Air line question - Dead end or continous loop?

[RTcat]

32 X 50 shop. Going to use 3/4 black pipe. Compressor sits in one corner and I need to get air to the opposite corner. Plus I'll have drops on the way to that opposite corner. Is there any advantage to continuing on from that opposite corner and running pipe back to the point where the flexible hose of my compressor starts the black pipe? Would there be less pressure drop at that opposite corner if it continued on back to the compressor?

 

[Falcon67]

With a 3/4" main, I'd say no. You won't see any volume loss worth mentioning between one end and the other. You can go 1/2" to 100' and not have any appreciable drop in pressure, so 3/4" will be plenty good for a dead end run.

 

[38Chevy454]

If you had something that really used a lot of air, the extra volume might help. But then you could also just use 1 inch pipe vs 3/4. I agree with Chris that 50 ft shop length you are fine dead end run.

However if you want air drops on all of the walls, then it is probably good to have looped as it would not tkae much additional pipe to make that happen.

 

[shopnut]

The advantage of a continous loop is having equal pressures at any given drop in the loop. Think of any drop as having 2 paths leading to it, one from one half of the loop, and one from the other. The sum of the two loops is always an equal length, regardless of where the drop is in the loop, and this it the reason for the equal pressures. Of course, a larger number of bends in one leg compared to the other will throw this off slightly.

As others have said, going larger in pipe size will minimize the differential in drop pressures of a dead end circuit, most likely to an acceptable level.

 

[Greatbear]

Looped runs tend to be most beneficial if you have two separate outlets on the compressor. If a loop is fed by a single outlet, the restriction in that feed will affect the whole loop. If there is only one outlet on the compressor, the loop should be fed with the largest practical pipe; a 1" pipe feeding a 3/4" loop, for example.

 

[buzz4041]

You will not see any advantage to running a loop in your shop. The larger the pipe the more reservoir you have per say so you won't see a drop. In your case 3/4" is good and 1" is better.

 

[mzahn]

PSI is equal at all locations in the system. Friction loss in the pipe must be calculated. I can't see any advantage to a loop but have been wrong before.

 

[shopnut]

PSI is equal at all locations in the system. Friction loss in the pipe must be calculated. I can't see any advantage to a loop but have been wrong before.

You are right - PSI is equal at all locations, but only if the air is not moving. As soon as air starts flowing, friction losses come into play and pressure keeps dropping as the air travels further and further in the line. It matters more if you are using a large/continuous flow of air for your tool (sprayers/grinders). It doesn't matter so much for tools that use short bursts of air (nail gun) because the air line has a chance to equalize in pressure or catch up between bursts.

My statement in the reply above was made assuming flowing air not static air, which is what's important to someone using it.

 

[tdkkart]

If you're only feeding a couple drops on one side of shop then a loop doesn't make any sense, but if you're looking at 2 or 3 or more drops on both side walls you've already got 3/4 of the loop, might as well finish it out.

 

[djjsr]

In the future, if you find that you have too much pressure drop from inadequate volume at the far end of your building, you can install another storage tank at the far end of your piping. This is often done in industry and it works very well.

 

[Shadowdog500]

How many CFM are you planning to flow, and how much loss is acceptable for you?

The table in the link below shows that if you flow 20CFM at 120PSI through 3/4 pipe you will only have a 0.3PSI pressure drop in 100' of pipe. 50CFM with the same pressure and length will give you a 1.8PSI pressure drop. I doubt anyone would ever flow anything close to 50CFM in a shop your size, so those slight pressure drops probably won't even be noticeable.

The only benefit from running a loop is if you plan to flow ungodly amounts of air through a factory (which you aren't going to do in a shop your size), or if you want to run much smaller pipe to save money(which would probably wouldn't even be a wash if going from 3/4" straight run to a 1/2" loop.

Just run 3/4" straight run, that is sloped with drip lines on the bottom, and air feeds off the top and you should be fine.

http://www.engineeringtoolbox.com/compressed-air-pressure-loss-d_1014.html

I really wish this forum had a shop air section, or at least a sticky!

Chris

 

[RTcat]

Thanks for everyone's input! As TDK says I'm part way there. It might be nice to have a drop or two on the return wall that has the two overhead doors if I'd ever want to use some air outside the shop.

I've got 10' ceilings. On your drops, how far down (or how high up off the floor) do you end your drops? My main use will be running a blow gun and air nailers in woodwork end and an impact gun on the hoist end for tire on/off.

 

[buzz4041]

Thanks for everyone's input! As TDK says I'm part way there. It might be nice to have a drop or two on the return wall that has the two overhead doors if I'd ever want to use some air outside the shop.

I've got 10' ceilings. On your drops, how far down (or how high up off the floor) do you end your drops? My main use will be running a blow gun and air nailers in woodwork end and an impact gun on the hoist end for tire on/off.

Put them where you want. I like mine at about switch height for my air filter regulator on my drops and then I run a blow down leg a couple feet lower from their.

 

[Falcon67]

I put them depending on what's around. Mostly close to 4' or a little less off the floor.

 

[eboy]

RTcat: don't sweat the loop, not necessary-however, can the black pipe. Iron pipe is totally old school. It rusts, you can't add to or alter, and can't repair leaks! Just did my new shop (10,000 sq, ft) with Kaeser Smart pipe. This stuff is a joy to work with. It's a bit pricey, but you will have no regrets. Second choice would be copper