Joining Thin Wall Aluminum Tube (.035" wall or less) 1

[iainuts]

I have a project in which I’ll need a piping system (nominal diameter 2”) with the lowest possible thermal mass. Pressure is less than 1 psi at -450 F (worst case) cryogenic helium gas. Piping will be insulated to minimize heat transfer.

At this point I’ve concluded that aluminum has the lowest thermal mass for any given diameter and wall thickness. The thinnest I’ve found is 2” x .035” wall (6061-T6). I’d like to go thinner and have a special mill run of 2” x .020” wall, but the problem is with joining this material. I’ll need to join them end to end and also have Ts and transitions made up, and there seems to be no easy way to do this. Installing threaded couplings such as Swagelok fittings results in significant added thermal mass, so I want to avoid these types of fittings.

My preference would be to have something simple since this system will all be field routed. Welding might be possible, but very time consuming, and awkward. I wonder if there’s any kind of soldering or brazing technique that could be used. If there is, could such a technique be used with copper pipe fittings? If I have a special mill run made that’s 2.125” OD and very thin, I could use standard copper fittings which would solve the problem. Otherwise, if I have to have special aluminum fittings made up, there will no doubt be a huge cost for these fittings.

Can copper and aluminum be soldered/brazed together? If so, how?

Is there anyone that makes an aluminum solder or weld fitting? I’ve had no luck finding anything on the web.

Can this be welded? I see one company in Germany that may make an orbital welder for aluminum and haven’t talked to them yet, but something along this line might also be possible.

Thank you.

 

[EdStainless]

Stainless steels are automatically orbital welded often. Try talking with AMI (Arc Machines) about the equipment.
Sometimes very light wall tubing is joined with transition pieces that are a bit heavier.

You will be able to have this tubing supported continuously? Especially in Al it sure won't be very stiff.

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[iainuts]

Hi Ed, I'm aware of orbital welding for stainless which is why I mentioned it, but would prefer some kind of soldering or brazing technique I could use with copper fittings. Orbital welding of aluminum seems to be very rare from what I gather.

Regarding support, that won't be a problem. In fact, the thermal contraction will be much more of a problem so I'll be doing a flexibility analysis of the piping.

 

[unclesyd]

Here suppliers of alloy thin wall tubes along with one supplier of thin wall Al refrigeration tubing. I believe that you can get alloy tubing in thinner wall than Al. Also it has been my experience that thin wall alloy tubing is a lot easier to weld.

http://www.alloybellows.com/tubing/index.htm

http://www.brazeway.com/extrusion/specs/round_tube_specifications.pdf

http://www.veridiam.com/weldedtube.html

http://www.kj-tubing.com/products_services.html

Here are two of many companies that supply micro-welding equipment.

http://www.precisionjoining.com/index.html

http://www.weldlogic.com/default.asp

 

[iainuts]

Thanks unclesyd. The very thin wall stainless seems like it would work if I had a way of joining it. Can .010" wall tube be orbital welded? Are there any fittings (T's or adapters) you know of? I'll have to give them a call and see what they can suggest. Thanks.

 

[iainuts]

Thanks again unclesyd, I ended up going with the very thin walled (~ .010") stainless tube you suggested and having it special made for this application so I can braze it to copper fittings using silver braze (AWS BAg-24 was recommended). I'll be testing out some sections shortly, but the quotes look good.

 

[jedward]

indium corporation has solder & flux for joining aluminum to copper