ML25325A210
| ML25325A210 | |
| Person / Time | |
|---|---|
| Site: | Monticello, Prairie Island  |
| Issue date: | 11/20/2025 |
| From: | Papke M Curtiss-Wright Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML25325A210 (0) | |
Text
November 20, 2025 U.S Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001
Subject:
Final Part 21 notification report on CW supplied Namco Limit Switches PN: EA700-80926, Date Code: 0425.
Dear Sir or Madam:
Reference:
Curtiss-Wright Interim Notification Report dated 7/25/2025 (Event No. ML25210A055/Log No. 2025-15-00) & follow-up report dated 9/23/2025 (Event No. ML25272A241/Log No. 2025-15-01) on a failure of two Curtiss Wright (CW) supplied NAMCO Limit Switches PN: EA700-80926, Date Code: 0425.
This letter serves as the final report in accordance with 10CFR Part 21.21 On 5/21/25 Xcel Energy notified Curtiss-Wright about the failure of two NAMCO Limit Switches provided under CW project CJ21087 (Tag number CJ2108701 S/N: 01 and S/N: 04) which were dedicated by CW and shipped 2/28/2025 to Xcel Energy.
Based on comments from Xcel Energy by email and subsequent phone conversation, the units failed a bench test which aimed to verify that the contacts properly revert to their original state during spring return. After manually rotating the arm until actuation, the test was to slowly allow the arm to return to center while monitoring the contact states (Slow Latch Test). They found that the contacts reverted to their original state prior to the audible click/snap which was supposed to indicate contact changeover.
The two units were returned to Curtiss-Wright and received on 5/29/2025. The Slow Latch Test as described by Xcel was performed by Curtiss-Wright and the results they found, in which the contacts reverted prematurely during spring return, were replicated for S/N: 04. For S/N: 01, it was found that intermittently its contacts would not revert to their original state whatsoever, even after complete spring return to center. The technician needed to wiggle the arm back and forth to get the contacts to change over. While not identical to the issue described by Xcel, it was similar and constituted a failure.
On 6/26/2025 CW sent the relays to NAMCO for repair; the parts were then returned to CW on 7/14/2025. CW retested the Limit Switches and one failed for the same issue as noted earlier, the failed limit switch was returned to NAMCO for a full evaluation.
The NAMCO evaluation/report issued to CW 9/4/2025 concluded that the failure was caused by improper sizing of the hub on the top of the shuttle/slide assembly. The hub was too small which prevented proper fit with the latch and therefore the switch could not open or close as intended.
NAMCO confirmed that this failure was only reported on date code PN: EA700-80926, Date Code: 0425 and also confirmed that the design of PN: EA700-80926 nor supplier of the shuttle/slide assembly has not changed in many years.
November 20, 2025 NAMCO has changed their supplier for the shuttle/slide assembly since the manufacture of date code PN: EA700-80926, Date Code: 0425.
It should also be noted that NAMCO now performs the Slow Latch Test as stated above on all limit switches not just the E700 series.
To address this issue Curtiss Wright will be revising all affected NAMCO Limit Switches dedication plans to incorporate the Slow Latch Test.
Curtiss Wright recommends that end users should perform slow latch testing as a part of their bench or field test procedures upon receiving any Namco limit switches. These actions should preclude a possible recurrence of this failure mechanism.
Please note that CW has not supplied P/N: EA700-80926 of the impacted date code 0425 to any other end users.
Sincerely:
Mark Papke QA Manager Curtiss-Wright 4600 East Tech Drive, Cincinnati, OH 45245 UNITED STATES mpapke@curtisswright.com l www.curtisswright.com Ph: 513-201-2118