ML19294B633
| ML19294B633 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Mcguire, McGuire  |
| Issue date: | 01/06/1977 |
| From: | Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Parker W DUKE POWER CO. |
| References | |
| IEC-77-01, IEC-77-1, NUDOCS 8003050178 | |
| Download: ML19294B633 (3) | |
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January 6, 1977
- . ?eply 3e:er To:
t I.: ::I;CL' 5C-359 50-370 50-269 50-270 50-287 Duke Power Company ATTN:
Mr. William O. Parker, Jr.
Vice President of Stean Production h22 South Church Street P. O. Box 2178 Charlotte, North Carolina 282h2 Gentlemen:
The enclosed IE Circular 77-01 is forvarded to you for your infornation.
No written response is required.
this Should you have questions concerning this letter contact office.
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Enclosure:
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IE Circular 77-
> ate: 1/6/77 Page 1 of 2 MALFUNCTIONS OF LIMITORQUE VALVE OPERATORS DESCRIPTION OF CIRCUMSTANCES:
On October 28, 1976, Portland General Electric Company *cported that the two motor operated (Limitorque) valves located between the Ref ueling Water Storage Tank and the charging pump suction at the Trojan Nuclear Plant failed to open in response to a spurious safety injection (SI) signal. The malfunction in both valves resulted from the torque linit switch in the opening circuit becoming activated before the valve was fully off its seat.
The Licensee's investigation revealed that in each case the valve had been manually closed hard on its seat following a maintenance operation.
The licensee's investigation of this occurrence revealed dif ficulty in the opening of three additional motor operated (Limitorque) valves in the inlet and outlet piping of the Boron Injection Tank.
Each of the valves failed to open in response to a single actuation of its nanual control switch.
In each case, the cause for failure was attributed to premature activation of the valve's torque limit switch.
These valves had opened in response to the SI signal on October 28, 1976, following which they were closed normally using their motor operators.
i Subsequent investigation by the licensee revealed that each of the valves which malfunctioned was equipped with a torque limit switch in the opening circuit, the actuation of which stops valve motion.
The valves are also equipped with an adjustable bypass switch which defeats the function of the torque limit switch when the valve is being moved from its full open or full closed position.
Each of the valves which malfunctioned was found to have its bypass switch adjusted such that it allowed the limit torque switch to be unby-passed and operable in the circuit before the valve was moved from its seat.
Examination by the licensee revealed similar improper ad-justment of the bypas switches on several other motor operated valves in safety related systems.
Corrective actions by the licensee included the establishment of procedural controls to insure that valves which are manually closed are checked for proper operation (by cycling them open with the motor operator) prior to their being declared operational.
The by-pass switches on all similar motor operated valves were checked and their position in terms of proper valve travel adjusted.
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6 1/ /77 IE Circular 77-01 Date:
Page 2 of 2 Reconnended Action by Licensees:
If valves similar to those described are in use in safety related systems, y'.u should verify that your procedures contain adequate provisions to insure that these valves are adequately checked for operation f ollowing maintenance or manual losure, and that operating personnel are properly instructed to assure conformance with the procedures. You should also verify that measures are taken to insure the proper setting of torque limit switches and limit switch bypasses, to assure that the bypass function is not negated prematurely in either the opening or closing cycle.
t No written response to this Circular is required.
If you require i
additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
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