ML19208D897
| ML19208D897 | |
| Person / Time | |
|---|---|
| Issue date: | 07/26/1978 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| IEC-78-16, NUDOCS 7910010706 | |
| Download: ML19208D897 (4) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
,,, ASHINGTON, D. C.
20555 W
July 26, 1978 IE Circular 78-16 LIMITORQUE VALVE ACTUATORS Description of Circumstances:
At Rancho Seco, a Limitorque Type SMB-2 motor-driven valve actuator in a safety feature system failed to function.
The failure resulted from clutch wear which was due to manual operation of the valve and improper heat treatment of the clutch parts.
Other SMB valve actua-I tors at Rancho Seco had been aubjected to undue clutch wear but were still operable.
Based on information obtained from the licensee and from Limitorque Corporation, undue wear appears to be limited to Type SMB-0, 1, 2, and 3 valve actuators equipped with 3600 rpm motors.
The type SMB valve actuator is provided with a handwheel so that the valve can be actuated manually in the event that power is unavailable.
To shift from motor drive to handwheel drive, the operator must manually position a clutch so that the motor is disengaged from the drive train and the handwheel is engaged.
The clutch latches into this posittan and cannot be manually repositioned.
The next time that the motor is energized, the latch releases automatically and a spring repositions the clutch so that the motor engages the drive train.
When the clutch is repositioned, a pair of lugs on the motor-side of the clutch engages a pair of lugs on the valve-side.
At the instant the lugs engage, the lugs on the motor-side are being accelerated to full speed and the lugs on the valve-side are stationary.
Before the motor is energized, the relative position of the lugs is random.
This initial position determines the depth of engagement or bite at the instant the lugs make contact..
When a full bite occurs, no damage is caused to the lugs. When a grazing bite occurs, the edges of the lugs are chipped or upset.
After the edges are sufficiently rounded, the clutch will not engage and hold for motor actuation.
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July 26, 1978 IE Circular 78-16 The licensee estimated that the failure of the Type SMB-2 valve actuator occurred after it had been clutched 25 to 100 times.
The valve which failed to function at Rancho Seco (SFV-25003) is operated by the actuator and is a safety features valve in a line connecting the borated water storage tank to a high pressure safety injection pump and a decay heat removal (low head safety injection) pump.
The valve actuator is wired so that the valve which it controls will drive to the fully open or fully closed position once the motor is energized.
FV-25003 is used for various routine operations during refueling, e.g.
adding borated water to the primary cooling system.
In these instances, the operator uses SFV-25003 as a throttle valve.
To do this, the valve must be actuated manually, giving rise to the potential damage to the lugs as described above.
This would not occur with the type of valve l
actuator that is clutched with the motor at rest.
Likewise, a separate l
throttle valve for supplying borated water during routine operation would preclude the need for manual operation of the subject valve ac5"ator.
Limitorque Corporation has a test program in progress for determining the clutch life of Type SMB 0, 1, 2, and 3 valve actuators.
Results to date are inconclusive.
Pending other resolution of the problem, the licensee has stated that the valve will be stroked with the motor drive to ensure that the clutch has engaged the motor following manual actuation of the valve.
All licer. -s and construction permit holders should consider:
For Limitorque Type SMB-0, 1, 2, and 3 valve actuators with 3600 rpm motors which are used or will Lc used in engineered safety systems; 1)
The potential for failure of the actuators resulting from manual operation,
- 2) Means for minimizing manual operation and,
- 3) Procedures for verifying that the actuator is operable with the motor after manual neration.
No written response to this Circular is required.
If you require additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
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IE Circular No. 78-16 July 26, 1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Date Issued To Circular Subject of Issue No.
78-01 Loss of Well Logging 4/5/78 All lloiders of Well Logging Source Source Licenses 78-02 Proper Lubricating 011 4/20/78 All liolders of Reactor OLs or for Terry Turbines cps 5/12/78 All Holders of 78-03 Packaging Greater Than Reactor OLs, cps, Type A Quantities of Fuel Cycle, Low Specific Activity Priority I Material Radioactive Material and Waste Disposal for Transport Licenses 78-04 Installation Error That S/15/78 All Holders of Reactor OLs or Could Prevent Closing of cps Fire Doors 78-05 Inadvertent Safety Injection 5/23/78 All Holders of Reactor OLs or During Cooldown cps 78-06 Potential Comnon Mode 5/23/78 All Holders of Reactor OLs or Flooding of ECCS Equipment cps Rooms at BWR Facilities 78-07 Damaged Components of a S/31/78 All Holders of Reactor OLs or Bergen-Paterson Series cps 25000 Hydraulic Test Stand 78-08 Environmental Qualification 5/31/78 All Holders of Reactor OLs or of Safety Related Equipment cps at Nuclear Power Plants 78-09 Arcing of General Electric 6/5/78 All liolders of cps Conpany Size 2 Contactors Enclosure Page 1 of 2 032
IE Circular No. 78-16 July 26, 1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Dr.te of Issued to Circular Subject Issue No.
6/14/78 All Medical 78-10 Control of Scaled Licensees in Sources Used in Categories G Radiation Therapy and G1 6/15/78 All Holders of 78-11 Recirculation M-G BWR OLs or cps Set Overspeed Stops 6/30/78 All Hciders of
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HPCI Turbine Control BWR OLs or cps 78-12 Valve Lift Rod Bending for plants with HPCI Terry Turbine 7/10/78 All lioiders of 78-13 Inoperability of Multiple Reactor OLs and cps Service Water Pumps except for plants located in: AL, AK, CA, FL, GA, LA, MS, SC 7/12/78 All Hciders of BWR 78-14 HPCl Turbine Reversing OLs or cps for Chamber Hold Down Bolting plants with a HPCI Terry Turbine excepting Deane Arnold and Monticello 7/20/78 All Holders of 78-15 Checkvalves Fail to Reactor OLs or cps Close In Vertical Position Enclosure Page 2 of 2 l
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