Information Notice 1996-50, Problems with Levering-In Devices in Westinghouse Circuit Breakers
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555-0001
September 4, 1996
PROBLEMS WITH LEVERING-IN DEVICES IN
WESTINGHOUSE CIRCUIT BREAKERS
Addresses
All holders of operating licenses and construction permits for nuclear power
plants.
PurDose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees that some 4.16 and 6.9 kV circuit breakers may fail
to close on demand because worn levering-in devices can provide a false
indication that the breaker is completely engaged onto the bus and ready to
close. The problems affect all 4-15 kV range Porcel-line DHP magnetic circuit
breakers manufactured by Westinghouse Electric Corporation (Westinghouse). 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
On October 19, 1995, during Refuel Outage AlRO5 at Braidwood Station Unit 1, Commonwealth Edison Company (ComEd) discovered that a diesel generator output
breaker (Westinghouse Model 50DHP250) failed to close on demand.
ComEd
determined that the levering-in device on the breaker was worn, permitting the
device to 'spin free" before the breaker was fully engaged.
Discussion
When installing a Model DHP breaker, a plant equipment operator first pushes
it into a cell in the switchgear until the rail latch catches and stops
further movement toward the rear of the cell.
At this point the breaker is in
the TEST position and the levering-in device is not yet engaged.
By pressing
down on the rail latch, the operator can push the breaker another small
increment until the levering nut at the rear of the breaker contacts the
levering screw in the cell.
The operator then attaches a manual crank to the
levering shaft at the front of the breaker and turns the crank.
Turning the
crank causes the levering nut to traverse the levering screw, drawing the
breaker into the cell until the breaker stops moving toward the rear of the
cell and the crank and levering shaft spin free, indicating that the breaker
is fully engaged.
Figure 5 is a schematic diagram of the levering-in device.
PoR
OE'
Ht4O+.s 9(,Oab
os
fo7Oz
9608290151 c
/:q://(
,
L~f
qZ311
September 4, 1996 If the levering-in device is worn, the operator receives an erroneous
indication that the breaker is fully engaged and ready to operate, when in
fact the floor tripping mechanism is still engaged.
The floor tripping
mechanism consists of cam plates on the cell floor that lift trip levers on
the underside of the breaker while the breaker is being inserted or removed
from the cell.
With the floor tripping mechanism engaged, the breaker will
not close onto the bus.
The Braidwood licensee subsequently removed the
defective levering-in device and replaced it with a redesigned levering-in
device.
The root cause of the failure was a worn levering shaft key and a worn and
cracked guide tube. The mating surfaces between the shaft key and the guide
tube were worn and permitted the levering-in device to spin free while the
breaker was still about a quarter inch from being fully engaged on the bus.
An NRC search of industry data revealed that other nuclear power plants have
experienced similar breaker failures because (1) a levering-in shaft was found
to be worn or cracked; (2) the guide tube for the levering-in device was
cracked or broken, with one of its "ears" rounded off and catching under the
guide tube, causing it to bind; and (3) the key on the levering-in device was
found to be rounded off because of wear.
In response to the problems seen at Braidwood, Westinghouse issued the
enclosed Technical Bulletin 96-05-RO, "DHP Breakers: Levering-In Device," on
June 19, 1996. The bulletin explains that the spinning free of the levering
crank and observance of a small space between the face of the breaker and the
steel support barrier of the breaker cubicle are not sufficient to ensure the
breaker is fully engaged.
The best way to check that the breaker is in the
correct position is to actuate the breaker.
When breaker actuation is not
feasible, the Westinghouse bulletin describes a two-step process that the
operator can employ to determine if the breaker is properly positioned.
An analysis of the failures seen in the industry, and discussions with
operators at plants that recently experienced failures, indicate that the
levering-in devices were not maintained properly. Recommended maintenance
entails cleaning and removing old grease from the device components, and
subsequent application of fresh Westinghouse-recommended grease. Damaged or
worn parts can be detected by inspection and replaced, if necessary, during
routine maintenance, but some plants do not include detailed inspection of the
levering-in device in the maintenance procedure. The vendor manual does not
specifically address inspection and cleaning of the levering-in device.
The Westinghouse technical bulletin recommends that the inspection and
lubrication of the levering-in device be included in the maintenance
procedures. The levering-in device is designed to insert and withdraw the
breaker 100 times. Because nuclear plants may subject breakers to numerous
levering operations during initial construction and periodic surveillance
testing, the levering-in devices may require inspection and replacement during
their service life in nuclear applications.
September 4, 1996
Westinghouse redesigned the levering-in device in 1982 to extend its service
life.
Figures 1 and 2 in the attached Westinghouse bulletin show the original
and redesigned device installed in the breaker.
Figure 6 is a sketch
illustrating the difference in the guide tubes and levering shafts of the two
designs.
Interface between licensees and vendors in accordance with Generic
Letter 83-28, "Required Actions Based on C3neric Implications of Salem ATWS
Events," issued July 8, 1983, can help ensure that information on safety- related components is complete and up to date.
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 Regulation (NRR) project manager.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Kamalakar Naidu, NRR
(301) 415-2980
E-mail: krn@nrc.gov
Zelig Falevits, R-III
((718) 829-9717 E-mail: zxf@nrc.gov
David L. Skeen, NRR
(301) 415-1174 E-mail: dls@nrc.gov
Attachments:
Attachment - Westinghouse Technical Bulletin 96-05-RO
Figure 5 - Schematic of Levering-in Device and Interlock
Figure 6 - Difference in Original and 1982 Redesigned
Levering-in Devices
List of Recently Issued NRC Information Notices
4""
'70- r /a-
ENER64 SYSTEMS
BUSINESS
UNIT
Attachment 1
September 4, 1996
Westinghou'
1 of
Technical Bulletin
An advisory notice of a recent technical development pertaining to the Installation or operation of Westinghous-uppfled
Nuclear Plant equlpment Recipients should evaluate the Information and recommendation, and InItha
action where approprIate.
P.O. BOX 355, Pittsburgh, PA 15230
SuJ;>ect
Number
DHP BREAKERS: LEVERING-IN DEVICE
ESBU-TB- 96-05-RO
Systertl(s) BALANCE OF PLANT SWITCHGEAR USING TYPE DHP
Date
Win9s6
MAGNETIC AIR CIRCUIT BREAKERS
Affeted PlantS CAE. CBE. CCE, CDE, GOLN1, KDAVI, CSTLI. CSTL2. Cow, AN, ORqAl. oTZ
S.O.(s)
KPR, B3MM1, OSUSI, OSUW
KFRK SCE "CcI, CM OWNP2 References Wesatnghous irndB o s< 1. 82253*2 Wst
1.1 Afc Safety
Yes
Sheet
1 of 7
322253;4A & 4B. tnstudons tr ProWli
TypofHP7 Mqnetic Air Cguerwit
I Related Equipment
No 0
INTRODUCTO
This technical bulletin addresses levering the DHP breaker into the OPERATE/ENGAGED position in the
switchgear cell and confirming that it is properly levered into the OPERATE/ENGAGED position.
BACKGROUND
The existing instruction books, I.B.32-253-2 and l.B.32-253-4A &-48, describe procedures for installing
the breaker in the switchgear cell including all the safety precautions to be observed. This is a two step
process involving moving the breaker into the TEST position then to the OPERATE/ENGAGED position.
The breaker is first pushed into the cell until the rail latch at the front of the guide channel catches in the
notch in the guide rail and stops further movement of the breaker toward the rear of the cell. The breaker
is now in the TEST position. At this point the levering-in device is not engaged. The secondary contacts
can now be engaged for electrical testing of the breaker.
To move the breaker to the OPERATE/ENGAGED position first press down on the rail latch on the right
side of the breaker and push the breaker toward the rear of the cell as far as it will go, about 1/4 inch. Be
sure the breaker is pushed until it stops. This should only require a few pounds of push. This brings the
levering nut on the breaker up to 'he screw in the cell. Engage the crank on the levering shaft, push
moderately toward rear of the cell. After the breaker starts to move it is not necessary to push. C.antinue
Additional Infmauion. if Required, may be Obtained from the Originator. Telephone 412- 829-3739 or (WIN)
244-3739 riginator
1f R. Critchlow
Assembly, Qualification and Test Operations
',17 , >I-
(J. Sandrovich
Regulatory and Licensing Initiatives
T. D. Moser, Manager
Assembly, Qualification and Test Operations
Nenher Wastrighouse Etectnc Corpontaon nor as aripbs make any waranty or represenation wth respect to the socuracy. copteness or usefulness
5523Q("M9t the information contained in tha report or assume any rsapnaebdiy or tbidly or amlnage whier may resut from the use of such intoration.
Attachment 1
September 4, 1996
ESBU-TB-96-05-RO cranking until the crank turns freely and the breaker stops moving. When the breaker is fully
engaged the front steel barrier should be about 114 inch or less from the cell frame angles. This
is the OPERATE/ENGAGED position. The breaker can now be closed and tripped electrically
using the control switch on the cell door.
It has come to our attention that some utilities may be relying on the crank going spin free and/or
the steel barrier being 1/4 inch or less from the cell frame angles as the only indication that the
breaker is in the fully OPERATE/ENGAGED position rather than actually closing and tripping the
breaker. These two visual indicators may not be the best means of determining that the breaker
is fully engaged.
The spin free of the crank could occur prematurely if the levering-in device is worn at the mating
pieces of the shaft and tube. Refer to Figures 1 & 2 for the two versions of the levering-in devices
and the area of wear. The earlier version has a key welded in one side of the shaft and the later
version has a pin through the shaft that protrudes on both sides. The key/pin interfaces with the
slot in the tube and as the crank is turned the key/pin travels along this slot to the end of the tube.
At the end of the tube the key/pin reaches the tapered part of the sleeve on the tube and no longer
engages with the slot and the crank becomes spin free stopping travel of the breaker. When this
area at the end of the tube and the key/pin become worn, the crank can go spin free before the
breaker has traveled all the way to the proper OPERATE/ENGAGED position.
The 1/4 inch dimension between the breaker barrier and the cell frame is a reference dimension.
This gap may be larger or smaller depending on how square the barrier is in relation to the circuit
breaker. The gap may also vary depending on the final position of the breaker in relation to the
center line of the breaker cubicle due to the offset levering-in mechanism.
Because these two initial checks may not be sufficient, without the actual testing of the breaker, Westinghouse is advising all utilities to follow the recommendations stated below.
RECOMMENDED ACTION
A.
The actual operation of the breaker after it has been positioned in the OPERATE/ENGAGED
position is still the best/preferred way to insure that the breaker is properly levered into this
position. However, if this is not possible, a good visual check is to determine that the floor
trippers are not hung up. Refer to l.B. 32-253-2, Figure 6, item 2, and l.B. 32-253-4N4B,
Figure 14 item 12 and Figure 28. The utility can accomplish this check by performing the
following two steps:
1.
Lever the breaker into the TEST position. Look under the front panel to see that the
levers are down at the rear. Note the relative position of the tripping and closing
Attachment 1
September 4, 1996
ESBU-TB-96-05-RO linkage on the front panel (refer to Figure 3). From an operator safety standpoint when
the breaker is in the TEST position the main contacts are not engaged as they remain
behind an insulating shutter in the cell.
2.
Lever the breaker from the TEST position to the fully OPERATE/ENGAGED position.
Note the relative position of the tripping and closing linkage on the front panel. They
should be in the same position noted in the TEST position. If not, remove the breaker
and perform complete examination of the levering-in device and floor trippers as they
may need replaced.
B.
The levering-in device on the DHP breakers is designed per ANSI/IEEE standard C37.20.2 for inserting and withdrawing the breaker from the TEST to the OPERATE/ENGAGED
position 100 times. Because the breakers at nuclear plants have been subjected to
numerous levering operations over the constructing and testing phases of the plant, it would
be prudent to include the inspection and lubrication of the levering-in device in the
preventative maintenance procedures.
During preventive maintenance inspection, or when the breaker is out of the cell between
maintenance intervals, the following checks should be made to insure that the levering-in
device is in good working condition:
- The tube and shaft are free of cracks
- The pin or key and the mating area of the tapered part of the sleeve on the end of the tube
are not worn
- The levering-in nut (refer to Figure 4) has a coating of Molykote BR2 Plus grease
(Westinghouse P/N 53701QB1 2J)
- The threads on the levering-in nut and screw should be checked with go/no-go thread
gages
- Additionally, the floor trippers should be checked to insure that they are not bent.
Attachment 1
September 4, 1996
ESBU-TB-96-05-RO Area of
Levering-in
Wear
Tube
Nut\\
I
Rod
I
I
Rd
Key
Figure 1. Levering-in Device Prior 1982
Attachment 1
\\
,
September 4, 1996
ESBU-TB-96-05-RO Levering-in
!Tube
Nut
I
Area of
Rod
Wear
I
I1
/
Pin
Figure 2. Levering-in Device After 1982
Attachment 1
September 4, 1996
ESBU-TB-96-05-RD Note Position
of Trpln
l, I
& lsn ikg
Figure 3. Breaker Front Panel
Attachment 1
</-
September 4, 1996
ESBU-TB-96-05.RO Levering-in
Nut
Figure 4. Breaker Rear
a. Breaker in Withdrawn or Test Position Breaker
Spring Pole Unit Levering
Open
Levering-ini Interlock Disengaged
Operating Interlock
Shaf
fAS
l
S
A
-a1
b. Breaker in F ully i ngaged or Energized Position
1 Breaker Closed
Levering-in Interlock Engaged
-0 U)D
_
-
-Oi
CD 2 cC-,.
D c-+
0D Cj
(D O
0
Figure 5 - Schematic of Levering-in Device and Interlock
Attachment 3
September 4, 1996 LEVER
SHAFT
K Er
GUIDE
UBE
POINTS
OF WEAR
Original Design Levering Shaft and Guide Tube
or f
LEVERING -/-
SHAFT
I
T Ii
3UIDE TUBE
7
/su
=
1982 Redesigned Levering Shaft and Guide Tube
Figure '
-
Difference in Original and 1982 Redesigned Levering-in Devices
Attachment 4
September 4, 1996 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
96-49 Thermally Induced
08/20/96
All holders of OLs or CPs
pressurization of
of Nuclear Power
facility Piping
for nuclear power reactors
96-48
96-47
96-46
96-45
96-44
96-43
96-42
96-41 Motor-Operated Valve
Performance Issues
Recordkeeping, Decommis- sioning Notifications for
Disposals of Radioactive
Waste by Land Burial
Authorized Under Former
10 CFR 20.304, 20.302, and Current 20.2002
Zinc Plating of Hardened
Metal Parts and Removal
of Protective Coatings
in Refurbished Circuit
Breakers
Potential Common-Mode
Post-Accident Failure of
Containment Coolers
Failure of Reactor
Trip Breaker from Cracking
of Phenolic Material in
secondary contact assembly
Failures of General
Electric Magne-Blast
Circuit Breakers
Unexpected Opening of
Multiple Safety Relief
Valves
Effects of a Decrease in
Feedwater Temperature on
Nuclear Instrumentation
08/21/96
08/19/96
08/12/96
8/12/96
8/05/96
08/02/96
08/05/96
07/26/96
All holders of OLs or CPs
for nuclear power reactors
All U.S. Nuclear Regulatory
Commission licensees
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for pressurized water
reactors
OL - Operating License
CP = Construction Permit
September 4, 1996
Westinghouse redesigned the levering-in device in 1982 to extend its service
life.
Figures I and 2 in the attached Westinghouse bulletin show the original
and redesigned device installed in the breaker.
Figure 6 is a sketch
illustrating the difference in the guide tubes and levering shafts of the two
designs.
Interface between licensees and vendors in accordance with Generic
Letter 83-28, "Required Actions Based on Generic Implications of Salem ATWS
Events," issued July 8, 1983, can help ensure that information on safety- related components is complete and up to date.
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 Regulation (NRR) project manager.
original signed by
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Kamalakar Naidu, NRR
(301) 415-2980
E-mail: krn~nrc.gov
Zelig Falevits, R-III
((718) 829-9717 E-mail: zxf@nrc.gov
Attachments:
David L. Skeen, NRR
(301) 415-1174 E-mail: dls~nrc.gov
Attachment - Westinghouse Technical Bulletin 96-05-RO
Figure 5 - Schematic of Levering-in Device and Interlock
Figure 6 - Difference in Original and 1982 Redesigned
Levering-in Devices
List of Recently Issued NRC Information Notices
- Can
my-pu4iniC
ennrio~rrnra
-
4vuC VI
T w ua
u.9 W
..
-
OFC
PECB:DRPM v
PSIB:DISP
C/PSIB:DISP
C/PECB.DRPM
NAME
DLSkeen NVJ
KNaidu*
RGallo*
AEChaf
iee
DATE 1 8/Z./96 J 8/22/96
8/26/96 J 8/'?7/96 OFC
D/DRPM
NAME
TTMartin
DATE I8/Z>/96
_
.,~
_ _6 t.
[OFFICIAL RECORD COPY]
DOCUMENT NAME: G:\\DLS\\IN96-XXW.BKR
IN 96-XX
August XX, 1996 ATWS Events," issued July 8. 1983. can ensure that information on safety- related components is complete and up to date.
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 Regulation (NRR) project manager.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Kamalakar Naidu, NRR
(301) 415-2980
E-mail: krn@nrc.gov
Zelig Falevits, R-III
((718) 829-9717 E-mail: zxf@nrc.gov
David L. Skeen. NRR
(301) 415-1174 E-mail: dls@nrc.gov
Attachments:
Attachment - Westinghouse Technical Bulletin 96-05-RO
List of Recently Issued NRC Information Notices
- Spp nrevious concurrence
/4'>-)
OFC
PECB:DRPM
PSIB:DISP
GilI X
P
C/PECB:DRPM
NAME
DLSkeen*
KNaidu*
Calto
AEChaffee
DATE 1 8/22/96
8/22/96
&8' 96
8/ /96 V56 OFC
D/DRPM
NAME
TTMartin
DATE
8/ /96
[UFFICIAL RLLUKU LUPYJ
DOCUMENT NAME:
G:\\DLS\\IN96-XXW.BKR
IN 96-XX
August XX, 1996 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.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Kamalakar R. Naidu, NRR
(301) 415-2980
E-mail: krn~nrc.gov
Zelig Falevits, R-III
(718) 829-9717 E-mail: zxf@nrc.gov
David L. Skeen, NRR
(301) 415-1174 E-mail: dls@nrc.gov
Attachments:
DOCUMENT NAME:
Attachment - Westinghouse Technical Bulletin 96-05-RO
List of Recently Issued NRC Information Notices
.: _.
\\ _N
J..
.......
.BKR
OFC
l PECB-DR!
PS
"PSIB:DISP
l C/PECB:DRPM
NAME
DLSkeen16- KNf. i
'rGallo
AEChaffee
DATE
8lS2J96 L
1
8/ /96
1 8/ /96 OFC
D/DRPM
11 NAME
TTMartin
DAT
/ /96
--
--
_. ,.
UFFICIAL KECORD COPYJ