ENS 57680
ENS Event | |
|---|---|
04:00 Apr 24, 2025 | |
| Title | Part 21 Report - Solenoid Valve Fails to Operate After Extended DE-ENERGIZATION |
| Event Description | The following is a summary of the information provided by ASCO via email:
This report relates to the failure of a single air-operated valve identified by Dominion Energy at North Anna due to failure of the associated solenoid valve. The solenoid valve periodically failed to reposition, or only partially repositioned, after periods of extended de-energization. As part of testing, the ASCO NP8321 solenoid valve series and all ASCO NP-series solenoid valves were qualified to sit in a normally energized position and were not tested for extended periods of de-energization. The U-cup seal was tested and ASCO determined that this U-cup seal experienced performance limitations at low air operating pressures (below 40 psi) and the valve did not shift completely to an energized state. An alternative valve (NP8300) is recommended by ASCO for this customer application. In the interim, ASCO recommends increasing the inlet air pressure to the valve to at least 80 psi not to exceed the maximum 150 psi to conservatively ensure proper operation of the NP8321 series valve in a de-energized state. ASCO concludes based on design and known operating experience that only the NP8321 model valve exhibits this condition. ASCO does not have adequate knowledge of the actual installation and operating condition of this valve to determine whether this condition would create a `substantial' safety hazard as defined in 10 CFR 21.3. The report is intended to provide investigation results and recommendations. Each end user needs to perform their own evaluation based on the information provided in this notification. Bryan Causey Quality Engineer Bryan.Causey@Emerson.com The only plant known to be affected at the time of the report is North Anna.
The following is a summary of the information provided by ASCO via email: ASCO performed extensive testing on this valve with a variety of U-cup seals and found all U-cup seals used for the NP8321 series have low pressure de-energized dormancy performance limitations. For applications where the valve is at 80 psi, ASCO will be updating guidance to indicate that a minimum pressure rating of 80 psi must be maintained when switching from the de-energized state to the energized state for normally closed valves. For normally open valves, 80 psi must be maintained when switching from the energized state to the de-energized state. ASCO ensures application at or above 80 psi would meet its equipment qualification requirements. For applications between 40 and 80 psi the utility has not observed any low-pressure dormancy issues on valves that have already experienced the applications longest possible period of de-energization, ASCO advises that the valve remain in service for the rest of its equipment life, during this time ASCO recommends looking for an appropriate alternative valve and solution for this system. ASCO recommends an NP8300 or NP8316 valve as a suitable replacement. For applications at or below 40 psi, the utility should consult with ASCO at the earliest opportunity. The NP8300 is a potential replacement for the NP8321 series but it is not a drop-in replacement. The NP8300 series consumes twice the wattage of NP8321 and has a lower flow rate. If the lower flow and higher wattage of the NP8300 are acceptable limitations for the utility's application, then ASCO would recommend a NP8300 valve. If the application requires the same wattage and can manage higher flow, a NP8316 can replace a NP8321 but the higher flow rate may require changes to the specific system in place. The NP8316 does have a lower minimum operating pressure differential of just 10 psi instead of 15 psi, but the flow is several times higher than the NP8321. For this solution to work, the system would need to be tolerant of this higher flow and ensure that the minimum operating pressure differential of 10 psi (measured between in the inlet port and exhaust port) is maintained with appropriate piping/regulators and exhaust pipes capable of ensuring that the minimum pressure is maintained. This could include changing out piping and regulators for larger sized pipes and regulators to match the higher Cv [valve flow coefficient] of the NP8316 series. ASCO concludes that for applications at or above 80 psi, the NP8321 series valve meets its full equipment requirements. For applications below 80 psi, ASCO recommends replacing the value based on the above guidelines. Notified R2DO (Davis) and the Part 21 groups (email). |
| Where | |
|---|---|
| Asco Valve Aiken, South Carolina (NRC Region 2) | |
| Organization: | Asco Valve |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+11.93 h0.497 days <br />0.071 weeks <br />0.0163 months <br />) | |
| Opened: | Bryan Causey 15:56 Apr 24, 2025 |
| NRC Officer: | Josue Ramirez |
| Last Updated: | Jul 11, 2025 |
| 57680 - NRC Website | |
Asco Valve with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
WEEKMONTHYEARENS 576802025-04-24T04:00:00024 April 2025 04:00:00
[Table view]10 CFR 21.21(d)(3)(i), Failure to Comply or Defect Part 21 Report - Solenoid Valve Fails to Operate After Extended DE-ENERGIZATION 2025-04-24T04:00:00 | |