Information Notice 1994-51, Inappropriate Greasing of Double Shielded Motor Bearings
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
July 15, 1994
INAPPROPRIATE GREASING OF DOUBLE SHIELDED MOTOR
BEARINGS
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the potential for failure of safety-related
equipment as a result of inappropriate greasing of double shielded motor
bearings. 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 January 20 and January 21, 1994, two different emergency diesel generator
fuel oil transfer pumps failed to start at the North Anna Power Station when
the motor breakers tripped on overload during testing. On January 22, 1994, the licensee tested the remaining six diesel fuel oil transfer pumps, and two
more of the pump motor breakers tripped on thermal overload. These two pumps
supply the same diesel generator. Consequently this diesel generator was
declared inoperable.
There are eight fuel oil transfer pumps at North Anna; two redundant pumps
supply each of the station four emergency diesel generators from underground
fuel oil storage tanks.
The transfer pumps are located in an unheated
building near the fuel oil tanks.
This building is continuously supplied with
outside air to reduce the oil fumes. As a result, the temperature in the
building was about the same as that of the outdoor air, which was abnormally
cold: -15°C [5°F].
The licensee installed temporary heaters in the building
and, after a short warmup period, successfully tested all of the transfer
pumps.
Discussion
The licensee investigation of the problem showed that the failures to start
the pumps were caused by excessive grease in the motor bearings, which became
very stiff at the abnormally low temperatures. This caused abnormally high
starting loads that prevented the motor from accelerating past the low
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IN 94-51 July 15, 1994 rotational speeds that cause the motor to draw high starting currents. The
sustained high starting currents caused the motor power supply breaker thermal
overload devices to trip.
This determination was confirmed by placing the motors in a freezer for
2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at -14°C [6'F] and applying power to them. At this temperature
some of the motors drew 6 amperes when the rated 460 volts were applied to the
motor terminals, compared to the rated full load current of 0.75 amperes.
These motors continued to run at a slow speed in the start-up current range.
When tested at the same temperature after the bearings were replaced, the
motors ran at normal speed and drew only 0.4 amperes.
The motor bearings are of the double shielded type, which are supplied by
several different manufacturers, and normally require no greasing after they
are installed. However, station records showed that 7 of the 8 motors had
been greased every 18 months since 1986.
The old bearings were found to be
completely full of grease. According to the bearing vendors, a high grease
content inside the bearing shields could not only cause high starting loads, but could also cause the bearing to overheat and solidify the grease under
normal operating conditions.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12,
1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response.
If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation project manager.
ian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: Rick McWhorter, RII
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
4 Attachment
July 15, 1994 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
94-50
94-49
94-48
94-13, Supp. 1
94-47
94-46
94-45
94-44
94-43
Failure of General
Electric Contactors
to Pull in at the
Required Voltage
Failure of Torque
Switch Roll Pins
Snubber Lubricant
Degradation in High-
Temperature Environments
Unanticipated and Unin- tended Movement of Fuel
Assemblies and other
Components due to Improper
Operation of Refueling
Equipment
Accuracy of Information
Provided to NRC during
the Licensing Process
NonConservative Reactor
Coolant System Leakage
Calculation
Potential Common-Mode
Failure Mechanism for
Large Vertical Pumps
Main Steam Isolation
Valve Failure to Close
on Demand because of
Inadequate Maintenance
and Testing
Determination of Primary- to-Secondary Steam
Generator Leak Rate
07/14/94
07/06/94
06/30/94
06/28/94
06/21/94
06/20/94
06/17/94
06/16/94
06/10/94
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 U.S. Nuclear Regulatory
Commission Material
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 pressurized water
reactors.
OL = Operating License
CP = Construction Permit
Il
IN 94-51 July 15, 1994 rotational speeds that cause the motor to draw high starting currents. The
sustained high starting currents caused the motor power supply breaker thermal
overload devices to trip.
This determination was confirmed by placing the motors in a freezer for
2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at -14°C [6°F] and applying power to them.
At this temperature
some of the motors drew 6 amperes when the rated 460 volts were applied to the
motor terminals, compared to the rated full load current of 0.75 amperes.
These motors continued to run at a slow speed in the start-up current range.
When tested at the same temperature after the bearings were replaced, the
motors ran at normal speed and drew only 0.4 amperes.
The motor bearings are of the double shielded type, which are supplied by
several different manufacturers, and normally require no greasing after they
are installed.
However, station records showed that 7 of the 8 motors had
been greased every 18 months since 1986. The old bearings were found to be
completely full of grease. According to the bearing vendors, a high grease
content inside the bearing shields could not only cause high starting torques, but could also cause the bearing to overheat and solidify the grease.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12,
1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropiate Office of Nuclear
Reactor Regulation project manager.
rin .ignid-f
Brian K.
Glme
Brian K. Grimes,1lrrector
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact:
Rick McWhorter, R11
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
- See previous concurrence
I
OFFICE
- OGCB:DORS
- TECH ED
- C/EELB:DE
- REGION II
- REGION II
NAME
DCKirkpatrick
CHBerlinger
RMcWhorter
ABelisle
DATE
05/03/94
05/02/94
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94
06/06/94
06/20/94 I
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06/20/94
06/20/94
07/f/94 DOCUMENT NAME:
94-51. IN
IN 94-xx
June xx, 1994 rotational speeds that cause the motor to draw high starting currents. The
sustained high starting currents caused the motor power supply breaker thermal
overload devices to trip.
This determination was confirmed by placing the motors in a freezer for
2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at -140C [60F] and applying power to them.
At this temperature
some of the motors drew 6 amperes when the rated 460 volts were applied to the
motor terminals, compared to the rated full load current of 0.75 amperes.
These motors continued to run at a slow speed in the start-up current range.
When tested at the same temperature after the bearings were replaced, the
motors ran at normal speed and drew only 0.4 amperes.
The motor bearings are of the double shielded type, which are supplied by
several different manufacturers, and normally require no greasing after they
are installed.
However, station records showed that seven of the eight motors
had been greased every 18 months since 1986.
The old bearings were found to
be completely full of grease. According to the bearing vendors, a high grease
content inside the bearing shields could not only cause high starting torques, but could also cause the bearing to overheat and solidify the grease.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12,
1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: Rick McWhorter, RII
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
- See previous concurrence
I
OFFICE
- OGCB:DORS
- TECH ED
- C/EELB:DE
- REGION II *REGION II
NAME
DCKirkpatrick
CHBerlinger
RMcWhorter
ABelisle
DATE
05/03/94 I
05/02/94
_05/26/94
06/06/94
06/20/94
=
_
- REGION IT I *AC/OGCB:DORS I D:DORS
JRJohnson
RLDennig
I BKGrimes
06/20/94_
06/20/94
1.
06/ /94
_J.
DOCUMENT NAME: GREASMTR.IN
IN 94-xx
June xx, 1994 rotational speeds that cause the motor to draw high starting currents. The
sustained high starting currents caused the motor power supply breakers
thermal overload devices to trip.
This determination was confirmed by placing the motors in a freezer for 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at -14'C [60F] and applying power to them. At this temperature some of
the motors drew 6 amperes, when the rated 460 volts were applied to the motor
terminals, compared to the rated full load current of 0.75 amperes. These
motors continued to run at a slow speed in the start-up current range. When
tested at the same temperature after the bearings were replaced, the motors
ran at normal speed and drew only 0.4 amperes.
The motor bearings are of the double shielded type, which are supplied by
several different manufacturers, and normally require no greasing after they
are installed.
However, station records showed that seven of the eight motors
had been greased every 18 months since 1986.
The old bearings were found to
be completely full of grease.
According to the bearing vendors, a high grease
content inside the bearing shields could not only cause high starting torques, but could also cause the bearing to overheat and solidify the grease.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12,
1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact:
Rick McWhorter, RII
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
- See Drevious concurrence
OFFICE
- OGCB:DORS
- TECH ED
- C/EELB:DE
- REGION II *REGION II
NAME
DCKirkpatrick
CHBerlinger
RMcWhorter
ABelisle
DATE
1 05/03/94 j 05/02/94
[05/26/94
06/06/94 j 06/20/94
- REGION II I A AD)DORS I D:DORS
I
JRJohnson
Rennig
BKGrimes
06/20/94
061)0/94
06/ /94 DOCUMENT NAME: GREASMTR.IN
a
.
&
IN 94-xx
June xx, 1994 rotational speeds that cause the motor to draw high starting currents. The
sustained high starting currents caused the motor power supply breakers
thermal overload devices to trip.
This determination was confirmed by placing the motors in a freezer for 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at -140C [6*F] and applying power to them.
At this temperature some of
the motors drew 6 amperes, when the rated 460 volts were applied to the motor
terminals, compared to the rated full load current of 0.75 amperes. These
motors continued to run at a slow speed in the start-up current range.
When
tested at the same temperature after the bearings were replaced, the motors
ran at normal speed and drew only 0.4 amperes.
The motor bearings are of the double shielded type, which are supplied by
several different manufacturers, and normally require no greasing after they
are installed.
However, station records showed that seven of the eight motors
had been greased every 18 months since 1986.
The old bearings were found to
be completely full of grease. According to the bearing vendors, a high grease
content inside the bearing shields could not only cause high starting torques, but could also cause the bearing to overheat and solidify the grease.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12,
1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response.
If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact: Rick McWhorter, RII
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
- See Drevious concurrence
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Ir
-~
OFFICE
- OGCB:DORS
- TECH ED
- C/EELB:DE
REGION II
lEWO. II l
NAME
DCKirkpatrick
CHBerlinger
ort
DATE
05/03/94
05/02/94
05/26/94 f6/e494
6/9X 94 I
.REGION IL_. LAC/OGCB:DORS
I D:DORS
Johnson
RJKiessel
BKGrimes
06,)C/94
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06/ /94 DOUMN NAE
GREASMIR.. IN_
DOCUMENT NAME:
GREASMTR.IN
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~IN
94-xx
May xx, 1994 6.0 amps of current, compared to the name plate rating of 0.75 amps, and ran at
a speed that was slower than normal. When tested at the same temperature after
the bearings were replaced, the motors drew only 0.4 amps and ran at normal
speed.
mnt rs arc Westinghouse Model TBEP, Stylo 7.ZA 5C5G, 1/2 horscpower motrs.
ehsy
opcrate on 460 volts ac at 3525 rpm
The motor bearings are of the double
shielded type, which are supplied by several different manufacturers, and
normally require no greasing after they are installed. However, station records
showed that seven of the eight motors had been greased every 18 months since
1986. The old bearings were found to be completely full of grease.
According
to the bearing vendors, a high grease content inside the bearing shields could
not only cause high starting torques, but could also cause the bearing to
overheat and solidify the grease.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12, 1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response. If you
have any questions about the information in this notice, please contact
the
technical contact listed below or the appropriate Office of Nuclear Reactor
Regulation project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact(s):
Rick McWhorter, RII
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
- See previous concurrence
__l_X
OFFICE
- OGCB:DORS
- TECH ED
C/EEL :DE
REGION II
REGION II
NAME
DCKirkpatrick
CHBerlinger
IRMcWhorter
MSinkule
DATE
05/03/94
05/02/94
05/&V/94 Q_
/94
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IIl
REGION II
I AC/OGCB:DORS
I D:DORS
JRLJohnson
A4ug <X eR/4
2BKGrimes
Of/
/94_
O/
94
0 f/ /94 DOCUMENT NAME:
GREASMTR.IN
I
.
I
IN 94-xx
May xx, 1994 6.0 amps of current, compared to the name plate rating of 0.75 amps, and ran at
a speed that was slower than normal. When tested at the same temperature after
the bearings were replaced, the motors drew only 0.4 amps and ran at normal
speed.
These motors are Westinghouse Model TBEP, Style 72A35856, 1/2-horsepower motors.
They operate on 460 volts ac at 3525 rpm. The motor bearings are of the double
shielded type, which are supplied by several different manufacturers, and
normally require no greasing after they are installed. However, station records
showed that seven of the eight motors had been greased every 18 months since
1986. The old bearings were found to be completely full of grease.
According
to the bearing vendors, a high grease content inside the bearing shields could
not only cause high starting torques, but could also cause the bearing to
overheat and solidify the grease.
Related Generic Communications
NRC Information Notice 88-12, "Overgreasing of Motor Bearings," April 12, 1988.
NRC Information Notice 93-26 and Supplement 1, "Grease Solidification Causes
Molded-Case Circuit Breaker Failure To Close," April 7, 1993, and
January 31, 1994.
This information notice requires no specific action or written response. If you
have any questions about the information in this notice, please contact
the
technical contact listed below or the appropriate Office of Nuclear Reactor
Regulation project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contact(s):
Rick McWhorter, RII
(703) 894-5421 Attachment:
List of Recently Issued NRC Information Notices
- See previous concurrence
OFFICE
OGCB:DORS
TECH ED
C/EELB:DE
REGION II
REGION II
NAME
DCKirkpatrick
CHBerlinger
RMcWhorter
MSinkule
DATE
05/-3/94 J 05 /
4
,05/
/94
-05/
/94
05/ /94
.
.
.
REGION II
I AC/OGCB:DORS
I D:DORS
JRJohnson
l
BKGrimes
05/ /94
05/
/94
_
_05/
/94 DOCUMENT NAME: GREASMTR.IN