[T3] Air compressor ?

[William Jahn]

The tube I got is a replacement and it's the same wall thickness as the
original. The only issue I see is for some reason the tube is not perfectly
round . It is 1/2" OD and 3/8" ID . The leak is not real bad yet I'd prefer
there were no leaks. The Unloader releases the head pressure. I don't need
the head to check valve tube to help out.

 If I could just take a 3/8" drill bit shank or whatever bit that fits and
tap it in 3/4" it might round the copper and create a seal between the
ferrules and copper tube. Since the ferrules are in place they would keep
the OD of the copper from expanding. I don't really want to try to tighten
the fittings more and end up with a ferrule that collapses the OD of the
copper like the very old original one was at the head end. I bought a new
1/2" compression fitting because I needed the nuts and ferrules I could use
the body , fit the new pipe with the ferrule then try to fit a 3/8" drill
bit shank  in to make  certain the ferrule remains round. I would smooth
the bit and taper the end a bit more and lube it so as not to destroy the
inside of the copper.

 As is livable it's better than before. The new replacement copper is
really tough to bend like the old one was. I tightened it finger tight then
1/2 turn more and it leaked and gave it another 1/2 turn same thing. This
was what I found on you tube sites. I normally finger tight then use a
wrench till it feels snug and never crushed the copper or had leaks. The
original tube at the head was tightened so much that the ferrule was barely
more than the copper OD and I could see the ferrule past the nut. I never
noticed this until I replaced the check valve and the check valve end was
fine . The fellow I traded for it might have cranked down on the heads
fitting to cure a leak. I know the new copper is not round yet it measures
the same OD as the original . Once I realized it leaked I removed it to see
why and found the ferrule made contact all around except one small area . I
doubt more tightening will help.

 This stuff drives me nuts when you get a new pipe and find it has a small
flat spot and I slide a new ferrule down the entire pipe and it has that
slight flat spot the entire length.



On Sun, Jul 26, 2020 at 5:44 PM Jim Adney <jadney at vwtype3.org> wrote:

> One thing to keep in mind is that copper tubing comes in different wall
> thicknesses. The thinner wall stuff is not suitable for any of the ferrule
> style
> sealing methods, because the wall will just collapse rather than being
> stiff
> enough for the ferrule to bite into it and seal.
>
> I learned this lesson many years ago, when i was working on a small system
> that had to be helium leak-tight. I could make a leak tight joint at one
> end of
> the tube, but as soon as I did ANYTHING to the other end, the movement
> would open up a leak on the first end. The thing I was working on was a
> network of maybe 20 connections in a couple square feet, so until I
> switched
> to heavy wall copper, I was just chasing one leak after another.
>
> I finally found recommendations from Parker and Swagelock regarding the
> min. wall thicknesses for various diameter tubes that could be reliably
> sealed. Look here:
>
> https://www.swagelok.com/downloads/webcatalogs/EN/MS-01-107.PDF
>
> Read the section about gas service on page 2, as well as the chart on page
> 7 regarding copper tubing. The note at the bottom of page 7 seems to
> indicate that the minimum wall thickness for air in 1/2" copper tubing
> would
> be 0.049".
>
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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