Who is supposed to designate the boundaries of a classified area?

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Dustyswartz

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Electrician
Working on a data mine. There is no engineer. Vapor gas generators are fed from a compressor building. There is a LNG tank outside of the compressor building. The generators are 50, 60, and 70 feet away from the compressor building but 20, 30, 40 feet away from the LNG tank. Are the generators in a classified area? Someone made a comment saying electrical equipment cannot be withing 150ft of flammable vapors. I'm not seeing that anywhere in the code. I was always under the assumption that 10ft. From the opening is a classified area. Any ideas? Directions for me to look?
 
Generally the only classified location on such a setup would be in area where connection for filling or dispensing into portable containers might be and maybe near any relief vents. Otherwise if vapors aren't ordinarily present in free air during normal conditions there is no classified locations.
 
petersonra said:
You should ask that person where he came up with that number and what code it comes from.
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Generator tech. I asked him and he said he didn't know. Just that that number sticks in his mind. Which doesn't mean he's right at all. The only thing even remotely close to that that I know of is the regulations of distance from a flare stack. That's 100ft.
 
The answer to the original question, “Who is supposed to designate the boundaries of a classified area?,” shouldn’t be answered by members of this forum. Depending on the edition of the NEC used, the general answer will be found somewhere in Section 500.4 as noted in Post #2.
All areas designated as hazardous (classified) locations shall be properly documented. This documentation shall be available to those authorized to design, install, inspect, maintain, or operate electrical equipment at the location.
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In any case, the owner/operator of a facility is responsible to have it done.

The documentation can be done by anyone qualified to do so. Whoever said 150’, isn’t one.

In some cases, classification can be done directly from the Code if one of the Articles 511 to 517 directly apply. Your description of the facility so far indicates that they don’t. In most cases, one of the references in Section 500.4 Information Notes is necessary. NFPA 59 appears to be the most likely candidate.
 
kwired said:
Generally the only classified location on such a setup would be in area where connection for filling or dispensing into portable containers might be and maybe near any relief vents. Otherwise if vapors aren't ordinarily present in free air during normal conditions there is no classified locations.
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And in these areas the 10ft. Rule applies correct? But I've never heard of a 150ft rule.
 
rbalex said:
The answer to the original question, “Who is supposed to designate the boundaries of a classified area?,” shouldn’t be answered by members of this forum. Depending on the edition of the NEC used, the general answer will be found somewhere in Section 500.4 as noted in Post #2.

In any case, the owner/operator of a facility is responsible to have it done.

The documentation can be done by anyone qualified to do so. Whoever said 150’, isn’t one.

In some cases, classification can be done directly from the Code if one of the Articles 511 to 517 directly apply. Your description of the facility so far indicates that they don’t. In most cases, one of the references in Section 500.4 Information Notes is necessary. NFPA 59 appears to be the most likely candidate.
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Thanks! Great info
 
don_resqcapt19 said:
What 10' rule are you talking about?
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Once you are outside the classified area there are no distance requirements. If a generator is outside the classified area its all good. Now if an engineer wanted to come in and classify an area say 25' around the tank then you have to abide by that and move the generator. Otherwise you're good.
I also remember a superintendent telling me there was a rule at a compressor station that said anything outside within 10ft of a door to the compressor building was classified the same as the inside of the building. That may have been an AHJ spec specific to Northern Natural Gas plants but I don't see that in the code book either.
 
Dustyswartz said:
Seals. 10ft from either end leaving or entering a classified area to a non classified area. That's the only rule I know of at all.
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When you do have a classified area you need a seal at the boundary, That seal can be on either side of boundary, didn't look up any distance from boundary but seem to recall no other fittings allowed between seal and boundary - which the fact the conduit comes in 10 foot lengths would naturally limit you to putting it no more than 10 feet from the boundary. I do know it is common for underground runs to have that seal much more than 10 feet from the boundary, yet still needs to be first fitting once you emerge from underground. Note: only fitting exempted from this "first fitting thing" is reducing fittings at the seal fitting when they are needed.
 
I wrote the original API Proposal text for the “10’ rule.” Until then, there was no specificity in the distance for boundary seals and many AHJs assumed 18” was the maximum. We picked 10’ since it was a common standard raceway length.

Actually, several acceptable raceways are readily available up to 20’; some even longer. As kwired pointed out, the real concern was there shouldn’t be any fittings between the seal and boundary that would permit gas/vapor migration across the boundary. The rule had to be “wordsmithed” a bit when UL disclosed (25 years after the fact) that seals were only tested for 25% fill. So the rule permits listed explosionproof reducers.
 
Dustyswartz said:
Generator tech. I asked him and he said he didn't know. Just that that number sticks in his mind. Which doesn't mean he's right at all. The only thing even remotely close to that that I know of is the regulations of distance from a flare stack. That's 100ft.
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Check out NFPA 497. Usually a qualified licensed engineer would establish the area. There is alot of different scenarios/variables/calculations that go into the classification of an area. Volatility of the substance, atmosphere, ventilation etc. Big can of worms
 
Dustyswartz said:
Yeah I think the seal has to be no more than 18" when coming up out of the ground.
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No less than 18" comes up in some situations because that is how high off grade/floor the hazardous location exists in many instances.

Otherwise the seal generally needs to be first fitting on either side of the boundary.
 
Also, Where i work we have Class 1 Div1 and 2 areas. Im in a bottling plant that uses Ethyl Alcohol and Acetone in its products. Our boundaries are much smaller in area than what a large process with large equipment would have. There is actually chart to determine the size of your process, equipment, pressure. Piping, flow of material and pressure can all affect the boundaries. sounds like you are working in a "large" process environment
 
BrandonMD said:
Check out NFPA 497. Usually a qualified licensed engineer would establish the area. There is alot of different scenarios/variables/calculations that go into the classification of an area. Volatility of the substance, atmosphere, ventilation etc. Big can of worms
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And often that engineer is not an electrical engineer....many time is a process or mechanical engineer.
 
Dustyswartz said:
Yeah I think the seal has to be no more than 18" when coming up out of the ground.
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Not quite. We can discuss installations here but not specific facility classifications. With the exception of fuel dispensing facilities, the underground is usually unclassified. With few restrictions, if above grade is classified with a shallow envelope, it is usually acceptable to stub-up through the 18” (or higher) envelope to the unclassified location above. See Sections 501.4(A)(4) Ex No .1 and 501.15(B)(2) Ex No. 1.

Unless the compressor facility is for motor fuel dispensing, treating the underground as classified is unnecessary. If it is a motor fuel dispensing facility, it can be classified per Section 514.3(B)(2). The facility description so far does not appear to be applicable to Article 514.
 
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