Copper Air Lines - Good Sweat Joint

[ddawg16]

One of the more 'emotional' subjects here has been what material to make air lines out of....

I'm doing mine out of copper....why? Well....I had a few pieces of 3/4" left over from a plumbing project....and copper is easier to cut and fit on the spot than black pipe....(I didn't feel like draging a pipe threader home). All of it is commercial thickness....plenty strong. When done I'll have 4 drops around the garage including a couple in the ceiling so that it's easy to reach up and plug in one of those pretty yellow coiled hoses....

So...I thought I whould show off...I mean share a couple of pics of the joints before the pipe got closed up inside the ceiling....

Some guys have asked about doing a proper sweat joint....the first pic (from a POS digital that wants to focus on a distant object) shows the solder up inside....when you have a good joint, it will wick up into the inside...the silver ring (fuzzy silver ring) is the solder...

A few key points to getting a good joint.

1. Clean...and I mean clean surface. Solder does not stick well to dirt.
2. Not too tight...not too loose. You should be able to slid the parts together without much effort but they should not flop around.
3. Heat....get plenty of heat before you apply the solder. I always touch it on the opposite side...if it melts there...it's hot enough.
4. Wipe with a wet cloth to clean and set the joint...

And this is my regulator and filter setup....I used stainless because we have plenty of it at work....

 

[C2C6Z06]

Nice work...Will SS and Copper have corrosion issues? Are you going to go hog wild and polish/varnish the copper so it looks new forever?

 

[probesport]

Looks nice, I did my air system out of PVC, I never considered copper - good work.

 

[porschedude996TT]

You are refering to Galvanic Corrision

In harsh inviornment there should be less than .15 Volt difference between the two metals based on a Anodic Index Chart. Copper is 0.35V and 18% Chromium Stainless Steel is 0.50V, so those two metals are at there limit for Harsh Invironments. For normal environments it is 0.25V difference. It should be fine for many years...

Reference Source: http://www.engineersedge.com/galvanic_capatability.htm

 

[ironroad 9c1]

plus he has a brass bushing as a go between.

 

[C2C6Z06]

I missed the bushing....and Porschedude, thanks for the detail and link..

 

[Chris Adams]

Good advice, ddawg16, and nice looking work.

I would add something that would seem obvious.
Get a good or new torch. I don't mean pay a lot. When I decided to do my lines in copper I had two older propane torches, both pretty expensive but both very old and had been sitting.

After some excitement, and loss of half an eyebrow I went down to Lowe's and bought a cheap but NEW torch. End of excitement. The torches themselves go bad after awhile, it seems. Did not know that. Do now.


Copper is cheap right now, by the way. Very cheap.
The elbows and such can cost more than the long pieces.

Home Depot did not have some of the end pieces I wanted, but the local hardware store did, a Truevalue.

 

[tcianci]

Copper makes for great air lines. I do question your recommendation about the wet rag to "set" the joint. I was always taught to let the copper cool on its own otherwise you will end up with a "cold" joint where the solder has crystalized instead of set solidly. Even if I'm wrong about that, I know for sure you don't want to use a wet rag on a hot joint because the heat turns the water into steam immediatly and it goes right through the cloth and will burn you quick as a bunny. Most fluxes wipe off with a damp rag just fine after the joint has cooled.

 

[Bull]

My father has been a plumbing and HVAC guy since the 1950s. Watching him work is really neat...he's an old school craftsman and they are hard to come by these days. He makes exceptionally clean solder joints.

He'll often let the joint cool for a short time, then hit it with the wet rag. I've also seen him clean/smooth hot joints by applying flux or brushing with steel wool.

Your joints do look very clean, and not all glopped with solder.