Hazardous (Classified) Location - Rusty Threads and Corrosion!

This is a hazardous (classified) location.

Why?

What rules are required to be followed?

[Linked Image]

North of the border, this would be considered a "Category 2" location as it appears liquids and corrosion are present. Is the N.E.C. similar in defining this area.

Whats the location ?

Wow, that looks like an agonizing quandary, for likely corrosives and flammable vapors are anticipated. I’m not up on the latest in enclosure innovations from Appleton or Crouse-Hinds, but it looks like “combination” NEMA type 6 or 6P and 7 enclosures [99NEC Table 430-91] would be needed.

There is another wrench-in-the-gears here. In typical situations for this type of equipment, it would seem to be insanity not to use some sort of anti-seize compound on ALL threaded surfaces. Is there anything listed for such an application that will preserve explosion-proof integrity?

[This message has been edited by Bjarney (edited 11-16-2003).]

Other than the electrical equipment being explosion proof, is there something else in the picture that indicates flamable vapors? I don't have a very good monitor and some details are not clear.

I am not very good with hazardous location work but the fact it is a pit has some influence I believe.

Bjarney

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it would seem to be insanity not to use some sort of anti-seize compound on ALL threaded surfaces.

But why? all that stuff will unthread easily. [Linked Image]

All those wires dangling out of that box on the right looks like a bad idea here :-(

iwire — No personal offense intended, but I disagree with you on this. I'll bet rusted threads would make disassembly of pipe and cover threads very difficult.

I was only clowning around, I would think all those smallish cover screws would break before coming loose.

And the large diameter fine threaded J box covers would be just plain imposable to remove with out the "red" wrench. (heat) [Linked Image]

Sorry iwire — I missed the smiley face in your post.

In some plants, anti-seize goo {like “Never-Seize” or “Fel-Pro C5A”} is a means of survival if anything threaded needs survive corrosion, but for explosion-proof fittings is not compatible with the ignition "venting process" as I understand it.

Contrary to what many think, explosion-proof equipment does not prevent an explosion but “contains“ it when it occurs in an electrical enclosure. Exhaust gases/flames are cooled as they pass through many cover threads. http://www.appletonelec.com/PDF/Hazardous1.pdf http://www.appletonelec.com/PDF/Hazardous6.pdf

Bjarney, As I said I have not done much of this type of work but I agree with you.

Most electricians do not understand the equipment contains an explosion inside.

Kind of a strange concept in it's own right.

The last explosion proof job I was involved with was all PVC coated components.

480 volt 3 phase outlets and control stations. $$$$$

OK, so just to make sure I have this right, "explosion proof" keeps the sparks and flame inside the box, rather than allowing it to enter the explosive atmosphere around it?

Would it survive an arc flash?

But, the box with all the wires hanging out of it looks like a meter socket. [Linked Image]

See the following definition in Article 100 and Article 500.

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Explosionproof Apparatus. Apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby.

FPN: For further information, see ANSI/UL 1203-1999, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations.

I am pretty sure that the enclosure where the wires are exposed is not a meter socket. Maybe someone can help us with a reference.

Think good yes that is right, pretty cool.

Mean Gene I agree that looks like a meter socket but that is a junction box for hazardous locations.

The cover is a very heavy solid disk that threads into that round hole.

Very fine threads it takes many turns to full tighten it.

You do not even want to think about the cost of this device.

One price of this type of equipment I know is a thermostat for heat trace cable.

Normal location one would cost us about $20.00 the ones we need for hazardous locations cost us almost $800.00 and it is about the size of the round j box on the left between the switches.

Check this out for a picture of a similar box. http://www.hubbellonline.com/wiring/killark/pdf/2SecF/SecF55-F56.pdf

The j-box on the far wall looks similar to an Appleton GUBB catalogued at http://www.appletonelec.com/pdf/K-2thru8.pdf The intent is not to stop hazardous vapors from entering, [that’s a loosing battle] but if contained vapors or gases ignite, then the threads or lapped surfaces “cool” the combustion products to limit high-temperature propagation outside the enclosure, reducing the chance of igniting airborne materials outside the enclosure.

NEC Chapter 5 wiring is a whole different animal and almost needs piecemeal assembly drawings to install correctly.

Petrochems, distilleries and NASA launch pads are unique in that regard. As can be imagined, the liability is tremendous.

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The j-box on the far wall looks similar to...

Reminds me of a guy with whom I used to work. He could ID old auto parts at a glance. People would bring stuff in to try to stump him.

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Petrochems, distilleries and NASA launch pads are unique in that regard. As can be imagined, the liability is tremendous.

Fireworks factories?

Boy Howdy, TG. That's a little trickier, for vapors and dusts are handled a bit differently.

Here are rules that help to identify the requirements:

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NFPA 1124
Code for the Manufacture, Transportation, and Storage of Fireworks and Pyrotechnic Articles
1998 Edition

4-3 Electrical Requirements.

4-3.1
All electrical fixtures in storage buildings at fireworks manufacturing plants shall be dusttight. All electrical wiring shall comply with Article 502 of NFPA 70, National Electrical Code.

4-3.2
Electrical receptacles or unguarded light fixtures shall not be permitted within 25 ft (7.6 m) of any fireworks. Light fixtures within 25 ft (7.6 m) of any fireworks shall have guards.

4-3.3
An electrical disconnect shall be located outside each storage building, and the disconnect shall be arranged to deenergize all electrical power to the building.

4-3.4
All electrical fixtures and wiring for storage buildings shall comply with NFPA 70, National Electrical Code.

4-3.5
No extension cords or other temporary wiring shall be permitted within 25 ft (7.6 m) of any stored consumer fireworks.

the installation of explosion proof equipment is to creat a heat sinc which allows the ignition inside to cool off enough to stop ignition of the outdide atmosphere. the switch boxes are mated to their covers and should never be mixed up. at the factory they are mated individually. but my real question is: doesnt this look like a sump and if so the entire pit (which the guy in the photo is standing in ) could and probably does fill with liquid until the sump can catch up with the incoming liquid. if so why put thew electrical installation below the top edge of the pit?