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-   -   PEX for air compressor lines (http://www.diychatroom.com/f2/pex-air-compressor-lines-173867/)

lifestooshort81 03-07-2013 07:00 PM

PEX for air compressor lines
 
anyone here using PEX for running compressed air lines? I don't plan on putting super crazy pressure through the lines, just 120psi or whatever max pressure my air compressor will allow for. I know steel/copper lines are suggested for safety and condensation but I have a ton of PEX left from a job and it's much easier for me to run it in the odd spaces i need to run it in.

I will not use a hard plastic like PVC or CPVC because of their ability to explode and send plastic shrapnel everywhere BUT from what I see, PEX won't explode into shards. As a soft plastic if it would burst I imagine it would split.

Any thoughts? I have done quite a bit of research through google and haven't found any solid information. I'm not worried about the fittings, just if the actual pipe is "safe" and can handle the pressure.

Thanks,
Al

Daniel Holzman 03-07-2013 07:06 PM

  • 200F at 80 psi
  • 180F at 100 psi
  • 120F at 130 psi (1/2" Wirsbo AQUAPEX tubing only)
  • 73.4F at 160 psi
These are Uponor ratings for their PEX, however since PEX is a relatively standardized product their rating is likely to be comparable to other manufacturers.

joecaption 03-07-2013 07:08 PM

I'd pass on that idea.
This is how a properly layed out air system is done.
http://www.sharpe1.com/sharpe/sharpe...+Piping+Layout

No one that knows what there doing is going to ever suggest using copper,

Use black iron pipe instead, reason being a filter will remove rust.

PoleCat 03-08-2013 07:38 AM

Back in the early 90's I worked at a facility that had multiple outlets in two separate buildings all plumbed to one big compressor. The director was a bit of a safety nazi and decided the aging iron & galv. piping had to be replaced before it ruptured. The replacement was a green plastic pipe. I remember being skeptical about this idea at the time. I wonder if it is still in service.

joecaption 03-08-2013 09:13 AM

Here's a tip and time your running an air manifold use the largest pipe possible.
The pipe acts like an accumulator and and increaces the avalible flow to the tool so it does not start off with full pressure then slow down from lack of air.
Just going from 1/2 to 3/4" increases the flow by about 25%.

Nailbags 03-08-2013 10:44 AM

Pex is not rated for air! it is rated for water PSI of 150 you want the air rating take that 150 and divide it by 3 you get 50 PSI max rating for your air line. Now you know. use stainless steal tubing with nutts and ferrels.

Nailbags 03-08-2013 10:47 AM

Quote:

Originally Posted by joecaption (Post 1132003)
I'd pass on that idea.
This is how a properly layed out air system is done.
http://www.sharpe1.com/sharpe/sharpe...+Piping+Layout

No one that knows what there doing is going to ever suggest using copper,

Use black iron pipe instead, reason being a filter will remove rust.

I would use stainless steal better and less long term problems.

1985gt 03-08-2013 01:19 PM

Used Pex in our shop, been going strong for 5 years now, will let you know in another 5, then another 5. A good drier/filter is a must.

123pugsy 03-08-2013 01:52 PM

Quote:

Originally Posted by Nailbags (Post 1132389)
Pex is not rated for air! it is rated for water PSI of 150 you want the air rating take that 150 and divide it by 3 you get 50 PSI max rating for your air line. Now you know. use stainless steal tubing with nutts and ferrels.


I thought pressure was pressure?

I do know that a pound of feathers is lighter than a pound of lead though.....:whistling2:

Nailbags 03-08-2013 02:19 PM

Quote:

Originally Posted by 123pugsy (Post 1132526)
I thought pressure was pressure?

I do know that a pound of feathers is lighter than a pound of lead though.....:whistling2:

PSI is PSI the manufacure of Pex states not to use compressed air and if you do take the rating and divide by three. for safe operations. Theirwords not mine.

Thurman 03-08-2013 03:21 PM

@"PoleCat": I also have seen/used the "greenish" colored "plastic" type pipe for compressed air. We ran a lot of this in the mid '80's in our plant. I was skeptical of this at first but it proved to be a quality product. Then just as I was convinced that this was a good product and was useful to us, some contractors came in to run some new fire protection piping using an orange colored "plastic type pipe product". At first thought one may say: "Well, this stuff will surely melt if there is a fire". Yes it will. But by the time the temperature around this pipe gets that hot, the fires too big for the sprinkler system to fight anyway. I currently have my entire shop ran with 1" CPVC piping with four 3/4" drops within the shop. Not one leak since 1996. My training and understanding is that PVC/CPVC will not "explode" if there is a weak spot in the piping. Rather, it will just develop a crack running with the run of the pipe along the piping and allowing air to escape loudly.

joecaption 03-08-2013 04:01 PM

CPVC and PVC should never be used for at least two reasons. One if you happen to have a compressor that uses oil, the oil bypasing the ring will degrade the tubing.
And any plastic pipe can expode!!

Pressure is differant for water and gas:eek:
So much for Boyle's law.

Maintenance 6 03-08-2013 04:41 PM

Quote:

Originally Posted by Nailbags (Post 1132545)
PSI is PSI the manufacure of Pex states not to use compressed air and if you do take the rating and divide by three. for safe operations. Theirwords not mine.

Which manufacturer and where can I read that? Seems pretty odd that they would say not to do something and then give you a formula to follow just in case you do decide to ignore their advice.

Daniel Holzman 03-08-2013 04:55 PM

Seems like there are a lot of opinions that are not specifically backed up with verifiable facts. Couple of points to bear in mind. From the perspective of a pipe, pressure can come from any fluid, whether that fluid be air, water, mercury, or for that matter any liquid or gas. The pipe from a mechanical standpoint behaves exactly the same whether it is subject to 50 psi from air or water, so there is no basis to the claim that 150psi water is the same as 50 psi air.

Certain types of pipe are not rated for specific chemicals. This is a chemical, NOT a mechanical issue. For example, if you want to carry nitric acid, you need glass pipe, because other common types of pipe degrade when in contact with nitric acid. All plastic pipes have temperature ratings, as they typically weaken with rising temperature, hence their pressure rating is temperature dependent. Dry compressed air should not chemically interact with any commonly available plastic pipe.

If a specific PEX manufacturer states that their PEX pipe is not rated for compressed air, that probably means only that the manufacturer has never tested their product for use with compressed air, hence they are not going to warranty it for that particular use. This says nothing about allowable code use. It also says nothing about whether PEX will work acceptably with compressed air, it simply means that manufacturer is not going to warranty their PEX for use with compressed air.

I have found a number of articles claiming that PEX-AL-PEX, which is a particular type of PEX tubing which includes aluminum as an air barrier, is acceptable for use with compressed air. I cannot verify this, however a call to Wirsbo or another manufacturer of this particular type of tubing, commonly used in hydronic heating applications, should confirm if it is OK with compressed air.

A Squared 03-09-2013 06:01 AM

Quote:

Originally Posted by joecaption (Post 1132329)
The pipe acts like an accumulator and and increaces the avalible flow to the tool so it does not start off with full pressure then slow down from lack of air.
Just going from 1/2 to 3/4" increases the flow by about 25%.

You're going to be hard pressed to find air tools outside of an industrial setting that will be limited by a 1/2"pipe. 1/2 " pipe should be good to about 20cfm/100psi for 50' of pipe. Gonna be tough to find an air tool in a home shop that nees even half that.


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