PEX for compressed air?

[marfaguy]

Anybody run PEX for a compressed air line? Since I'm running underground conduit
for a 100 amp line from the main electrical panel out to the shop now's the time to also
run a compressed air line from the shop to the car port (across the breeze way from where
the main panel is). From what I've been able to tell plain old standard 3/4" PEX available from
Loews/HomeDepot is rated at 150 psi for what they call out as potable water lines. I can't see
needing more than 100-120 psi air in the car-port. Air up the tires, blow leaves and crud out of
whatever, and such like.

I know there's a PEX-AL-PEX product made for compressed air but that seems like way over kill for
what I need.

I'd run the run the line inside of a gray PVC electrical conduit probably twice
the diameter of the PEX just in case I need to replace it at some point. 

 I like the PEX idea since I should be able to get it at length so I don't have an underground joint,
not to mention the price difference between it and a k type copper pipe. I've heard bad things
about using PVC for compressed air and given my soil type (heavy black clay with chunks of
limestone that tends to move a lot) I think PVC would be a bad choice. The run's about 150 feet.

What do ya'll (my West Texas origins peeking out) think?

-Charles

[Gazz292]

i used nylon pipe for my airlines around the garage, the stuff trucks use for their brake lines, rated for something like 300psi or more, pretty cheap too, buy it off the reel from any truck parts supplier, or aggricultural type place that sells spares (i got mine from a hydraulics pipe supply shop)

one thing to be carefull with tho, you will get water from the compressor migrating to the lowest point of the pipe, which will be underground, so you may want to see about an air drier/water trap before the pipe goes underground.

[picclock]

And when the water collects it freezes and no air. So then your out in the snow dribbling anti freeze down the pipe and all over your hands wishing you lived in a temperate climate .. .

Don't ask

picclock

[PTsideshow]

Nylon semi rigid tubing, PEX is for liquid only! They clearly state on any site that sells it that it not rated for gas pressure use air or other.  I have two of the horrible fright  whole garage air systems seems they are getting rid of them. has a 100/ft 1/2" nylon semi rigid tube, a number of fittings for a basic set up. everything but the mounting clamps, and the air fittings. So far everybody that has put them in is satisfied with them. Since it is still cold out and I have to finish cleaning the shop. I will be waiting till I get the new compressor in and running.
The fitting for PEX are also not rated for air. and have a tendency to pop off.
I plan on running at 130psig,then regulate at the taps.
brand of speed fittings
For the extra ones that I need.
The semi rigid nylon is about $71.00/100 feet With the 20% coupons the kits were around $35.00 each I wish they had another one, they were a real deal. Some of the end blocks are sort of dorky but I can live with that.

[PTsideshow]

I forgot to add that, PEX tubing cannot be used in applications exposed to sunlight, as it degrades fairly rapidly. Prior to installation it must be stored away from light, and needs to be shielded from daylight after installation. Leaving it exposed to direct sunlight for as little as 30 days may result in premature failure of the tubing due to embrittlement. this also means reflected UV radiation/light, will cause material deterioration. As with the people that use PVC hard pipe for air lines. Every maker and seller clearly states that it should not be used. And since like that If you use it and have a catastrophic failure, with injury's you probably only make a lawyer rich trying to collect from the company.
I had a PVC air line set up in the basement overhead, It had a catastrophic failure mid pipe length and plastic  shrapnel was embedded into the wall board. Sorry no  photo's it was BDC (before digital cameras) 
what ever you choose to do, be aware of what can happen.
 

[marfaguy]

Thanks Gazz, Picclock and PT,
Ok looks like PEX is out.  I suspect I'll want .50" ID. So it looks like nylon-12 should be a good choice. Or is
there something else I should be looking at?  Anything else I need to be aware?

Picclock,
I won't ask but it's killing me not to.

[bigmini]

I forgot to add that, PEX tubing cannot be used in applications exposed to sunlight, as it degrades fairly rapidly. Prior to installation it must be stored away from light, and needs to be shielded from daylight after installation. Leaving it exposed to direct sunlight for as little as 30 days may result in premature failure of the tubing due to embrittlement. this also means reflected UV radiation/light, will cause material deterioration. As with the people that use PVC hard pipe for air lines. Every maker and seller clearly states that it should not be used. And since like that If you use it and have a catastrophic failure, with injury's you probably only make a lawyer rich trying to collect from the company.
I had a PVC air line set up in the basement overhead, It had a catastrophic failure mid pipe length and plastic  shrapnel was embedded into the wall board. Sorry no  photo's it was BDC (before digital cameras) 
what ever you choose to do, be aware of what can happen.
 

PE and PVC aren't the same. Yes, PVC will crumble away under exposure to UV in a short time. PE can work in the sun, but you need the black version with carbon filler, or the special white version with the titanium filled coating (like sunscreen).

I've seen black PE used with great success in mining applications in 50degC daytime temperatures, and on my uncle's farm with stock treading on it, vehicles running over it, etc. It's very tough and when it does fail, it tends to bulge like a tyre giving plenty of warning rather than shatter like some grades of PVC will do.

In Sydney a lot of natural gas lines use PE(http://www.vinidex.com.au/page/gas_pipe.html so I'm not sure that it's usage is restricted to liquids only either.

Definitely do not use PVC for air lines or gases of any kind, especially the brittle stuff you buy from the hardware store , and definitely keep PVC out of the sun.

There is a grade of PE for Compressed air applications: http://www.vinidex.com.au/page/vinidexair_pipe.html

A reference for usage of polyethylene pipe (Australian):

http://www.vinidex.com.au/page/pe_pipe_systems.html

There are other suppliers of the same material. These guys are the most familiar to me and have lots of on-line info about their products.

[marfaguy]

PE and PVC aren't the same. Yes, PVC will crumble away under exposure to UV in a short time. PE can work in the sun, but you need the black version with carbon filler, or the special white version with the titanium filled coating (like sunscreen).

I've seen black PE used with great success in mining applications in 50degC daytime temperatures, and on my uncle's farm with stock treading on it, vehicles running over it, etc. It's very tough and when it does fail, it tends to bulge like a tyre giving plenty of warning rather than shatter like some grades of PVC will do.

In Sydney a lot of natural gas lines use PE(http://www.vinidex.com.au/page/gas_pipe.html so I'm not sure that it's usage is restricted to liquids only either.

Definitely do not use PVC for air lines or gases of any kind, especially the brittle stuff you buy from the hardware store , and definitely keep PVC out of the sun.

There is a grade of PE for Compressed air applications: http://www.vinidex.com.au/page/vinidexair_pipe.html

A reference for usage of polyethylene pipe (Australian):

http://www.vinidex.com.au/page/pe_pipe_systems.html

There are other suppliers of the same material. These guys are the most familiar to me and have lots of on-line info about their products.

GAHHHH!!! OK so PEX is out as is PVC. Nylon is in and now PE is also a contender. Ok guys I've got about 150' (feet) run. This includes about 10' on both ends
for fixturing/fittings. Anticipated/allowed pressure is going to be in the 100-120 psi range. Should price be my main concern at this point?

[lordedmond]

do it proper

copper or galvanised iron pipe with condensation traps in the drops

Just for fun look up the pressure drop on that run bet you will need 1 inch pipe if you draw any amount of air


Like the RO l over A losses in electrical circuits

Stuart

[Gazz292]

the nylon pipe i use is the 12mm stuff, which is the standard air line size for trucks it seems, i run my compressor at 150 psi, and draw off about 8cfm max, but i only have about 40 feet of the pipe, plus a pull out hose reel about 20 meters long,

but for your length of pipe, i would deffo think about going up a few sizes in the pipe,

i can't recall what the nylon pipe cost me, but i am a professional tight arse, so i wouldent have bought it if i thought it was too expensive, fittings were cheap too,

[bigmini]

do it proper

copper or galvanised iron pipe with condensation traps in the drops

Just for fun look up the pressure drop on that run bet you will need 1 inch pipe if you draw any amount of air


Like the RO l over A losses in electrical circuits

Stuart

By my rough back of an envelope calculation , for a 25mm ID pipe over that distance you'd get 25 l/s free air discharge with a pressure drop of 0.1 bar - assuming no bends or fittings.

You'd have to convert that into old fashioned units yourself

In SI units the equation (from Atlas Copco) is: PressureDrop=450*length*FreeAirDischarge^1.85/(workingPressure*diameter^5)

pressure in bar, length in metres, FAD in l/s, working pressure in bar (in your case about 8), and diameter in mm. (use the actual diameter, not the nominal diameter)

Doesn't take into account roughness of the inside of the pipe or any bends, filters, etc. You'd add all that on. You can see that a small increase in diameter reduces the pressure drop a lot

[PTsideshow]

PE and PVC aren't the same.

Don't know anything about PE  The PEX that he asked about is not UV stable And the warning from the manufactures state this. As it is used in the walls or as a in the concrete floor for heating before it is poured.

Never mentioned anything about PE so I don't understand why you are quoting my posts in your answers, and mixing the types.

[marfaguy]

K grade copper at (currently, approx.) $5.00 a foot is a definite budget buster. Galvanized Iron/steel pipe is probably also a budget
killer, not to mention would require underground jointing which I REALLY want to avoid (do manufacturers  even
make +- 150' lengths of Galvanized?). So nylon, probably nylon-12 in a .5" ID is the current choice for me.  
I can't see needing that much CFM in the car port. If for some odd reason I suddenly have a need to run impact
tools in the car port I'll either move the project to the shop or rent a compressor. If after I pass on some future owner
finds the run inadequate then he can install his own dang pipe.  

 Anything else I've forgot, or am not considering?  

[bigmini]

PE and PVC aren't the same.

Don't know anything about PE  The PEX that he asked about is not UV stable And the warning from the manufactures state this. As it is used in the walls or as a in the concrete floor for heating before it is poured.

Never mentioned anything about PE so I don't understand why you are quoting my posts in your answers, and mixing the types.

I'm pretty sure PEX is another name for HDPE, also called PE100 here in Australia It's short for cross linked polyethylene. PE80 also has similar properties but is lower density.

[PTsideshow]

If you have a woodcraft store in your area, the local store here sells the same kits and parts for the garage air kits with the nylon tube that Harbor freight sold. The extra fitting fittings cost more than I pay at US plastics.
Compressed-Air-Piping-System
Super Speedfit® Polypropylene Union and Swivel Elbows1/2" size is the size for the tubing.

[marfaguy]

BTW,
Just to finish this thread out. I went with a 3/8" ID nylon air hose rated at 250 PSI in a buried 1" PVC electrical conduit. I was able to order a 150' length so there are no joins in the air hose any where in the buried conduit. For I want it for it should work fine.