View Full Version : Copper pipe for compressed air system?
08-07-2001, 01:52 PM
Does anyone know what the pressure capability of copper plumbing pipe is?
I was thinking of using copper for the compressed air lines in my shop. My reason is mainly for ease of working with it.
Thanks in advance!
I'm pretty sure 1/2" copper is okay -- a friend of mine is using it, with no problem.
I'm using flexible plastic tubing (polyethylene?), which is *really* easy to work with. MSC sells the stuff, and it's also sold at my local lumberyard for use with pneumatic nail guns. I got 3/8" i.d., which is good up to a working pressure of 90 psi or something, with a safety factor beyond that. Since I typically run about 60 psi off the compressor's regulator, I'm well within its limits. MSC also sells easily installed, easily removed hose fittings that I would recommend. I used barbed fittings and clamps, but the kind that just slip on and grip with some kind of collet arrangement are easier to install, don't restrict the flow at all, and can be taken off if you want to rearrange things.
The thing **NOT* to use is rigid PVC pipe. Although the pressure rating may be okay, it can shatter into shrapnel if it ever does crack. The flexible tubing will just rip.
There is a special grade of copper pipe for compressed air,or so the boss was told and paid for. I have seen Cu. pipe as tubing for the out pipes of industrial compressors. Watch the cheaper grades of flex tubing in cold weather. Also, they will work harden and break at fittings. Use the strain relief flex springs on the fittings in all cases if you have them. Do not drop the working end, this causes premature failure of the line at the air chuck. There is no pucker factor like unto that of an air hose propelled by 90psi air flailing around your personal space. At work, there are no longer any suspended vinyl hoses or coil hoses. Use rubber please, for a vertical drop. Support the hose with a strain relief to take the load off the fitting. A good practice is to shut off air at the compressor outlet and bleed the lines down after use or when they will be idle for a while. I have been bit by all the above plus a hotwater tank air reservoir exploding at a buddy's garage.
08-08-2001, 08:16 PM
We have had a copper supply line system for over 22 years, it works great!! Make sure you have a large water extractor........water will come out through the system if you don't. I made a larger reservoir using 2 inch copper, some sweat fittings, and a drain valve. Use either "L or M" grade 1/2" tube and sweat fittings. The standard thread to sweat fittings are available as well. Good Luck!!!-Mark A.
I thought "K" was the heaviest grade of copper tubing, not "M", but I may have it backwards.....
08-12-2001, 01:07 PM
Finally a topic I know something about....
I owned a service and repair plumbing company for 20 or so years.
Type M is the thinnest wall tubing.
Type L is the medium wall thickness
And Type K is the thickest wall and much harder to find.
Type M will work just fine, off the top of my head the bursting pressure is around 300 psi.
You will only save $50 or so running an M system, so just go with L. M always has red letttering on it and L is always blue.
When you terminate the tube, use what is called drop ear 90's. They have ears on them with holes for securing to the walls.
We use to put in air lines all the time in copper. PVC shcedule 40 or schedule 80 (gray) plastic does work fine too, although you have to saddle clamp the ends real well. PVC will save you some $ and is quicker to fabricate.
08-18-2001, 05:52 AM
I plumbed my shop with copper after looking into it a bit. I was shooed away from PVC from quite a few people because of its explosive nature when it fails. Some folks have undoubtedly had PVC for years with no problems, but I wasn't willing to leave the safety of others and myself to blind chance.
I found some good info on copper tubing from a .pdf handbook on copper tubing at the following link:
The lowest grade of flexible copper will easily handle compressor pressures. I brazed the joints since I was a bit worried about the solder joints failing with 200psi. But I have since heard from quite a few guys who had good results from simple soft solder, and one guy even did a test of a solder joint where the copper caved before the joint did. In the future I plan just to soft solder if I add any new drops.