Class 1 Div 2 boundary for gas meters located inside a building

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rootboy

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We decided to go ahead and install intrinsically safe barriers for every gas meter that we attach a pulser to that is located inside a building. It probably isn't necessary, but we would rather err on the safe side.

So the next question is, what would be the boundary limits for a gas meter? If I use Table 514.3(B)(2) "Electrical Equipment Classified Areas for Dispensing Devices", I get 5 feet for compressed natural gas if I treat the meter as a "Dispensing Device".

That seems a tad bit close to me, but I couldn't find a good match in the NEC for this type of installation.

Any ideas?

Thanks!
 
rbalex said:
Who owns the meters? And what is the highest pressure?
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The US Navy owns them, and all of them are on various bases here and there (I don't have any numbers of how many meters that will have to have the I.S. barriers on them), and I think that most of them will be on systems that run at just a few PSI.

Thanks. :)
 
Art 514 does not apply; see its "Scope" in 514.1.The appropriate document to use is NFPA 54, National Fuel Gas Code.

It may surprise you, but you need no boundary at all, especially with low pressure systems that are otherwise installed correctly for the location; for example, that vicious earthquake on the east coast. (I'm from California, 5.8 wouldn't even get me out of bed - or wake me up for that matter ;) ) While it would be prudent to use 3 feet as an "avoidance" zone even that is not an absolute requirement. Some local utilities may have certain restrictions but it is rare that it exceeds 3 feet.
 
rbalex said:
Art 514 does not apply; see its "Scope" in 514.1.The appropriate document to use is NFPA 54, National Fuel Gas Code.

It may surprise you, but you need no boundary at all, especially with low pressure systems that are otherwise installed correctly for the location; for example, that vicious earthquake on the east coast. (I'm from California, 5.8 wouldn't even get me out of bed - or wake me up for that matter ;) ) While it would be prudent to use 3 feet as an "avoidance" zone even that is not an absolute requirement. Some local utilities may have certain restrictions but it is rare that it exceeds 3 feet.
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Well, we went back and forth on even needing it, so it's no surprise.

Oddly enough, I got a call from one of our PM's in Texas about installing a I.S. barrier today. While I had him on the phone I had him read me off the PSI on the meter. For that meter it was 275 PSI. So way more than I ever expected.


Thanks again!
 
rootboy said:
Well, we went back and forth on even needing it, so it's no surprise.

Oddly enough, I got a call from one of our PM's in Texas about installing a I.S. barrier today. While I had him on the phone I had him read me off the PSI on the meter. For that meter it was 275 PSI. So way more than I ever expected.


Thanks again!
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"Low" is generally 100 PSI or less. 275 PSI is "moderate." Depending on the ventilation and pressure rating of the meter flanges, I might change my initial recommendation. Probably not by much.
 
rbalex said:
"Low" is generally 100 PSI or less. 275 PSI is "moderate." Depending on the ventilation and pressure rating of the meter flanges, I might change my initial recommendation. Probably not by much.
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I spec'ed 20 feet from the meter with sealoffs, etc... I think that should be fine.

Thanks again for all of your help! :)
 
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