# Repairing UG steel gas line.



## plumber666 (Sep 19, 2010)

Customer has a 2 1/2" UG 10 psi welded gas line with a leak. Worked till 7 last night trying to find it. Have a bunch of ground exavated with a hoe, shovels, and even a big sucker truck. Last thing I did was fill the hole up with water and saw lots of bubbles so I know we'll find the actual leak first thing this morning.
So, any of you ever welded a repair patch, or filled a small pin hole on a live, leaking gas line before? My welder says he'll talk to his bro in law who works for the gas company as a welder, but he's pretty sure you can safely do it.
Off to work, hope to see you all again....


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## plumbpro (Mar 10, 2010)

plumber666 said:


> Customer has a 2 1/2" UG 10 psi welded gas line with a leak. Worked till 7 last night trying to find it. Have a bunch of ground exavated with a hoe, shovels, and even a big sucker truck. Last thing I did was fill the hole up with water and saw lots of bubbles so I know we'll find the actual leak first thing this morning.
> So, any of you ever welded a repair patch, or filled a small pin hole on a live, leaking gas line before? My welder says he'll talk to his bro in law who works for the gas company as a welder, but he's pretty sure you can safely do it.
> Off to work, hope to see you all again....


I've seen the gas compay weld a live line, scared the chit out of me. Apparently it's not uncommon


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## Tankless (Jun 12, 2008)

They do it all the time....and under a lot more pressure than 10 pounds. I have never seen a plumber do it...just the gas company


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## mssp (Dec 15, 2009)

My grandpa was a welder for gas co. I loved to hear him talk about welding a live gas line. I have never done it but if he said he did it then it can be done.


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## G3farms (Oct 29, 2010)

it is done all the time, the gas company will construct a tent like structure over the area the weld will be made in and gas levels allowed to rise above the explosion limits. It take a certain ratio of gas and oxygen to be an explosive atmosphere, it the gas level is too high or too low there it will not burn.


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## OldSchool (Jan 30, 2010)

G3farms said:


> it is done all the time, the gas company will construct a tent like structure over the area the weld will be made in and gas levels allowed to rise above the explosion limits. It take a certain ratio of gas and oxygen to be an explosive atmosphere, it the gas level is too high or too low there it will not burn.


natural gas is explosive or flamable only between 4 and 14 % anything under it will not ignite and anything over it will not ingnite..

So the movies use see where I guy turns on the gas range and runs out of the building then throws in a lighter and the whole building explodes is just pure fiction


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## OldSchool (Jan 30, 2010)

Now propane is a total different story.... it is heavier than air and will pool in the lowest point..... pure fuel will not burn with out oxygen.... the problem with propane is it does not mix with the air it just sits there leaving the air on top... any source of ignition above the pure propane will surely cause an explosion.

On the other hand natural gas is lighter than air and mixes with the air right away... so any concentration of natural gas between 4 and 14% in the air will explode.


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## G3farms (Oct 29, 2010)

well there you go, I knew it was something like that. 

thanks for the info.


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## 422 plumber (Jul 31, 2008)

Is the pipe wrapped? Whenever our fitters put carbon steel pipe underground they have to "tapecoat" it.


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## Tommy plumber (Feb 19, 2010)

When I solder with a B tank and torch, the flame doesn't travel back from the tip, through the hose and into the tank causing an explosion. Even without a regulator I don't think the B tank would explode. Seems like welding live gas line is the same principle.


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## OldSchool (Jan 30, 2010)

Tommy plumber said:


> When I solder with a B tank and torch, the flame doesn't travel back from the tip, through the hose and into the tank causing an explosion. Even without a regulator I don't think the B tank would explode. Seems like welding live gas line is the same principle.


Thats why there is a saying A before O or up you go.....You only have to worry about when you are using any flamable gas and oxygen....


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## plumber666 (Sep 19, 2010)

Ended up abandoning the whole underground 2 1/2" line. Weird set up. 6" 10# gas main runs through the trades building at the college. It leaves the building, goes underground to the central heating plant. Feeds all the big Cleaver Brooks boilers then goes back outside to a meter bank. The leaking line was the one that doubles back in the same trench to the trades building.
Me and a welder put a 2 1/2" nipple onto the 6" main and the 2 1/2 line in the automotive shop. We shut the gas down and I drilled a 2 1/8" hole through the two nipples into the mains. I screwed 2 1/2 x 2 reducing couplings and 2" valves and plugs on and we turned the gas back on. Went back the next weekend and piped the 80 feet of 2" between them and relocated the meter. Cool job. I asked the gas inspector in advance if he was OK with 2 screwed 2 1/2" joints and it was all good.


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## DIZ (Nov 17, 2010)

plumber666 said:


> big Cleaver Brooks boilers then goes back outside to a meter bank.


Brought back memories of being inside CB boilers as an 18yo reapacking the walls and changing hand hole rubbers......good times.


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## Gasser (Dec 22, 2011)

*Live gas repair*

If the repair/weld must be made under pressure, if possible use a digital thickness gauge taking reading around area of hole. This will determine how severe the corrosion is. If it is determined that the wall thickness immediately around the leak can support a weld without a burn through then you can weld an encircment around the leak. Weld close enough to the leak to be able to hammer/ chisel close the leak then weld over this hammer shut. You won't be able to weld directly over an open leak as it will blow the molten metal away never allowing the leak to seal. If the wall thickness is to thin from corrosion or the leak is to large for hammering shut then you can put a temporary clamp/patch over the leak and install a Dresser two piece welded incircment repair sleeve over the temp. Patch. The dresser "pumpkin" is larger than the existing pipe slowing the temp path to be completely inclosed. The pumpkin is considerably longer than your area that has the hole which usually allows the weld area tb away from the repair patch. Be sure to use the digital thickness gauge as a safety procedure before doing any work on "loaded"lines. Hope this helps.


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## plumber666 (Sep 19, 2010)

Man, that was such a cool job. Lots of crap on the line there, whole college could have been screwed, but we fixed them up. That was the first time my nephew used a threader.


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