It's harder than it looks

[john_bud]

John,

You can get the pipe cut and threaded at Home Depot or just about any plumbing supply store for just a few bucks. If not, I'd buy short lengths and thread them together to get the right length. I gave up trying to weld things that needed to be air or watertight years ago. That's a skill that I'm just not capable of.

Eddie

Yeah, but the nearest one is 20 min drive each way. Pretty spendy in fuel and time - that would really slow me down. A buddy took pity and loaned me a treader. Works good. Those fittings are tight, but there are some that are still loose that I have to find.

jb

 

[Egon]

It's good to hear you now have a threader!

Did you consider drilling the threads out of an ordinary fitting and slipping the pipe into the fitting before welding?

Some of those leaky threaded joints could be backwelded.

 

[john_bud]

Yeah, but the effort wasn't worth it. The pipe is hard against wood members and there isn't a 240V outlet close enough for the welder. Meaning that even if I could rig up a thermal shield, I couldn't weld it in place. If I had to take it down, it was quicker to put an abrasive blade in the skil saw and slice it free and thread in a patch.

On the slip fit - then weld. Uh, "now you tell me!" Yeah, that WOULD have been smarter.

jb

 

[Egon]

Musings from a NON WELDER.

John, I be thinking that if you had done a little practice on the pipe welding you would have had no problem. In the very recent past you have adapted to welding on high mass objects of different iron composition than the thin walled black iron pipe. Just a little practice and you would have adapted your methods for the new material.

 

[gemini5362]

I cannot imagine why you would not use copper pipes. HVAC units that have the compressor outside and the condenser inside use it to move freon between the two units. I believe that the pressure side of the compressor is a higher pressure than you would be likely to have in your shop.

If I have to cut pipe out of something I just use my sawzall (reciprocating saw) and a metal cutting blade.

 

[scott_vt]

Mornin John,
I thought you may have considered 3/8" steel lines and a cheap tubing bender ? We went that route over the firehouse for are breathing air compressor to get high pressure air on the other side of the fire house. You need the steel lines, a tubing bender and a flairing tool and some fittings. Im sure the pressures we are using far exceed what your doing in your shop.

Just another idea !

 

[john_bud]

I cannot imagine why you would not use copper pipes.

Let's see $24 for a 3/4" copper stick 10' long or $8 for a 3/4" black iron 10' long... $20 for a 1/2" copper stick 10' long or $6 for a 1/2" black iron 10' long.


I bought 10 sticks of 3/4" and 4 of 1/2". That would be an imaginary savings of more than $200 bucks. ;-)


Scott, I use enough air flow that the pipe restriction would be too much. It leads to a big pressure drop at the end of the line. But little tube would work for smaller air flow requirements.

jb

 

[gemini5362]

Let's see $24 for a 3/4" copper stick 10' long or $8 for a 3/4" black iron 10' long... $20 for a 1/2" copper stick 10' long or $6 for a 1/2" black iron 10' long.


I bought 10 sticks of 3/4" and 4 of 1/2". That would be an imaginary savings of more than $200 bucks. ;-)


Scott, I use enough air flow that the pipe restriction would be too much. It leads to a big pressure drop at the end of the line. But little tube would work for smaller air flow requirements.

jb

Yeah john I just bought some copper pipe and could not believe the price. I dont know how much the black iron pipe is now. I wont even go into the issue with water getting into the black pipe and rusting it through. I was just pointing out that from a pressure issue only that there is no reason not to use copper. Financially is another matter.

 

[gbick]

Ironicly, I recently completed plumbing a 3/4" copper air header loop around my shop. Yes, inspite of its cost. I figured the benefits of copper will still be there long after I would have spent the difference on coffee and beer. The air lines at the mill where I worked were black steel. When you blew the dust off yourself, you were birdshotted with flecks of rust from inside the pipe. I'm guessing copper won't do that. Also, copper's heat transfer is better. And that is the key to dry air. The main function of this header is as an air dryer for sand blasting. My 2 stage, 80gal IR compressor sits in one corner. This is the highest point of the loop. It slopes 1/4"/ft toward the diagonal corner, where the condensate drains. The pressure in the loop is regulated to 110psi. GREG

 

[dbdartman]

The problem using copper in air lines isn't the pipe, it's the soldered joints. They will come apart because the solder fails. A/C lines are copper, that's true. What's not commonly known is they are silver-soldered as plumber's solder (used to be 50% lead 50% tin, now 95% tin & 5% "other") will not last with the pressures used in A/C.