Compressed Air Line Question

[ray66v]

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.

Enjoy.

 

[Scrambler82]

This stuff looks interesting... From Northern Tool !

http://www.northerntool.com/shop/to...ontent=20921&gclid=CInPy8TY5M4CFQmRfgodK-UP0g

 

[TemporaryKubotaOwnerMark]

Northern tool is not Harbor Freight.

 

[TemporaryKubotaOwnerMark]

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

Safety and Health Information Bulletins | The Use of Polyvinyl Chloride (PVC) Pipe in Above ground Installations

There ya go.

 

[PILOON]

Re diesel and PVC,
I used some re-enforced clear PVC as a fuel line to fuel my tractor as I liked the flexibility.
Within a month I could have used the PVC as a fishing pole it got so hard and stiff.
Looks like there is a reaction between PVC and fuel.

 

[Deere Dude]

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.

They might be professional, but they must really suck at it.

If the threads are fair to midland a good Teflon paste will seal it up as will LocTite 242. Tape is iffy.

Sch. 80 pipe should never have to be use for light air. Sch. 40 is much cheaper and works fine. The only sch. 40 that failed on us is when an air drop is hit with a fork lift or a scissors lift or some other man caused problem. that shears them off, but the same would happen with sch 80.

 

[SPYDERLK]

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

Safety and Health Information Bulletins | The Use of Polyvinyl Chloride (PVC) Pipe in Above ground Installations

I use black poly which does not present the shattering problem. --The thicker wall, rated ~ 200psi.-- But still only for feeds to the work area - not in the work area. I do have a 4' section above ground in a corner in the heat in the barn. Its only 160psi rated at 70F. Its been fine running at 150 PSI for 17 yrs.

 

[TractorGuy]

I did hear of a guy getting thrown off a ladder by driving a nail through a PVC air line. You can't protect from stupidity.

I ran 3/4 schedule 40 PVC in a shop and never had any trouble with it. It's rated for 480 PSI.

JM eagle 3/4 in. x 1 ft. PVC Schedule 4 Plain-End Pipe-57471 - The Home Depot

 

[ray66v]

Northern tool is not Harbor Freight.

I've been telling my mother that, for 20 years!

I finally gave up.

 

[Stimw]

Here is an option, DOT Air Brake Tubing- Velvac 1 2 Blue Nylon Air Hose Tubing Dot Approved 1 Foot Roll 4deg to 2degF | eBay
It's easy to attach standard fittings you just have to use brass inserts. When you compress the ferrel it clamps the hose to the insert.
There is over a million feet of it in use, just look when a semi goes past! this is what is used for tractor and trailer air lines. Hoses are used from frame to axles.

 

[Scrambler82]

Northern tool is not Harbor Freight.

I've been telling my mother that, for 20 years!

I finally gave up.

What are you guys talking about !

LoL !

Now if you had said,"it is only good to 175 psi", I would have said ok you got me !
There 190 psi rated tubing kit... is $1000.00, now that is a reason not to use it too !

 

[Redneck in training]

Hi,
I'm moving soon and will want to run some air lines in my garage and basement. Thinking of putting the compressor in the garage and would like a couple of ports and a hose reel. Then run a line to the basement for some light duty work... airbrush, blowing saw dust etc.

I've been reading up on the topic and have some questions about what material to use...

PVC - Cheap, easy to work with. Not recommended for air, but people use it anyway.
Copper - More expensive. Not as easy to work with, but I am comfortable with cutting and soldering. Don't think it's rated for air, but at least it won't shatter like PVC if it fails.
Iron pipe - More expensive and hard to work with (assuming I need to cut and thread odd lengths).
Air hose - Cheap, easy to work with. May need to use something rigid near the ports to stabilize the connectors.

I'm tempted to run 1/2" air hose for the long runs from the compressor across the garage and into the basement, then end the runs with short copper "L" sections to the quick connector. What do you think?
Would I need to purge the pressure in the air hose when not in use?
Would copper be better in the long term?

What have you done in your shops and garages?
Thanks,
Doug

Google Rapid Air. It is easy to install.

 

[ray66v]

What are you guys talking about !

LoL !

Apparently, we have no idea.

 

[TemporaryKubotaOwnerMark]

The only sch. 40 that failed on us is when an air drop is hit with a fork lift or a scissors lift or some other man caused problem.

How many times do I have to tell you??? It's not forklift rated!!!!

 

[KennyG]

This thread is getting pretty well exhausted, but I would like to clarify a couple of things from a Mechanical Engineer perspective.

PVC pipe is subject to unpredictable aging problems but, even when new, it can shatter on impact when pressurized and metal piping will not do this. There is a basic difference between gas and liquid service such that pressure ratings cannot be the sole basis. Liquid, being relatively incompressible, will immediately depressurize with a failure. Gas, because it expands, maintains a higher pressure and has much greater potential for "explosive" failures. This, combined with the PVC brittle shatter behavior, is why it can't be used in exposed locations.

PVC is OK to use for gas service underground. Depending on the environment it may last longer or shorter time than metal. I doubt I would choose it but it's not a safety problem when buried.

Schedule 80 is not justified for air service unless your primary concern is forklifts, etc. Schedule 40 steel pipe in the sizes we are discussing has a code allowable of over 200 psi at room temperature. The actual burst strength is more like 2000 psi. Properly threaded fittings are only slightly less capable than the pipe itself. I've never seen a threaded fitting fail (break) from pressure, only from impact or external force. I'm not a professional pipefitter, but I've threaded a lot of water and natural gas piping and the only failures I've had is when I threaded a pipe too far and damaged a valve.

 

[SPYDERLK]

This thread is getting pretty well exhausted, but I would like to clarify a couple of things from a Mechanical Engineer perspective.

PVC pipe is subject to unpredictable aging problems but, even when new, it can shatter on impact when pressurized and metal piping will not do this. There is a basic difference between gas and liquid service such that pressure ratings cannot be the sole basis. Liquid, being relatively incompressible, will immediately depressurize with a failure. Gas, because it expands, maintains a higher pressure and has much greater potential for "explosive" failures. This, combined with the PVC brittle shatter behavior, is why it can't be used in exposed locations.

PVC is OK to use for gas service underground. Depending on the environment it may last longer or shorter time than metal. I doubt I would choose it but it's not a safety problem when buried.

Schedule 80 is not justified for air service unless your primary concern is forklifts, etc. Schedule 40 steel pipe in the sizes we are discussing has a code allowable of over 200 psi at room temperature. The actual burst strength is more like 2000 psi. Properly threaded fittings are only slightly less capable than the pipe itself. I've never seen a threaded fitting fail (break) from pressure, only from impact or external force. I'm not a professional pipefitter, but I've threaded a lot of water and natural gas piping and the only failures I've had is when I threaded a pipe too far and damaged a valve.

:thumbsup: ... Thank you for bringing it all together well and cohesively. This is what the thread should be built from.

,,,,,,,,,,,,,,Anybody have a question to clarify some area?

 

[bspeedy]

Rapidair 95 Master Kit, 1/2-Inch x 1-Feet - Air Compressor Accessories - Amazon.com

I've been using this kit for a couple of years now in an un-heated and un-cooled shop. 100% satisfied. Quality product, good price, good volume for running air tools. For what it includes for the money you can't go wrong. And it looks cool.

 

[ray66v]

Liquid, being relatively incompressible, will immediately depressurize with a failure. Gas, because it expands, maintains a higher pressure and has much greater potential for "explosive" failures.

Thank you for putting that well enough, for everyone to here to understand.

 

[Dougryan]

WOW! Thank you all for a ton of information to consider. There are definitely some strong opinions on PCV. Comes down to risk exposure for me... Probability x Impact = Exposure.

PVC might have a low probability of failure, say 1 out of 10... But the impact of a failure is high... exploding plastic pieces, that's a 10 out of 10 for me.
1 x 10 = 10.
Versus using air hose or copper or steel pipe. Probability of failure is still low, 1 out of 10. But the impact is low too, maybe 2 out of 10.
1 x 2 = 2.

Right now I'm thinking I'll put a quick connect on each side of the garage door (inside) and a spool in the center at the back of the garage. Then run a single line to the basement with another spool. I'm going to use rubber air hose to all 4 outlets. Hose right into the spools. Hose to some type of copper creation for the quick connects at the garage door.

I'll post some pictures after the move with some details about my project.

Thank you all for the great information and examples from your home and business experiences.
Very much appreciated.
Doug

 

[dstig1]

This thread is getting pretty well exhausted, but I would like to clarify a couple of things from a Mechanical Engineer perspective.

PVC pipe is subject to unpredictable aging problems but, even when new, it can shatter on impact when pressurized and metal piping will not do this. There is a basic difference between gas and liquid service such that pressure ratings cannot be the sole basis. Liquid, being relatively incompressible, will immediately depressurize with a failure. Gas, because it expands, maintains a higher pressure and has much greater potential for "explosive" failures. This, combined with the PVC brittle shatter behavior, is why it can't be used in exposed locations.

PVC is OK to use for gas service underground. Depending on the environment it may last longer or shorter time than metal. I doubt I would choose it but it's not a safety problem when buried.

Alright...I tried to stay out of it... The big issue is a physics one, and it is not trivial. It comes from fluid dynamics. First point has been well covered: gasses vs liquids. Gasses are compressible, liquids are not, so there is a lot of potential for a big explosion when something gives way with a compressed gas vs compressed liquid at these pressures (spare me your stories about 10,000 psi hydraulic systems in jetliners - yeah, they are seriously dangerous if they fail). The other is what people don't quite get because it does not quite make obvious sense. Pressure is not pressure. At least not quite. The forces exerted are dependent on the pressure AND the VISCOSITY of the "fluid" in question. The lower the viscosity, the higher the forces at a given pressure. This is the second reason why air does not equal water in these systems. Viscosity of a gas is generally far lower than any liquid, so that adds to the issue. The PVC pipe might be rated for 200 psi water, but that does not mean 200 psi air is OK. In fact it is probably not. Thus all the OSHA warnings you have seen in this thread. Yeah if you want to bury PVC it won't pose a safety hazard, though it still may not last. Don't ever use PVC in an exposed shop application for compressed air. It just isn't worth it. Even good old regular PEX tubing is far safer. Polyethylene is pretty resistant to most solvents and oils. Crosslinked PE (aka PEX) is even more so. That is the cheap and easy route. Me? I used Type L copper. I work at a Fortune 100 R&D/mfg company and they use it for all labs and plants for compressed air. If they are OK with it, I am OK with it for my home. It ain't that hard to work with and is not really that expensive given the lifetime it will be in service.

YMMV, IANAL, etc.