Part 21 Report - 1995-059
ACCESSION #: 9503100009
Farwell & Hendricks, Inc.
February 24, 1995
United States Nuclear Regulatory Commission
Mail Stop M/S 0-9A1
Mail: Washington, DC 20555
Express: 11555 Rockville, Maryland 20852
Telephone #: (301) 415-2995
Telecopy #: (301) 415-2968
ATTENTION: Mr. Steven Alexander
SUBJECT: Notification of Identification of a POTENTIAL DEFECT
Dear Mr. Alexander;
Per our discussion of 02/22/95, Farwell & Hendricks, Inc. (F&H) is
forwarding this letter to your attention for advice on a future course of
action, beyond F&H notifying its clients of a potential problem. Per our
discussion it would appear likely that:
o The Siemens/ITE MCCBs generally affected are magnetic style
HE3AXXXs and HE3L050 (low setting 50 amp) and HE3H050 (high
setting) having a 050191 date code.
o HE3 style Molded Case Circuit Breakers (MCCBs), date code
050191, after acceptance would probably not fail in service,
but may not relatch. Not relatching may result in rendering
the equipment in which it is installed non-operational.
Therefore, if installed within a technical specification
system, it could potentially degrade the operation of the
system. This is beyond the capability of F&H to evaluate.
o The specific HE3 style MCCB failure appears to be a PREMATURE
event after being processed to an acceptance level of
mechanical cycles and adjustable instantaneous high and low
trips. This premature failure appears coincidental with poor
quality workmanship resulting in stripped screws and holes in
the trip bar retaining plate, as discussed. The premature
failure is probably caused by a marginal latch trip bar "bit".
o The HE3 style MCCBs that are potentially subject to premature
failures, even though 050191 date code is approximately four
years old, could be in the distribution system today since date
codes older than five years have been routinely observed. A
potential information notice might be beneficial since multiple
suppliers could have or could be supplying these MCCBs.
USNRC.ltr 02/24/95
Page 1 of 54
4600 East Tech Drive o Cincinnati, Ohio 45245 o (513) 528-7900 o FAX
(513) 528-9292
United States Nuclear Regulatory Commission
February 24, 1995
Page 2
o F&H, per 10CFR21.21(b) is informing all prior clients of this
condition since, F&H has determined that it does not have the
capability to perform the evaluation to determine if a defect
exists.
This is written notification of the initial identification of a
POTENTIAL DEFECT which, per 10CFR21,21.3 Definition (d) (4)..., could
contribute to the exceeding of a safety limit, as defined in the
technical specification of a license for operation issued pursuant to
Part 50 of this chapter. This notification is structured per
10CFR21,21.3 (i) and (ii) written notification to the extent known, as if
it was a defect. The following written notification (report) is
formatted per 10CFR21, section 21.21, paragraph 4.
(i) Farwell & Hendricks, Inc. (F&H) at the address listed
below is the organization informing the USNRC. Dr.
Charles R. Farwell, Jr., F&H Corporate Officer, of the
same address is the specific individual informing the
USNRC.
(ii) The basic component supplied by F&H which contains the
defect is the Siemens/ITE molded case circuit breaker
style "HE3". Additional information is provided in
Attachment A.
(iii) F&H is the identification of the firm that supplied the
basic component listed above.
(iv) The nature of the defect is provided in Attachment A and a
PRELIMINARY safety evaluation is provided in Attachment B,
although F&H IS UNABLE TO EVALUATE THE SAFETY HAZARD WHICH
COULD BE CREATED BY THE DEFECT AS ANY POTENTIAL EFFECT IS
"APPLICATION-SPECIFIC", CONSISTENT WITH 10CFR21,21.3 (d)
(4).
(v) The date on which the information of the potential defect
was obtained is 02/23/95. A chronological history and
course of events is provided in Attachment C.
(vi) The potential specific number and specific site locations
of all such devices supplied by F&H is fully compiled and
being evaluated. The total list of prior sales is
provided in Attachment D.
(vii) The corrective action is per the F&H action plan which is
provided in Attachment C.
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United States Nuclear Regulatory Commission
February 24, 1995
Page 3
(viii) Advice related to the defect will be provided to all F&H
clients with preliminary conclusions in Attachment E.
Please know, based on all preliminary findings, F&H concludes this
could only be a concern based on unusual circumstances and
misapplications of the molded case circuit breaker.
Steve, should F&H send a copy of this report to the Operations Desk
for log-in purpose?
If you should have any questions please feel free to contact Mr.
Roy A. Woeste at the telephone number listed below.
Written By: Reported By:
Mr. John Hendricks, P. E. Dr. Charles R. Farwell, Jr., P.E.
Technical Director Chairman/Chief Executive Officer
President
Mr. Roy A. Woeste
Director of Quality Assurance
tmw
Attachments
FARWELL & HENDRICKS, INC.
4600 East Tech Drive
Cincinnati, Ohio 45245
Phone: (513) 528-7900
Fax: (513) 528-9292
USNRC.ltr 02/24/95
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TABLE OF CONTENTS
Section Description Page No. # of Page
Cover Letter Written Notification 1 3
Table of Contents Directory 4 1
Attachment A Nature of Defect 5 2
Attachment B Preliminary Safety 7 2
Evaluation
Attachment C Chronology of F&H 9 1
Evaluation and
Corrective Action Plan
Attachment D Preliminary List of All 10 5
HE3 Style MCCBs Sold
by F&H
Attachment E Preliminary Advice 15 1
Related to the Defect
Attachment F FP&L Seismic Test Letter 16 11
Attachment G Generic Seismic Levels 27 27
and Post Functional
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ATTACHMENT A
Nature of Defect on the HE3 Style Siemens/ITE MCCBs
The MCCBs involved are manufactured by Siemens/ITE. The styles are
magnetic only: HE3AXXXs HE3L050 and HE3H050 (50 amp low or high setting,
respectively). Currently this does not generally appear to affect the
thermal magnetic MCCB styles HE3BXXXs or HE3MXXXs (50 degrees C rated).
The potential defect is defined as a significantly higher percentage of
problems specifically related to a 050191 date code. Although a HE3B015,
date code 9103, with no loose case screws and proper function had one
screw loose on the tie down bar over the trip bar, thereby requiring on-
going analysis.
These defects included stripped screw holes in the outer case which holds
the cover and internal stripped screw holes in the hold down bar for the
trip cam assembly. Both cases involve self tapping screws which are
installed by the manufacturer into the 'plastic' material of the breaker
housing. The term "stripped screw" describes where the hole's plastic
threads were stripped.
There are two screws, one each holding down a small bar which forms part
of the enclosure in which the trip cam rotates. In several cases one or
both of these screw holes were found stripped.
Front cover screws:
The stripped case screws were noted initially by Florida Power & Light
Company (FP&L) during removal of the front cover. There are 4 each #6 x
3/4" screws holding the outer cover in place. FP&L reports that most of
the time only one of the four screws was stripped, some had two screws
stripped, and in rare cases three of the four cover screws were stripped.
These were found under either of two conditions, noting a lack of torque
prior to removal, or not being able to re-torque these screws upon
reinstallation of the cover. The ITE HE3 type breakers were not meant to
be repeatedly opened. Discussions with the site technician indicates
that the case screws were not always checked for torque prior to removal.
Therefore the number of stripped external case screws may not reflect the
condition of the screws prior to removal. FP&L was performing a special
MCCBs evaluation which included removing the cover from the case, a task
not normally performed by FP&L.
Stripped screws on the hold-down bar for the trip cam:
The internal stripped screws consisted of two #2 x 5/16" screws installed
in the plastic body of the breaker, which hold two small 1/8" x 1/2"
metal bars in place. In turn, the metal bars are retainers for the trip
cam assembly, and forms part of bearing surface when the trip bar
rotates. These stripped screws were found by applying a small amount of
torque to the installed screws. FP&L indicated that there may be
correlation between stripped screws on the hold down bars for the trip
cam, and breakers which exhibit resetting problems.
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ATTACHMENT A - Continued
Breakers which exhibit problems with the reset mechanism:
FP&L has noted that a number of the ITE HE3 style breaker exhibit
problems with resetting. These include complete inability to reset
and/or intermittent difficulty to reset. The resetting problem appears
to be related to the latch "bit" with the trip bar being marginal.
Date Code Limited:
Most of the stripped screw problem breakers display an ITE 0591 date
code. Farwell & Hendricks, Inc. (F&H) indicates that the ITE HE3 style
breaker was manufactured in Wilmington, N.C. from 1986 through 1991.
Manufacturing was moved to Bellefontaine, OH approximately in January,
1992. FP&L had placed a large order for ITE HE3 style breakers which
were received in 1991. The large size of the FP&L order and the planned
impending facility relocation may have had an effect on the large number
of problems seen with breakers manufactured in 1991. Random samples of
later date codes by FP&L of 92-01 and 92-02 and F&H samples of 0791, 1291
and early 1992, had no indication of stripped screws. Although only
limited examples prior to 1991 are available at F&H and FP&L, there has
been minimal indication of stripped screws on breakers with date codes
prior to 1991.
In addition, FP&L Electrical Maintenance has been testing a percentage of
the existing installed breakers on a periodic basis and has not noted any
failures of this type in the HE3 style breakers installed in the plant.
Discussions with FP&L Electrical Maintenance has not indicated any
unacceptable trends with respect to failures of the installed ITE HE3
style breakers. Maintenance has reported that they have experience
resetting problems with HE3 breakers during testing but prior to
installation. Although specifics are not available for these rejected
breakers, most failures were in the 1991 batch of breakers in stock, and
shows that the Electrical Maintenance testing practices screen out
unacceptable breakers. Also, F&H has had no other utility report similar
failures prior to FP&L's issue.
Since 1991, at FP&L over 50 breakers have been replaced with only a few
being due to breaker problems. It should be noted that one failure
characteristic attributed to the 1991 batch, the failure to be able to
reset the breaker after tripping, is also a common failure on these
breakers at end of life. Thermal magnetic breakers are UL type tested
for several thousand operations.
F&H and FP&L are continuing to evaluate the HE3 style. Today a potential
isolated example has occurred wherein a thermal magnetic HE3B015, date
code 9103 operated successfully, no loose case cover screws, although one
of the two internal screws was stripped as discussed above.
In conclusion, it appears to be premature failures on manual reset after
10-20 minimum cycles which appear to coincide with the loose screws
holding the metal bar over the top of the trip bar. These loose metal
bars seem to coincide with the loose screws on the molded case circuit
breaker case and cover which relate to a specific date code of 050191.
USNRC.ltr 02/24/95
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ATTACHMENT B
Preliminary Safety Evaluation
(Not All Inclusive)
The following evaluation has been conducted to determine that these
molded case circuit breakers DO NOT APPARENTLY CONTRIBUTE TO A
SUBSTANTIAL SAFETY HAZARD, although it is not all inclusive and each
individual utility must evaluate specific application which is defined by
their license commitment unique and/or specific applications that F&H
would not be aware of:
o The manufacturer performs low-middle-high magnetic calibration
on adjustable trip, mechanical operations and continuity checks
per NRC Inspection Report 99901177/90-01.
o The acceptance as a basic component screens out-all-failures
via:
o Receipt/Inspection
o Dielectric withstand
o Mechanical cycles of 5 or 6 manual
operations
o Magnetic only MCCBs are tested per pole
on both a high and a low setting
NOTE: ALL MCCBs THAT HAVE BEEN ACCEPTED FOR BASIC COMPONENT
APPLICATIONS
HAVE BEEN CYCLED 10-20+ TIMES.
Most utilities check MCCBs for operability prior to acceptance into the
system, for example.
FP&L Electrical Maintenance has been functionally testing all
breakers received from the warehouse prior to installation as
standard practice. Testing includes manual operation of the
breakers, and electrically testing the trip functions. Any
breakers with loose covers, or breakers which exhibit resetting
problems, would have detected and rejected by Electrical
Maintenance prior to installation. However, Electrical
maintenance does not and should not open molded case circuit
breakers.
Due to the 'loaded spring' design of the circuit breakers any
loose parts, poor tolerances, etc. tend to cause these
breakers, to trip rather than interfere with the tripping
action. There have been no examples of breakers found with
problems related to not tripping.
USNRC.ltr 02/24/95
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ATTACHMENT B - Continued
Thus, prior to installation all MCCBs have demonstrated
operability and ability to reset. Additionally, molded case
circuit breakers are not normally used as ON/OFF switches
although they are used to secure power during maintenance or
similar evolutions. The resetting problem will occur when the
breaker is OFF (or tripped) and in the process of being turned
on (closed). At that time the equipment is already out of
service and in the worst case would delay the equipment return
to service. There is no evidence that the observed defects
which would cause the breaker to fail to trip when called upon.
Neither the external stripped cover screw holes nor the
internal stripped screw holes on hold down bar for the trip cam
affect the ability of the breaker to trip. These screws are
the only screws in the breakers which are threaded into the
plastic housing.
The safety function of the MCCB is usually to maintain electric
continuity and to open to protect the safety related equipment from
nuisance tripping and short circuit protection. Additionally, when
remote control activation is required the starter or relay performs the
operation and the MCCB is performing its safety function of remaining
closed. Thus, F&H took two MCCBS, HE3A010 and HE3A003, that FP&L
indicated with both internal screws stripped and free movement of the
bars over the top of the trip bar, with one MCCB having stripped
case/cover screws as test samples which were:
(1) Baseline Tested
(2) Seismic Tested to 5 OBE's and 1 SSE site-specific level
(3) Post seismic tested (Attachment F)
(4) Generic shake table limits test for 5 OBE's and 1
SSE for SQURTs utilities and F&H clients
(5) Post seismic tests (Attachment G);
after initially being dedicated by F&H, which performed satisfactorily in
fulfilling the above safety functions while in the degraded condition.
Additionally, reasonable assurance is demonstrated by:
(1) limited number of potential MCCBs, HE3 magnetic only
manufactured with a date code of 050191 and a few
potential related weeks.
(2) Existence of redundant safety systems.
Therein, preliminarily after MCCBs are acceptance tested, the specific
MCCB should not fail in service; Although, they may not relatch and
thereby provide the equipment non-operational.
USNRC.ltr 02/24/95
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ATTACHMENT C
Chronology of F&H Evaluation
02/17/95 Received a telephone call from Florida Power & Light
Company (FP&L) concerning loose screws and reset
problems on the HE3 style MCCBs
02/21/95 FP&L arrives at F&H with the subject MCCB. FP&L and
F&H perform evaluations and determines that the MCCB
reset performs the safety function before, during and
after an earthquake.
02/22/95 F&H has preliminary discussion with Siemens on the
subject MCCB and schedules a visit on 03/01/95 to the
Siemens Factory at Bellefontaine to aid in
determining the root-cause failure.
02/23/95 F&H Contacted the NRC, Mr. Steve Alexander, to
discuss technical information. The result of the
phone conversation is to send him a letter on
"POTENTIAL 10CFR21" due to uniqueness of premature
failures.
02/24/95 Generic seismic satisfactory tested same two MCCBs.
Mail the NRC a letter.
TO BE DONE PER THE ACTION PLAN
02/23/95 Identification of Potential 10CFR21.
03/01/95 Visit the Siemens factory.
03/02/95 Contact F&H clients of the potential 10CFR21 for
their evaluation.
Before Issue the final evaluation within F&H's capabilities.
04/14/95
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ATTACHMENT D "Preliminary List of all HE3 Style MCCBs Sold by F&H,"
5 pages, omitted.
ATTACHMENT E
Preliminary Advice Related to the Defect
(Suggestion, Not All Inclusive)
1. The utility needs to evaluate the number of HE3 style MCCBs
installed and in the warehouse with respect to date codes. (F&H
will provide its clients with F&H provided date codes. Sample
attached.)
2. The specific application:
- Safety function
- Technical specification application
- Effect of not re-setting per system application
3. The date range selected, i.e. such as, March through July, 1991
4. Screen all new orders for the above date range.
5. Establish selection criteria before usage of the MCCBs.
6. Inspection of MCCBs to confirm that date code 050191 is the only
problem MCCB.
NOTE: THE NRC MAY BE ISSUING AN INFORMATION NOTICE ON THIS ISSUE.
F&H would appreciate being the central point of coordination and can
keep utilities informed of any additional evaluations, date code data and
types of data. All correspondence should be addressed to Mr. Dan
Kobida.
USNRC.ltr 02/24/95
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ATTACHMENT F
FP&L Seismic Test Letter
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Page 16 of 54
Farwell & Hendricks, Inc.
February 22, 1995
Florida Power & Light Company
Turkey Point Nuclear Plant
P.O. Box 3088
Florida City, Florida 33054
Telephone #: (305) 246-7215
Telecopy #: (305) 246-6231
Attention: Raj Kundalkar, Engineering Manager
Subject: F&H Seismic Test of Siemens HE3A MCCB's per FP&L Condition
Report 95-083 Concerning Stripped Screw Holes for The Trip Bar
Retaining Plate
Dear Mr Kundalkar:
Presented herein is a summary of the seismic testing of Siemens HE3A
magnetic only MCCB's by F&H to evaluate FP&L concerns of their Condition
Report 95-083. In this report FP&L documented Siemens HE3A MCCB's that
would not reset after being tripped or manually transitioned. FP&L
removed the cover of the MCCB's and inspected the internal mechanisms of
the breakers. FP&L identified that on some samples either one or both of
the screws securing the trip bar retaining plates were loose. These
screws were able be turned freely with a screw driver. They could not be
tightened down completely because their holes in the phenolic were
stripped.
FP&L personnel demonstrated to F&H this anomaly on two Siemens HE3A
samples previously provided to FP&L by F&H (F&H Tag 8005804 S/N 67,
Siemens P/N HE3A010 and F&H Tag 8005806 S/N 21, Siemens P/N HE3A003).
These two samples were then subjected to seismic testing at FP&L site
specific levels with the breakers in the "ON" position. This was done to
ensure that breakers with this anomaly would not trip spuriously during a
seismic event.
Five OBE level and one SSE level test were successfully performed.
Neither sample tripped during seismic testing. Both items successfully
completed baseline and post seismic functional testing. Attached are the
SSE level seismic plots, a summary of the functional data, and
photographs of the trip bar retaining plate setup inside the breaker.
4600 East Tech Drive o Cincinnati, Ohio 45245 o (513) 528-7900
FAX (513) 528-9292
USNRC.ltr 02/24/95
Page 17 of 54
Thus it is established that Siemens HE3A MCCB's with stripped screw holes
of the trip bar retaining plate will not spuriously trip during a seismic
event of the attached SSE levels when the breakers are in the 'ON'
position.
Please let me know if you need any additional information.
Sincerely,
FARWELL & HENDRICKS, INC.
Timothy A. Geers Mark D. McClung
Project Engineer Quality Assurance Specialist
Enclosure
cc: 80058 MF
JRH
DBK
USNRC.ltr 02/24/95
Page 18 of 54
Enclosures consisting of figures, tables and graphs, pages 19 thru 26 of
54, are omitted.
Attachment G
Generic Seismic Levels and Post Functional
The two MCCBs were retested at generic fragility levels. The SSE
energized and SSE de-energized are attached. The post functional
data is attached. All acceptance criteria were satisfied.
The final report number for EPRI-SQURTS members is 50090.9.
USNRC.ltr 02/24/95
Page 27 of 54
Enclosures consisting of figures, tables and graphs, pages 28 thru 40 of
54, are omitted.
Table "FUNCTIONAL TESTING DATA SHEET FOR MOLDED CASE CIRCUIT
BREAKERS,"
Pages 41 thru 43 of 54, omitted.
Table "SEISMIC OPERABILITY DATA SHEET FOR MOLDED CASE CIRCUIT
BREAKERS
(MCCB)" omitted.
USNRC.ltr 02/24/95
Page 44 of 54
Table "FUNCTIONAL TESTING DATA SHEET FOR MOLDED CASE CIRCUIT
BREAKERS,"
Pages 45 thru 50 of 54, omitted.
Table "SEISMIC OPERABILITY DATA SHEET FOR MOLDED CASE CIRCUIT
BREAKERS
(MCCB)" omitted.
USNRC.ltr 02/24/95
Page 51 of 54
Table "FUNCTIONAL TESTING DATA SHEET FOR MOLDED CASE CIRCUIT
BREAKERS,"
Pages 52 thru 54 of 54, omitted.
*** END OF DOCUMENT ***
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