Purging a gas line for welding

newlove

Tom, do as biguhg says. welding is much safer that way as
apposed to purging. you know what is in the existing line.
newlove.

Tom Shannon

Purging a gas line in preparation for welding

I need a formula to calculate the amount of C02 necessary to evacuate, or purge, 100' of 4" gas line so I can weld on a thread-O-let. Can anyone help?

Thanks.

Gary Fereday

been ther done that!

just make sure the gas is off. then go ahead, the gas can only burn if it reaches oxygen. You sometime hear it ignite down the pipe length, a weird sound. but sooner or later it will become to rich to burn, not to mention the fire douseing gasses that are produced. Shut dowm the line. allow the pressure to disapate, If you place your -O-let and weld it, you can then drill if after the weld is made. A correctfitting hole saw does the trick. Great for thread-O-lets

Unknown

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Dale

You may want

to purchase an electronic flammable gas tester. We weld on live gas pipe every day outdoors, no problem as long as it's full of gas. A burnthrough isn't any big deal either, just weld it shut. Indoors the prudent thing to do is isolate the gas source and purge with nitrogen or CO2. CO2 is heavier than air and displaces oxygen so be very careful indoors with larger amounts unless you are oxygen monitoring. FLow the nitrogen until the gas test shows no gas, like soldering a refrigeration system. If you need to do this alot Mueller, Ridgid and TDW make hot tap equipment so you never have to shut the gas off, pricy though.

Arthur

Welding a gas line

Greetings from NZ
That paradise in the South Pacific (It's summer time down hear)

I've never had a problem with welding gas pipe work yet in over 20 yrs. Fitted a branch recently and had to silfos a joint in bad light and mistakenly rebrazed an existing joint instead of the new one of course it leaked just turned the gas off and brazed it up no sweat. Didn't even flare.