A question arises every now and then on whether or not PVC pipe, yes the stuff from your local hardware store that says it is rated for 200 psi, is safe to use as compressed air supply line. The answer is always the same, NO! OSHA agrees – see their statement here.
Schedule 40 PVC pipe is not designed nor rated for use with compressed air or other gases. PVC pipe will explode under pressure, it is impacted significantly by temperature and can be difficult to get airtight.
PVC pipe was originally designed and tested for conveyance of liquids or products that cannot be compressed, rather they can be pressurized. The largest concern is the failure method of the piping itself. When being used with a liquid that cannot be compressed, if there is a failure (crack or hole) then the piping will spring a leak and not shatter. When introducing a compressed gas, such as compressed air, if there is a failure the method ends up being shrapnel. This YouTube video does a good job of illustrating how the pipe shatters.
While it may seem that it takes a good amount of pressure to cause a failure in the pipe, that is often not the case. I have chatted with some local shop owners who decided to run PVC as a quick and cheap alternative to get their machines up and running.
They each experienced the same failures at different points in time as well. The worst one was a section of PVC pipe installed over a workbench failed where an operator would normally be standing. Luckily the failure happened at night when no one was there. Even though no one got injured this still caused a considerable expense to the company because the compressor ran overnight trying to pressurize a ruptured line.
Temperature will impact the PVC as well. Schedule 40 PVC is generally rated for use between 70°F and 140°F (21°-60°C). Pipes that are installed outside or in non temperature controlled buildings can freeze the pipes and make them brittle.
If you haven’t worked with PVC before or do not let the sealant set, it can be hard to get a good seal, leading to leaks and a weak spot in the system.
The point of this is the cheapest, quick, and easy solutions are more often , the ones that will cost the most in the long run.
If you would like to discuss proper compressed air piping and how to save compressed air on your systems, please contact us.
Image courtesy of: Dennis Hill, Creative Commons License