Class I, Div 1, groups A-F

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Thread Starter

Mike Johnson

If I took a device, say a transmitter, that is not rated for a Class I, Div 1 area and place it
in a explosion-proof enclosure/housing, will that make it pass for a Class I, Div 1 approved device
or does it have to be inspected by authorative body like UL or something? If a device is explosion-proof, does that make Class I, Div 1?
If a device is explosion-proof and only handles 120Vac, can that device be used in a Class I, Div 1 location?
Or does the voltage level do not matter as long as it is explosion-proof? If that is the case, then why use intrinsic safe circuits if being explosion-proof is all that is needed?

Mike Johnson
 
W
It's been done. It is also possible to install it in a purged housing, such as those made by Bebco and others. However, this gets into the area which is muddy and gray, called "designed to meet."

If FM or CSA or UL or BASEEFA approves the design, what comes with the approval is that their lawyers will defend you at their expense if it really wasn't explosion proof. That's why FM and the others have the good old fashioned collywobbles if you use the term "explosion proof" or "explosion safe". They use the term "nonincendive." They say that there is no such thing as "explosion proof."

If you just buy a transmitter and stick it in a Nema 7 or Nema 9 enclosure, or the European or Asian equivalent, and it blows up the plant anyway, it's your neck.

Most manufacturers will not do "designed to meet" anymore, even though many would, up to the early 1990s, for this reason alone.

If you have any questions about what your employer would want you to do, ask first. One of the best defenses against damage suits is to blame the employee who did it, and fire that employee and blacklist that employee throughout the industry. So, unless you want a new career selling siding or venetian blinds, don't do it.

Walt Boyes

---------SPITZER AND BOYES, LLC-------------
"Consulting from the engineer
to the distribution channel"
www.spitzerandboyes.com
[email protected]
21118 SE 278th Place
Maple Valley, WA 98038
253-709-5046 cell 425-432-8262 home office
fax:801-749-7142
--------------------------------------------
 
Dear Mike,

I think Walt boyes has given the proper answer only thing remained to answer is why to use Intrinsic safe device ?
The answer is : For Exproof itm is written on the instrument " Isolate elsewhere before openng" which makes live maintance of the instrument
impossible. which is possible with intrinsic safe instruments. Again for intrinsic safe instruments energy level is below 1 w .which dosen't cause
any personal injury.

Amol Savant
 
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Mike Johnson

I am not talking about a practice I want to do but about an existing practice. Would one use an instrument that takes 120Vac for power in a Class 1, Zone 1 area?
If the instrument was in a Nema 7 or 9 enclosure and did not offer instrinsic safe circuitry for
additional protection, would it be advisable to use this instrument in a Class 1, Zone 1 area?
As long as the instrument was in a NEMA 7 or 9 enclosure regardless of power
considerations,
an authorizing broad will approve this instrument for a Class 1, Div I , Zone 1
type location?
Would there not be a restriction on the power as well as the enclosure or at least consideration on what potentially the open circuit voltage or short circuit current for the device could be and will this cause enough heating to cause an ignition of the vapors or gases in a Class 1, Div I, Zone 1 area?
 
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Bob Peterson

In a message dated 6/3/02 2:55:33 PM Central Daylight Time, [email protected]
writes:

> If I took a device, say a transmitter, that is not rated for a Class I, Div 1 area and place it
in a explosion-proof enclosure/housing, will that make it pass for a Class I, Div 1 approved device<

Generally yes, however its probably not all that practical since you would not be able to make a process connection since anything coming into the
explosion proof enclosure must pass through a seal. Best to buy as an assembly.

It could also be Class II.

> If a device is explosion-proof and only handles 120Vac, can that device be used in a Class I, Div 1 location? Or does the voltage level do not matter as long as it is explosion-proof?<

Voltage level is not an issue. Whatever explosion proof apparatus you want to use must be suitable for the area classification. Your area
classification also denotes what group it is as well (A/B/C/D). Your apparatus also has to be suitable for the group as well as being labeled
Class I, Division 1. The group denotes the specific explosive gas that might be present. Many times equipment is rated for group C and D but not for A and B.

> If that is the case, then why use intrinsic safe circuits if being explosion-proof is all that is needed?<

IS circuits are inherently power limited (they can only deliver less energy to the field device than what would be required to generate a spark). Thus IS circuits are not something you can use in a situation where any significant power is required (such as a motor).

IS circuits are generally far less expensive than an equivalent explosion proof system. They are also probably somewhat safer, and a whole lot easier to deal with.

This is not something you want to make design decisions on without knowing a whole lot more than what you can learn on a mailing list. I suggest you acquire some books on the subject and reading them. Start by reading the sections in the NEC (and a good NEC handbook) that deal with hazardous areas.

Pressurization is another means of protecting against ignition of hazardous gases. You can also locate a general purpose device in a non-hazardous (or sometimes a Division II) area and avoid the issue altogether.

Bob Peterson
 
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I don't think you understand what I said.

If the instrument is not third-party approved for the specific hazardous area classification required to locate it in a particular area of the plant, it does not matter whether it is in a "explosion proof" enclosure (NEMA7/9) or not. It is not good practice to use that instrument in that location, and you, personally, can be found both civilly and criminally liable and face heavy fines and jail terms if the device causes an accident.

So don't do it.

Walt Boyes

---------SPITZER AND BOYES, LLC-------------
"Consulting from the engineer
to the distribution channel"
www.spitzerandboyes.com
[email protected]
21118 SE 278th Place
Maple Valley, WA 98038
253-709-5046 cell 425-432-8262 home office
fax:801-749-7142
--------------------------------------------
 
Thanks, Walt. Now I think we understand what you're saying... but that leaves me confused as to XP enclosures and wiring methods. NEC Art. 501
defines enclosure and wiring requirements for Class 1 Div. 1 and Class 1 Div. 2 areas. In both cases, it seems that code says I can use non-intrinsically safe devices as long as I am using XP or purged/pressurized enclosures, as well as a wiring method approved for the Class/Division area. Also, I had always thought that XP enclosures were intended to keep the explosion/conflagration *inside* the enclosure, not to necessarily eliminate any possibility of explosion. Are you saying that *merely* complying with the code is not sufficient to protect the engineer in a court case?

Paul T
 
This comment about live maintenance of equipment in explosion-proof enclosures being impossible is incorrect. Common practice is to get a hot work permit or some times called a gas free permit which requires that the area be checked with a combustible gas sniffer to insure that no flammable gas concentrations are present before and during maintenance. A bit more involved but certainly possible.

Bill Mostia
===========================================
William(Bill) L. Mostia, Jr. PE
Partner
exida.com
Worldwide Excellence in Dependable Automation
[email protected](b) [email protected](h)
www.exida.com
281-334-3169
These opinions are my own and are offered on the basis of Caveat Emptor.
 
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Bob Peterson

> Are you saying that *merely* complying with the code is not sufficient to protect the engineer in a court case? <

The sad fact is that even being completely innocent is not enough to protect you in court. You need to keep in mind that you can be right but still go bankrupt if you don't have the funds to pay for the litigation. Lawyers are not cheap. Liability and malpractice insurance is not really about liability or malpractice. Its about having the wherewithall to defend yourself in court. And remember that even if you comply with exisitng codes today this does not guarantee that you will not be sued in the future over something you did today that does not meet the 2020 version of the code.

Bob Peterson
 
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Yeppers. That is exactly what I am saying. That is why NO company supplies standard area classification equipment simply installed in NEMA 7 or NEMA 4/7 or NEMA 7/9 enclosures.

That's why positive purge systems have such a bad name UNFAIRLY I MIGHT ADD...I don't want the Bebco's and the other purge system makers mad at
me...and I believe that at least Bebco has gotten FM or UL approval on their systems.

In the 1980s and 1990s, it was quite common to see "designed to meet Class I Div 1, Groups C & D" on instruments. They'd be in a Crouse-Hinds or Adalet or Whoever enclosure, and while the instrument itself _might_ be FM approved in another enclosure, and the NEMA 7 enclosure itself _might_ be approved, in the early 1990s, FM took the position that putting an instrument into an approved enclosure voided the approval of the enclosure, and therefore the configuration itself had to be approved.

QED.

Walt Boyes

---------SPITZER AND BOYES, LLC-------------
"Consulting from the engineer
to the distribution channel"
www.spitzerandboyes.com
[email protected]
21118 SE 278th Place
Maple Valley, WA 98038
253-709-5046 cell 425-432-8262 home office
fax:801-749-7142
--------------------------------------------
 
Well, yeah... I hear that. What's your interpretation of NFPA70 though? I have in the past bought transmitters, for example, that are sold... (listed? I can't remember if they were!) for use in Class/Division areas.

The only difference between what you get when buying it for a classified area vs. unclassified is the enclosure that it comes in, and then of course the wiring method you use to install it. So... how do we interpret NFPA70 when working in classified areas?

Paul T
 
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Mike Johnson

I do not expect to learn anything from a mailing list. I am asking for opinions on a subject matter. Also the title of this E-mail should be Class I, Div 1, Groups B-D, Zones 0 and 1 for locations inwhich Flammable gases or vapors are present continously or sometimes.
 
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Bob Peterson

I am not all that sure that what you are saying about XP versus non-XP instruments is true. It may well be that additional issues above and beyond the enclosure itself have to be considered, especially the process connection
itself. Obviously the whole instrument cannot be put inside an XP enclosure and still have some way for the instrument to connect to the process. To make the process connection, some part of the instrument must be outside the XP enclosure, thus some part of the penetration of the XP enclosure is not made via a conduit seal, which is the only "legal" way to bring something
into the XP enclosure. And I am pretty sure the only thing the code allows you to bring into an XP enclosure is wiring, and then only through a seal.

OTOH - for something which can be completely enclosed inside the XP enclosure, with only wiring leaving the XP box through seals, it would seem to be a different case. Perhaps Walt could comment on this point since he brought up the point about "designed for" type equipment that is not actually listed.

A second issue is that AFAIK, OSHA requires you to use only listed devices in Division I (maybe even Division II) areas IF a suitable device is available. Thus if there is an listed XP device available for a specific use, using a "designed for" type device would not meet this requirement.

It really is not that big of a deal anymore. Just about anything is now available with the proper listing. In a few cases, you might end up having to use pressurization as a means of protection, and the Bebco systems are now listed, so you should be covered. OTOH - this is not so much an engineering issue as a legal issue. You never know what some legal weasel will convince
a jury of 20 or 50 years from now.

Best approach is to avoid the issue as much as possible. With some thought you can often locate things in non-hazardous or Division II areas instead of putting them in Division I areas. This is really the best solution.

BTW - want to make yourself nuts? I am told UL refuses to list cable seals for use in Division I areas. The code allows the use of cable in a few cases in Division I areas, but to my knowledge, NO ONE makes a listed cable seal to run the cable into the XP box. A couple companies sell them, but they do not carry UL listings. In fact, as I understand it they are an assembly consisting of a standard seal coupled with a standard cable bushing to protect the cable where it enters the seal. The assembly comes with a special tag on it noting that the assembly is NOT listed, even though the seal itself has a UL listing on it.

Bob Peterson
 
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Mike Johnson

That is what I am talking about. Without naming companies, I have a position transmitter that is suppose to be able to use in a Class I, Div 1,
groups C and D, but the only difference between it and one that is not to be use in a Class I, Div 1 area is the enclosure. They even print in the Spec/description under options " Enclosure for hazardous locations for Class I, Division 1,
Groups C and D, or Class II, Division 1, Group E,F, and G"
No where do they show UL or FM approval. As a matter a fact they show no approvals at all.
Which seems to satisfy Art. 500-4 (a). I know I sound like a dumb ass, but it just seems like
Art 500-4 (a) and (e) should be required for UL and FM approval. That way one can sure that the energy to the device is lower then what it will take to ignite anything and faults within the device is contained within the device.

Mike Johnson
 
Only Groups A-D fall into the Class I category(explosion-proof) while Groups E-F, actually E-G, are Class II groups(Dust-Ignition-Proof).

> If I took a device, say a transmitter, that is not rated for a Class I,
> Div 1area and place it in a explosion-proof enclosure/housing, will that
> make it pass for a Class I, Div 1 approved device or does it have to be
> inspected by authorative body like UL or something?

Yes you can without specific approval or inspection of a National Recognized Testing Laboratory(NRTL) but it must be acceptable to your local authority having jurisdiction. It is, however, necessary as with all hazardous area
equipment that you maintain the explosion-proof integrity of the enclosure per the manufacturer's specification, the NRTL's rating for the enclosure, and meet any appropriate requirements of the NEC.

If only wires come into or out of the enclosure, then it should not be any problem, this is done all the time.

If you bring a flammable material into the enclosure, that a whole another ballgame. For this type of application, you must as a minimum maintain the explosion-proof integrity at the entrance of the flammable material, at the exit if there is one, and also the internal integrity must be considered. In general, I would not recommend that a user do this and if you are a manufacturer and you bring a flammable gas into the enclosure( for example, an analyzer), I
would certainly recommend that you have it approved.

> If a device is explosion-proof, does that make Class I, Div 1?

No! Traditionally(and occasionally still), an "explosion-proof" rating in a manufacturer's spec meant only Class I, Group D, Division 1. You can only use an explosion proof enclosure for specific area that is has been rated (approved/listed) for plus a few exceptions allowed for by the NEC.

> If a device is explosion-proof and only handles 120Vac, can that device be
used in a Class I, Div 1 location?
> Or does the voltage level do not matter as long as it is explosion-proof?

Explosion-proof does not depend on voltage level but the NEC requires that you use appropriate equipment for the voltage level you use. Generally, a standard explosion-proof enclosure would be limited to 600 volts or less.

> If that is the case, then why use intrinsic safe circuits if being
> explosion-proof is all that is needed?

Intrinsic safety is a different type of protection method. Intrinsic safety is a low voltage, low power method and 120 vac stuff, motors, and other high voltage/high energy stuff cannot use it. Where both are applicable, there
are proponents of the use of both methods. In the US, intrinsic safety is not nearly as popular as in Europe. This is probably because explosion-proof has historically been the method of choice in the US, 80% of the US is Division 2, and it is generally easier to apply but these are obviously not the only reasons one might consider the
selection of a protection method and intrinsic safety certainly has its merits. One must pick the protection method appropriate for the application and the overall environment that it is installed in.

I suggest that you consider reading Ernest Magision's book "Electrical Instruments In Hazardous Areas, 4th Ed" from ISA, ISBN: 1-55617-638-4. Another good book is "Electrical Installations in Hazardous Locations," by Peter Schram and Mark Early, from NFPA, ISBN: 0-87765-356-9.

Let it be clear that engineering and installing systems in hazardous areas is not for the un-informed and while getting a clarification of something from a mailing list or getting resources or references is reasonable, getting basic knowledge or expertise from a mailing list is flat dangerous.

Bill Mostia
=====================================================
William(Bill) L. Mostia, Jr. P.E.
Partner
exida.com
Worldwide Excellence in Dependable Automation
[email protected](b) [email protected](h)
www.exida.com 281-334-3169
These opinions are my own and are offered on the basis of Caveat Emptor.
 
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Mike Johnson

I know he is right. Walt is dead right!!!! That is the answer I would expect. My point is that I think some people practice in this manner all the time. I need to investigate a little more but I really do think some people do this and gets approved like using a NEMA 4X enclosure with an automatic purging/pressurization or sticking a transmitter in a NEMA 7 or 9 enclosure. I feel that IS circuits are needed and devices in a Class 1 Div I Zone 0 or 1 type area is absolutely necessary in order to be sure that one is NOT delivering enough energy to ignite flammable vapors or gases that are present continously or may be there due to a leak or something.

Mike Johnson
 
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Bob Peterson

Just out of curiousity, what can you put in an explosion proof enclosure if not general purpose equipment? I tend to concur that just putting an instrument inside an XP box is probably not such a great idea since the process connection is an issue. I would not trust such an arrangement.

However, there does not seem to be a good reason why one could not put general purpose equipment (say an LED display) inside an XP enclosure, where all the entries are sealed. In this case, FM's position seems to defy logic.

Bob Peterson
 
You are changing tracks on us. Now we are talking about Zones.

> I am not talking about a practice I want to do but about an existing practice. Would one use an instrument that takes 120Vac for power in a Class 1, Zone 1 area?<

Yes if the equipment is approved for a Zone 1 Area or is rated for Division 1 area(NEC Article 505-20(B) Exception #1).

> If the instrument was in a Nema 7 or 9 enclosure and did not offer instrinsic safe circuitry for additional protection, would it be advisable to use this instrument in a Class 1, Zone 1 area?<

I don't understand the question. Why would you even want additional protection in a Zone 1 area?

Anyway NEMA 7(indoors) per NEC Article 505-20(B) Exception #1 can be used in a Class 1, Zone 1 area but not NEMA 9. NEMA 9 is dust-ignition-proof not explosion-proof.

> As long as the instrument was in a NEMA 7 or 9 enclosure regardless of power considerations, an authorizing broad will approve this instrument for a Class 1, Div I , Zone 1 type location?<

One cannot judge what ever an "authorizing board" is will approve but the answer would be the same if you are talking about the authority having jurisdiction as they have the final word and they are occasionally finicky but if they follow the NEC NEMA 7 should be ok indoors but not NEMA 9 at all.

> Would there not be a restriction on the power as well as the enclosure or at least consideration on what potentially the open circuit voltage or short circuit current for the device could be and will this cause enough heating to cause an ignition of the vapors or gases in a Class 1, Div I, Zone 1 area?

I'm not sure where this obsession with voltage and power is coming from but look at any major supplier of explosion-proof hardware(Crouse-Hinds,
Killark, etc) and you will see 240v, 277v, 480v and 600v rated equipment.

Give me a call and I give you a few minutes of free consulting and maybe we solve whatever problem you have been talking about or talking around.

Bill Mostia
=====================================================
William(Bill) L. Mostia, Jr. P.E.
Partner
exida.com
Worldwide Excellence in Dependable Automation
[email protected](b) [email protected](h)
www.exida.com 281-334-3169
These opinions are my own and are offered on the basis of Caveat Emptor.
 
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Bruce Durdle

Paul,

In the IEC world, you must first buy a certified explosion-proof enclosure. This has undergone tests for pressurisation and flame suppression - as an empty enclosure.

You can then put your equipment into it. This need not be certified.

You must then get the enclosure re-certified with the equipment fitted. This tests for things like pressure piling (the increased pressure from a
secondary explosion if gas or va;pour is forced into an isolated part of the enclosure before ignition, and probably more important temperature
rise. The empty enclosure has no surface temperature rating as that depends on the power dissipation of the contents.

I don't think things are that different in the US..
Cheers,

Bruce.
 
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Bob Peterson

Class I, Div 1 is a US protection scheme. Zone 0 and 1 are the European scheme. You can't really mix the two, although a few devices I have seen
lately are dual rated as class I div 1 (explosion proof) and EExd (flameproof). BUT, I do not believe you can use flameproof enclosures in a
zone 0 area.

Bob Peterson
 
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