Hi,

I am new to this site, having more questions than answers on NFPA70E (seems like a familiar thread).
The site holds a lot of great information and I look forward to some interesting discussions.
I am currently in charge of an Instrumentation team, my company's Health and Safety department has adopted 70E with gusto, the issue being that a lot of the work performed is in a clean area (gowned, meltable gowning!) and no FR gowning has been sourced or validated. Our site has performed an arc flash analysis only on MCCs and main switchgear, leaving local control panels (some of which are fed with 480) unchecked.
To be clear, I would appreciate some confirmation of my understanding of NFPA70E;
1. >50V requires non melting clothing to be worn regardless of 130.3 Exception 1
2. You cannot apply tables 130.7(C)(9) unless short circuit and clearing times are known. Basically you require system impedance and protective device information to calculate.
3. Meltable gowning is not allowed over FR rated clothing.

Great site and thanks for any feedback

Correct and Exception 1 goes away with the 2012 Edition. It will still remain in IEEE 1584 for the calculation studies (for now).



Correct. So my way of thinking has always been, if you know this information, why not perform the arc flash calculation study. You're half way there.




Correct.




Great having you aboard. Welcome!

Thanks Brainfiller.
Meltable gowning for the biopharmaceutical industry really poses a big problem.
We have many deep control panels in clean areas that have relatively small flash protection boundaries, the code reads that meltable gowning can be worn if outside the flash boundary (right?), therefore a deep control panel with door open allows visual inspection with meltable gowning if outside the flash zone. Your thoughts? Not sure if I would like to take this one to court.

Why not use arc rated cleanroom garmets?, White knight and Dupont make them.

70E was adopted by the site prior to sourcing a vendor. We are currently working with a vendor to source clean room FR garments. Validation requirements puts us at mid year before any garments are approved and in place.

And there you have it, the problem with companies in the USA. What happened to the days where you could pick up the phone and order some stuff?

So because of politics and the purchasing process your workers are left unprotected. Not ragging on you, just venting a little about the way things work these days.

I am the new guy, you can rag on me!

Any feedback from my previous qustion "We have many deep control panels in clean areas that have relatively small flash protection boundaries, the code reads that meltable gowning can be worn if outside the flash boundary (right?), therefore a deep control panel with door open allows visual inspection with meltable gowning if outside the flash zone. Your thoughts? "

What are you going to wear to open the door?

If the flash boundry does not exceed the distance form the terminals to the door then is meltable gowning OK?
Does the flash protection boundary start at the door or the electrical terminals?

From the potential arc source, but I have a hard time believing that boundary would be inside the door.

Another thing to keep in mind, the AFB is based on 1.2cal/cm2, which is where exposed skin will recieve a 2nd degree brun in 0.1 second. That is still a lot of heat, and meltable materials may melt into the skin at Ei's lower than that. Hugh might have some good data on that, Hugh? You around?

We often find AF boundaries of <6".