Compressed Air Piping

[dcyrilc]

I put PVC in my shop 20 years ago. I ran it on top of the 2x6's for the outside wall of the pole barn. This allowed me to turn the corners. My walls were then insulated and finished. The first winter, I was using a nail gun and one of the corner joints burst as a result of the cold and slamming of the air from the rapid discharge of the air gun. The broken pipe is still inside the walls. Since then, I've just dragged an air line around the shop. I intend to pipe it again, but no PVC this time. I don't like things that break. I'm just now learning about the explosion hazard, but it makes sense. This time I plan to have it exposed so that it can be worked on. After my past experiance with PVC and reading this thread, now it is double NO to PVC for me.

 

[dcyrilc]

I 'd like to Thank those types of people for providing me with job security.

I won't be one of them. I'ld love to meet ya, but not professionally!!

 

[ray66v]

They way I see it, if you feel comfortable with PVC go for it. I think we are all aware of the danger. Some of us dont wear seatbelts, smoke cigarettes, and eat cheeseburgers from McDondalds. It's all a matter of what you feel safe with.

It's not the same as eating a cheeseburger. Those are risks that have a very low probability of immediate harm.

I was "comfortable" with it once, about 25 years ago, before the mountain of evidence of how dangerous it was.

I learned the hard way what can happen.

Anyone who "feels" comfortable with pvc air pipe is only doing so out of ignorance. There is no such thing as safely playing with a loaded gun.

To those who would rather ignore this advice: If a bystander like a friend, wife, or a child, gets injured, maybe loses an eye as a result of an unnecessary risk that you decided to take, good luck feeling comfortable with that.

 

[LRTX1]

It's not the same as eating a cheeseburger. Those are risks that have a very low probability of immediate harm.

I was "comfortable" with it once, about 25 years ago, before the mountain of evidence of how dangerous it was.

I learned the hard way what can happen.

Anyone who "feels" comfortable with pvc air pipe is only doing so out of ignorance. There is no such thing as safely playing with a loaded gun.

To those who would rather ignore this advice: If a bystander like a friend, wife, or a child, gets injured, maybe loses an eye as a result of an unnecessary risk that you decided to take, good luck feeling comfortable with that.

The point I was trying to make is everything is dangerous. I know that a cheeseburger wont injure you as quick as a busted PVC pipe. Although the end result might be the same. It is a risk that has be known after lets say the first or second reply. Obviously this is not a risk you would take, and I never once suggested that you take that risk.

Again, if one is "Ignorant" to do so after lets see the first or second reply let them do it.

To me it is no different than telling someone to go ahead and build a bridge if their engineering skills have not let them down so far! That might qualify as an immediate harm type of thing if one was not quite the engineer he thought he was....

 

[Egon]

cheeseburger wont injure you as quick

Sure it could if you choke on it!

 

[greasemonkeyok]

I have galvanized pipe carrying air to a pig in my garage, with a flexible rubber hose link to the compressor. But, I might have used PVC if the galvanized pipe hadn't been available.

That said, I appreciate this discussion because it raises awareness of safety issues that were not taken into consideration when the system was installed. I have learned a lot trolling around this BB.

Thank you.

 

[Raindem]

I feel the simplest is surface-mounted sweated copper. And of course, as said before, slope it all backwards to the compressor for easy draining.

I have heard of systems designed both ways, sloping towards the tank or away from it, with accompanying arguments for each. Some say sloping it to the tank makes it easier to drain. Others say sloping it away from the tank helps keep the tank dry and puts the moisture in the traps where it belongs (assuming you've designed a moisture trap into each of your drops).

Is the consensus here to slope it back towards the tank?

Great discussion BTW.

 

[radioman]

ok - if using metal piping like gavlanized pipe is an issue with rusting and ruin a paint job, how do you "clean compressed air" before it exits ? All I know is air driers jusst removes moisture from compressed air. I have one from HF in at connection of air hose and this winter I couldn't use my air due to forgotten to remove the water from drier and it froze !! Had to switch hoses around to use air directly without drier to do what i was doing. How do I prevent this from happening in a unheated garage?

 

[CurlyDave]

Is the consensus here to slope it back towards the tank?

I don't think it makes any difference.

The reason is that any substantial use of air will cause flow rates that entrain water and anything else in the pipe. You need to trap & dry this out of the air before you use it for any critical application in any event. You need a trap & drier at the air outlet no matter which way the lines slope.

The tank is going to collect water because the compressor compresses both air and the water vapor in it. If the relative humidity of the atmospheric air is over 10-15% water will always condense in the compressor tank, and this water must be drained out periodically.

Bottom line is you have to remove water at both ends of the line.

How do I prevent this from happening in a unheated garage?

I don't think you can prevent it. I would think you could melt the water with an electric space heater and cure the problem in an hour or two.

You could also try a hair drier or heat gun, but I know that if I did that I would want to go too fast and overheat the air drier...

 

[eazyduzzit]

You could use the plastic tubing that is used on class 8 trucks for air brakes. I've been selling truck parts for 30 years and the tubing used hasn't changed in all those years. I've never heard of a failure unless something cut it or it was in a fire.

I'm using it in my garage. Brass fittings are available to adapt it to normal pipe thread sizes, so you can use regular quick disconnect fittings at the termination points or anywhere along the length.

 

[radioman]

thanks curly dave- i thought of using the hair dryer triuck but its a plastic housing, last thing i need is a melted unit. I just simply didnt have the time to stand there and watch it melt. Anyways it finally melted duing the mini january thaw, but I am afraid of it filling up and freeze again over the winter.

 

[spo307]

what about schedule 80 pipe, grey not the white stuff, its meant for direct bury in the ground, so it should be able to hold air pressure.

 

[wedge40]

I'm guessing most of the reason for choosing one method over the other is Co$t. Those on tight budget will use PVC, those who just won the lottery will use copper. I looked at HD yesterday and there was a big difference in price between PVC and Galvanized. Not so much between Galvanized and Copper.
I figure when the time comes if I can plumb my air for 1-2 hundred that wont be too bad.

Wedge

 

[Redneck in training]

PEX is good for 160 psig at 73 F, 140 psig at 110 F etc. Burst pressure is about four times as much. PEX doesn't shutter. I think PEX would do fine in shop air installation. I have some leftovers from my heating installation and I will definitely use it for compressed air. Google REHAU for more info.

 

[ray66v]

I think PEX would do fine in shop air installation.

If it would do fine, the manufacturers would have gotten the rating, so that it would be approved for air.

Some people have used pex sucessfully.

Three short comings for Pex that I have noticed of are: Compressed air can get much hotter than the working pressures can allow. Pex is not supposed to be exposed to UV light once installed. Pex is very hard to get to lay flat in horizontal installations, so the condensate water can be drained out of the system.

 

[ray66v]

what about schedule 80 pipe, grey not the white stuff, its meant for direct bury in the ground, so it should be able to hold air pressure.

Sch 80 pvc is stronger, but also more expensive, and still not rated for compressed air. Pressure is not the only issue.

 

[ray66v]

I'm guessing most of the reason for choosing one method over the other is Co$t. I looked at HD yesterday and there was a big difference in price between PVC and Galvanized. Not so much between Galvanized and Copper.

Wedge

Black iron is about half the cost of galvanized, and around here is pretty much all anyone uses.