Information Notice 1993-98, Motor Brakes on Valve Actuator Motors
~'i
K-
Kv
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 20, 1993
NRC INFORMATION NOTICE 93-98: MOTOR BRAKES ON VALVE ACTUATOR MOTORS
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 potential problems with the performance of
motor-operated valves (MOVs) resulting from improper operation of motor brakes
used on valve actuator motors. 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.
Background
Some MOVs have motor brakes installed to help minimize the inertial loads
during valve closure after the control switch has tripped. Motor brakes also
help prevent MOVs with non-locking gear mechanisms from inadvertently opening.
One type of motor brake is designed to be electromagnetically released and has
friction pads to slow the motor shaft following control switch trip.
Improper
operation of motor brakes can result in problems with the performance of MOVs.
Description of Circumstances
In Maintenance Update 92-2, Limitorque Corporation informed the nuclear
industry that it had discovered, through operating experience and testing, that motor brakes do not substantially minimize the thrust load caused by
inertia when closing MOYs.
Limitorque also stated that it did not qualify
motor brakes through its nuclear qualification testing. Limitorque warned
that voltage variation into the motor brake may render the brake inoperable.
Limitorque noted that disconnection of the brake leads does not render the
brakes inoperable and specified that the friction pads be removed.
Each of
the following reports involve valves with Limitorque motor operators.
On August 4, 1993, the licensee of Crystal River Nuclear Plant, Unit 3, reported (Licensee Event Report 93-008) that seven MOVs with motor brakes
installed might receive insufficient voltage to allow the motor brakes to be
released under degraded voltage conditions. Of these seven MOVs, the licensee
9312150064 I
o v' t
3-o1S
PD9 I e
19 3c)
0
IN 93-98 I-'
December 20, 1993 declared a normally closed high-pressure injection suction NOV to be
inoperable on July 6, 1993. The licensee removed the friction disks and
electrical power connections from this NOV as well as from normally open
borated water storage tank suction NOV.
The licensee tested another of the
seven MOVs to ensure that its motor brake would release under degraded voltage
conditions. The remaining four MOVs are locked in their safety function
position during plant operation.
On September 14, 1993, the licensee of Millstone Nuclear Power Station, Unit 2, notified NRC that it had declared four feedwater supply MOVs with
motor brakes installed inoperable when it determined that the MOVs might
receive insufficient voltage during degraded voltage conditions to allow the
motor brakes to release. The licensee relies on these MOVs as a backup for
feedwater isolation in the event of a main steam line break. The licensee
shut down Millstone Unit 2 in accordance with its plant technical
specification requirements. The licensee subsequently removed the motor
brakes.
On September 28, 1993, the licensee of James A. FitzPatrick Nuclear Power
Plant notified NRC of problems with the operation of motor brakes on two low- pressure coolant injection MOVs. The licensee determined that the motor
brakes were undersized to prevent the actuator spring pack from relaxing and
causing the torque switch to restart the actuator motor on a repeated basis.
Continuous restarting of the actuator motor can cause (1)
damage to the motor
from overheating, and (2)
excessive stress to the NOV by driving the valve
disk into its seat (sometimes referred to as a 'hammering" effect).
Discussiosn
In Generic Letter (GL) 89-10, 'Safety-Related Motor-Operated Valve Testing and
Surveillance," the NRC staff requested nuclear power plant licensees to
confirm the capability of safety-related MOVs to perform their intended
functions by reviewing NOV design bases, verifying NOV switch settings
initially and periodically, testing MOVs under design-basis conditions where
practicable, improving evaluations of NOV failures and necessary corrective
action, and trending NOV problems. In response to GL 89-10, licensees are
implementing programs to evaluate the design-basis capability of MOVs within
the scope of tbe generic letter.
As indicated by the discovery of NOV operability problems at Crystal River and
Millstone, some licensees may not be evaluating the minimum voltage required
to ensure the proper operation of motor brakes when determining the design- basis capability of MOVs with motor brakes installed.
Improper operation of
motor brakes on MOVs could allow the motor to restart repeatedly as found at
FitzPatrick.
.
I
K2IN 93-98
December 20 1993 Related Generic Communications
NRC has issued other information notices pertaining to MOVs. During the past
year, these have included NRC Information Notices 93-74, wHigh Temperatures
Reduce Limitorque AC Motor Operator Torque;" 93-54, "Motor-Operated Valve
Actuator Thrust Variations Measured With a Torque Thrust Cell and a Strain
Gage;" 93-01, 'Accuracy of Motor-Operated Valve Diagnostic Equipment
Manufactured by Liberty Technologies;" 92-83, 'Thrust Limits for Limitorque
Actuators and Potential Overstressing of Motor-Operated Valves;" and 92-70,
"Westinghouse Motor-Operated Valve Performance Data Supplied to Nuclear Power
Plant Licensees."
In addition, the hammering effect was specifically addressed in
Information Notice 85-20, "Motor-Operated Valve Failures Due to
Effect," and its supplement.
NRC
Hammering
This information notice requires no specific
you have any questions about the information
one of the technical contacts listed below or
Nuclear Reactor Regulation project manager.
action or written response. If
in this notice, please contact
r the appropriate Office of
_
Z24_-_O_
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
P. K.
(215)
Eapen, RI
337-5150
Thomas G. Scarbrough, NRR
(301) 504-2794 Attachment:
List of Recently Issued NRC Information Notices
At&.dchment
December 20, 1993 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
93-96
93-95
93-94
93-93
Failures of Yokes
Installed on Walworth
Gate and Globe Valves
Improper Reset Causes
Emergency Diesel
Generator Failures
Storm-Related Loss of
Offsite Power Events
due to Salt Buildup
on Switchyard Insulators
Unauthorized Forced
Entry into the Pro- tected Area at Three
Mile Is-land Unit 1 on
February 7, 1993
Inadequate Control of
Reactor Coolant System
Conditions During Shutdown
Plant Improvements to
Mitigate Common Depend- encies in Component
Cooling Water Systems
Inadequate Quality
Assurance Program of
Vendor Supplying
Safety-Related Equipment
Debris in Containment
Emergency Sumps and
Incorrect Screen
Configurations
12/17/93
12/14/93
12/13/93
12/09/93
12/08/93
12/07/93
12/07/93
12/03/93
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
located close to a large
body of salt water.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
Al I
for
holders
nuclear
power reactors.
91-21, Supp. 1
89-77, Supp. 1
All holders of OLs or CPs
for nuclear power reactors
and all recipients of
NUREG-0040, License Con- tractor and Vendor Inspec- tion Status Report" (White
Book).
All holders of OLs or CPs
for nuclear power reactors.
OL = Operating License
CP - Construction Permit
-
KJ~
December 20, 1993 Related Generic Communications
NRC has issued other information notices pertaining to MO s. During the past
year, these have included NRC Information Notices 93-74, "High Temperatures
Reduce Limitorque AC Motor Operator Torque;" 93-54, "Motor-Operated Valve
Actuator Thrust Variations Measured With a Torque Thrust Cell and a Strain
Gage;" 93-01, "Accuracy of Motor-Operated Valve Diagnostic Equipment
Manufactured by Liberty Technologies;" 92-83, "Thrust Limits for Limitorque
Actuators and Potential Overstressing of Motor-Operated Valves;" and 92-70,
"Westinghouse Motor-Operated Valve Performance Data Supplied to Nuclear Power
Plant Licensees."
In addition, the hammering effect was specifically addressed in
Information Notice 85-20, "Motor-Operated Valve Failures Due to
Effect," and its supplement.
NRC
Hammering
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 project manager.
Original signed by
Brian K. Grimes
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
P. K. Eapen, RI
(215) 337-5150
Thomas G. Scarbrough, NRR
(301) 504-2794 Attachment:
List of Recently Issued NRC Information Notices
- See nravinui concurrence naae
OFFICE
- EMEB/DE/NRR
- C:EMEB/DE/NRR
- D:DE/NRR
- OGCB/DORS/NRR
NAME
TGScarbrough
JANorberg
JTWiggins
RJKiessel/vsb
DATE
9/20/93
9/27/93
12/01/93
10/21/93 OFFICE
- Tech Ed
- EB/DRS/RI
l *C:EB/DRS/RI
- D:DRS/RI
NAME
DGable
PKEapen
JPDurr
WDHodges
DATE
10/22/93
1 i
11/29/93
11/29/93 OFFICE
- C:OGCB/DORS/NRR
NAME
GHMarcus
I/
DATE
12/03/93
12(
-Document Name: Y3-9U.IN
K>1 IN 93-xx
December xx, 1993
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 project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
P. K. Eapen, Region I
(215) 337-5150
Thomas G. Scarbrough, NRR
(301) 504-2794 Attachment:
List of Recently Issued NRC Information Notices
C t4
'd'0
- See nrevious concurrence naae
OFFICE
- EMEB/DE/NRR
- C:EMEB/DE/NRR
N
- OGCB/DORS/NRR
NAME
TGScarbrough
JANorberg
~
T~igginsk
RJKiessel/vsb
DATE 1 9/20/93
1 9/27/93
1tI!\\ 93
10/21/93 OFFICE
- Tech Ed
- EB/DRS/RI
- C:EB/DRS/RI
- D:DRS/RI
NAME
DGable
PKEapen
JPDurr
WDHodges
DATE
10/22/93
111/29/93
,
1/29/93
11/29/93 OFFICE
C:OGCB/DORS/NRR
D: DORS/NRR
NAME
I
GHMarcusmW
BKGrines
DATE
1 f1/3 /93
_1_/ _/93
__
_p
Document Name: nrcin.3al
V
Effect," and its supplement.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
AL.
---
&-
-
IJ
L
L.1
-
-
&LL -
--
l
-
-
.-
....
_
.A.
U11ne orIei
I
Nuclear Rea4
Technical cc
Attachment:
Transmitted
LecMicUa
conMACU I ILsu D0OW or fne dppropridite urTice Ot
- tor Regulatibn project manager.
Brian K. Grimes, Director
Division of Operating Reactor Supp t
Office of Nuclear Reactor Regula on
ontacts: P. K. Eapan, Region I
(215) 337-5150
Thomas G. Scarbrough, NRR
(301) 504-2794
List of Recently Issued NRC Info ation Notices
by JANorberg memorandum date September 27. 1993 is concurrence page
- SPP nrpvioni
OFFICE
- EMEB/DE/NRR
- C:EMEBDE/NRR
D:DE/NRR
- OGCB/DORS/NRR
NAME
TGScarbrough
JAN berg
JTWiggins
RJKiessel/vsb
DATE
9/20/93
9//7/93
1i/ /93
10/21/93i
OFFICE
- Tech Ed
/EB/DRS/RI
A
C:EB/DRS/RI
D:DRS/RI
NAME
DGable
PKEapan
.0, >
JPDurr
I
Modge
DATE T
10/22/93
11
93
'
I I g
93V
11 V 93 OFFICE
C:OGCB/MfRS/NRR
D: DORS/NRR
NAME
GHMar
II
BKGrimes
DATE
II///93
11/
/93 Document Name: nrcln.3al
F
(215) 337-5240
Thomas G. Scarbrough, NRR
(301) 504-2794 Attachment: List of Recently Issued NRC Information Notices
Transmitted by JANorbera memorandum dated Sentomhbr 27. l
4 OB/DRS/RI
C:OB/DRS/RI
D:DRS/RI
- EMEBI
D NRR
- C:EMEB/DE/NRR
JSStewart
LHBettenhausen
M4WHodges
TGS
brough
JANorberg
1O/ /93 IO/ /93
10/
/93
120/93 a 9/27/93 OGCB/DORS/NRR
Tech Ed
D:DE/NRR
/C:OGCB/DORS/NRR
D:DORS/NRR
RJKiesselftk , k
JTW~ggins /
GHMarcus
BKGrimes
10
/93
10.ZZ/93
10/ /93
10/ /93
10/ /93 uoPcumenr name: nrcin.al
/