Class II Div I Group G type of equipment allowed

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oggie

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Mike,
I work in a federal building (safety officer so I know very little about electrical codes etc) and have 2 rooms that are designated as Class II Div I Group G Hazardous locations. One is designated as our plant/forage grinding room and the other is designated as our plant/forage ashing room.

Is there special equipment that I must purchase for these rooms or is the standard equipment used in my area of research appropriate to place in these rooms?
In the grinding the standard piece of equipment would be a Wiley Mill (Wiley Mill 4) and for the ashing room a muffle furnace (Isotemp muffle furnace) would be the standard. We do have explosion proof plugs for these pieces of equipment.
thank you
oggie
 
I apologize for not dealing with this earlier.

It appears that the area classification was developed by someone using Class I principles rather than Class II.
  • Explosionproof equipment is neither required nor suitable by itself in Class II.
  • Except for Group E, Division 1 is usually rare in Class II and somewhat difficult to achieve; especially for an entire room.
I personally have no experience with Wiley mills or muffle furnaces; however, I doubt a wood grinding mill would produce wood dusts in sufficient quantities and if dusts did exist in the furnace room the furnace would usually eliminate the need for area classification.
 
I should have done it first; but, after googling "Wiley mils" and "muffle furnace," I feel even more confident in my analysis. I don't believe either room should be classified at all.
 
Thank you very much for your time looking into this matter. Hopefully, this will allow us to continue on with business as normal.:)
 
Many details in using EP stuff

Many details in using EP stuff

Explosion proof is a term applied to devices that have a NEMA 7 or 9 rating. NEMA 7 is for gases and NEMA 9 is for dust. Most enclosures that are explosion proof have both but you have to read the label. Also the enclosure may not be listed for the hazard you have, in the NEMA 7 lots are rated for Group C &D, but because of the molecule size of gases in A& B they cost more and not as many exist. Some enclosures are listed only for one hazard. Take a look at articles 500-503 of the NEC. Also look at NFPA 499, 654, and 664 also deal with dust hazards. Also the However, if you have NEMA 7 or 9 enclosures and don't properly use conduit seals, they are just overpriced enclosures. Most of the manufactures of NEMA 7 & 9 fittings have a great handbook that they give away(probably can download). They are based on there fittings, but a great reference.

The equipment you install needs to be rated for the area. Adding an explosion proof plug to a non-rated items for the area classification does not make it a listed piece of equipment.

It also pays to look at the activity, and placement of the equipment, common solutions are the place panelboards in a "safe" area and run conduit to the location, typically less expensive than EP panelboards.

You are lucky you work for the feds as the OSHA rules don't apply, but since that sugar factory explosion down in South Carolina, they are cracking down on industry with dust.
 
Tarbaby said:
Explosion proof is a term applied to devices that have a NEMA 7 or 9 rating. NEMA 7 is for gases and NEMA 9 is for dust. Most enclosures that are explosion proof have both but you have to read the label. Also the enclosure may not be listed for the hazard you have, in the NEMA 7 lots are rated for Group C &D, but because of the molecule size of gases in A& B they cost more and not as many exist. Some enclosures are listed only for one hazard. Take a look at articles 500-503 of the NEC. Also look at NFPA 499, 654, and 664 also deal with dust hazards. Also the However, if you have NEMA 7 or 9 enclosures and don't properly use conduit seals, they are just overpriced enclosures. Most of the manufactures of NEMA 7 & 9 fittings have a great handbook that they give away(probably can download). They are based on there fittings, but a great reference.

The equipment you install needs to be rated for the area. Adding an explosion proof plug to a non-rated items for the area classification does not make it a listed piece of equipment.

It also pays to look at the activity, and placement of the equipment, common solutions are the place panelboards in a "safe" area and run conduit to the location, typically less expensive than EP panelboards.

You are lucky you work for the feds as the OSHA rules don't apply, but since that sugar factory explosion down in South Carolina, they are cracking down on industry with dust.
Click to expand...
Read the definitions of explosionproof and dust-ignitionproof in Section 500.2. Then read 502.5 for the applicability of explosionproof in Class II locations. .
 
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