"Hazardous" Areas

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charlie b

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Lockport, IL
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I need a quick answer on what I hope is a simple question. I don't know Article 501 very well, and I didn't see my answer there.

My issue relates to a shipboard application, so the NEC does not apply. The rules that do apply do not distinguish between "Class I, Division 1," and "Class I, Division 2." All they say is that a specific area is classified as "hazardous," by virtue of flammable liquids and vapors.

Here's the question: The owner issued a spec said that a transformer must be "explosion proof." The supplier gave the owner a "Class I, Division 2" transformer. Did this transformer meet the spec?

I think not. But I would like to have an NEC citation to back up my response to the owner.
 

jwelectric

Senior Member
Location
North Carolina
Re: "Hazardous" Areas

As a general rule I teach the following:
Class I is flammable gas or vapor, Class II is flammable dust, Class III is flammable fibers.

Division I it is there and Division II it could be there

Does this help?
:)
 

charlie b

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Re: "Hazardous" Areas

Thanks. But that part I understood. What I need to know is whether a "Class I, Div 2" transformer is "explosion proof."

I would also like to be able to cite an article that says that "Class I, Div 1" must be explosion proof, and another article that says "Class I, Div 2" need not be explosion proof.
 

jwelectric

Senior Member
Location
North Carolina
Re: "Hazardous" Areas

I know that you knew this I was just trying to impress everyone else. Did it work?

Look at 500.5 and see that helps. It is a little lengthy.
:)
 

dillon3c

Senior Member
Re: "Hazardous" Areas

Originally posted by charlie b:

I would also like to be able to cite an article that says that "Class I, Div 1" must be explosion proof, and another article that says "Class I, Div 2" need not be explosion proof.
Charlie,
Directing you to 501.100(A) Class 1 div. 1

And 501.100(B)Class I div.2

edited:maybe not exactly, what your looking for..

[ September 12, 2005, 03:30 PM: Message edited by: dillon3c ]
 

nhee

Member
Re: "Hazardous" Areas

I don't think I've ever seen an explosion-proof transformer. What is the size? Is it a distribution transformer or control transformer?

Interesting that 501.100(B) does not mention that transformers must be approved for Div 2, only that they must comply with certain sections of Article 450.
 

charlie b

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Lockport, IL
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Re: "Hazardous" Areas

Thanks again for the replies. But I still haven't gotten my question across clearly.

What I am looking for is an article that says "anything in a Class I, Div 1 location shall be explosion proof," and another article that says "anything in a Class I, Div 2 location need not be explosion proof."

I am looking to "marry" the phrase "explosion proof" to the phrase "Class I Div 1."

Any other ideas?

Aside to NHEE: It's a 9KVA, 460-120 volt, three phase, power transformer, installed within an explosion proof enclosure. The transformer itself is not explosion proof.
 

petersonra

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Northern illinois
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engineer
Re: "Hazardous" Areas

Just about any component can be installed inside an explosion proof cabinet, assuming you can get a big enough ecnlosure for it.

These are listed by class and group. All are listed as suitable for both the class and group, so to know if it is suitable for your application you would need to know what the area is classified for.

To my knowledge, anything that is listed for division 1 is also suitable for use in division 2.
 

charlie b

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Re: "Hazardous" Areas

Originally posted by petersonra: . . . you would need to know what the area is classified for.
That's my problem. It's classified as "hazardous," without any correlation to Div 1 versus Div 2. The maritime rules do not appear to make that distinction.
To my knowledge, anything that is listed for division 1 is also suitable for use in division 2.
I agree. But I have to go the other way. I have a Class I Div 2 transformer. Can I use it in an application that calls for "explosion proof," or do I have to send it back and buy another?
Just about any component can be installed inside an explosion proof cabinet, assuming you can get a big enough enclosure for it.
That just might be our best option. I'll look into it. But wouldn't that require the manufacturer to say that it is ok (i.e., for heat dissipation issues) to completely enclose their transformer within some other box?
 

nhee

Member
Re: "Hazardous" Areas

What I am looking for is an article that says "anything in a Class I, Div 1 location shall be explosion proof,"
500.7 defines acceptable protection techniques for hazardous areas - there are more than one acceptable protection technique for Div 1 (explosion-proof, purged and pressurized cabinet).

and another article that says "anything in a Class I, Div 2 location need not be explosion proof."
Again, 500.7 lists a number of non-explosionproof methods of protection for Cl 1, Div 2 applications, implying that a Cl 1 Div 2 device is not necessarily explosion proof.

Is that what you are looking for?
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Re: "Hazardous" Areas

Charlie B:

I think you just have to look at the definition of "Explosionproof Apparatus" in article 500. If it isn't in an explosionproof box, its not explosionproof.

Like Nhee said, you can use other methods to make equipment safe for a class I location, but that doesn't make it explosionproof.

If you want the make the xformer explosionproof, put it in a explosionproof box, and prove the transformer won't heat up the box enough to ignite gases on the outside surface of the box.

Steve
 

petersonra

Senior Member
Location
Northern illinois
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engineer
Re: "Hazardous" Areas

You are responsible to insure whatever you put inside the box does not exceed the maximum amount of heat allowed.

You can do this in several ways. One is by calculation. Another is by having some kind of thermal protection inside the enclosure. I have heard of but never seen the second way implemented.

The manufacturer can help you calculate how much heat you can put inside the box and not have it exceed the allowable surface temperatures for the group if it is a division 1 area.

I have seen some charts in the past on this.

Also, UL has a program now where they offer custome built UL listed assemblies for hazardous areas. I suspect the panel shops in this program could make you an explosion proof anything (maybe not quite anything).

I do not believe the term "explosion-proof" is ever used to refer to something that is not in an explosionproof enclosure. There are other means of protecion such as encapsulation that are used primarily in areas classified using the zone method that you might want to look at.

501.2 B) In Class I, Division 2 locations, transformers and capacitors shall comply with 450.21 through 450.27.

It appears to me that in division 2 areas, you are not required to do anything special.
 

charlie b

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Re: "Hazardous" Areas

I have sent my response to the client. I started by sending my opinion to the AHJ that a Class I, Div 2 transformer would be acceptable for the specific application. I included my reasoning for the belief that that if this specific space had been installed in a shore-side facility, it would have been classified as "Class I, Div 2." We'll see what the AHJ has to say.

I also gave the client two options, in case the AHJ does not agree with my views. One option is to install the new transformer within an explosion proof enclosure. The other is to install a mechanical forced ventilation system, which would put the space into the arena of 500.5(B)(2)(2).

Many thanks for the support.
 

john m. caloggero

Senior Member
Re: "Hazardous" Areas

Charlie: As you have correctly stated, the NEC does not apply to shipboard electrical systems. I spent 2 years aboard a navy oil tanker as an electrican. None of the transformers were explosion-proof, nor were the 500Kva generators or the emergency generators with diesel prime movers, nor the oil-fired boilers for steam propulsion. I believe that the problem is probably with the person writing the specs. The location might not be a Class I, Div 1. If the ship is a gas tanker, the tanks are sealed and have venting elevated above the decks. According to the NEC. An explosion-proof transformer would have to be designed and built to withstand an internal explosion without igniting the surrounding explosive atmosphere.
 

friebel

Senior Member
Location
Pennsville, N.J.
Re: "Hazardous" Areas

I am replying to the question of explosion proof.
That term in my opinion is very misleading. We should speak in terms of Class, Division and Group.
I will give you a good example: The spec. will say that you are in a Class I, Div.2, Group D.
And they will incorrectly say to install a explosion proof motor. Now to install an explosion proof motor is not wrong, but it is not needed in a Class 1-2-D area.
In a Class 1-2-D area you could install a open type non-arcing motor. The same goes for a transformer. A transformer can be install in a Class 1-2-D area, providing the temperature of the transformer does not exceed 80% of the AIT, (Auto-Ignition-Temperature). I have never seen a transformer made for a Class 1-1-D area.
Again, I will say that when I hear the term explosion proof, I will ask what is the Classification, is it Class 1 Div 1, or Class 1, Div. 2. There is a big difference, and when you are talking cost, there is a huge cost difference.
 

rbalex

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Mission Viejo, CA
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Re: "Hazardous" Areas

While the NEC does not directly apply, the Coast Guard rules probably do and they "officially" use the same terminology and definitions "by reference."

API RP500 and RP14F both contain shipboard and offshore recommendations that are consistent with Coast Guard requirements. The Coast Guard is a primary contributor to 14F.

Because of multiple confined spaces, maritime applications tend to have more, if not larger, locations classified as Division 1. The basic rules of investigation to determine electrical area classification are still pretty much the same: Material involved, volume, pressure, containment, ventilation, etc. As several respondents noted though the area may still not be Division 1 and as friebel properly pointed out in his reply, a general-purpose transformer is usually acceptable in Division 2. See [2002] 501.2(B) for general applications and 500.8(A) for actual temperature limitations.

The simple answer to your initial question however is ?no.?

Section [2002] 500.7 specifies the various acceptable protection techniques in Class I locations. ?Explosionproof Apparatus?, ?Purged and Pressurized?, and ?Intrinsically Safe? are the only protection techniques generally recognized in Class I, Division 1 and a ?Division 2? transformer may be one of several other recognized techniques - including general purpose.

Since ?intrinsically safe? is not available in this class of equipment, your basic approach is sound, assuming the location is not actually Division 1. If it is Division 1, I recommend ?Purged and Pressurized? per NFPA 496. Note that 501.2(A) does not specify the enclosure or protection technique at all for typical oil-filled transformers - only the installation techniques. In fact, if the transformer does not contain liquid that will burn, it need only be ?approved? - not listed, labeled or identified ? and ?purged? is an excellent application in that case.. See the last sentence in 501.2(A) (2).

As an aside, I have indeed purchased small (less than 150kVA) ?explosionproof? transformers. The typical application is for electro-static oil separators. It turns out most ?oil-filled? tanks in that size can meet the explosionproof requirements with little or no modification.

Edit Spelling/grammar

[ September 13, 2005, 10:33 AM: Message edited by: rbalex ]
 

charlie b

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Lockport, IL
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Re: "Hazardous" Areas

Originally posted by rbalex:API RP500 and RP14F both contain shipboard and offshore recommendations that are consistent with Coast Guard requirements. The Coast Guard is a primary contributor to 14F.
I am not familiar with the terms "API" and "RP." Are they maritime rules or "shore-side" rules, or are they standards of some professional society?
 

charlie b

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Re: "Hazardous" Areas

I withdraw that last question. A co-worker told me they stand for "American Petroleum Institute" and "Recommended Practice." I didn't believe him. I am sure they stand for "Advocacy for Precocious Infants" and "Reality Programming." Thanks. :D
 

rbalex

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Mission Viejo, CA
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Re: "Hazardous" Areas

Both are NEC FPN references. See 500.4(B) FPNs 2 and 5, for example. They show up in a few other places too.

RP500 is a general petrochem electrical area classification document and RP14F is an installation document.
 
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