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Aluminum pipe Purging

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Aluminum pipe Purging

Postby burnellmech » Sun Apr 09, 2017 11:56 pm

Hello All,
I am Tigging up a couple of 1.5" x 14" long sections of Aluminum pipe to a 1/2" thick x 3" wide x 60" long. I have welding three pieces of pipe to the 60" long so when fixed the 3" x 60" piece will to bolted vertical to a van shelving unit with the piping horizontal. This will be to hang electrical extension cords on, with a small 1/2" thick oval welded to the other end, to prevent the cords from sliding off. It is certainly overkill for extension cords but it's just how I like to do it and many welded components in my vehicle such as acetylene tank holders and very shelving all welded with aluminum make for great conversation pieces whenever anyone is around when I open up the van on service calls. Anyhow I can keep going but my question is I will have the 3" wide x 60" long lying horizontally on my table and I will be welding the aluminum pipe vertical this is just too wild it and then it will be being rotated 90° to be fastened to the shelving in the vehicle...... my question is does or should I purchase the inside of the pipe while welding the outside for example putting some tape over the one and with a hose adding argon to the inside of the pipe? I did another post a few weeks back regarding carbon steel plate cracking and I appreciate all of the responses it was amazing also if someone can tell me how to attach a picture to these posts if possible I wouldnt have to write such a long story trying to explain exactly what I'm doing I would be able to just attach a photo !
Any advice is greatly appreciated thank you David Burnell
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Re: Aluminum pipe Purging

Postby burnellmech » Mon Apr 10, 2017 12:03 am

Sorry for the typos
iPhone seems to Change half of what I type...
I am tig welding three 14" long 1.5" dis aluminum pipe to one flat aluminum 3" wide 1/2" thick 60" long stick and and curious if I should purge the inside of the pipe? I realize I must drill a hole to allow for pressure build up, when welding oval on other end
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Re: Aluminum pipe Purging

Postby cj737 » Mon Apr 10, 2017 6:06 am

There's no need to purge AL tubing. If you are welding both ends "closed" to a flat plate, you do need to keep in mind pressure and heat building up on the inside. If you weld one side closed, then promptly flip to weld the other side closed (against flat plate for instance) you can have the internal pressure accumulate enough to cause a blow out as you attempt to finish your weld.

Allowing a small gap in your final weld for the pressure to escape while the tubing cools down some prevents this. Or, flip the welded side up vertically, weld at the bottom. This buy you some extra time as the heat rises in the pipe and away from your welding position. 5-10 minutes of cooling is often enough to buy that time, but really depends upon how thick the tubing is, and how much heat you poured into it.

I welded up a new base frame from 3x3x0.25 square tubing. I welded these sections fully and to do both ends, did the top first with the bottom only tacked. Welded the bottom closed and had sufficient distance (>24") between both ends that the pressure hadn't built up sufficiently within the tube to force gas/heat out of the bottom welds. But if I did it in reverse, she spit back hard as I closed up.
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Re: Aluminum pipe Purging

Postby burnellmech » Mon Apr 10, 2017 2:39 pm

Thanks for the response...... I appreciate it!
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Re: Aluminum pipe Purging

Postby exnailpounder » Mon Apr 10, 2017 4:28 pm

Drill a hole in your tube somewhere inconspicuous to let expanding air out, weld up everything nice and let it cool and then weld the little hole shut...or don't weld the little hole shut. Boom.
Ifyoucantellmewhatthissaysiwillbuyyouabeer.
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