ML19296D621
| ML19296D621 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 02/28/1980 |
| From: | MISSISSIPPI POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML19296D619 | List: |
| References | |
| NUDOCS 8003120599 | |
| Download: ML19296D621 (1) | |
Text
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Description of De ficiency Circuit breaker testing of ITE 4.16 KV switchgear revealec a f ailed auxiliary switch, Type L2, in circuit breaker 152-1902. The switch was found to have a broken housing at a throut;L bolt.
This failed switch was returned to the vendor for investigation.
Subsequently, all switchgcar and load centers having this type auxiliary switch were inspected for cracks and broken housings.
This inspection re-vealed some 200 auxiliary switch assemblies with hairline cracks in the switch colding. None of these switches exhibited broken hcusings as was found on the initial switch.
A sampling of switches exhil itin;r hairline cracks was returned to the vendor for additional investir,ation.
II.
Evaluation and Safety ITolications The investigations into this matter revealec no link between the single switch failure with a broken housing and the switches exhibiting hairline cracks. The evalnation concluded that this deficiency consists of two separate problens.
Addressing the hairline crack problem, the supplier ccaducted life tests on these switches. These tests included thermal cycling and breaker mounted endurance cycling. No structural or switch malfunction was noted during these tests.
Seismic situlation tests were conducted by hyle Laboratories to further demonstrate the integrity of switches with hairline cracks.
All devices Tunctioned normally before, during and after the seismic testing. No.oss or impair:cnt of function was ev1.-
dent.
The cracks showcd no signs of propagation.
Therefore, it is concluded, that the hairline cracks will not result in a switch f ailure or breaker calfunctica, and thus, it is not cen-sidered to be a reportable deficiency under 10 CFR 50.55(e).
By virtue of an assembly torquing study which was incorporated
.ato the above acntioned rife testing, it was concluded that the switch with the broken housing was an isolated case due to over-torquing. This switch could have resulted in a calfunction of one component, however, its redundant safety componcat would have functioned properly. I!cnce, this would not have adversely affected the safety of plant operations.
III. Corrective Action Taken All auxiliary switches now undergo 100% inspection for cracks before being assembled on the circuit breakers.
it the jobsite, the s itch with a broken housing has been replaced. Octails cf this investipatior and corrective acticas will be sue arized in Bechtel " CAR-CGSS No. 47, and will be available for your review at the Grand Gulf jobsite.
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