Re: Flame Arrester

Sajit:

Your situation is unclear. Is your pipeline carrying a flammable gas, or a flammable mixture of gas? There is a big difference. Natural gas is flammable, but the gas is transmitted (piped) in nearly pure form, with no oxygen. As such it is not a flammable mixture. It is not ignitable. It is well over the Upper Flammability Limit (UFL).... it cannot burn nor sustain a flame. One is highly unlikely to transmit a flammable mixture of natural gas and air. Or for that matter, any flammable mixture. It's dangerous, costly, and there is seldom reason to do so. This being the case, the deflagration type is almost always used. Also be aware that the detonation type, for a fire internal to the pipe, is proportionately much larger. It has to drop the velocity down from sonic to sub-sonic. Because it is larger, it can be extremely expensive and difficult to mount (or find room to mount). Work with a knowledgeable supplier for guidance.

... Bruce D. Bullough ...
Lead Process Engineer
Foth Production Systems, LLC
8550 Hudson Boulevard North, Suite 100
Lake Elmo, MN 55042
Direct: +651-288-8598 Fax: +651-288-8551 <a href="http://www.foth.com">http://www.foth.com</a>

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Subject
[PipingDesign] Flame Arrester

An end of line Flame arrester is to be provided on a vent line carrying flammable gas mixture.

To decide the type of the arrester, i.e. whether a deflagration or a detonation type, it needs be decided on which side of the arrester is the flash likely to occur. It seems to me that the what is normally provided on
a vent line is an end of line deflagration type. This is based on the consideration that the flash will occur on the outside. Is it that, there is no likely hood of a flash occurring within the pipe, even though the gas
mixture is a flammable one. The BS standard on this 12874 does not address this. Neither does the literature that I saw at Elmac.

A detonation type is used to quench a flame front of sonic velocity originating on the inside of the pipe. Where would this type be used, in light of my query above, as to what would cause a flash to occur within the
pipe.

Sajit

Save a tree...please don't print this e-mail unless you really need to. Received on Wed Feb 07 09:05:00 2007