Air lines

Keep in mind, if ANYTHING hits pvc even lightly it could blow out in that spot any time, even at a later date. Also pvc gets it's rateing at a certain temp, change the temp, and the rateing changes too.

Use the proper pipe, and you won't have to worry about if it's done right or not!!!

Robert

PVC is appealing because of the cost and ease of installation but it is potentially unsafe in that application. A failure of the piping can result in flying plastic shards that can do serious damage. Many have used it successfully but commercial type installations would be prohibited in many areas and there is no manufacturer that I know of that recommends it for compressed air use. I doubt you will find any responsible authority that would endorse such a use. See here, here and here for some background information.

Rod

Sure, I think copper makes an excellent material for standard compressed air lines. You might want to consider using the 95/5 solder rather than the 50/50. The solder joints are the weak link in pressure ratings for copper tubing. See this link for actual pressure ratings, depending on maximum operating temperature.

Rod

That was very interesting- thanks. I too used copper, with 50/50 solder, on my present system. No problems whatsoever and now I know why.

My next compressor, for another building, has a MUCH higher psi rating and I'd wondered what line might be appropriate. Not sure I want to go much over 200 psi, but the compressor and tank are good for it. I'll have to take a look at regulator ratings and give a little thought as to why I might want higher pressure.

Thanks, I understood that. The new-to-me compressor is tested at 500 psi at 450* F. That's WAY off the copper chart and I don't think I want to know what the regulator price might be. Not to mention that I don't have the cojones to be anywhere other than on the back side of a concrete wall away from that kind of pressure.

The other thing that happens when you run a compressor at lower pressure is you get substantial more cfm, if more frequent cycles. That's one reason I get by sand blasting with a 5 hp IR.

The only doubt I have is whether or not it would put through the volume of air needed to run air tools, etc.. They are only designed to feed a diver's air needs at whatever depth the diver might be at. However, if it was suppying air at 140-160 psi and you are breaking that down to 90 psi with a normal compressed air regulator, that may just take care of the supply question. Might be worth making some enquiries.

Re the cojones question: I can relate to that. I replied to a post on the crawler forum about welding up a fuel tank on a Cat 22 crawler. I mentioned that I had oxy-acetylene welded a car gas tank many years ago by running exhaust gas through it before starting welding and during the process. I gotta tell yer, my cojones were a tad nervous during that little adventure 'cos they were going to be the first thing after my knees to know about it if anything went wrong. BTW, I've done it and I survived but I sure DO NOT recommend it -- especially if you have a nervous disposition. (See link below.)

Hope this helps.

You have a wonderful day. Best wishes. Deas Plant.

• Cat 22

I'll keep that in mind, when I get the building built and am installing the air system. But Vince, never say never.

I was out buying a 600 gallon tank, for a solar system, from a guy when he asked if I was interested in a compressor. It was so cheap I didn't pay much attention until I got it home. My compact tractor hemorrhaged getting just the head out of my truck and I realized it was a LOT more compressor than what I was using. No telling what it originally cost, but when big companies have surplus, sometimes it ends up cheap. Certainly I had no idea I'd ever have a compressor like it either. 35cfm IIRC. Way more than I need, but it's here.

I ran thousands of feet of CU type ACR for refrigeration piping thats tested for 500psi with a typical working pressure of 350psi. About the same wholesale cost as type K (common hard CU pipe) and type L soft CU.

Type M is a good choice for air line as it's slightly cheaper than type ACR but heavier wall than type K and rated for the psi.

I clean the outside of the pipe with 80grit emery paper, the fitting inside with a fitting wire brush, then sweat the joint using Oxy/Acet with 15% silver solder. Pre-clean the solder rod with 80 grit emery. Harris brand on the 15% silver solder is the best.

A flux is not required providing you keep the filler rod with in the gas envelope or close too the flame. This keeps the joint and filler rod from oxidizing making the solder flow easy.

A purge gas of 5c/hr of AR, HE, Co2 or nitrogen works well to keep the inside joints from scaling while welding. Use a piece of masking tape for the end not being welded with a pencil lead size hole for purge gas to escape.

They make a non-silver bearing filler rod called Harris Stay-Silv. Although it will do the job at 1/2 the cost ($24 vs $48/lb) of 15% silver solder, there is a big difference it the way the two solders flow into the joint. Pay the extra cost and get the 15%.

T_Bone

I've got a copy of this with the copper pressure-temp ratings I saved. ACR wasn't listed. K,L,M with 95-5 solder will give me all the pressure I really want. I haven't played with the pressure switch to see what range it has, but I can always replace it if it doesn't go low enough. I like having more than one tank hooked in. Presently have 140 gal storage which works well with my 120 psi cutoff.