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.

 

[ultrarunner]

Here is a quote for what I posted about being underground and/or encased.

The Plastics Pipe Institute recommends against the use of thermoplastic pipe to transport compressed air or other compressed gases or the testing of such piping with compressed air or other compressed gases in exposed above ground locations, e.g. in exposed plant piping. It is recommended that all thermoplastic piping used to transport compressed air or other compressed gases be buried underground or encased in shatter-resistant materials. In designing thermoplastic piping to transport compressed air or other compressed gases, the strength at the operating temperature, the pressure, the energetics, and specific failure mechanism need to be evaluated.

And here is the Government Link

https://www.osha.gov/dts/hib/hib_data/hib19880520.html

 

[SPYDERLK]

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.

So the air is the more benign load because there are no pressure spikes. Lets not confuse things. -- The problem arises elsewhere. ... Oil, inherent brittle failure mode, stored energy.

 

[ray66v]

So the air is the more benign load because there are no pressure spikes. Lets not confuse things. -- The problem arises elsewhere. ... Oil, inherent brittle failure mode, stored energy.

I guess you don't realize, that compressed air systems often have large ball valves, that can be, and often are fully opened rapidly, when starting systems in the morning, or after maintenance, creating pressure spikes.

If you don't want to confuse things, how about focusing on the opposition?

 

[downsizingnow48]

The shop in Mendocino county had fixed air lines installed by the previous owner. Mix of plastic and galvanized. Steel and plastic valves. All the steel valves were rusted because no drops were used. I tried all the plastic valves one was stiff and cracked off in my hand. I ripped out all that mess and just use air hose. I have five 50' Goodyear hoses now decades old never a problem.

 

[SPYDERLK]

I guess you don't realize, that compressed air systems often have large ball valves, that can be, and often are fully opened rapidly, when starting systems in the morning, or after maintenance, creating pressure spikes.

If you don't want to confuse things, how about focusing on the opposition?

Spikes are much quicker than that - a faster rise time. ... Like what happens when flowing water in a pipe is stopped suddenly. Happens everytime you turn off a faucet, but more from solenoid valves in washing machines, dishwashers, etc. ... Still confused?

 

[ray66v]

I have five 50' Goodyear hoses now decades old never a problem.

I always buy Devilbiss rubber hoses. At least one of them is 30 years old.

If you don't burn holes in them, and drive over them everyday, they last a long time.

 

[ray66v]

Still confused?

I wasn't confused to start with.

 

[Gary Fowler]

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 isn't difficult to turn a pipe threader, but I cant count the number of leaks I have encountered when testing threaded pipe installed by professional pipe fitters. You need high quality dies and good cutting oil to make good threads and then properly tightened, not too tight as to damage the threads but tight enough to not leak which takes a bit of experience to get it right.
You also need to use schedule 80 pipe because if using schedule 40, the threading cuts away over half the wall thickness which leaves a very weak joint.
If I were using black iron, I would go with socketwelded connections rather than threaded. They are quicker to make if you have a welder and are proficient at using it and repairs (if it has a leak) are pretty easy to do. A threaded joint has to have a union installed in order to tighten a leaking joint which makes 2 more joints that may need to be repaired.
The easiest would be to use copper pipe and silver soldered joints which are pretty easy to do. Fab up your runs so that any welds to be made in place would be with the joint vertical and facing up, it is much easier to make them that way.

I wouldn't use PVC due to its brittle nature after exposure to UV rays AND it is very brittle in extreme cold (32F or lower) which would cause it to fail catastrophically.

 

[SPYDERLK]

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.

So the air is the more benign load because there are no pressure spikes. Lets not confuse things. -- The problem arises elsewhere. ... Oil, inherent brittle failure mode, stored energy.

I guess you don't realize, that compressed air systems often have large ball valves, that can be, and often are fully opened rapidly, when starting systems in the morning, or after maintenance, creating pressure spikes.

If you don't want to confuse things, how about focusing on the opposition?

Spikes are much quicker than that - a faster rise time. ... Like what happens when flowing water in a pipe is stopped suddenly. Happens everytime you turn off a faucet, but more from solenoid valves in washing machines, dishwashers, etc. ... Still confused?

I wasn't confused to start with.

Good, then I will just deal with statements you make that could lead others into a misunderstanding of pertinent physical issues and how they relate.

 

[Scrambler82]

I thought I had posted to this thread but looking at all of the posts again indicate a no !

I am not sure of pricing but the easiest by far to install and it is durable is Air Hose.

Maximize your runs to save on hose but it will last for a long time.

I installed 300 psi hose in my shop over 15 years ago and it has never had a major leak, never failed, never exploded, was easy to install and the only hard pipe was at the outlets.
Oh ya, no rust coming out of the air lines too !

I used 3/4" but there is a lot of sizes depending on air volume needed. A 3/4" or 1" main line and tap off of it for outlets !

Even if the air hose, in the size you want, is a little more expensive, the extra cost will be off set by the ease of install.

You can use the air hose as a vibration isolator for the compressor to.

Compare pricing, compare ease of install, and decide.

Oh ya, when draining the water from your system, use the air in the system to blow out the lines. By adding a ball valve at the end of the main line and on a branch line or two you can bleed off most of the water in your system.
AND, the rubber hose does not create as much moisture as iron or copper or even plastic so the will be less water in the system and remember to drain the tank at night or after each use.