Welding Aluminum AC Lines

[tonyvol]

Hey guys, has anyone welded together Aluminum AC Lines before? I need to make some lines that are bent differently than the traditional straight, 90 or 45. Here is a picture of a line that I got in my vintage AC kit. It has been welded together. My buddy can Tig Weld Aluminum and I was wondering if there is anything special you need to do? Also, can I just cut off the end of a fitting, bend and weld one of these lines together?

http://www.vintageair.com/2013catalog/2013%20VintageAir%20Catalog%20Webpgs%2077.pdf

[parsonsj]

Yes, no, yes.

You should try and rig up a test rig and spray the weld joint with soapy water before assembly, and double check with a vacuum pump once you've got your system together. Good luck!

[Schwartz Performance]

Exactly what Mr Parsons said!

-Dale

[raustinss]

I third that just make sure the aluminum is clean, if your buddy can tig it for you you should be fine, do some homework regarding what pressure to test them to..other then that good luck
Ryan Austin

[BuzzKillian]

I had a guy that is certified for welding aerospace type components, weld a tube together for me. He ran argon through the tube as he was welding.
I did not see him do it, but that is what he said he did.

[raustinss]

Yep that's perfect the argon helps shield the backside of the weld...also aids in penitration I would guess that after hearing that the piece should be strong and stable, but I don't know what kind of pressure is in a AC system I vaguely recall hearing something once about a high pressure side and a low pressure side...could be wrong though too
Ryan Austin

[Twentyover]

Yep that's perfect the argon helps shield the backside of the weld...also aids in penitration I would guess that after hearing that the piece should be strong and stable, but I don't know what kind of pressure is in a AC system I vaguely recall hearing something once about a high pressure side and a low pressure side...could be wrong though too
Ryan Austin

Operationally, high pressure side pressures can get up to 350 psig. Most OEM systems will shut down at 400 psi or so to protect the compressor. I've seen 425 in a tunnel test emulating a long idle in a hot climate (many Persian Gulf residents will keep the engine running while parked to keep the car cool.) We had to put a bigger engine cooling fan on to bring discharge pressure down.

Typical ASME standards are for burst pressure to exceed 8X working pressure.

OK, now for practical application- I work as a Teir 1 auto HVAC supplier Our standards are:

Low pressure: Leak: 15 kg/sq cm (213 psig)
Proof: 22.5 kg/sq cm (320 psig)
Burst: 40 kg/sq cm (569 psig)

High pressure: Leak: 40 kg/sq cm (569 psig)
Proof: 60 kg/sq cm (853 psig)
Burst: 100 kg/sq cm (1422 psig)

[jlcustomz]

My lines were welded by a local ac shop, was a teenage kid there doing the welding at the time. No problems from it. As long as the weld is mostly built up over the 2 pipes & not causing any thin spots from too much heat, it should have more than enough strength. Mine are built up even more than yours. You're going for strength more than looks on the buildup.
So far, I can weld aluminum better with a tig than I can steel.
this was done about 5 years ago.
https://static1.pt-content.com/images/noimg.gif (http://s1094.photobucket.com/user/jlcustomz1/media/DSC00606.jpg.html)

[MonzaRacer]

Tig welding is little over kill. Most AC repairs have been silver solder for decades. I have toyed with idea of using the durafix rods, they work on radiators and I have seen some of those running upwards of 30 psi with NO issue. And heat cycle much worse than AC.
As for back purging, aluminum does not "sugar" the welds,thats stainless steel, also AC welding in TIG is used to "blow" the aluminum oxidation off the metal in a cleaning action.

[raustinss]

The sugaring your referring to lee is also seen in some form with aluminum....try pulse mig welding aluminum, you'll see the oxidized coating. Leaving a frosty appearance and feeling. Also not being cocktail here but how does one silver solder aluminum..I've never heard of it.... I can ask me explain father in law but I'm positive AC systems run way higher pressures then cooling systems. Btw..back purging is yes overkill...but doesn't do any harm and, gives greater piece of mind yes?