon-coated
fiberglass) bushings (especially the prop bushings) have been replaced with
aluminum-bronze bushings, have recently experienced unreliable latching.
However, it should be noted that this failure ultimately results from a
combination of contributing factors and not all breakers of the potentially
affected type and configuration are prone to failure. In addition, there have
been a few instances (although not recently) of one-prop spring breakers with
Tuf-Loc prop bushings that have failed to latch due to other unsatisfactory
conditions within the breaker such as excessive wear, hardened or insufficient
lubrication, and/or being severely out of adjustment. No failures are known
to GE or the NRC to occur in breakers equipped with two prop springs (included
as original equipment since 1968, or added during maintenance or repair). The
failure analysis testing appeared to confirm the GE position that breakers
with two prop springs should not experience this problem. The details of the
failure mode are discussed in Attachment 1 to this information notice.
Attachment 2 shows the prop springs.
It should be noted that, depending on the severity of the various contributing
conditions, the onset of failure to latch reliably in these breakers may vary, and a breaker that has successfully passed rigorous post-maintenance testing
and further receipt inspection and preoperational testing may subsequently
start failing to latch reliably in service. In recent instances, failures to
latch have begun to occur after about 35-50 operations (cycles) following
overhaul or repair of the operating mechanism. Once started, the failure
frequency has been observed during testing, to vary from 1 failure to latch in
as many as 50 consecutive operations to 16 failures in 24 attempts. The
operating characteristics of a given breaker (in particular, adequacy and
consistency of prop action as explained in Attachment 1) can indicate the
likelihood of unreliable latching. According to GE, the desired prop action
positions the prop fully forward against its stop, thus providing maximum
engagement under the prop pin (called prop wipe). However, affected breakers
that start (or are likely to start) failing to latch reliably typically
exhibit inconsistent (and often less than the design minimum) prop wipe even
when they do latch.
The NRC and licensees have expressed concerns regarding increased suscepti- bility to unwanted tripping with less than minimum design prop wipe caused by
vibration or shock (e.g., during a seismic event). The Magne-Blast design
engineer has stated that because of the geometry and magnitude of forces
acting on the prop, once the mechanism has successfully latched (even if only
barely), it would be extremely unlikely for the shocks or vibration associated
with seismic events to cause the prop to move backwards and olut from under the
prop pin. Nevertheless, a breaker that is latched, but with less than the
design minimum prop wipe, is not in a condition for which it was analyzed or
in which it was tested during seismic qualification.
IN 94-54 August 1, 1994 Normal prop wipe can be confirmed with the breaker in its cubicle and closed
(in test position if necessary) in most installations by visual inspection
(using an inspection mirror and light) without having to get too close to
energized components or hazardous mechanism parts if the switchgear cabinet
door can be opened with appropriate safety precautions. Pending issuance of a
service advice letter (SAL) by the manufacturer on this problem or a safety
communication by GE NE, Attachment 2 illustrates an inspection hole in the
right side of the mechanism frame through which the prop and prop pin position
may be viewed. While the fully forward prop position (to the stop) is the
desired condition (maximum wipe), the absence of failures to latch along with
consistent and greater than minimum allowed prop wipe is, according to GE,
indicative of continued reliable latching. However, because minimum prop wipe
is not a published design specification, and because certain other factors
(e.g., opening spring adjustment) may influence latching reliability, GE has
requested that any licensee experiencing Magne-Blast breaker latching problems
or noticing changed, inconsistent or apparently abnormally low prop wipe, particularly following overhaul or repair including prop bushing replacement, contact GE NE PDS at (610) 992-6049.
Pending installation of a second prop spring in affected breakers, Maine
Yankee has shifted, to the extent possible, its available dual prop spring
breakers to locations where operability requires assured latching reliability
for closure or reclosure during a design-basis event. For the remaining
potentially affected breakers, Maine Yankee is planning expedited inspections
with the assistance of GE NE PDS to aid in its operability determinations.
Related Generic Communications
Information Notice 84-29, "General Electric Magne-Blast Circuit Breaker
Problems," dated April 29, 1984.
Information Notice 90-41, "Potential Failure of General Electric Magne-Blast
Circuit Breakers and AK Circuit Breakers," dated June 12, 1990.
Information Notice 93-91, "Misadjustment Between General Electric 4.16-KY
Circuit Breakers and Their Associated Cubicles," dated December 3, 1993.
Information Notice 94-02, "Inoperability of General Electric Magne-Blast
Breaker Because of Misalignment of Close-Latch Spring," dated January 7, 1994.
- August 1, 1994 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR
(301) 504-2995 Kamalakar Naidu, NRR Sikindra Mitra, NRR
(301) 504-2980 (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices
47 g AnJ-L
^d
Attachment 1 IN 94-54 August 1, 1994 DETAILS OF THE FAILURE MODE AND CONTRIBUTING FACTORS
The cause of the failures to latch cited in the body of the Information Notice
is related to a component of the Type ML-13 breaker operating mechanism called
the prop (see Attachment 2). The breaker will fail to latch closed when the
prop does not travel forward fast enough (relative to the motion of the
closing linkage) to be in the proper position under the prop pin of the
closing linkage as it rises above then descends onto the prop during the
closing cycle (whether manually or electrically initiated). Absent a trip
condition upon closing, the prop is permitted (by the rotation of the main
cam) to be pulled forward under the prop pin by the prop reset spring (or
springs when two are fitted). If the slower speed of the prop relative to the
pin is such that the pin passes down in front of the prop instead of landing
on top of it (called latching) as it is supposed to, the linkage will
"collapse" causing the moving contact arms to immediately drop down to the
open position. This condition or action is also called the trip-free
condition because it occurs in the same manner as if a trip signal were
present at the breaker tripping mechanism when the breaker attempts to close, thus preventing the prop from moving forward and latching.
According to GE, and as apparently confirmed by testing, several conditions
must be present to render a given breaker susceptible to this failure mode.
Most fundamental are the individual breaker model and configuration, mechanism
type, and vintage. Within these constraints, certain modifications or
upgrades that have (or have not) been performed on a given breaker influence
its susceptibility. Finally, the condition of the breaker mechanism in terms
of age and type of moving parts, wear, lubrication, and adjustment can
ultimately be the determining factor with regard to latching reliability.
Due to their particular combination of operating (opening and closing) spring
configurations, all 4.16-kilovolt (Kv)-rated, vertical-lift, air-magnetic
(Magne-Blast) breakers of 350-million volt-ampere (MVA) interrupting rating
(Type AM-4.16-350-1H) that are fitted with only one prop spring are considered
by GE to be potentially affected. Also potentially affected, owing also to
their particular operating spring configurations, are those 4.16-Kv, 250-MVA-
rated Magne-Blast breakers with one prop spring that have a 78-kilo-ampere
(kA) close-latch rating (called a "high momentary" rating), which includes
Models AM-4.16-250-6, -7, -8, or -9HB (the "H" suffix indicates the ML-13 type
mechanism and the "B" indicates the high momentary rating).
Within this population, the major factor determining susceptibility is the
number of prop springs installed. With one anomalous exception (a breaker
suspected of being grossly out of adjustment), only breakers with one prop
spring have thus far been reported to experience unreliable latching.
Breakers of these models built before about 1968 were originally fitted at the
factory with a single prop spring. After this time, breakers with close and
latch ratings of 77 Ka or 78 Ka were factory fitted with two prop springs, in
order, according to GE, to make the breakers less sensitive to fit and
adjustment tolerances and to facilitate factory setup. The failure analysis
testing indicated that breakers built with or modified subsequently to add a
second (upper) prop spring, and that are not otherwise in severely out of
tolerance condition, should not be susceptible to this failure mode.
Attachment 1
- IN 94-54 August 1, 1994 The breaker manufacturer, in GE Service Advice Letter (SAL) No. 073-348.1, issued in December 1990, recommended replacement of the main (lower) prop the
spring with an improved spring (called the "gold" prop spring because of
color of its cadmium plating). NRC Information Notice 90-41, "Potential
Failure of General Electric Magne-Blast Circuit Breakers and AK Circuit fitted
Breakers," also addressed this problem. The gold prop spring has been original
in breakers built since 1971, due to fatigue failures reported in the
spring. Although SAL 073-348.1 did describe the dual prop spring
configuration, it did not address the addition of a second prop spring. See
Attachment 2.
Recent breaker overhauls/repairs that included replacement of the Tuf-Loc
(Teflon-coated fiberglass) prop bushings with aluminum-bronze prop bushings, in conjunction with cleaning and relubrication of the closing linkage and
renewal of worn parts have not been demonstrated conclusively to be the sole
cause of the recently reported failures to latch. However, they appear to
have been the common precipitating events. In breakers of the affected models
with one prop spring that have had all the Tuf-Loc bushings (except for the
prop bushings) replaced with aluminum-bronze, the recently reported failures
to latch have begun to occur after about 35-50 operations (cycles) after prop
completion of overhaul or repair that included replacement of the Tuf-Loc
bushings with aluminum-bronze. Since 1975, these breakers have been fitted
with aluminum-bronze sleeve bearings or bushings in their mechanisms (except
for the prop bushings) for improved wear characteristics. Many of the older in
Magne-Blast breakers, in accordance with GE SAL 073-318.1 (and .1A), issued
1977, and 318.2, issued in 1979, have had their original Tuf-Loc bushings "GE
replaced with the aluminum-bronze bushings. IE Information Notice 84-29, Magne-Blast Circuit Breaker Problems," also addressed this issue. The factory
bushing replacement kits, supplied under catalog no. 0156C9403G001, did not
include replacement bushings for the prop. Hence, most prop bushing
replacements have been performed only recently.
When other conditions in a breaker are conducive to marginal latching, it
appears that the new bushings, in conjunction with reduced friction in the
closing linkage from the overhaul, cleaning and new lubricant, may shift the
force and speed balance in the mechanism. The shift can be sufficient to
speed up the motion of the closing linkage and prop pin relative to the prop
(which also may actually be slightly retarded) beyond design margins. Under
these conditions, a single prop spring can no longer move the prop forward
fast enough to latch reliably, or if it does latch, to ensure the desired prop
wipe. Where the second prop spring has been installed in conjunction with the
mechanism overhaul, failure to latch reliably in the manner described hereinnot
has not been reported, and according to GE, as confirmed by testing, would
be expected to occur. Disassembly and detailed inspection of the Maine Yankee
breaker operating mechanism after testing revealed no additional significant
factors contributing to the failures to latch experienced by the test breaker.
Therefore, the test results appear to have confirmed the factors to which
close-latch reliability is most sensitive.
Attachment 2
1, IN 94-54 August 1, 1994 Page 1 of I
MAGNE-BLAST OPERATING MECHANISM PROP DIAGRAMS
1. Handle
2. Trip Coil Support
3. Trip Coil
4. Trip Armature
5. PROP SPRING
5A. SECOND PROP SPRING
(if fitted)
6. Cam Follower Roller
7. Trip Shaft
8. Trip Latch
9. Trip Latch Roller
10. Roller Support
11. Crank Shaft
12. Cranks
13. PROP PIN
14. PROP
15. Drive Shaft
16. Cam
17. PROP BUSHING
FRONT OF BREAKER
Figure 1 (Adapted From Figure 7 of GE Instruction Book GEI-88761)
Figure 2: Right Side View of ML-13 Operating Mechanism
(From Figure 4 of GE Instruction Book GEI-88761)
Attachment 3
' IN 94-54 August 1, 1994 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information Date of
Notice No. Subject Issuance Issued to
91-45, Possible Malfunction of 07/29/94 All holders of OLs or CPs
Supp. 1 Westinghouse ARD, BFD, for nuclear power reactors.
and NBFD Relays, and
Magnetic Contactors
94-42, Cracking in the Lower 07/19/94 All holders of OLs or CPs
Supp. 1 Region of the Core Shroud for boiling water reactors
in Boiling-Water Reactors (BWRs).
94-53 Hydrogen Gas Burn Inside 07/18/94 All holders of OLs or CPs
Pressurizer During Welding for nuclear power reactors.
94-52 Inadvertent Containment 07/15/94 All holders of OLs or CPs
Spray and Reactor Vessel for nuclear power reactors.
Draindown at Millstone
Unit 1
94-51 Inappropriate Greasing 07/15/94 All holders of OLs or CPs
of Double Shielded Motor for nuclear power reactors.
Bearings
94-50 Failure of General 07/14/94 All holders of OLs or CPs
Electric Contactors for nuclear power reactors.
to Pull in at the
Required Voltage
94-49 Failure of Torque 07/06/94 All holders of OLs or CPs
Switch Roll Pins for nuclear power reactors.
94-48 Snubber Lubricant 06/30/94 All holders of OLs or CPs
Degradation in High- for nuclear power reactors.
Temperature Environments
94-13, Unanticipated and Unin- 06/28/94 All holders of OLs or CPs
Supp. 1 tended Movement of Fuel for nuclear power reactors.
Assemblies and other
Components due to Improper
Operation of Refueling
Equipment
OL = Operating License
CP = Construction Permit
IN 94-54 August 1, 1994 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
orig /s/'d by CIGrimes/for
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR
(301) 504-2995 Kamalakar Naidu, NRR Sikindra Mitra, NRR
(301) 504-2980 (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED
SAlexander* KNaidu* GCwal ina* MMejac*
05/19/94 04/14/94 05/19/94 04/18/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR
LNorrholm* CERossi* SMitra* CBerlinger*
05/24/94 05/27/94 07/06/94 07/11/94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR
PWen* ELDoolittle* BKGrimes(Y-
07/13/94 07/14/94 OT/94
07D NAM 1 OFFICIAL RECORD COPY DOCUMENT NAME: 94-54. IN
NOTE: The PMs for Maine Yankee (E. Trottier) and Millstone-1 (J. Andersen)
have been informed of the development of this information notice, and
their comments have been incorporated.
Steve Alexander of the Vender Inspection Branch has consulted with GE on
the technical accuracy of this information notice. GE's comments have
been incorporated.
Peter Wen, 7/13/94
IN 94-XX
July XX, 1994 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR
(301) 504-2995 Kamalakar Naidu, NRR Sikindra Mitra, NRR
(301) 504-2980 (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED
SAlexander* KNaidu* GCwal ina* MMejac*
05/19/94 04/14/94 05/19/94 04/18/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR
LNorrholm* CERossi* SMitra* CBerlinger*
05/24/94 05/27/94 07/06/94 07/11/94 OGCB: QRS:NRR AO/ :DORS:NRR D/:DORS:NRR
PWen tV\1 E 4ff^1ttl e BKGrimes
07/13 /94 07/" /4 07/ /94 4 OFFICIAL RECORD COPY DOCUMENT NAME: GEMAGNET.IN
NOTE: The PMs for Maine Yankee (E. Trottier) and Millstone-I (J. Andersen)
have been informed of the development of this information notice, and
their comments have been incorporated.
Steve Alexander of the Vender Inspection Branch has consulted with GE on
the technical accuracy of this information notice. GE's comments have
been incorporated.
Peter Wen, 7/13/94
IN 94-XX
July XX, 1994 Normal prop wipe can be confirmed with the breaker in its cubicle and closed
(in test position if necessary) in most installations by visual inspection
(using an inspection mirror and light) without having to get too close to
energized components or hazardous mechanism parts if the switchgear cabinet
door can be opened with appropriate safety precautions. Pending issuance of a
service advice letter (SAL) by the manufacturer on this problem or a safety
communication by GE NE, Attachment 2 illustrates an inspection hole in the
right side of the mechanism frame through which the prop and prop pin position
may be viewed. While the fully forward prop position (to the stop) is the
desired condition (maximum wipe), the absence of failures to latch along with
consistent and greater than minimum allowed prop wipe is, according to GE,
indicative of continued reliable latching. However, because minimum prop wipe
is not a published design specification, and because certain other factors
(e.g., opening spring adjustment) may influence latching reliability, GE has
requested that any licensee experiencing Magne-Blast breaker latching problems
or noticing changed, inconsistent or apparently abnormally low prop wipe, particularly following overhaul or repair including prop bushing replacement, contact GE NE PDS at 610-992-6049.
Pending installation of a second prop spring in affected breakers, Maine
Yankee has shifted, to the extent possible, its available dual prop spring
breakers to locations where operability requires assured latching reliability
for closure or reclosure during a design-basis event. For the remaining
potentially affected breakers, Maine Yankee is planning expedited inspections
with the assistance of GE NE PDS to aid in its operability determinations.
NRC Information Notice 94-XX, issued May XX, 1994, discusses other recently
identified problems impacting Magne-Blast operability, related to defective
and improperly installed GE CR2940 limit switches.
This information notice requires no specific action or written response.
If you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
ORIG /S/'D BY BKGRIMES
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR Kamalakar Naidu, NRR
(301) 504-2995 (301) 504-2980
Sikindra Mitra, NRR (301) 504-2783 Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices *See previous concurrence
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED
SAlexander* KNaidu* GCwalina* MMejac*
05/19/94 04/14/94 05/19/94 04/18/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE(PR, 1 C/EELB:DE:N f )
LNorrholm* CERossi* Smityaafb' Cjerlinger
05/24/94 05/27/94 cuff/94 OV/tt/94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D7:DORS:NRR
PWen BKGrimes
07/ /94 07/ /94 07/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I MAGNE3AT.GE
IN 94-XX
May XX, 1994 Normal prop wi can be confirmed with the breaker in its cubicle and closed
(in test position if necessary) in most installations by visual inspection
(using an inspectio mirror and light) without having to get too close to
energized components r hazardous mechanism parts if the switchgear cabinet
door can be opened wit appropriate safety precautions. Pending issuance of a
service advice letter (SAL) by the manufacturer on this problem or a safety
communication by GE NE, Attchment 2 illustrates an inspection hole in the
right side of the mechanism ame through which the prop and prop pin position
may be viewed. While the fully forward prop position (to the stop) is the
desired condition (maximum wipe), the absence of failures to latch along with
consistent and greater than minim allowed prop wipe is, according to GE,
indicative of continued reliable la thing. However, because minimum prop wipe
is not a published design specificatio, and because certain other factors
(e.g., opening spring adjustment) may i'hluence latching reliability, GE has
requested that any licensee experiencing 14 gne-Blast breaker latching problems
or noticing changed, inconsistent or appare tly abnormally low prop wipe, particularly following overhaul or repair in uding prop bushing replacement, contact GE NE PDS at 610-992-6049.
Pending installation of a second prop sprin in affected breakers, Maine
Yankee has shifted, to the extent possible, its aailable dual prop spring
breakers to locations where operability requires assured latching reliability
for closure or reclosure during a design-basis event. For the remaining
potentially affected breakers, Maine Yankee is plannin expedited inspections
with the assistance of GE NE PDS to aid in its operabilMty determinations.
NRC Information Notice 94-XX, issued May XX, 1994, discusles other recently
identified problems impacting Magne-Blast operability, rela ed to defective
and improperly installed GE CR2940 limit switches.
This information notice requires no specific action or w *tten response.
If you have any questions about the information in this notice, lease contact
one of the technical contacts listed below or the appropriate Of ce of
Nuclear Reactor Regulation (NRR) project manager.
ORIG /S/'D BY BKGRIMES
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR Kamalakar Naidu, NRR
(301) 504-2995 (301) 504-2980
Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices *See previous concurrence
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED
SAlexander* KNaidu* GCwalina* MMeJac*
05/19/94 04/14/94 05/19/94 04/18/94 C/VI BDRIL:NRR D/D I *N ChftA EELB:DE:NRR C/EELB:DE:NRF
LN I film SMitra CBerlinger
'05JK1 /94 05/17g 4\ 05/ /94 05/ /94 OGCB:DORS:NRR AC/OGCB:DORS :NRR D/:DORS:NRR
PWen AJKugler BKGrimes
05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: I MAGNE3AT.GE
IN 94-XX
May XX, 1994 Normal prop wipe can be confirmed with the breaker in its cubicle and closed
(in test position if necessary) in most installations by visual inspection
(using an inspection mirror and light) without having to get too close to
energized components or hazardous mechanism parts if the switchgear cabinet
can be opened with appropriate safety precautions. Pending issuance of a
serv' advice letter (SAL) by the manufacturer on this problem or a safety
communic ion by GE NE, Attachment 2 illustrates an inspection hole in the
right side the mechanism frame through which the prop and prop pin position
may be viewed. hile the fully forward prop position (to the stop) is the
desired condition aximum wipe), the absence of failures to latch along with
consistent and grea than minimum allowed prop wipe is, according to GE,
indicative of continue reliable latching. However, because minimum prop wipe
is not a published desig specification, and because certain other factors
(e.g., opening spring adjus ent) may influence latching reliability, GE has
requested that any licensee e eriencing Magne-Blast breaker latching problems
or noticing changed, inconsiste or apparently abnormally low prop wipe, particularly following overhaul o repair including prop bushing replacement, contact GE NE PDS at 215-992-6049.
Pending installation of a secon rop spring in affected breakers, Maine
Yankee has shifted to the extent possibe, its available dual prop spring
breakers to locations where operability quires assured latching reliability
for closure or reclosure during a design-b is event. For the remaining
potentially affected breakers, Maine Yankee planning expedited inspections
with the assistance of GE NE PDS to aid in it operability determinations.
NRC Information Notice 94-XX, issued May XX, 19 , discusses other recently
identified problems impacting Magne-Blast operab ity, related to defective
and improperly installed GE CR2940 limit switches.
This information notice requires no specific ac ion or written response.
If you have any questions about the information in th notice, please contact
one of the technical contacts listed below or the appro late Office of
Nuclear Reactor Regulation (NRR) project manager.
ORIG /S/'D BY BKGRIMES
Brian K. Grimes, Directo
Division of Operating Reac or Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR Kamalakar Naidu, NRR
(301) 504-2995 (301) 504-2980
Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices
VIB:DRIL VIB:DRIL SC V :DRIL TECHED
S~lexanderl'J K &aicu, G& S1na MMejac*
05/(9/94 04/ W 94* O'5/94 04/18/94 C VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR CIEELB:DE:NRR
Lgrrholm CERossi SMitra Caerlinger
05/ /94 05/ /94 05/ /94 05/ /94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR
PWen AJKugler BKGrimes
05/ /94 05/ /94 05/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNE3AT.GE
<&c rfmtC'al Cak"vyc.t
IN 94-XX
April XX, 1994 Prop wipe can be etermined in most installations by visual inspection without
having to get too lose to hazardous mechanism parts if the switchgear cabinet
door can be opened fely. Pending issuance of a SAL by the manufacturer on
this problem (and/or Service Information Letter by GE NE), Attachment 2 illustrates one locatlo where the prop position may be seen. While fully
forward prop position (t the stop) is the desired condition (maximum wipe),
the absence of failures to latch along with consistent and greater than
minimum allowed prop wipe is according to GE, indicative of continued
reliable latching. However, cause minimum prop wipe is not a published
design specification, and becau certain other factors (e.g. opening spring
adjustment) may influence latchin reliability, GE has requested that any
licensee experiencing Magne-Blast eaker latching problems or noticing
changed, inconsistent or what appear to be abnormally low prop wipe, parti- cularly following prop bushing replacemnt, contact GE NE PDS at 215-992-6049.
In the meantime, pending installat n of a second prop spring in its
affected breakers, Maine Yankee has shift to the extent possible, its
available dual prop spring breakers to loca Ions where operability requires
assured latching reliability for closure or closure during a design basis
event. For the remaining suspect breakers, Mane Yankee has undertaken
expedited inspections with the assistance of G E PDS to aid in its operabil- ity determinations. NRC Information Notice 94-X issued April XX, 1994, dis- cusses other recently identified problems impactin Magne-Blast operability, related to defective and improperly installed GE CR 940 limit switches.
This information notice requires no specific ac on or written response.
If you have any questions about the information in thi notice, please contact
the technical contacts listed below or the appropriate ffice of Nuclear
Reactor Regulation (NRR) project manager.
ORIG /S/'D BY BKGRIMES
Brian K. Grimes, Directo
Division of Operating Reac or Support
Office of Nuclear Reactor R ulation
Technical contacts: Stephen Alexander, NRR
(301) 504-2995 Kamalakar Naidu, NRR
(301) 504-2980
Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued NRC Information Notices
VIB:DRIL VIB:DRIL SC/VIB:DRIL TECHED
Salexander Knaidu Gcwalina 41./V (,AA-
04/ /94 04/ /94 04/ /94 04/AR/94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR
Lnorrholm CERossi SMitra Cberlinger
04/ /94 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR
PWen AJKugler BKGrimes
04/ /94 04/ /94 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN
IN 94-XX
April XX, 1994 Prop wipe can be termined in most installations by visual inspection without
having to get too c eto hazardous mechanism parts if the switchgear cabinet
door can be opened sa ly. Pending issuance of a SAL by the manufacturer on
this problem (and/or a rvice Information Letter by GE NE), Attachment 2 illustrates one location ere the prop position may be seen. While fully
forward prop position (to t stop) is the desired condition (maximum wipe),
the absence of failures to lat h along with consistent and greater than
minimum allowed prop wipe is, a cording to GE, indicative of continued
reliable latching. However, bec se minimum prop wipe is not a published
design specification, and because ertain other factors (e.g. opening spring
adjustment) may influence latching eliability, GE has requested that any
licensee experiencing Magne-Blast breker latching problems or noticing
changed, inconsistent or what appears o be abnormally low prop wipe, parti- cularly following prop bushing replacem t, contact GE NE PDS at 215-992-6049.
In the meantime, pending installatlo of a second prop spring in its
affected breakers, Maine Yankee has shifte to the extent possible, its
available dual prop spring breakers to loca ions where operability requires
assured latching reliability for closure or eclosure during a design basis
event. For the remaining suspect breakers, M ne Yankee has undertaken
expedited inspections with the assistance of G NE PDS to aid in its operabil- ity determinations. NRC Information Notice 94- , issued April XX, 1994, dis- cusses other recently identified problems impact g Magne-Blast operability, related to defective and improperly installed GE R2940 limit switches.
This information notice requires no specific ction or written response.
If you have any questions about the information in \this notice, please contact
the technical contacts listed below or the appropri te Office of Nuclear
Reactor Regulation (NRR) project manager.
ORIG /S/'D BY BKG IMES
Brian K. Grimes, irector
Division of Operat ng Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen Alexander, NRR
(301) 504-2995 Kamalakar Naidu, NRR
(301) 504-2980
Attachments:
1. Details of Failure Mode and Contributing Factors
2. Magne-Blast Prop Mechanism Diagram
3. List of Recently Issued_ RC Information Notices
VIB:DRIL VIB:DRI SC/VIB:DRIL TECHED
Salexand9k Knaidu Gcwalina
04//5'/94 04/14/94 s '4, 04/ /94 04/ /94 C/VIB:DRIL:NRR D/DRIL:NRR EELB:DE:NRR C/EELB:DE:NRR
Lnorrholm CERossi SMitra Cberlinger
04/ /94 04/ /94 04/ /94 04/ /94 OGCB:DORS:NRR AC/OGCB:DORS:NRR D/:DORS:NRR
PWen AJKugler BKGrimes
04/ /94 04/ /94 04/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: MAGNBLST.IN