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air compressor pipe head to tank, is this copper ACR?

metalmagpie

Titanium
Joined
May 22, 2006
Location
Seattle
I am resurrecting an air compressor, putting together parts from various sources. The air pump is a Champion R30A which I did a valve and ring job on. It came to me mounted on a 120 gallon horizontal tank which failed hydrotest. I found an 80 gallon Kellogg-American ASME vertical tank which did pass hydrotest. I cut the top plate (sometimes called 'saddle') off the horizontal tank and welded it to the vertical tank in place of its too-small top plate. The tank was completely cleaned and painted. Now it's time for final assembly, wiring and plumbing.

The R30A pump has two jugs in a vee configuration. Like this:

shinyJugs.jpg


Champion used 3/4" copper tubing for its discharge tubes. There are 2 tubes which are routed down behind the pump and which join to an aluminum manifold. Champion calls this assembly the "aftercooler" which isn't exactly the sense I had understood for the word. This is the whole discharge tube arrangement:

pipes2.jpg


The two aftercooler tubes are to the right in this image, where the aluminum manifold can easily be seen as well. On the horizontal tank, a single 3/4" tube continues from the manifold down to the tank with an inline check valve and some plumbing. As you may well imagine, this last tube (from the manifold down to the tank) does not fit the vertical tank at all. So I need to make a new one which does fit. I am going to need a piece of the copper tubing material less than 3 feet long. I have some pieces of the same stuff which had been intercooler tubes on a different compressor, and which I'd unwound the crinkly aluminum spiral from. That tube has the same heft as the tubes fitted to the R30A pump. I measured it carefully and got 0.750" OD and 0.625" ID. This would of course give it a 1/16" wall thickness, or 0.062" wall. However, I don't see tube in this size listed anywhere. I know this isn't type K, L, or M domestic water tubing. I figured it was probably type ACR. However, 3/4" type ACR copper tube does not come with 0.062" walls. Mostly what I see is 0.042" thick walls with the OD and wall thickness specified but the ID not specified.

OK, thanks for reading all that. Is there another grade of copper tube I'm not considering? Did I make a mistake measuring?

Please help me source this material.

By the way I plan to form the bends with a Hossfeld bender. No idea how that's going to work out. I do have some type L 3/4" tube to experiment with so I don't screw up a $50 piece of new tube in the bending.

metalmagpie
 
Did you weld after the hydro test? Welding on the saddle isa probably okay. I would not trust many welders welding onto a pressure vessel.
Sounds like you have thicker then needed tube. use it if the outside diameter is correct. Tube can be measured/called out by inner or outer diameter. Depend son liquid or gas use. This means the exact same piece of tube can be two different sizes like 1/4 and 5/16 might be the same.
Bill D
 
Did you weld after the hydro test? Welding on the saddle isa probably okay. I would not trust many welders welding onto a pressure vessel.
Sounds like you have thicker then needed tube. use it if the outside diameter is correct. Tube can be measured/called out by inner or outer diameter. Depend son liquid or gas use. This means the exact same piece of tube can be two different sizes like 1/4 and 5/16 might be the same.
Bill D

Yes, I waited to weld on the bigger saddle until I knew the vertical tank tested good. And it's one thing to weld up a pressure vessel where your weld has to hold air pressure and entirely another to weld something to the surface of an existing pressure vessel. Also, the top of a vertical tank is unlikely to have any rust inside, since any water on the inside runs down to the bottom of the tank. So I was welding onto full thickness metal. I have been welding for 50 years anyway, doubt it's going to be a problem.

I had always heard tube called out by its OD, whereas pipe is called out by its (nominal) ID.

metalmagpie
 
Make the single tube going from the Tee to the tank a larger diameter or coil up 50 feet and have a condenser.
I did this and got a larger diameter tank check valve.
 
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Unfortunately the copper tube you buy today is junk compared to 50 years ago .......thin ,hard ,ID not concentric with the OD ,and very hard to bend to tight curves without failure ............the reason soldered connectors are used now is because the junk tube wont seal with flares or olives.
 
I'm not having any problem finding 3/4 OD copper tube, 0.65 wall and others.

It's soft, and for the type of bends you need bends by hand with a simple exterior coil spring bender.

Even if you got "5/8" tube with 3/4 OD and 0.042 walls, it's rated for 632psi...
 
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