Compressed Air Line Question

[ray66v]

As far as the hype goes, I was injured by a PVC air line failure.

You can't just say, it's rated for "x" pressure, I'm below that, so I'm good.

First, with PVC, temperature is a big factor. The pressure rating drops fast when you heat the pipe. Compressed air can get very hot.

Secondly, the pressure rating is for water, which basically doesn't compress. Air does, that is a different kind of load, and a different test.

Third, there are oils, and other contaminates inhaled by your compressor that effect the integrity of you pipe.

Yes, if you have had to deal with it as I once did, you can figure out how to make a PVC system that is reasonably failure proof.

But, why? PVC isn't cheap anymore, especially SCH 80, and their are lots of great alternatives.

It's not worth it.

 

[ultrarunner]

If you want to risk it make sure nothing is exposed... not even a fitting.

All pipe is concealed in a wall or fully underground.

A lot of people now use oil less compressors which would eliminate one of the problem areas.

Still might have a vibration problem depending on how plumbed and type of compressor.

Just note the install would be off label should there ever be a problem...

 

[Sprinklerman]

Tha'ts why I said I will use Schedule 80, not 40. 3/4" is rated at 690 PSI.

That's a 5.5 times safety margin over my system pressure (125 PSI). I think that's probably good enough for an underground run.




Intermittent pressure is a whale of a different animal than constant pressure, and you are only introducing 100 psi into an open pipe, not closing the system and holding 100 psi in the pipe, and your air is cold when it's blowing through that pipe.

I am quite aware of thet , but there are times when the system is closed and it gets pressurized .

 

[Handloader109]

If I could get pvc cheap enough to warrant it's use, and I put it all over a foot underground, I might use it. Oil, heat, pressure and uv radiation will ultimately make it fail. Much sooner than you think and with zero warning. Use at your own risk. I'd use black pipe if it were me and I was going to bury it.

 

[TemporaryKubotaOwnerMark]

Third, there are oils, and other contaminates inhaled by your compressor that effect the integrity of you pipe.

PVC is used for diesel and oil applications.

And for a 200' run, it's far cheaper than any of the alternatives.

Oil, heat, pressure and uv radiation will ultimately make it fail.

There's not a lot of UV radiation 2 feet underground. Last time I checked, anyway. And as mentioned above, PVC is used for diesel and oil applications, so no problem there.

I think your black pipe will rust through long before buried PVC will fail.

 

[bigtiller]

We haven't heard from the OP since he asked his question. I hope he heard the warnings about PVC. I'd hate to see anyone get hurt from following advice given on TBN.

 

[ray66v]

PVC is used for diesel and oil applications.

Are you trying to suggest that it's safe to use for compressed air, because it's used for some oils?

To draw the conclusion, that because one has been done, the other is no problem, is a big leap.

Oil from a compressor, is contaminated oil. It contains, among other things, anything the compressor inhaled. This can include volatile compounds like acetone, and toluene, which are commonly sprayed in paint, and are known to damage plastics.

I have seen the effect of this, as well as been injured by a PVC air line failure.

I would be very interested in an application, where they suggest the use PVC for oil, or diesel, at pressures exceeding 100 psi, which would be common in compressed air.

PVC was never rated for compressed air, has been proven to be unfit for that purpose, and is outlawed for good reason.

Some people like to take unnecessary risks. Have at it. But, don't try and suggest it isn't a risk. That's been settled a long time ago.

 

[k0ua]

I never done it but how difficult is it to use a pipe threader?
HF has them for $75.

It is not difficult, but you need a pipe vise as well. It helps to have two people, one to thread, and one to drip lubricant and add a hand on the pipe vise.

 

[k0ua]

Are you trying to suggest that it's safe to use for compressed air, because it's used for some oils?

To draw the conclusion, that because one has been done, the other is no problem, is a big leap.

Oil from a compressor, is contaminated oil. It contains, among other things, anything the compressor inhaled. This can include volatile compounds like acetone, and toluene, which are commonly sprayed in paint, and are known to damage plastics.

I have seen the effect of this, as well as been injured by a PVC air line failure.

I would be very interested in an application, where they suggest the use PVC for oil, or diesel, at pressures exceeding 100 psi, which would be common in compressed air.

PVC was never rated for compressed air, has been proven to be unfit for that purpose, and is outlawed for good reason.

Some people like to take unnecessary risks. Have at it. But, don't try and suggest it isn't a risk. That's been settled a long time ago.

The people that make the stuff tell you not to use it for compressed air. A simple google search will find plenty of pictures and articles

Can PVC or CPVC pipe be used for compressed air lines? | US Plastic Corporation

 

[ray66v]

It is not difficult, but you need a pipe vise as well. It helps to have two people, one to thread, and one to drip lubricant and add a hand on the pipe vise.

It's not difficult to thread pipe.

The problem is, the sch 40 pipe is all made in China now. And, it's junk.

It is really hit and miss. One piece threads okay, the next is hard, and the threads tear. It's especially difficult to thread by hand.

If you are only doing a small amount of threading, it's often a lot easier, and cheaper, to take the few pieces you need to thread, to the hardware store, and let them suffer with it.