HiLevel (Electrical)
22 Aug 13 11:04
I posted this in the codes and standards forum and I'm "reposting" it here. I apologize if this is bad practice; however, it seemed that most discussions around natural gas are in this forum.
I have a gas rack located a distance away from an enclosed duct burner. It's a typical gas rack with <5 psig natural gas. Another design engineer has classified the area around the burner as Class I Group D Division 2. And, the result is a big change order and delay from the gas rack manufacturer. There are no other sources of flammable gas in the area, only the natural gas in the pipe. The design engineer is looking at codes like NFPA 497 and API 500 figure 104 to justify the classification. Their position (and these standards) is that the gas rack contains numerous threaded connections and devices such as SSOVs, and instruments that make it a high risk area. So, a Class I Div 2 classification is assigned. However, if this is the case, why don't the burner manufacturers design their equipment to meet this classification? I've never seen a gas rack with Div 2 equipment and wiring, and manufacturers of things like SSOVs (Honeywell, ASCO) don't even make Div 2 certified models. (I see that Maxon now makes a Div 2 valve) I know that NFPA and API both say you don't have to classify an area around a flame; duuuh. But, I don't have this typical condition to fall back on this time. I also know that the codes API 500 5.4.2 and others allude to lighter than air gases (natural gas) being less likely to accumulate; however, they don't go to the point of recommending classifications.
Why don't the burner and gas rack manufacturers build their systems to meet this classification if these standards are truly applicable.
Does anyone know of a reference? I see AGA XF 0277 for electrical classification of gas systems; however, I'm seeing a lot of focus on gas compressors and none on your basic low pressure burner gas rack. So, my guess is that like API their tables, charts, etc. will apply to systems from 0 to 250psig. That's quite a spread. Anyone have experience with this standard? EN 60079-10 appears to be the British equivalent.
Thanks ahead of time!
Bill
HiLevel (Electrical)
22 Aug 13 18:40
Well, I hate to follow up on my own post; however, I just blew $400 on AGA XF0277 "publication".
Based upon this publication it looks to me like we need to shut down every gas fired steam heating system in the country without explosionproof equipment and wiring. How can companies like Honeywell and ASCO sell their SSOVs when they're not listed for Class I Div 2 areas? "'
I see that Maxon now makes an optional Div 2 labeled valve. I looked into this several years ago and they did not at that time.
What am I missing here?
If the connections to the valve create the hazardous classification, how can the valve not comply?
Thanks for listening, any insights would be welcome.
