McElroy Discussion Forums

Methane levels
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Author:  PitPullMan [ January 22nd, 2013, 8:16 pm ]
Post subject:  Methane levels

Hey if I am tying onto to an existing methane line at a landfill, does the methane need to be shut off? Or is it not combustible at normal levels traveling through the pipe? I know the Pitbulls can cause a spark, but the super at the field does not seem to be concerned.

Author:  Joshua [ January 23rd, 2013, 11:06 am ]
Post subject:  Re: Methane levels

Here is some background for those unfamiliar with methane. I got this from Wikipedia:

Methane is not toxic; however, it is extremely flammable and may form explosive mixtures with air. Methane is violently reactive with oxidizers, halogens, and some halogen-containing compounds. Methane is also an asphyxiant and may displace oxygen in an enclosed space. Asphyxia may result if the oxygen concentration is reduced to below about 16% by displacement, as most people can tolerate a reduction from 21% to 16% without ill effects. The concentration of methane at which asphyxiation risk becomes significant is much higher than the 5–15% concentration in a flammable or explosive mixture. Possible health effects of breathing in methane at high concentrations, resulting in oxygen deficiency, are increased breathing and pulse rates, lack of muscular coordination, emotional upset, nausea and vomiting, loss of consciousness, respiratory collapse and death. Methane off-gas can penetrate the interiors of buildings near landfills and expose occupants to significant levels of methane. Some buildings have specially engineered recovery systems below their basements to actively capture this gas and vent it away from the building.
Methane gas explosions are responsible for many deadly mining disasters. A methane gas explosion was the cause of the Upper Big Branch coal mine disaster in West Virginia on April 5, 2010, killing 25.

There are some variables here that one would have to accurately measure to know if an explosion hazard exists. Here is what the CDC says about the explosion hazards of methane in landfills and the conditions that have to be met for an explosion to occur.

I know that methane is a huge deal at the coal mines I have been to. But, I am not knowledgeable with methane to air ratio in typical landfill gas gathering lines. Nor do I know how much it can fluctuate or concentrate given various conditions. Based on the Wiki article it would seem that it is quite possible to have dangerous concentrations and methane to air mixture. So personally, I would most definitely err on the side of caution. This is even more true if I were in a ditch. McElroy has a procedure for fusing in gaseous or explosive environments. It is documented in the manual for any given machine. I would use these fusion procedures if I weren't able to shut the flow off and vent the area.
I would encourage you to research this question within your industry and with those who would be more familiar with the potential hazards you're working with. I would bet that there are generally accepted industry guidelines out there somewhere.
I moved this post to the Technical Support area of this forum. Please feel free to post there with any more solid information that you find. I am interested to know.

Author:  Joshua [ January 23rd, 2013, 11:15 am ]
Post subject:  Re: Methane levels

I found this in that CDC document. It lists accidents and the year they occurred. Look at the incident in 1975...

Although landfill gas explosions are by no means common occurrences, a number of incidents known or suspected to have been caused by landfill gas explosions have been documented.

1999 An 8-year-old girl was burned on her arms and legs when playing in an Atlanta playground. The area was reportedly used as an illegal dumping ground many years ago. (Atlanta Journal-Constitution 1999)

1994 While playing soccer in a park built over an old landfill in Charlotte, North Carolina, a woman was seriously burned by a methane explosion. (Charlotte Observer 1994)

1987 Off-site gas migration is suspected to have caused a house to explode in Pittsburgh, Pennsylvania.(EPA 1991)

1984 Landfill gas migrated to and destroyed one house near a landfill in Akron, Ohio.Ten houses were temporarily evacuated. (EPA 1991)

1983 An explosion destroyed a residence across the street from a landfill in Cincinnati, Ohio. Minor injuries were reported. (EPA 1991)

1975 In Sheridan, Colorado, landfill gas accumulated in a storm drain pipe that ran through a landfill. An explosion occurred when several children playing in the pipe lit a candle, resulting in serious injury to all the children. (USACE 1984)

1969 Methane gas migrated from an adjacent landfill into the basement of an armory in Winston-Salem, North Carolina. A lit cigarette caused the gas to explode, killing three men and seriously injuring five others. (USACE 1984)

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