ENS 51053
ENS Event | |
|---|---|
04:00 May 7, 2015 | |
| Title | Potential Part 21 Involving Struthers Dunn Relays With Contact Resistance Greater Than One Ohm |
| Event Description | The following is excerpted from a report submitted by QualTech NP, Nuclear Division, Curtiss-Wright Corporation:
Subject: PSEG reported failures for Struthers Dunn 219BBX200 relays related to greater than 1 ohm contact resistance. Two relays were evaluated by Exelon Power Labs. Of these, one had a failure consisting of a contact resistance greater than one ohm. Struthers Dunn has also provided an evaluation in this regard and does not agree with the failure mode as inferred in the Exelon Power Labs report. Lab and OEM report key difference: The Power Labs' Report(s) shows fiberglass fiber(s) embedded into gold plated contacts on one relay believed to result in a contact resistance greater than one Ohm (1.7 Ohm Max). The second relay, from stock, had evidence of fiberglass present but was not considered to have affected functionality. The Struthers Dunn evaluation suggests that the fiber embedded on the gold contact is not at the mating point of the contacts and should not impact operability. Struthers Dunn also indicates that the relay's application is operating below their minimum current. Discussion: The actuator board on the evaluated relays is manufactured from a printed circuit board (PCB) type fiber board. The fibers from the edges of the board could become airborne. [. . . ] this specific board material was utilized beginning in March 2010. Since there have been no prior reports of this issue, it is possible that the 2010 material change introduced a foreign materials exclusion (FME) concern. Since then, and solely for those relays manufactured in the USA, the material changed again in November 2014 and was incorporated into the products starting January 2015. The newest version of the actuator board is a molded material that does not contain fiberglass fibers. Struthers Dunn relays with base part numbers 219, 236, 237, and 255 have the common PCB type fiber board. This fiber board was used in relays with date code 1009 through 1452 with or without letter suffix (where the letter indicates made outside of the USA). Customer Input: 1st 219 series relay failed due to contact issue, considered a random failure & discarded. 2nd 219 series relay failed due to contact resistance & sent to Exelon Power Labs. Five parts from inventory bench tested. One had high resistance and it was sent to Power Labs Note: All parts provided were 100% functionally tested for contact resistance during dedication process and passed testing at QTNP. Vendor Input: Struthers Dunn has, since 2010, experienced only one field complaint (PSE&G) on continuity issues related to fiberglass on these 219 relays. The material change to ULTEM 2300 was considered an ongoing quality/process improvement process to reduce potential defects proactively. Over the four years using this PCB type material, 13,000 relays were sold. Struthers Dunn has also questioned the application having current below the manufacturer's recommended value of 50mA, requiring bifurcated contacts. Please see their attached report and current product catalog for details. Recommendation: The root cause of the failure is inconclusive. Exelon Power Labs said 'The irregular contact surface patterns in conjunction with the presence of the embedded fiberglass fibers are the most likely cause of the excessive resistance. This finding is considered to be a manufacturing defect.' While the manufacturer sees the failure as a misapplication of its product and that the fiber 'was not located at the 'mating point' of the 2 contacts so therefore has no effect on the performance of the contacts or relay.' QualTech NP recommends an application review for the named relays. A review of the Exelon Power Labs reports and the vendor's report should also be completed by the utility to evaluate the impact on the safety function. |
| Where | |
|---|---|
| Qualtech Np Cincinnati, Ohio (NRC Region 3) | |
| Organization: | Qualtech Np |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+10.52 h0.438 days <br />0.0626 weeks <br />0.0144 months <br />) | |
| Opened: | Tim Franchuk 14:31 May 7, 2015 |
| NRC Officer: | Steve Sandin |
| Last Updated: | May 7, 2015 |
| 51053 - NRC Website | |
Qualtech Np with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
WEEKMONTHYEARENS 549982020-08-26T04:00:00026 August 2020 04:00:00
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