3/8" Compressor Output - 3/4" Copper Overkill?

[bikesandcars]

An additional consideration is the psi you want to run the connecting line at. You will get more water to come out and cooler air if you run it at a lower pressure. SCFM calculations being relative to pressure: The velocity is thus higher through the pipe to maintain the same SCFM at a lower pressure, which magnifies the effect of the pipe size.

 

[bugsysiegals]

Thanks for all the feedback, I'll stick with 3/4", the extra $100 isn't going to break the bank and I can always get a bigger compressor later ... who knows, maybe one of my sons will want to build a car with me down the road and then I'm set.

FWIW - I'm filtering water by letting the air flow through the copper pipe 100' before the outlet which will have a water, oil, separator. I'm not sure how well that will work but since I'm spraying waterborne product, I'd suspect it's NOT critical to have 0% moisture.

I had a leak from the drain on bottom of my tank so I unbolted the compressor and laid it on it's side. I then noticed the bottom bung has a reducer in it. Could I swap the reducer with a 3/4" reducer and use the bottom bung as the output? I'd add a Tee with ball valve to drain water and feed the air into the bottom of the last drawings drain loop so all water settles to the bottom. Would this work to allow higher flow?

 

[metlmunchr]

Definitely do not use the bottom of the tank as the outlet.

The 3/8 pipe outlet is of no appreciable consequence for the flow rate you'd have even if using the full output of the compressor.

I'd run 3/4 type M copper. Plenty of pressure capability and the thinner wall increases heat transfer (cooling of the compressed air). 1/2" copper has plenty of flow capability but 3/4 can be run with less supports as its not nearly as flexible as 1/2.

Most all high end spray gun manufacturers recommend supplying air to the gun in the 80-90 psi range and then regulating the pressure to the gun via a regulator mounted at the gun inlet.

Single component moisture cured polyurethanes typically contain isocyanates. I sorta doubt it would be a good idea to spray your basement full of iso's unless its very well ventilated. Isocyanates can kill you or cause permanent lung damage. Not something you'd want to expose your family to, and I doubt they'd want to hang around the house wearing respirators while you spray in the basement.

 

[sberry]

Re: 3/8" Compressor Output - 3/4" Copper Overkill?

Thanks for all the feedback, I'll stick with 3/4", the extra $100 isn't going to break the bank and I can always get a bigger compressor later ..

There is nothing wrong with the 3/4 but,,,, a bigger comp doesn't really make a difference unless there is more air demand. We had someone a while back figures he has a 15 hp comp so he needs big line. He is going to run the same tools. If you upgrade the electric service from 100 to 200 the wire going to a 20A circuit doesn't change.

Would this work to allow higher flow?

You can get more flow but its irrelevant unless the tool needs more air. You can put a larger wire to an electric drill,, it will allow more flow but the drill doesn't use more or make more power. Its got a 20A wire in the wall to an outlet where its connected by a 10A cord to a drill uses 5A.

 

[sberry]

Someething else to consider when reading all the drop charts is distance that s often missed to some extent. A 3/8 ****** a couple inches with a valve doesn't add much, not the same as reading a loss chart for 100 ft. I have 18 inches of 1/2 pipe feeding my 3/4 manifold from comp,,, not a deal worth changing as st the other end reduces to 1/2 pipe, then regulator and 50 ft of 3/8 hose on a reel. I was short on fittings for a bit when I did it,,, it can drive a guy crazy if he thinks about it but got to realize it makes no difference in operation. Even if there was 1/2 # or # extra loss in wide open operation wouldn't mean a thing as its regulated later secondary.
Electric is often calculated the same way,,,, guy reads the chart for v drop for 20A at 100 ft. In reality most circuits closer to 60 ft than 100, most loads plugged in to it are thru a 16 cord, the other 4% are from 14 and 12 so rare its not really much issue for general circuits. Most of the chart is for sizing feeders and for fixed loads. Got a vacuum cleaner with 25 ft of 16,,, how much loss we think is going to happen on a 12 wire circuit?

The 3/8 pipe outlet is of no appreciable consequence for the flow rate you'd have even if using the full output of the compressor.

None at double the output.

 

[tfb]

That last drawing is a waste of pipe.
https://www.garagejournal.com/forum/showthread.php?t=427525

From the source run up to the height of the main run and just add tees where you want a drop, if you change direction with a 90 ell, use a tee instead with a male thread adapter and screw plug for future use.

Anywhere you add your drops add a drip leg with a manual bleed, or an automatic one.

As for the pipe size I would stay with the 3/4 since you mentioned spraying and you are going to need as much volume as you can get. 3/4 will yield almost twice the volume as 1/2 inch so think of it as adding tank space. It will also has less friction loss across the total developed length, but its so minimal at these distances its not worth even considering. Your compressor will take longer to get up to full pressure though.

 

[sberry]

you are going to need as much volume as you can get.

You only need as much as you need. He would outrun compressor wayyyyyyyy before the pipe size was an issue. The spray gun is fed with a 3/8 hose,,, if it needed more they would be fed with 1/2.
Look at the little dinky reg feeds mine. That setup will feed 2 guns, comes down 1/2 pipe 60 ft from reg to there, 3/8 hose whip. Not only can paint,,, can paint 2x.

 

[tfb]

You only need as much as you need.

He says he's spraying... He'll need as much as he can get out of his stated equipment.

 

[sberry]

Yes, I see now he listed the air caps. The second would be about the limit for 100% due to the comp which I suspect to be around 3 hp maybe. This is only assumption most 5/60 are single stage econo units. But again,,, the pipe and certainly the bung wont have much to do with it at this volume.

 

[bugsysiegals]

The solution I was planning to isn't catalyzed and doesn't contain isocyanates. After reviewing the chemistry documentation, it does have some lung irritants. While it's minimal with this Waterborne solution, I'm just going to spray in the garage where I can open doors to ventilate and be safe ... thanks for pointing this out!

 

[bugsysiegals]

Yes, I see now he listed the air caps. The second would be about the limit for 100% due to the comp which I suspect to be around 3 hp maybe. This is only assumption most 5/60 are single stage econo units. But again,,, the pipe and certainly the bung wont have much to do with it at this volume.

I've 6.5hp with twin cylinder ... not sure what single stage is.

 

[sberry]

What is the listed cut out pressure?