Gas Line

Got the gas line set-up today. Not installed and ready for operation, but the major components are there, all linked up. The picture shows from left to right

  • NPT/Swagelok 1/8” adaptor
  • Mass flow controller (MFC)
  • 1/8” to 1/4” Swagelok adaptor
  • Pneumatic valve
  • Swagelok to Conflat adaptor.

Not shown is the dual stage regulator, that’ll connect to the NPT adaptor just before the MFC and in turn fits onto the deuterium lecture bottle, with a CGA 350 fitting - CGA fittings are Compressed Gas Association connections, with different types specified for use with different gases. CGA 350 is one of those used with hydrogen/deuterium.

Gas line

Also, the pneumatic valve needs an air line and pilot solenoid valve attached to it. Operation is going to be completely remote controlled, so a pneumatic shut-off is used instead of a manual valve.

In real operation, the tubing between components will be longer for some. The 1/8” tubing is accommodating to bending and will extend from the middle level of the Fusor cart around to the top. Space is limited on top with the chamber and immediate equipment there, it makes more sense to have the deuterium bottle below and link to above with 1/8” tube.

I have a laser-drilled orifice for a VCR fitting ready to use too, this is to restrict the flow of deuterium even more than what the MFC does. A long hypodermic coil of tubing is sometimes used for the same purpose of flow restriction. However, the MFC should do fine, and inserting a lone VCR fitting is hassle. If the MFC isn’t sufficient flow restriction - I expect it to be enough - I’ll insert the orifice in the line.

Ran into an issue with the old ferrules in the MFC Swagelok fittings. The larger ferrules were a bit wonky, and wouldn’t take the 1/8” tubing. Replaced them with new ferrules (have a set of spares), the defective ones have a bore that’s smaller than the standard 1/8” they’re meant to take. Weird. A Swagelok fitting is just a nut that screws onto a thread, but inside the nut there are two conical ‘ferrules’ that grip the pipe inserted into the nut when the nut is tigthened.

Swagelok exploded fitting

Based on this, there are a few little things to take care of: The air line and solenoid control for the valve and getting a fitting to connect to the gas regulator. Then we should be good to go.

Written on April 27, 2017