Arc Flash PPE - 2 Questions

[maryellen]

1. Level 0 (determined by calculations) does not have us wearing any FR clothing-- just Long sleeve natural fiber shirt & long pants. Is it acceptable to be wearing the synthetic cleanroom suit, hood, hairnet, beard cover over the long natural fiber garments?

2. In order to comply w/NFPA 70E is it required to wear a whole system arc flash suit (3 pieces) as one unit or can the same level be accomplished w/layering?

 

[zog]

1. Level 0 (determined by calculations) does not have us wearing any FR clothing-- just Long sleeve natural fiber shirt & long pants. Is it acceptable to be wearing the synthetic cleanroom suit, hood, hairnet, beard cover over the long natural fiber garments?

No. But there are FR cleanroom suits, hairnets, beard covers, and hoods on the market.

2. In order to comply w/NFPA 70E is it required to wear a whole system arc flash suit (3 pieces) as one unit or can the same level be accomplished w/layering?

Yes, but I have no idea why you would want to. The flash suits are multilayered (2-4) and when tested as a multilayered garment have much higher arc ratings than adding the seperate layers. I would not want to waer 5 layers of 8 cal coveralls. You still need the flash suit hood, even if you layer. If you are using the tables you have to use the PPE table. If you do an analysis you can select the PPE you need based on the study to provide adequete protection.

 

[davidr43229]

Zog,
Once again I find myself agreeing with everything you say. I would stress that a full analysis would yield wearing less PPE, that referring to the "Task" tables in the back of the NFPA-70E, which assumes worse-case situations of 50,000amps for 6 cycles (300,000KA).

 

[WDeanN]

I would stress that a full analysis would yield wearing less PPE, that referring to the "Task" tables in the back of the NFPA-70E, which assumes worse-case situations of 50,000amps for 6 cycles (300,000KA).

Almost true. At most facilities this may hold. My experience has been with a utility and large facilities. The 300,000 kA-cycle rule is sometimes not near enough! If you have large motors at your facility, you may also be under dressed. Of course, it's hard to know until you've done a short circuit calc, and a coordination study. So why not go ahead and do the whole thing right? For a small facility a proper arc flash analysis shouldn't be too expensive, and will eliminate the use of tables, and probably save a lot of time looking for the proper task, PPE, etc. For a large facility, a proper electrical analysis should be part of the EE's ongoing program anyway.

Bottom line, perform the analysis!

 

[WDeanN]

1. Level 0 (determined by calculations) does not have us wearing any FR clothing-- just Long sleeve natural fiber shirt & long pants. Is it acceptable to be wearing the synthetic cleanroom suit, hood, hairnet, beard cover over the long natural fiber garments?

maryellen, I would look at the material that the cleanroom bunny suit it made from. If it's a synthetic material or a paper product, and it probably is one of those two, you SHOULD NOT WEAR IT for electrical maintenance. It may not be necessary to buy the FR rated suits if all you are looking at is level 0. Just make sure they are a 100% natural fiber. The golden rule is: Don't wear anything that will make the hazard greater. It's better to be uncovered then to be covered in something that's going to burn or melt to you.

 

[WDeanN]

maryellen, I just noticed that you said they were synthetic already. Ignore me for being a little pompous.