Diameter of air lines

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On 22 Dec 2003 06:41:22 GMT, snipped-for-privacy@aol.com (Greg) wrote:

A lot of PVC is not UV stabilized. It can get brittle with age and sunlight exposure. There are also different types of PVC, in both plastic formulation and pipe construction. My PVC DC piping is clearly marked "Not for Pressure" all down the side of each tube.
OSHA forbids PVC pipe under pressure. The 'wreck's FAQ has a link to the actual OSHA article about PVC air pipes.
FWIW, installing iron or copper air pipe is really easy. Since you're using flex hose to the tools and compressor, you only need to get into the vicinity. No precision plumbing is necessary.
Barry
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Bob wrote in reply to my post shown below: Group: rec.woodworking Date: Mon, Dec 22, 2003, 5:17am (EST+5) From: snipped-for-privacy@att.net (<<<___Bob___>>>) I HOPE there's not a safety issue with using sweated copper for air .. . .. I just plumbed my whole shop with it !! !! !! What's the danger ?? ?? ?? Sir Edgar wrote: Brian wrote: Group: rec.woodworking Date: Sun, Dec 21, 2003, 8:00pm (EST+5) From: snipped-for-privacy@visi.com (Brian Elfert) My stationary air compressor has a 1/2" NPT fitting for the output. I will be using copper pipe for my air piping. Should I use 1/2" or 3/4" copper pipe for my main lines? The internal diameter of 1/2" copper pipe seems awful small. (Yes, industry does use copper for air piping.) Brian Elfert ********************************************** Please use soft copper tubing and compression fittings no matter what size you choose. Black iron pipe with threaded fittings is also extensively used but requires a pipe cutter and a stock and die. Do not use hard copper tubing and sweated (soldered) fittings. This suggestion is made for obvious safety reasons. Peace ~ Sir Edgar ****************************************************** Bob ~ Sweated copper piping is used for water piping. If a poorly sweated connection breaks loose there is only inconvenience from the possible water damage that occurs. If a joint fails with a pipe containing compressed air it comes apart with explosive force. You can demonstrate this by removing an air hose under pressure that uses a quick disconnect fitting. Also, most copper tubing is type "M" thin wall type which is made for water service only. There is a type "L" wth a thicker wall. If it were my shop I would redo it using the soft copper tubing and compression fittings. I avoided the expense and trouble of running tubing by installing an industrial type spring return hose reel next to my compressor and 50 ft. of hose. I also have an additional 25 ft. of hose that I can attach to it with a quick disconnect fitting if I need to. I did not mention never to use PVC pipe as I assumed the danger of doing this was well known and I am glad to see that it was covered in other posts. I apologize for the length of this post but I feel that it was warranted from a standpoint of avoiding possible injury to a fellow woodworker.
Peace ~ Sir Edgar
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On Mon, 22 Dec 2003 09:50:29 -0500 (EST), snipped-for-privacy@webtv.net (Sir Edgar) wrote:

why? the safety issue isn't clear to me at all. hard copper is probably easier to get a good solder joint with. I cant see rupture or corrosion being an issue with either of them.     Bridger
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Hard copper is often used in industrial settings. It is cost effective because it is cheap to install and if you have to make a cut in a line to add another station, copper fittings are generally much easier to work with than iron pipe.
As with any material, care should be used in installation. Any gas under pressure can have disastrous effects if a catastrophic failure should occur. Copper will not "explode" but would split or a fitting could come loose. Ed
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My copper is all in the attic and wall joists .. .. if something ever came apart, I'd certainly hear it but would not see it. When I finished sweating in the whole system, I charged it to over 200psi and left it for about 6 months. It didn't come apart nor did it leak, at least not after I made a few "repairs". I feel sure that this system is as safe as I can make it .. .. .. I don't plan to ever run more than about 125psi on a routine basis. I don't argue the point that it may be possible for a joint to come apart, but I don't see this ever happening in this particular installation., but thanx for the input. I did use the heavier-walled tubing which was recommended by a structural engineer where I work. We have miles of compresses air lines there and it is almost all sweated copper.

-- I AM NOT PARANOID .. .. .. but EVERYONE thinks I am !! !! !!
<<<__ Bob __>>>
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sweated copper done properly is FINE. I checked with the fire department and others when deciding what materials to use for an auto shop air system. Plastic is a definite no-no. There are three kinds of copper pipe, L, K, and M. Get "L"; it's the thickest.
dave
dave
<<<___ Bob ___>>> wrote:

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..
There is no danger of sweated copper pipes bursting! We often pressure test copper pipe at 300PSI with nitrogen. Copper in R22 air conditioning systems can see 400 PSI with no problems. Systems running R410 can see pressures over 600 PSI. If done correctly there is no danger. Any piping system done INCORRECTly is dangerous! Greg
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... Also with lots of vibration, heat and oil. A failure from a freon line is going to be a lot more explosive than air. Any advice that starts out saying a compression ring and ferrule is superior to a sweated fitting is suspect from the outset. An HVAC contractor would never use a jackleg device like a compression fitting
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mere O-rings contain freon on trillions of vehicles, Greg. A freon line doesn't necessarily have more pressure than a 175PSI air system. Depends on if it is the low or high side and if it is running or not. Different pressures in different "sides" of the system.
dave
Greg wrote:

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Bay Area Dave said:

Hmmm... Correct, to the point, non-inflamatory...
HEY, MISTER! What did you do with Dave. <g>
Greg G.
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I've taken over that miscreant's mind! :)
dave
Greg wrote:

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?? Am I misunderstanding you? Residential and commercial AC systems can and will see pressures over 300 PSI in regular service. More depending on the type of system or if there are problems with the system. I have never seen a burst copper AC line. A cracks perhaps, or worn through from vibration and the line rubbing on something, but never a burst line. Greg
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Greg O said:

Dave was talking automobile AC, but applicable to others as well. Pressure (High) side, yes - 300PSI+. Suction (Low) side - somewhere around 30-50PSI. I think he was being pedantic about the difference between high and low side pressures - both of which are present in an AC system.

Agreed. I HAVE seen auto AC lines burst - the rubber ones. And the occasional metal tubing failure, both copper and aluminum, from fatigue and abrasion.
Just my 2 cents,
Greg G.
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right on.
dave
Greg wrote:

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yes, you are misunderstanding my earlier post. As you are aware, there is less pressure on a non-functioning ac system than a 175 PSI air system. The high and low sides equalize. During operation, the high side can go up to 200+, depending on the, Freon type, the ambient temperature, the effectiveness of the condenser fan, etc. the low side is WAY less than any compressed air system. In auto A/C it's around 30#, give or take. I'm not sure of the exact low side pressure in commercial refrigeration as I've never worked with it; only auto A/C.
dave
Greg O wrote:

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Okey-dokey! Greg
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Go to: http://air.ingersoll-rand.com/AST/common.htm
This is an extract from their article:

that customers do not use plastic piping or soldered copper fittings as discharge piping for compressed air systems. Plastic piping is not recommended because some types might react with compressor fluids, soften due to heat or shatter due to pressure or pulsation of the compressor. Soldered, copper fittings will eventually work loose due to pulsating caused by the compressed air system >snip<
I rest my case.
Peace~Sr Edgar
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That sounds like a case made by lawyers, not engineers. It's like the warning on Qtips that says not to put them in your ear. Don't most compressors have buffer tanks that smooth out the pulsations?
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Go to: http://air.ingersoll-rand.com/AST/common.htm
This is an extract from their article:

pulsating caused by the compressed air system >snip<
I rest my case.
Peace~Sr Edgar
Not to argue the point, but the IR dealer put copper in our plant. He did, however, use flex couplings at the compressor to take out most of the pulsations. Ed
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I used about 2 feet of air hose to join my air system to the compressor.
dave
Edwin Pawlowski wrote:

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