Compressed Air Line Question

[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.