Thread: Length restrictions to fixed air line?

Originally Posted by LordBug

Would there be any problems with maintaining pressure to be able to run a couple of air tools if I did this? Also, is there any recommendation in what sort of piping I'd want to look at? The cost of the run alone could very well change my decision

Pressure is not usually a problem with length but air flow might be depending on what size pipe you run. If you run narrow pipes with lots of bends then flow will suffer.

Your choices for piping are
1) copper - expensive.
2) Plastic high pressure - also expensive.
3) Galvanized water pipe. Cheaper than 1 and 2 but some people say that the flakes of corroded zinc can affect air tools.
4) Black iron pipe (can corrode over time).

I used just under 18 m of 1" galv pipe to retic air to 6 places around my shed as I already had many galv fittings to suit and I was able to buy 6m lengths for $50 a length. While I was at it I put the compressor outside my shed in a sound proof enclosure making it much quieter inside the shed. I also have a home made auto tank venting valve that saves me having to go outside to vent the tank.

Some details and pics here.

Design of the pipe network so that a low point to act as a drain for the pipe network before the point of first use is also something to think about.

BTW 40 m of 1" pipe will add about 20 L to your pipe reservoir which can be handy but if it was mean I would add a valve to isolate the 40m run to your garage so that it did not have to fill that up every time unless you had to.

Definitely agree with the isolation valve. 1" gal pipe should be sufficient for most hand held tools and, as long as you have a good air cleaner/dryer, shouldn't pose too much trouble with internal corrosion - we've been running the same gal pipes at work for well over 20 years with no problems. Another option is to install a second, small tank in the garage which will give you a decent reservoir of air.

Air flow, water flow, and electrical current flow are similar in nature. As the distance increases, there will be a pressure drop while air is being drawn which can be minimised by going for a large bore pipe. When you are not drawing air, the static pressure at either end of the line should be the same, but once you start to draw, delivery end pressure will start to reduce in proprtion to the flow rate and distance and inverse proportion to the cross section of the line.

Depending on far end draw requirements, you could reduce pressure drop etc by installing a decent sized air tank at the far end. This would help maintain pressure for air tools like a drill or rattle gun used in short bursts, but would not be much help for high demand applications like spray painting.

One issue that you will have to face with a long feed fixed supply line is the time taken to pump up the line every time you want air at the far end. You could find that with a 40m line that line volume is somewhat greater than that of the tank supplied with the comp, and the pump up time increases accordingly. At work we one a 15HP comp with a 400L tank running through a drier and about 40m of 32mm High Pressure Poly. This takes about 4.5minutes to pump up from empty each morning, and the leaks in the fittings at the moment mean that the comp cycles for about 90 seconds every 10 minutes with no air drawn.

Also, you need drain points at the lowest points in the line to bleed off condensate, and if the line is underground, this can be difficult to arrange.

Originally Posted by malb

. . . When you are not drawing air, the static pressure at either end of the line should be the same, but once you start to draw, delivery end pressure will start to reduce in proprtion to the flow rate and distance and inverse proportion to the cross section of the line.

Sure I agree, but the flow/diameter/length of the pipe has to be significant to make a difference for hobby/light-industrial level compressor specs.

Using this pressure drop in air pipeline calculator the pressure drop for
10 CFM, 150 PSI, 120 ft length of 1" pipe is only 0.03 psi,
For a 0.5" diam pipe it's 1 psi.
For 20 CFM and 1" diam it's 0.12 psi
For 10 CFM and the pipe diam of 0.25" the pressure drop is 35 psi

So sticking to 1"+ diam pipe should be OK

Also, you need drain points at the lowest points in the line to bleed off condensate, and if the line is underground, this can be difficult to arrange.

Auto valves can be used for underground, worse is under concrete

Theres another kind of line you can use and thats industrail air/water hose, its the stuff they use to run many things from jack hammers to water jackets on furnaces... its super tough and reasonably cheap.

Originally Posted by Harry72

Theres another kind of line you can use and thats industrail air/water hose, its the stuff they use to run many things from jack hammers to water jackets on furnaces... its super tough and reasonably cheap.

Super Ultraflex is the one I looked at. It was not that cheap and I liked the idea of having a metal pipe rail running down the full length of the shed just under the central truss and sure enough it is really handy to hang stuff from; lighting, various squirt bottles, PPE, towels, angle grinder, chipping hammer etc - can't do that with hose.

We put gal pipe air lines in the shed where I work 30 years ago and have had no problems with it that I can see. Although there is a design fault, the pipe has low spots that hold water and every so often there is a gush of it from the pipe. It means that we have of purge the system every os often.

I can be fixed with a dropper and tap before the outlets to trap the excess water before it gets to the regulator.

Robert

Cheers everyone, very helpful input

It sounds like galvanised pipe would be my preference.
Thankfully, the lay of my block has a slight slope leading down to the shed, so I've already got an idea in mind of how I could set up an easily accessible & purposeful low point for burying the pipe.

BobL, I must admit that having the occasional flick through your shed build and your mention of fixed air lines is what gave me motivation (That, and finding out that I have 3 phase to the house with the required meter too, with a 10mm2 3ph cable run out to the shed already, just needs full connection in the meter box, though I'm not complaining about that minor necessity ) I had missed the post on your various fittings on previous viewings, so very very handy to see.

Are you able to share your source for the galvanised pipe?

Cheers

Originally Posted by LordBug

Cheers everyone, very helpful input

It sounds like galvanised pipe would be my preference.
Thankfully, the lay of my block has a slight slope leading down to the shed, so I've already got an idea in mind of how I could set up an easily accessible & purposeful low point for burying the pipe.

BobL, I must admit that having the occasional flick through your shed build and your mention of fixed air lines is what gave me motivation (That, and finding out that I have 3 phase to the house with the required meter too, with a 10mm2 3ph cable run out to the shed already, just needs full connection in the meter box, though I'm not complaining about that minor necessity ) I had missed the post on your various fittings on previous viewings, so very very handy to see.

Are you able to share your source for the galvanised pipe?

Cheers

Sure - here it is, GMP - Galvanized Medium Pipe - Valve & Fitting Supply

Their main products are massive flanges and industrial pipe fittings and pipes for the mining industry. Their warehouse is full of this sort of stuff so don't be put off by the fact that you won't see any pipe, it's all out the back. I'd ring ahead first and check if they have it in stock - they didn't have it the first time I went. They appear to deal just with businesses like mining companies via accounts so you have to say its a cash sale and bring cash along.

I see the price of the pipe has come down somewhat since I bought - I think their web prices are ex-GST.
At those prices you may want to consider going to 1.5" but the fittings will then cost a bit more.
Anyway Ii's way-way cheaper than any hardware. They also sell fittings but I didn't buy any there as I already had most of my 1" Galv fittings and the few more I needed I bought from Bunnings for about $2 a pop. The relatively most expensive thing for me was buying all the Nitto style fittings and the adapters from 1" to the 1/4" NTP thread.

Cutting the threads for the pipe network, and for you the 40 m of pipe to your garage, will give you a hefty workout. You will also need a 1" BSP die and suitable long handled die holder to cut the threads with.

Tip: Make sure you have a flexible coupling between the compressor and the pipe network otherwise the comp vibe gets into the pipe work and vibes the whole shed. I used a flexible SS sheathed gas line with 1" BSP ends but you can also just use a short length of compressor hose.

If you have any other questions just yell out.