Can you, or should you, use PVC plastic pipe for compressed air? What prompted this page was that I visited a friend of a friend’s house a while back. Got the tour of the place and I also got to see his latest restoration project, the re-building of a classic Jeep from the frame up.
I also saw his excellently plumbed air supply from his compressor throughout the garage. Took the drop legs from the top of the main lines, drains at the bottom of the drop legs, just a first class installation. Are you waiting for the but? Yes, there was one. The plumbing for his lovely compressed air mains and drops to his work bench were all PVC plastic pipe. Ouch!
Use PVC plastic pipe for compressed air?
No, you certainly should not!
The pressure rating for a particular PVC pipe may show that it appears to be rated for the pressures coming from a typical air compressor. The issue is that those rating ares predicated on normal 75 degree F temperatures, and as temperatures rise, the pressure capability of PVC pipe rapidly declines.
Unlike polyethylene air tube or rubber hose, which will bubble and pop if the air inside it gets too much for the wall strength, PVC plastic pipe, if it fails under pressure, will often shatter, spraying everyone and everything with plastic shrapnel. Not nice.
Why you shouldn’t use PVC pipe in a compressed air system?
PVC piping is so hazardous when used for transporting, storing, and testing compressed air, even the pipe companies issue stern warnings:
WARNING! The use of PVC pipe with compressed gasses or air can result in death or severe bodily injury.
This warning should be adhered to because:
When air is compressed, (even at low pressures) it produces an enormous amount of stored energy. PVC piping is an unbending thermoplastic material, which flops delicately.
PVC pipe can fail for reasons such as mechanical damage, improper assembly, excess or impact pressure. The failure will be very theatrical due to the unexpected release of that stored energy.
The fast escaping air will explode rubbles of plastic shrapnel in all directions, compromising the safety and health of adjoining personnel, and risking damage to luxurious equipment and tools.
Alternatively, if polyethylene piping like Maxair were ever to flop – or Aluminum or Stainless Steel for that matter – it would never be an issue as they’re all ductile materials.
Ductile material can be twisted and not broken – let your mind wander toward paperclip. A fragile material snaps and breakdown when you try to bend it. Again, let your mind wander toward matchsticks.
If PVC is so dangerous, why do people use it in compressed air piping systems?
I guess it’s because, at first glimpse, it looks perfect for the job. It is strong, low-cost, freely available. It is corrosion-resistant and very easy to install.
Some people have said that; perfectly sealed brand new PVC pipes are not as dangerous as the older PVC piping.
However, the major issue is that, in the long run, the plastic can oxidize, crack and smash to smithereens.
The ruin is also worsened by air compressor oils within the line, and the heat emanating from the compressed air.
If you are considering using PVC pipe of any kind for plumbing your compressed air, please visit the company’s web site to check on whether they recommended the use of their pipe for compressed air service. Odds are they will not, and so you should not use PVC to plumb air.
If I were plumbing air lines for my home workshop again, I would rather use sweated copper pipe or RVC (rubber vinyl compound air line hose) than plastic. Anytime.
An earlier blog commented on how I wouldn’t use plastic pipe (except for P.E. (polyethylene) and urethane tube). That blog got lots of attention.
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Even though the pressure rating for smaller diameter PVC, CPVC and PVDF may appear to suit the pressure requirements for compressed air, they are not approved for that use.
If we have to sing it like a broken record, we will so you can understand the gravity of what you are doing. By using PVC piping with compressed air, you’re setting yourself up for failure.
Using PVC piping is a dangerous choice because it can easily explode if it’s put under a certain level of stress that it can’t handle. There have been several cases of this happening within compressed air applications, therefore OSHA does not permit the conveying of compressed gases in above-ground applications
Another major problem you need to focus on when you’re using PVC piping with air compressors, is the leakage aspect. It is easy to set up PVC pipes incorrectly. Sometimes, the PVC cement isn’t given sufficient time to settle, or the thread sealant may not be applied correctly. These errors are hard to duck when using PVC and can extremely compromise a compressed air structure.
A third issue with using PVC for transporting compressed gases is the temperature problem. PVC pipe is plastic, for that reason alone, it is more vulnerable to constitutional alterations from external temperatures. When exposed to cold temperatures, PVC pipe can become fragile and shatter easily than it customarily would, so compressed gases shouldn’t pass through it.
What confuses numerous people considering the use of PVC pipes with compressed air is the psi rating. Most air compressors compress air between 125-175 psi, which doesn’t sound like much. Smaller sized PVC pipes are evaluated to be between 300-600 psi, then again, that’s only if the pipes are brand new and the system is impeccably sealed.
If a plastic pipe fails, it may shatter, with catastrophic results.
If you are using plastic to plumb your air, or if you are considering doing so, may I suggest that you contact the pipe manufacturer and ask them if they will sanction the use of their pipe for plumbing compressed air? And keep a copy of the documentation, just in case.
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