Compressed air piping: Fitting question

Copper is used, with Silpos brazed joints, for airconditioning and refrigeration systems without problems. They run similar pressures to compressed air. Geoff

Simular pressures? Not at all! Pressures in R22 systems can reach 300 PSI on a normally operating system, R410, twice that, or 600 PSI. I have seen pressures on R22 systems that are not functioning properly over 400 PSI, R410 it is possible to see twice that in a troubled system, or 800 PSI.

I have no problem runnng copper with compressed air, soldered joints, no problem. If it makes you feel better, use Silphos. Greg

Maybe I'll even give Jonathan Barnes an offer for his fine looking compressor:-

It looks as if there's nothing wrong with it that a cupola furnace couldn't cure :-)

Mark Rand RTFM

Code for industrial buildings in N. IL.

It's all over our plants (over 60 buildings in two locations)....Come to think of it the local snob car dealer (BMW, MERCEDES, ROVER, etc) newly constructed body/mechanical shop (about 40 stalls) has it all over as well..

FWIW.

I'm not trying to convince ya just passing on the info from the manual:-) BTW these compressors can run at up to 200 psi on all models and some of the smaller models ( about 10hp and less ) can run up to 500 psi I'm sure that if you used the heavy walled copper and BRAZED it there would be no problems.

William...

BTW I still want to hear about the exploding black iron pipe the other poster was talking about!

I work for the Navy as a mechanical engineer, we have had many instances of copper pipe (2 & 3 inch IPS sizes) joined with SilFos type joints which would "bulge" in service. This was in 100PSI steam service (heating steam) and was usually caused by softening of the pipe by heating when joining the pipe, the bulges were allways at joints. When a pressure excursion (caused by improperly set or working regulators) happened, the pipe would expand untill work hardening would toughen up the pipe enough to resist further expansion, stopping the bulge. When pointed out by a nervous sailor, we would write a repair to replace the bulged pipe using a coupling and nipple, with special instructions to the brazer to avoid heating the pipe as much as possible. A numerical check of the pipe alyways indicated the bulge was still quite serviceable, but a nervous sailor is hard to convince.

Steve Steven

Where I work, we have over 1000' of 1" copper air lines operating at 200 PSI. Most in place since 1973. It is just soldered. Some have plain old solder & some lead-free solder. Some pipe is type M & some is type L. Under pressure 24/7. Zero failures.

Bert

Be aware the issue the manual is trying to address might be work hardening of copper connections directly to the compressor.

Jim

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Wouldn't that be just as much a problem with compression fittings?

Ted

Compression fitting are typically used with soft refrigeration tubing, yes? It may be that the manufacturer simply wanted to be sure there was something either flexible, or resistant to hardening and fracturing, right at the unit.

Just a SWAG.

Jim

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Copper will work until there is a fire in your shop. When the soldered joint melts, compressed air is delivered to the flame.

Not the best idea for those who leave their systems charged 24/7.

Stick with the black pipe.

Sleep tight copper users

Jason

If my house catches on fire, you can be damn sure that the *least* of my worries is a few cubic feet of compressed air being delivered to the flames.

My family has a standing order - if the place lights up, get out instantly, and do not go back, for any reason. This is sound advice for any structure fire, but a 1900 ballon frame house makes it imperative.

Jim

Red herring! ;-) A few cubic feet of air escaping isn't going to make things any worse, though it might scare the cr*p out of any Fireman standing nearby at the time it lets go. (Piped gases like Oxygen or Acetylene, that would be a whole different situation...)

And if the copper pipe joints didn't let go in the heat, the small section of rubber hose to provide flex between the compressor and the hard piping would pop, or the seals on a safety valve, etcetera.

Of course, if using copper pipe for air soft solder wouldn't be my first choice, I'd use silver braze and put it together right. (Plus, the plumber won't try messing with it.) If it gets that hot, you have far bigger problems than the air line letting go.

And I would never use compression fittings on copper for air lines, they can come loose with nasty results.

Black pipe is a fine second choice for air lines - if you are very careful to put plugged tees everywhere for future expansion (because you can't just cut and braze in another tee whenever you want - after a few years if you try to modify the system you'll practically have to start over to stop all the leaks) and you are paranoid about sloping everything downwards, and provide drip-legs and trap drains all over the place.

And with black steel piping you'll need filters before all tool outlets, because if you get any rust scale in the pipes that breaks loose, it will inevitably get into a very sensitive tool or device valve and wreak havoc inside same...

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