ML20246D945
| ML20246D945 | |
| Person / Time | |
|---|---|
| Issue date: | 08/23/1989 |
| From: | Berlinger C Office of Nuclear Reactor Regulation |
| To: | Warsing D LIMITORQUE CORP. |
| References | |
| NUDOCS 8908280342 | |
| Download: ML20246D945 (3) | |
Text
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LAugust 23,'1989 y yc L
' Daniel.S. Warsing, Technical Manager Limitorque Corporation 5114 Woodall Road-s 4-Post Office Box 11318 Lynchburg,. Virginia 24506-1318
Dear Mr. Warsing:
- Th'e Nuclear Regulatory Commission is'in the process of preparing an information notics entitled " Failures of Actuator Housings of Limitorque Motor-0perated'
.Yalves."
- A copy of' the latest draft of: this information notice is enclosed for your revf.ew and comment.
Comments, particularity those dealing with the facts presented in the infor-mation notice, including.the significance of the change from gray. cast iron to -
ductile cast iron, received by September 22, 1989, will'be considered in the final version.
Sincerely,
^
/s/
Carl H. Berlinger, Chief Generic Communications Branch Division of Operational Events Assessment-Office of Nuclear Reactor Regulation
Enclosure:
Draft Information Notice Distribution w/ enclosure:
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DRAFT UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION MSHINGTON, D.C.
20555 August XX, 1989 NRC INFORMATI0fl NOTICE NO. 89-XX:
FAILURES OF ACTUATOR HOUSINGS OF LIMITORQUE MOTOR-0PERATED VALVES Addressees:
'All holders of operating licenses or construction permits for nuclear power reactors
Purpose:
This information notice is intended to alert addressees to potential problems resulting from the cracking of valve actuator housings supplied by Limitorque Corporation.
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 do not constitute NRC requirements; therefore, no specific action or written response is required.
Description of Circumstances:
During the time period of 1980-1981, six spring compensator housings failed on Limitorque Model SB-00 valve operators involving three nuclear plants (the Watts Bar Nuclear Plant, the Oconee Nuclear Station, and a foreign site).
As a result of these failures, Westinghouse NSD Data Letter No. 82-08 was issued to notify utilities of the situation. This data letter attributed the failures to overthrust conditions, the root cause of which was identified as an improper limit switch adjustment of one valve and bypass of the limit switch during maintenance on another. The cause of the overthrust on the other four valves was not determined.
Since that time, additional housing failures have been identified.
(1) During the period 1983-1984, two Limitorque Model SMB-00 housings failed at the Dresden Nuclear Power Station. These failures were attributed to mechanical overloads of unknown origin.
(2) During 1986, two housings failed at the Duane. Arnold Energy Center.
These failures were attributed to overthrust conditions that occurred as a result of torque switch installation errors.
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DRAFT fu'9Mx.1989 1
Page 2 of 2 (3) In October 1988, cracks were discovered on four Limitorque Model SMB-00 operator housings at the Fort Calhoun Station. The licensee reported that the root cause of the overthrust condition was most likely attributable to grease accumulation in the torc;ue switch spring pack. They hypothesized that the grease created a hydraulic lock that prevented proper spring compression, thereby resulting in excessive torque.
(4) Additionally, Limitorque Model SMB-00 housing failures have been reported at the Pilgrim Nuclear Power Station.
A common factor among several of the failed housings was Limitorque's use of gray cast iron for housings produced before 1974. Gray cast iron is not as tough as the ductile cast iron material currently used. Although Limitorque has successfully demonstrated the ability of the gray cast iron housings to withstand-overload conditions, the use of this material apparently increases the probability of failure.
Discussion of Safety Significance:
The NRC staff considers that the continuing failures of Limitorque valve operator housings poses a potential safety hazard.
Failure of the housing will cause the valve to fail to close and, if closed, could allow the valve to drift open. Additionally, upon failure, operator parts may be ejected with substan-tial ferce, resulting in significant hazard to nearby personnel. A common element of the cerrective actions taken by the affected licensees has been to caution their plant pctsonnel about the potential hazard and to revise appro-priate procedures (e.g., operating, maintenance, and surveillance) to facili-tate the detection of housing cracks.
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 NRR project manager.
Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical
Contact:
Marc P. Huber, Region III (312)790-5789
Attachment:
List of Recently Issued NRC Information Notices I
DRAFT