Plumbing a compressed air line question

by Donna
(Arvada, CO )

Is there any benefit when plumbing in a copper line for the compressor-to run it on the ceiling of the shop or would it be better to drop down (6"-12") from the ceiling?

The line will not be running along a wall it would just be below the ceiling in the middle of the room?????

Hi Donna...and thanks for your question. I'm sure I posted a response to your question before...but it's gone into the ether, so here goes again.

Interesting to hear that you're considering using copper pipe for your compressor air lines. I subscribe to that concept over black pipe anytime.

Is the ceiling of the shop in danger of freezing? That would be one reason that I'd want to move the air line down from the ceiling so that any water in it wouldn't freeze.

Another reason why you'd want some space is so you can take the drop line off the top of the main air line, not the bottom.

You do want to make sure that the copper air line runs at a bit of a decline from one side of the shop to the other, so that water that condenses in the pipe runs downhill to a drop line, where you can install a hand valve or auto-drain to get rid of that water from time to time.

Hope this helps.



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What is 'Cracking pressure'?

by Martin
(San Francisco, CA, USA)

Looking at check valves, I see specification such as this:

Cracking pressure 4 PSI

What is cracking pressure and in this example what does a cracking pressure of 4 PSI mean in a real world use.
Howdy Martin....

Consider, instead of "cracking pressure" the term "minimum operating pressure".

In a check valve, that means that the valve won't start to pass air until the cracking pressure, or minimum operating pressure has been reached.

Whatever the device is inside the check valve that helps the ball stay on the seat (or the flap to stay closed...whatever) will required a certain amount of PSI to overcome and allow air to pass.

If your air line has 3 PSI in it, and the cracking pressure of the device in line is 4 PSI, you won't get any flow through your line at all until the air pressure exceeds the cracking pressure.

Some applications call for very low compressed air pressures and if the cracking pressure or minimum operating pressure of an in line component is too high, the application will be starved for air. That's why they show the cracking pressure on the valve spec.

Hope this helps. Nice hearing from you.

Jim G. comments...
No flow in a check valve. Most check valves are spring loaded with a ball or flapper in them........air or oil in one side and nothing comes out. Air or oil in the other would open above a certain pressure and start a flow, I think what you mean cracking is when the seat of the check is cracked and flow in the permitted direction starts.

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regarding the right air hose

by Patti Kraegenbrink
(Medford WI 54451)

we are in need of air hose for Sullair 185 air compressor - we found some online but it's hard to buy on line when you can't actually see the product. Is a 4 sprial hose good quality for this big of and air compressor? We do whitewashing of barns so cows step on it and it gets dragged thru barns - we need good quality.
Patti, I don't have a Sullair 185 tow behind air compressor, and I have not been able to get specs on it to tell me the discharge hose size.

You refer to a 4 spiral hose, yet that format is available in everything from a 1/4" tube to a hose cover.

It were me, I would look at the specs for the hose. I would look for the burst pressure (should be 2-3 times the pressure the compressor puts out), the size of course (hose is measured on the I.D.), and the recommended uses for that hose. They often give examples of applications.

Regarding your friendly cow stepping on the hose and clamping it shut with a hoof, if that really happens often, and that is a significant detriment to your barn painting, then you have the option of getting an armored hose that won't squash, but it will be frightfully expensive and heavy.

If quality is paramount, stick with a name brand manufacturer such as Goodyear, Gates, Parker and so on.

I suspect on the hose page on this site there will be advertisers for all kinds of hose.

Good luck.


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