PEX for air lines from compressor?
highfigh
| Posted in Energy, Heating & Insulation on
Has anyone used PEX for compressor air lines? I have a garage and use it for my shop, but I want to use something that is non-reactive and won’t corrode with condensation. I could also install a Shrader valve to drain water at the lowest point. I also want it to be somewhat flexible. I know the max water pressure is rated as 180psi@73°,(shown on the side). Any experience with this stuff when it’s cold and pressurized? I use a temporary heater when I work out there in winter.
“I cut this piece four times and it’s still too short.”
Replies
Do you mean to use it between a connector and the air-tool? Have you ever seen PEX? It's pretty stiff stuff. Maybe you could use for stationary piping from the compressor to connectors, but I would hate to wrestle with it dragging it around and kinking it up.
Just from the compressor to the hose reel.
"I cut this piece four times and it's still too short."
I do believe it would stand the pressure...rated for 180#s...but would oil be a factor?
Some more knowledgeable PEX folks will be along.
My dad had a PVC air line burst in his body shop years ago, despite being well below the rated water pressure for the pipe. I don't know if it was due to the cold or what, but whatever the reason for the failure, with gases you've got a lot more potential energy stored up when it's under pressure (vs. incompressible fluids like water), so when the pipe burst it sent shards flying everywhere. Luckily no one was hurt in that case. I don't know if PEX shatters like PVC at lower temps, but it's something to think about. Also, if you're running air to your regulators/reels at ~150psi, and the PEX is rated 180psi at room temp, that's not much of a safety factor for lower temps.
I wasn't going to use PVC since it is outside, but PEX is polyethylene, which is somewhat flexible. I'm also not using pressure higher than 120 psi.
"I cut this piece four times and it's still too short."
"Has anyone used PEX for compressor air lines? "
HF,
Air lines need to be iron, galvanized steel, or copper pipe properly sloped, with end drains and vertical take offs. Don't even think about it. If you are running high PSI's (175+) go with copper. Aside from the safety issue, you will forever be plagued with moisture in your lines if you go any other route.
Jon
Pex has to be protected from light, as UV degrades it. For that reason alone I would think it would be a poor choice.
The PEX website doesn't say anything about using it for compressed air, and it's probably safe to assume that if they don't say you can, you probably shouldn't. A quick websearch didn't turn up anything else that says you can use PEX for airlines, but I did find several references that specifically said PEX-AL-PEX (also called multi-layer or PAP) is OK for compressed air systems. It apparently has a layer of aluminum in between an inner and outer shell of PEX.
Edited 11/7/2005 2:17 pm ET by Stuart
That sounds pretty pricey. I think I'll just use copper. Thanks, everyone, for the info.
"I cut this piece four times and it's still too short."
The problem with most plastics is that they weaken when subjected to high temps. Grab the outlet of the compressor and see how hot it is. Don't burn yourself.
Small-bore polyethylene, nylon and polyurethane tubing are all widely used for compressed air "drops" and small distribution networks. Neither material fails in a brittle fashion like PVC. Maximum size normally used is 1/2" OD, at which point you usually switch over to pipe or to braid-reinforced rubber hose. I've run miles of this stuff in industrial plants.
PEX tubing should be fine as well, but normal polyethylene (without crosslinking) will also be fine, is cheaper, and can be used with insert/grabber type fittings (Legris, Festo, Metalworx etc.). These fittings, available from most fluid power companies, are particularly sweet because they can be made up instantly without tools and you can take apart any joint to re-configure your system also without tools.
The discharge from the storage tank should be cool enough for any of these materials, but DO NOT use these materials to connect a direct compressor discharge to the storage tank, since this will be too hot. Keep the tubing out of direct sunlight and away from hot objects, and restrain it properly so that if a joint lets go it is unlikely to injure anyone.
That said, for a shop air system it's nice to have your quick connects rigidly mounted. There are malleable (black) iron elbows with ears for this purpose. You can choose to run your main header and drops with either rigid pipe or the tubing.
As noted before, neither PVC nor CPVC nor ordinary black ABS drain pipe may be used for compressed air. All three may (WILL!) result in sudden, explosive, brittle fracture with the generation of injurious schrapnel. I wouldn't recommend HDPE pipe either, and PP pipe would be pretty much as bad as PVC.