ENS 47488
ENS Event | |
|---|---|
05:00 Aug 2, 2011 | |
| Title | Part 21 Notification on Limitorque Smb-5T Actuator Clutch Lug Failure |
| Event Description | The following is a summary of information was received from Limitorque via facsimile:
On August 2, 2011, Flowserve-Limitorque was notified by Browns Ferry Nuclear (BFN) Generating Station that a Limitorque SMB-5T valve actuator (1-MVOP-074-052) had failed to run open automatically during the performance of a stroke test. Electrical maintenance personnel working at the valve reported an abnormal mechanical noise. Upon disassembly, it was found that the driving lugs on both the sliding clutch gear and the flexible clutch were seriously worn with a significant amount of deformation. Further investigation by BFN showed that the declutch mechanism would not allow full engagement of the drive lugs on the sliding clutch and flexible clutch. These lugs must be engaged for motor operation to take place. The declutch mechanism required adjustment to allow full drive lug engagement. Following reassembly of the SMB-5T on 1-MVOP-074-052, an inspection was performed of the SMB-5T on valve 1-MVOP-074-066 which was manufactured and supplied to TVA at the same time. This actuator was functioning normally at the time of the inspection. Disassembly of the clutch compartment revealed evidence of deformation of the clutch drive lugs. To better evaluate the operation of the clutch components, the grease was cleaned out of the compartment and a boroscope used so that the action of the clutch could be seen. Boroscope examination of several declutching and re-clutching tests showed that the clutch lugs would not engage fully. The major contributing factor in this issue was found to be the external declutch lever stop screw adjustment. Adjustment of the lever stop screw significantly improved the lug engagement. Subsequently, BFN personnel inspected four additional SMB-5T actuators. The declutch components were found to be adjusted correctly and no indications of abnormal clutch lug wear were found. The potential for this issue is limited to SMB-5 and SMB-5T actuators only. Other sizes of SMB/SB/SBD actuators are not affected. This issue, when it occurs can affect the safety related function of the actuator by preventing proper motorized operation. Indications of the issue can include failure to complete valve stroke, failure to remain in motorized operation, intermittent motorized operation resulting in longer than expected stroke time, and/or abnormal noise in the clutch compartment. Limitorque performed an investigation per the guidelines of 10 CFR Part 21. The failure of 1-MVOP-074-052 to operate was due to damage to the drive lug interface between the sliding clutch and the flexible clutch which resulted in the actuator disengaging from electric motor operation in mid-stroke of the valve. This lug damage occurred over time during normal operation of the actuator and is directly attributable to an assembly set-up error resulting in partial lug engagement. The actuators which were investigated at BFN Unit 1 were of relatively recent manufacture, having been shipped from the Limitorque factory in 2004. Limitorque's review of existing SMB-5/5T assembly procedures followed by interviews with assembly personnel led to the conclusion that the root cause of this event was that the Limitorque factory assembly procedure documents for the SMB-5/5T lack adequate detail to ensure reliable long term functionality of the clutching mechanism. Limitorque's review of previous industry operating experience did not show any history of problems related to drive lug engagement and/or declutch components in SMB-5/5T actuators. However to address the potential issue of insufficient drive lug engagement, Limitorque will issue a Maintenance Update to the MOV Users Group for distribution to the utilities (on or before January 15, 2012) containing recommendations for site inspection of the SMB-5/5T clutch mechanism as well as detailed instructions for set-up, adjustment and verification of proper clutch operation. As part of our internal corrective action, Limitorque will develop enhanced assembly and service procedures for the SMB-5/5T to include sufficient detail to ensure the proper set-up and function of the clutching mechanism. Limitorque assembly, field service, and QC personnel will be trained in the enhanced procedures. Technical contacts: John Thilking 434-522-9862 Jeff McConkey 434-845-9738 |
| Where | |
|---|---|
| Flowserve Lynchburg, Virginia (NRC Region 1) | |
| Organization: | Flowserve |
| Reporting | |
| 10 CFR 21.21 | |
| Time - Person (Reporting Time:+2867.42 h119.476 days <br />17.068 weeks <br />3.928 months <br />) | |
| Opened: | Jeff Mcconkey 17:25 Nov 29, 2011 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Nov 29, 2011 |
| 47488 - NRC Website
Loading map... {"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"350px","height":"250px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":6,"defzoom":14,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[],"imageoverlays":null} | |
Flowserve with 10 CFR 21.21, Notification of failure to comply or existence of a defect and its evaluation | |
WEEKMONTHYEARENS 474882011-08-02T05:00:0002 August 2011 05:00:00
[Table view]10 CFR 21.21, Notification of failure to comply or existence of a defect and its evaluation Part 21 Notification on Limitorque Smb-5T Actuator Clutch Lug Failure 2011-08-02T05:00:00 | |