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"Drive It Until It Breaks"
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Discussion Starter · #1 ·
I'm plumbing some 3/4in. copper line from my compressor to a little small blast cabinet I picked up from Harbor Freights. I've read that the run should be long enough to give the air time to cool. Would 25ft. be a long enough run to let the air cool? I plan on putting a in line desiccant filter at the cabinet to catch any moisture.
 

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Depends on where you are located. Here in the south there is no way to get rid of all the water. Spending money on copper to cool the air could almost pay for a good dehydrator.

Having said that, my lines are black pipe, 25 feet of it zig zaged with the supply on the top. The bottom leg runs straight down to a "T" with the side leg going back up hill to the desiccant/filter (a pricey one) to the paint gun supply line. I put the regulator on the input side of the zig-zag with the pressure gauge on the output of the filter.

Last thing to help control moisture is to have two lines. One for shop air and one for paint. The rubber and hard lines for my "paint air" are never used for anything but painting. It's a couple of bucks extra to have two supply lines but given the cost of paint and materials it is chump change!
 

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"Drive It Until It Breaks"
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267 Posts
Discussion Starter · #3 ·
Yeah, I’m in North Carolina. I have a little small shop. I don’t do any painting. But I have a blast cabinet for cleaning old parts. I could run a line straight to the blast cabinet that would come up to about 30ft. Or I could run it around the other side of the shop back to the cabinet which would be over 60ft. I’m only going to have one drop other than the blast cabinet. And I’m using copper because I was able to get a few 10ft copper pipes (3x4 L) for $100. I’m planning on putting a small inline dryer at the blast cabinet.
 

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Hates: Liver. Loves: Diesel
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This is interesting to me. The compressor increases the temperature of the air by the simple fact that it is being compressed via Boyle's gas law PV=nRT. Therefore when it exits and returns to atmospheric, it reduces its temperature by the same amount. In fact, air left in a tank for a short time already sheds enough heat that when you open the drain on the tank, the expanding air gets so cold that it freezes the escaping condensation.

This is a genuine question... why does the air need to be that cool? Even just using an air gun to blow dust off of my self, the air from the running compressor is cold coming out of the nozzle.
 
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