I just spoke with the compressor store concerning air supply piping.

They insist that you should avoid plastic piping as it gets brittle and shatters. They suggest schedule 40 iron pipe (black or galvanized your choice) for pressures up to 150-175 pounds. Above that pressure they suggest schedule 80 iron pipe with the high pressure fittings.

there is an aluminum piping with special fittings that can be used. And copper piping can be used if you use silver solder for the joints. There is also a compression fitting that can be used with copper.

On the compression fittings, copper piping used for refrigeration uses compression fittings, and can be used for air supply lines.

The fellow did mention that copper pipe used for water was measured by ID (inside diameter) but copper pipe used for refrigeration was measured by OD (outside diameter). You have to know which you are using and to get the correct fitting for the pipe being used.

He also cautioned against using hydraulic likes for air.for connecting the compressor and the receiver. The air leaving the compressor can be 400 to 600*F and degrades the hydraulic hose from the inside causing leaks.

We also discussed the oil needed for the compressor. His suggestion was 30 weight non-detergent oil (auto use). Synthetics are much better but you must match the synthetic oil to the o-rings and seals that are installed and in use in the compressor.

The compressor oil should be changes every 200-300 hours of use. This is adjusted by the duty cycle of the compressor, the type of use the compressor is subjected to and the duration of run time / cycling.

There seems to be more to compressed air piping than can be covered in a few short paragraphs, so talk with the manufacture of your compressor and get the full specs and full instructions on how to get the most from your system. I have found that they are glad to assist you, and have a wealth of information available for the asking.

Anyone else want to pipe in on this one :)

I always run sch 40 black iron but more because I'm afraid I'll hit a piece of PVC by accident while working and bust it. Grey PVC does lose its plasticizers but it takes a while (of course, you probably don't want to be around when it lets go). Copper is great but black pipe is cheap and easy.

I use Ingersol-Rand's synthetic compressor oil. It's a bit pricey but the little bit I use and the infrequency of the changes makes the oil cost neglible.

Thanks for the info. I wasn't sure if I should go for iron or copper. At least I knew enough to not use PVC. I was planning on using the oil my compressor manufacturer recommends. It runs about $13/gal and my compressor takes 2 1/2 gallons.

A friend of mine uses air line hose material for tractor-trailers (semi's). He uses it for short runs instead of elbows and precisely cut/threaded short pieces of schd 40. He buys the material from heavy truck supply houses, cut to length and fitted with compression fittings. I don't know anout max pressure or cost, but it sounds like it would be worth exploring.

copper will be better because it won't corrode,even with a dryer i'd suggest a drain at the low spots in the run. And what ever you use make a larger central manifold and take your run off it-it will have less pressure drop at the end. But above all, consider the way you run it. Keep it as protected as you can,and drain it and your tank on a regular basis. I took a drain off a truck that has a cable on it -that way when you drain tank you don't have to bend down or possably get dirt, etc. in your eyes-good luck, jimmy.sorry bout being so long winded..

Slant your pipe runs so they tilt toward a drip leg with a valve on it

I am guessing you mean to slant it with the flow direction of the air being downhill. That way it would push the water toward the drip valve.

Well that would be nice; but most of the time you will not have air moving in the pipes and you probably have a drier at the end by the tooling anyway. So it's the slant that's important---and hard to do as we want nice horizontal runs to look at!

black iron pipe is used all the time for hydraulic lines with pressures up to 3500 psi, and as for using short hydraulic hoses for vibration dampers between the compressor and lines. Hydraulic oil often gets as hot or hotter than the air ever will.

I just use the flexy hose (looks bit like garden hose pipe) from a hydraulic / air supply place, comes in 50 mtr coils and is hastle free to run.

If its near a danger point (hot or run over by fork lift !) run it down the inside of some old steel pipe / conduit.

This lazy approach avoids loads of potential leak points / joints, and if you do get the odd leak its easy to replace the whole lot.

Ive seen the odd 1/2 pipe 'pop' off an airtool which is your worst case scenario (dumps the whole tank) - (using a jubilee clip over a 'snap on' fitting) , this is waaaaayyyyy more dangerous than a permanantly piped shop line starting leakin a bit.

Chains only as strong as the weakest link etc

now I did once pop a 4" dia 'flexy' off the inlet of a double acting air stamp, it dumped a LOT of 120psi in a very short space of time, fourtunatly the steel pipes up to the flexy were secured or could have been worse than a bit of deafness for a few days - the laundery bill was high that day..:rolleyes:

Black iron properly installed should be leak free for decades after all it has been the standard for natural gas for better part of a century or more. Having designed many air systems for manufacturing plants it is important to have a pitch towards the compressor. It is also important to have an auto drain valve on your compressor to eliminate water build up. When making up a branch take off do it off of the top of the main line instead of the bottom or side as this will prevent water from entering the line feeding the tool and it will drain back to the compressor. Auto drain valves should be installed when ever you need to change elevation of the main air line. I can see no need to run a shop air main line at pressures above 150psi. There are no tools in my inventory that require pressures above that and most below. It is better to over size the main then to under size it. The larger size acts as an additional receiver.