PVC and PEX for Compressed Air

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Hunter79764

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Just a note that might be helpful info for folks wanting to run compressed air as cost-effective as they can...
I've heard good advice about PVC pipe not for use in compressed air systems, being that if/when it fails, PVC shards can be sent at high velocity through the neck of whoever happens to be in the way, but beyond that it seems to be unclear. In some unrelated air compressor research, I found a reference to recommendations from the Plastic Pipe Institute and their recommendations on the matter (see link below to get the source, 2 PDF's attached as well).

It states thermoplastic pipe should not be used for compressed gasses unless it is shrouded or otherwise protected, but does not "Ban" it unless covered by local code. Personally I take that to mean buried lines are ok since the shard potential is gone, and same for running pipe in stable locations where there is not a direct line from the pipe to people nearby (i.e., I'd feel relatively safe running in my metal building Z Purlin at 8' high). This is also in line with the other issue on PVC of UV exposure causing brittleness since anything shrouding the PVC is also likely to block sunlight.
This is common general advice out there, but again, here it is in writing even if it is between the lines. That said, PVC is not very durable, and even if it is safe buried underground, man it would suck to have to dig it all back up when you run a heavy truck through the area and crack a line. And even if the piping is not Line-of-Sight, a shard can easily ricochet and still cause problems.

What is interesting to me as well is the advice on pressure testing PEX with compressed air. To my knowledge, no one has approved PEX for compressed air, but this group draws a comparison between plastic pipe that breaks brittle vs PEX and PE-RT that remains flexible. Air testing PVC water lines is generally a no-no, but this recommends/allows air testing of PEX systems. Note this is not approval for use with compressed gasses so don't use this as evidence for your friendly neighborhood code inspector, but if it is "safe" to test with air, I feel safe using it for distribution in my own shop. It does have some good practical warnings about being careful of fittings and lines turning into whips in a failure, but a 3/4" or 1/2" PEX line anchored every 10' doesn't seem like a huge whip potential to me.


Anyway, just some info some of you might find handy and many might find boring...

 

Attachments

  • Recommendation B PVC with air.pdf
    66.9 KB · Views: 2
  • Recommendation F PEX with Air.pdf
    91.1 KB · Views: 2

Old Guy Bill

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The newest building at the mfg company I do maintenance work for has the AI-PEX all through it for pneumatic supply. It’s 1” blue, and has all brass fittings.
I’d never seen anything like it. It’s impressive stuff and the installation is top notch and I’m sure it was expensive. I’m trying to get some of it to add some ports needed as the business expands.
 

Hunter79764

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Is it RapidAir stuff? I've looked into it before, and we used it for a small area of our plant construction a few years back. Material cost is higher, but I think I've seen where overall install costs (when done 3rd party by professional pipefitters) end up being similar since the labor is so much less. I'm probably going to use PEX for my workshop to pipe my air supply (power is first, and no real plan yet on that so I'm a long way out), but if the RapidAir comes down in price, or I get a few extra dollars in my pocket, it's on the short list.

We also use more rigid aluminum (also blue plastic coated) for our compressor rooms lately, same story, cost is not much more but labor goes way down vs welding 4" and 6" pipe everywhere... All of that stuff gets so expensive it's hard to compare. Basically have to add a few zero's to everything. I have a 2.5hp compressor, might upgrade to a 5 or 8hp in the right circumstance, probably could spend $200 on adding a used unit or something. Work has 600-900hp of compressors on most buildings, one shop in particular has 9 different 300hp compressors at $200k each...
 

Old Guy Bill

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I’m not sure of the maker.. I’m overwhelmed by the projects that I’m doing and haven’t had a chance to look into it.
 

waterpirate

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It would be important to note here the service pressure. A high line vs. a regulated line is a whole nother bunch of grapes. Call me old fashioned but for a high line I want steel. A regulated line can be whatever you are comfortable with. I am also not a fan of shark bite or compression type fittings that often are used with the pex type tubing on high lines. YMMV
Eric
 

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