Air Piping Sizing and Material Choice

Wider diameters offer less resistance and more storage buffering. Pex is also an option to consider. April 20, 2008

Question
I’m preparing an air pipeline for a future CNC Rover or SCMI, around 10 hp with 4X8 table with two vacuum pumps. Is the ˝ inch copper enough to provide air for such a machine or not? What is a sufficient PSI and Gallon size compressor to run CNC and Edgebander in a small shop?

Forum Responses
(CNC Forum)
From contributor B:
I would run 3/4" at least. It is not much more expensive. A CNC can use quite a bit of air and I am sure a pressure drop would cause bad things to happen. You should have a specific machine in mind and find out the CFM requirements.


From contributor D:
I have 1/2" copper running in my shop with no problems at the CNC. Originally I was using a 5 hp 80 gallon 2 stage compressor. It was having trouble keeping up so I put in a 15 hp 120 gallon compressor and now I have air to run DA's also. Go big on the air compressor as you will always find a use for it.

From contributor B:
Depending on the length of the run 1/2", it could become a problem - especially if you are tapping off it in the middle of the run. We run 3/4" copper and at the end of the run we need to run the pressure way up to achieve the pressure under load we want. You also have to plan for future expansion.

We had a pressure problem that caused all kinds of sanding problems. We ended up adding a second 10hp compressor to fix the problem. We are also expanding the shop and we are going to move one of the compressors to be closer to the use point. There is line drop and you have to plan for it.



From contributor J:
Consider running a loop around the shop so there is no end of the line. I have 1.5" main line, and I wouldn’t consider anything less. I have never had to increase air pressure at the compressor so that the pressure at point of use is high enough.

From contributor J:
Oh another point to think about. The oversized main line is like adding a bigger tank for more storage. The air is just stored in the line closer to where it is going to be used, rather than in a large tank far away.

From contributor K:
I built a new building about a year and a half ago and by trade I am a GC (my real job). Our plumbing contractors have gone to pex piping and I got to thinking about using pex for air line. One of my plumbers stated that he had had pex for air line in his shop for over 7 years.

I contacted manufacturer and found that it could be used for air; only exception being uv light. It must not be in direct sunlight.

I installed 1" pex through out and did loop several times with over 60' of width and 140' length and have used the line for over a year with no problems and love it. It is very easy to add new fitting or lines and it allows no flow noise. It is not particularly bothered by hot or cold temperatures. I do have a large cnc machine and when air came through the ceiling I did go to copper just from a being able to stay ridged stand point.
There are all kinds of new pex pipe available and even larger sizes now with the cost of copper. Easy to run and easy to fix or repair. The flexibility is a little of a bother initially but you get use to it.
Hope this helps.

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