making a connection without admitting gas

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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Corby Dawson
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making a connection without admitting gas

Post by Corby Dawson » Wed Mar 27, 2019 1:46 am

Ok, Here is a tricky problem I have. I'm working on a 1985 vintage maser prototype that has NO documentation.
It is a completely sealed (welded) system.
It has a small external ion pump as well as an internal gettering system.
I have powered up the ion pump and it appears that the system has held its vacuum.
There is also a TC gauge tube welded onto the vacuum side and it also shows a good vacuum.
Now the problem.
There is a Hydrogen source capsule that utilized metal hydrides.
It looks as if there is no Hydrogen left!
What happens inside the source is that Hydrogen (at some pressure) is input to a (probably Nickel) thin walled tube.
The tube is heated by passing current through it and causes Hydrogen to diffuse thru the wall onto the vacuum side.
I can see the output line of the Hydrogen source and it does directly access the vacuum system.
There is a 3/8" copper pinch off on the other side of the Hydrogen source, which "I think" is on the Hydrogen side.
There is another bigger pinch off on the main cylinder which is on the Vacuum side.
So if I put a hole into the 3/8" pinch off it should not vent into the Vacuum side.
Such a hole could be connected to a new Hydrogen source from a small compressed gas tank and regulator.
I'd like to avoid getting any air into the pinchoff.
Is there a saddle tap/vampire tap/self tapping valve or some other method to make the hole and at the same time seal around it to prevent contamination? Maybe with low pressure Hydrogen flowing while the puncture is made?

ANY suggestions welcome!

Cheers,
Corby

Dan Knapp
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Real name: Dan Knapp

Re: making a connection without admitting gas

Post by Dan Knapp » Wed Mar 27, 2019 2:34 am

You can buy a saddle clamp valve made to attach to copper tubing at a hardware store.

Corby Dawson
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Real name: Corby Dawson

Re: making a connection without admitting gas

Post by Corby Dawson » Wed Mar 27, 2019 3:13 am

Dan,

I have seen those, would their valve be able to handle say 60PSI Hydrogen gas?

Corby

John Futter
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Re: making a connection without admitting gas

Post by John Futter » Wed Mar 27, 2019 3:41 am

refrigeration engineers do this all the time on small systems
If yo uare sure the hydrogen source side is seperate from the vacuum side then you cut off the swage weld / solder a new bit of copper pipe with a refrig fitting on the end--using refrig gauge set evacuate then back fill with hydrogen (you will have to make an adapter to suit the gauge set) crimp off the pipe cut off excess solder up end of pipe for permanent seal --same sort of thing happens to charge closed loop cryo pumps with Helium

Jerry Biehler
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Re: making a connection without admitting gas

Post by Jerry Biehler » Wed Mar 27, 2019 5:55 am

The taps that refrigeration guys are way better than what you can get at a hardware store. Get some of those. They can handle pretty high pressures, pressures in refrig systems can get pretty high, higher than your 60psi.

Dan Knapp
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Re: making a connection without admitting gas

Post by Dan Knapp » Wed Mar 27, 2019 11:29 am

Saddle clamp valves sold at the hardware store are commonly used for water lines, which can be over 100 psi.

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