Compressed air piping discussion.

[rustybronco]

As I really don't know where to place this and because off topic threads disappear after a certain length of time, I've decided this is the best place for it.

Mod's please move this post if you feel that it more appropriate elsewhere.

This post is a result from an attempt to remove moisture from the discharged air of my air compressor.

I had made a moisture condenser out of 1/2" NSF-PW 600 p.s.i. pressure rated PVC tubing but because of it low thermal conductivity it might not be the best choice of materials. There is also the matter of having to be de-rated for higher and possibly lower temperatures. (de-rating factor of .22 @140? F--- 600psi rated pvc de-rates to 132 psi)

http://www.exair.com/en-US/Primary Navigation/Knowledge Base/Air Data/Pages/CompressedAirPiping.aspx

Copper piping brings it's own issues such as solder joints not holding up under pressure. Obviously copper is one of the better materials to use for conducting heat, but it to is de-rated heavily when using 50/50 solder and the working temps are at or above 150 degrees. http://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf

You could use a 95/5 Tin Antimony solder on the copper's connections and the pressure rating will be in the 625 psi range when using 1/2" copper tubing or use a 15?% silver brazing rod but I suspect the normal garage mechanic may not have access to sufficient heat to make sound joints when using silver brazing rod. (mapp? oxy-act).

I'll see if I can get some temperature readings at the outlet of my air compressor and the inlet of my water separator using a PVC condenser under 'my' normal usage conditions.

(The ultimate question will be, is PVC or copper piping good enough or are we relegated to using black or galvanized pipe?)

 

[Guest]

If you want thermal conductivity then copper is by far your best choice, but I expect you already know that.


Mark

 

[rustybronco]

Mark, I do know that, but will a PVC condenser transfer enough heat to condense moisture out of the air, given the intermittent duty of an air compressor under normal home usage requirements? That is the question I'm looking to find out.

When I've used rubber hose in the past to connect my compressor to my air tools, moisture always condensed at the discharge port of the tool on relatively humid days. Considering air hoses are made from PVC or rubber which have fairly close thermal conductivity characteristics, will it matter? Copper brings it's own issues when used under pressure, but I'm getting ahead of myself.

 

[The Artful Bodger]

I've made two condensers for my compressor (only one used at a time), one from plastic pipe (origin unknown) and one from 10 mm soft copper pipe with the fittings lead soldered on the ends. Both of these are basically the pipe coiled and fitted inside a fire extinguisher (with the top cut off) which is filled with water. The dia. of the inside of the coils is enough for a 2 liter plastic milk bottle to be slipped inside. The milk bottle can be filled with water and frozen if extra cooling is needed. The water trap / pressure reg. follows the condenser.
I run my compressor at 120 psi and have had no issues of any kind with either condenser after several years of use, either condenser increases the amount of water I collect in the trap by more than 10 fold!! When I'm sand blasting on a humid day I have to remember to empty the water trap every hour as it's full. I paint and powder coat from this air supply and have had no water issues.
Colin

 

[rapidray]

Air lines should not EVER be made from PVC tubing!!! I have seen the aftermath of them letting go & I kid you not, they can KILL people!!! Copper is the best bet & I have no problem making solder joints hold 150 psi water pressure all the time.
Ray.

 

[tatu]

usually compression fittings do the job, what it the max pressure of the compressor?

I use compression fittings on mine and they working up to 2500psi on 25mm stainless tube.

 

[Guest]

The best way is to fit an air dryer to the compressor then fit air line on out feed of this, they can be expensive though.
Alternatively you could obtain a large self draining filter regulator?

 

[dorkburger]

Ive been in many facilities using copper for their production air, especially if they need a "clean" supply. Ill keep an eye out to see how the pipe is joined (soldered or brazed).
Mapp gas with a good tip is plenty of heat to braze 1/2" copper.

 

[rustybronco]

Air lines should not EVER be made from PVC tubing!!! I have seen the aftermath of them letting go & I kid you not, they can KILL people!!! Copper is the best bet & I have no problem making solder joints hold 150 psi water pressure all the time.
Ray.

Ray, air lines on semi's are plastic. NSF-PW is rated 600psi @ 73? F (de-rated .22 @ 140?F) Do you know for certain the correct materials were used and within the temps as spec'd?

usually compression fittings do the job, what it the max pressure of the compressor?

I use compression fittings on mine and they working up to 2500psi on 25mm stainless tube.

In my case I have the max pressure set at 105 psi (7.23 bar) I like my compressors to live as long as possible. (aluminum single stage compressor)

Ive been in many facilities using copper for their production air, especially if they need a "clean" supply. Ill keep an eye out to see how the pipe is joined (soldered or brazed).
Mapp gas with a good tip is plenty of heat to braze 1/2" copper.

IIRC when I soldered my A/C lines I had a hard time with MAPP on 3/4" copper. I suspect 1/2" can easily be hard soldered with MAPP on a conventional hand held 'torch head'.

I've made two condensers for my compressor (only one used at a time), one from plastic pipe (origin unknown) and one from 10 mm soft copper pipe with the fittings lead soldered on the ends. Both of these are basically the pipe coiled and fitted inside a fire extinguisher (with the top cut off) which is filled with water. The dia. of the inside of the coils is enough for a 2 liter plastic milk bottle to be slipped inside. The milk bottle can be filled with water and frozen if extra cooling is needed. The water trap / pressure reg. follows the condenser.
I run my compressor at 120 psi and have had no issues of any kind with either condenser after several years of use, either condenser increases the amount of water I collect in the trap by more than 10 fold!! When I'm sand blasting on a humid day I have to remember to empty the water trap every hour as it's full. I paint and powder coat from this air supply and have had no water issues.
Colin

Similar idea as those who have coiled rubber air hose inside a 5 gallon pal filled with ice water. I read that it works rather well at condensing out moisture.

 

[rustybronco]

1/2" SCH 80 is rated at 850 psi @ 73?F de-rated to .22 @140?F just like SCH 40 is. That equates to 187 psi @ 140?F

 

[posplayr]

1/2" SCH 80 is rated at 850 psi @ 73?F de-rated to .22 @140?F just like SCH 40 is. That equates to 187 psi @ 140?F

I would guess the fittings would be most suspect, and you would only want to use threaded fittings (carefully glued). Even then there is nothing that says you could not easily shear off a fitting end where copper might bend avoiding catastrophe.

 

[rustybronco]

Jim, from what I've read, PVC threaded fittings are to be de-rated 50%. If it were me, I stick with correctly glued fittings. But I'm far from an expert on plastic piping.

 

[posplayr]

Jim, from what I've read, PVC threaded fittings are to be de-rated 50%. If it were me, I stick with correctly glued fittings. But I'm far from an expert on plastic piping.

Not sure if you ever pay any attention to this type of stuff.

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




Assorted views on the subject

http://www.practicalmachinist.com/vb/general/ruptured-pvc-air-lines-what-not-do-230253/

 

[rustybronco]

Jim, I had came across that article or something similar to it in my snooping around. I would hazzard a guess that about puts an end to using PVC for compressed air applications.

On to M (L-K?) copper air line systems.

 

[dorkburger]

Quick note. If brazing copper without a nitrogen purge, the flaky black oxidation on the outside of the pipe will be inside as well.
Most can be blown out, but not necessarily all.

 

[rustybronco]

When I hard soldered my A/C lnes I used helium as the inert gas. CO2 and argon can be used in addition to nitrogen. I wonder how easily the internal scale can be removed with compressed air or by flushing with water?

 

[dorkburger]

I would think that would get most of it. Ive blown it it out with air after brazing together short pieces/fittings.

 

[SVSooke]

I had convinced myself to do a PVC like Dales.The feedback from this thread has me reconnoitering that.Cooper or steel?I don't really like the idea of getting steel wet:nightmare:

 

[bccap]

I've always been partial to copper myself Greg.......

 

[rapidray]

Jim, I had came across that article or something similar to it in my snooping around. I would hazzard a guess that about puts an end to using PVC for compressed air applications.

On to M (L-K?) copper air line systems.

Did you think I just recommended against PVC for no reason?
Ray.