05000281/LER-1978-033-03, /03X-1 on 780926:circulating Water Outlet Valve MOV-CW-200D Failed to Close When Operated Electrically. Caused When Actuator Cam for Shut Torque Switch Became Wedged Against Torque Switch Hold Down Screw

/03X-1 on 780926:circulating Water Outlet Valve MOV-CW-200D Failed to Close When Operated Electrically. Caused When Actuator Cam for Shut Torque Switch Became Wedged Against Torque Switch Hold Down Screw

ML18113A868
Person / Time
Site:	Surry
Issue date:	02/20/1979
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18113A867	List: 05000281/LER-1978-033-03, /03X-1 on 780926:circulating Water Outlet Valve MOV-CW-200D Failed to Close When Operated Electrically. Caused When Actuator Cam for Shut Torque Switch Became Wedged Against Torque Switch Hold Down Screw 05000281/LER-1978-038-03, /03X-1 on 781030:boric Acid Flow from Boric Acid Tank to Blender Was Interrupted.Caused by Blockage of Crystallized Boron at Elbow in Line 1-CH-356-152 ML18113A866
References
LER-78-033-03X, LER-78-33-3X, NUDOCS 7902260472
Download: ML18113A868 (2)

LER-1978-033, /03X-1 on 780926:circulating Water Outlet Valve MOV-CW-200D Failed to Close When Operated Electrically. Caused When Actuator Cam for Shut Torque Switch Became Wedged Against Torque Switch Hold Down Screw

Event date:
Report date:
2811978033R03 - NRC Website

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Surry rower Station, Unit 2 Docket No: 50-281 Report No: 78-033/03X-1 Event-Date:

9/26/78 Failure of'Circulating Water Outlet Valve MOV-CW-200D

1.

Description of Event

During steady state power operation, circulating water outlet valve HOV-CW-200D failed to operate electrically.

This is reportable pursuant to Technical Specification 6.6.2.b.(2).

2.

Probable Consequences and Status of Redunant Systems:

The corresponding inlet valve, MOV-CW-206D, was fully operable, providing full redundancy.

In addition, l10V-CW-200D was operable in the manual mode.

The health and safety of the general public were therefore not affected.

3.

Cause

Sometime prior to this event, MOV-CW-200D was manually closed to assure leak tight closure.

Manual closure of this valve causes the torque switch actuator cam to travel farther than when operated electrically.

This addition-al cam travel caused the torque switch cam to wedge against the torque switch hold down screw.

This situation did not interfere with the remote opening signal to the valve, but, the renote closure circuit was interrupted because of the wedged position of the switch.

4.

Immediate Corrective Action

An operator was immediately assigned for administrative control of MOV-CW-200D and it was closed manually.

5.

Subsequent Corrective Action:

The torque switch hold down screw lock washer was removed to provide a clearance between the actual cam and the.hold down screw, allowing full cam movement without interference.

All other circulating water valve operators were inspected and found to have adequate clearance.

6.

Action Taken to Prevent Recurrence:

The interfering lock washer was removed to allow for proper clearance for the torque switch actuator cam.

This washer is not required by the torque switch manufacturer and its removal will prevent a recurrence of this event.

The corresponding lock washers on all condenser inlet and outlet valves for Unit 1 and Unit 2 have been removed.

7.

Generic Implications:

None