Part 21 Report - 1995-185
ACCESSION #: 9508040285
Commonwealth Edison
1400 Opus Place
Downers Grove, Illinois 60515
July 31, 1995
U.S. Nuclear Regulatory Commission
Washington, D.C. 20555
Attn.: Document Control Desk
Subject: ComEd 10 CFR Part 21 Final Report (File 94-12)
Limitorque Actuator Potential Motor Pinion Key Failure
Reference: I. Johnson (ComEd) letter to U.S. NRC, dated March 31, 1995
Attached to this letter is the final evaluation report on the concerns
initiated by Commonwealth Edison Company (ComEd) regarding the subject
Limitorque AISI Type 1018 motor pinion keys.
ComEd initially informed the NRC Staff that AISI Type 1018 keys may have
insufficient strength to withstand normal operating torques for the
entire MOV life in certain MOV Limitorque actuators. After further
evaluation and testing of the AISI Type 1018 key under worst case
conditions, ComEd has determined that the AISI Type 1018 keys installed
at ComEd Nuclear facilities are qualified for plant life.
If there are any questions regarding this notification, please direct
them to Eric Steckhan at (708) 663-7437.
Respectfully,
Irene M. Johnson
Licensing Operations Director
Attachment: 10 CFR Part 21 Final Report
cc: H.J. Miller, Regional Administrator - RIII
R. Capra, Directorate III-2 Director, NRR
R. Assa, Braidwood Project Manager, NRR
U.S. NRC - 2 - July 31, 1995
G. Dick, Byron Project Manager, NRR
C. Shiraki, Zion Project Manager, NRR
J. Stang, Dresden Project Manager, NRR
R. Pulsifer, Quad Cities Project Manager, NRR
W. Reckley, LaSalle County Project Manager, NRR
M. Kunowski, Resident Inspector - Braidwood
H. Peterson, Senior Resident Inspector - Byron
J. Roton, Senior Resident Inspector - Zion
M. Leach, Senior Resident Inspector - Dresden
C. Miller, Senior Resident Inspector - Quad Cities
P. Brochman, Senior Resident Inspector - LaSalle County
Office of Nuclear Facility Safety - IDNS
k:\n1a\dresden\9412p21.wpf:2
10 CFR Part 21 Final Evaluation Report-File 94-12
Limitorque Actuator Potential Motor Pinion Key Failure
Applicability
This report is submitted in accordance with the requirements of 10 CFR
21, Section 21.21 (a).
Identification of Facility and Component
This report concerns AISI type 1018 motor pinion key failures for use in
Limitorque actuators on motor operated valves installed in safety-related
applications at all six ComEd nuclear stations.
Identification of Component Manufacturer
Limitorque Corporation
5114 Woodall Road
Lynchburg, Virginia 24506
Phone: (804) 845-9705
Nature of Defect
Failures of AISI type 1018 keys have occurred, which have been attributed
to insufficient material strength for certain Limitorque actuators.
Limitorque had previously notified the industry in 1983 that 4140 keys
are required in SMB-3, 4, and 5 actuators with 150 ft-lb. or larger
motors. ComEd, along with KALSI Engineering, evaluated AISI type 1018
motor pinion key failures in SMB-0 and SMB-2 actuators. Early results
from this evaluation indicated that key failure may occur at torque
levels below the published Limitorque actuator torque ratings (MATR).
During laboratory testing, KALSI failed 1018 keys three times
consecutively at approximately 200 cycles in a SMB-0 actuator with a 61.7
to 1 gear ratio and a 1800 rpm 40 ft-lb. motor. This appears to be
inconsistent with industry failure data which involved higher speed
actuators (for example, higher key loads).
ComEd nuclear stations have not reported any incidents of failure of a
SMB-0 actuator resulting from a sheared motor pinion key. One SMB-2
actuator failure was reported. Dresden, Quad Cities, and Zion Nuclear
Stations all have SMB-0 actuators which have been operated in excess of
200 cycles, which is the reported failure cycles at KALSI, without
incident.
k:\n1a\dresden\9412p21.wpf:3
10 CFR Part 21 Final Evaluation Report-File 94-12
Limitorque Actuator Potential Motor Pinion Key Failure
Evaluation Results
ComEd completed and evaluation of this issue with the following results:
o AISI Type 1018 keys are qualified for use in Limitorque
actuators with the exceptions noted by Limitorque.
o Motor pinion keys should be installed in accordance with
Limitorque Guidelines provided in Maintenance Update 89-01.
These results are based on the following:
1. ComEd successfully completed four tests at greater than 120% of the
torque rating for a SMB-0 Actuator.
o All tests exceeded 2000 cycles.
o Two tests exceeded 5000 cycles with the KALSI motor and overall
actuator ratio (OAR).
o Two tests completed 4000 cycles and 3/8" of the key not
engaged.
o No Key Failures.
2. The key material used during ComEd testing had a lower strength than
the keys used at KALSI and are representative of typical AISI Type
1018 keys.
3. Shear and bearing stresses at the key are significantly below
allowable stresses for all ComEd GL 89-10 MOV's.
Time of Discovery
On September 13, 1994, an evaluation was initiated for Part 21
reportability.
Corrective Actions
ComEd has issued guidelines to its six nuclear stations on the methods
for properly installing motor pinion keys.
k:\n1a\dresden\9412p21.wpf:4
10 CFR Part 21 Final Evaluation Report-File 94-12
Limitorque Actuator Potential Motor Pinion Key Failure
Number and Location of Potentially Defective Components
Each of ComEd's six nuclear stations have between 50-100 safety-related
SMB-0, SMB-1, and SMB-2 actuators.
Contacts
Questions pertaining to this notification should be addressed to:
Eric S. Steckhan
Nuclear Engineering Services
ComEd
1400 Opus Place, Suite 400
Downers Grove, IL 60515.
(708) 663-7437
k:\n1a\dresden\9412p21.wpf:5
*** END OF DOCUMENT ***
Page Last Reviewed/Updated Wednesday, March 24, 2021