Compressed natural gas lumped in article 514?

[greenspark1]

Hello,
I'm working on several projects with CNG and looking at the requirements of section 514. This was clearly written and designed for gasoline filling stations but does contain some language for CNG, LNG, and LP (514.3(2)). First question- is there a better place to find requirements for CNG?

The problem I see is that CNG is fundamentally different from gasoline. If there is a leak CNG cannot leak into the ground, puddle, or similar as it all evaporates. Even under pressure and cold temperatures it's still a gas and just evaporates. Especially concerning the underground conduit requirements (514.8), it seems like this should be refined depending on the type of fuel being used. I see this becoming more and more an issue as vehicles transition from regular gasoline and to alternatives.

Any input/discussion is very welcome, thanks.

 

[mgookin]

While liquids and gases have different physical properties, they are both still a hazard when there's a leak. Just because you can't see the gas does not mean a hazard is not present.

 

[GoldDigger]

:thumbsup:
Gasoline vapor is generally more dangerous than puddles of liquid gasoline.

Tapatalk!

 

[rbalex]

The OP is basically right -and Art 514 recognizes it - just not very well. [Section/Table 514.3(B)(2)] CNG, being lighter than air, has significantly different properties and often creates a different set of installation concerns.

I've said before, except for locations within the scopes of Articles 511 to 516, classifying locations need to use standards outside the NEC. Articles 511 to 516 are largely extracted from other NFPA documents by Technical Committees not all too familiar with the fundamentals of classified locations. They aren't stupid by any means, but they are more "process" and "fire-control" of mechanical systems oriented. "Correlating" those documents with the NEC falls to the NFPA Standards Counsel (SC) to resolve. Long before I was even in the business, since the SC didn't want to get involved too often and they weren't usually anymore knowledgeable about the issues, the SC basically solved its own problem by subordinating the NEC to the other documents. (That's why Articles 511 to 516 exist)

Left to Code Making Panel 14 (CMP14), many of the "unique" installation requirements for Articles 511 to 516 would be eliminated and left to Articles 500-506. For example, Section 501.10(A) Exception 2 was written solely to recognize "...the provisions of 514.8, Exception No. 2, and 515.8(A)." Without the unnecessary underground requirements created by Articles 515 and 515, Section 501.10(A) Exception 2 could be eliminated.

This isn't to say CMP14 doesn't recognize the value of providing direction for classifying locations within the Articles 511 to 516 scopes even if they don't always agree with them.