ENS 54467
ENS Event | |
|---|---|
05:00 Jan 8, 2020 | |
| Title | Part 21 - Inadequate Selenium Surge Suppressor Thread Modification |
| Event Description | The following is a summary of information that was received via facsimile:
On November 14, 2019, Engine Systems, Inc. obtained information of a defect or failure to comply associated with selenium surge suppressors. Three batches of suppressors supplied by Engine Services, Inc. between 2011 and 2013 utilize a thread modification that is inadequate for the application. The design specifies the use of a single 1/4-20 x 2-3/4" long bolt to compress the stack of selenium cells as well as mount the suppressor. Contrary to this requirement, the manufacturer used a #8-32 screw through the body of the stack and added a modified bolt to obtain the required 1/4-20 mounting threads. The modified bolt consisted of a 1/4-20 x 5/8" long bolt that was drilled and tapped in the head to accept #8-32 threads. An attempt to install the selenium surge suppressor by tightening the corresponding mounting nut may result in failure of the modified bolt threads. Use of this thread modifier significantly reduces the strength of the mounting threads. Failure of the mounting threads creates the possibility of the suppressor dislodging with the potential to electrically short between the positive and negative plates of the rectifier assembly. An electrical short would affect output of the voltage regulator system, which may prevent the emergency diesel generator set from performing its safety-related function. This issue is therefore considered to be a reportable defect as defined by 10 CFR Part 21. The affected part number is 8403049. A list of affected customers include: Point Beach Nuclear Plant and Surry Power Station. |
| Where | |
|---|---|
| Engine Systems, Inc. Rocky Mount, North Carolina (NRC Region 1) | |
| Organization: | Engine Systems, Inc |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+11.73 h0.489 days <br />0.0698 weeks <br />0.0161 months <br />) | |
| Opened: | Dan Roberts 16:44 Jan 8, 2020 |
| NRC Officer: | Brian Lin |
| Last Updated: | Jan 8, 2020 |
| 54467 - NRC Website | |
Engine Systems, Inc with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
WEEKMONTHYEARENS 565382023-03-28T04:00:00028 March 2023 04:00:00
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