Access Panel Integrity

[Bombo_M]

I hope I am putting my first question in the right spot...

I work at a nuclear power plant and have been asked to evaluate missing/loose fasteners on 480V Load Centers and Motor Control Centers access panels and am wondering...

Is the panel integrity compromised if one or two of the screws are missing or loose?

I tend to think so but not sure if there is an EPRI standard or anything else that would back up this thought...

5 of the 7 panels in question are safety related (1E) and the access panels are either on the side or back of the cabinets.

 

[charlie b]

First of all, welcome to the forum. Secondly, for those not familiar with nuclear power plant rules and regulations, this is a much harder question than you might think. Third, I know what ?1E? means, and there are a couple other forum members who also know what it means, but there are not likely to be very many members who do. So I do not know how likely it will be that we can answer your question.

If you were to think in terms of the ?safety function? of a class 1E MCC, I would say that it has to do with being able to continue to supply power to its loads, despite the postulated occurrence of a design basis accident or event, and despite the postulated occurrence of a seismic event. I am confident that the absence of a cover screw will not prevent the MCC from doing its SR function. Nor would a screw being ?less than fully tight.?

That said, if you were to call upon me to prove that the MCC could still do its SR function, and that the missing or loose screw would not compromise its ability to do that function, I could not offer any proof. The manufacturer would have arranged for the MCC to be put through a testing process, before being able to affix a UL (or other lab) label. It is a good bet that the screws would have all been in place, and all would have been tightened, before that test began. It wasn?t tested with a missing or loose screw. But does that mean that the UL listing becomes invalid, if you remove or loosen a screw? I cannot say.

Not a complete answer, and perhaps not a helpful one, but it is all I can offer. I have a notion of the type of evidence you would be interested in finding. I just don't know if it exists.

 

[Bombo_M]

Thanks Charlie,

Yeah, I was afraid it'd be hard to find the "exact" answer I was looking for but I appreciate your response.