Making a UHV gas line

Adding a minican to a 6 mm line. 

The ideal setup is: minican valve - fitting for valve - fitting for tube - tube

1. Messer CANgas dosing valve, Combination 5, Z742375-1EA. This valve fits in minicans with threaded outlets of 7/16". The common ones in UHV labs are coming from Buse, Messer or Linde, and all of them share the same metric for 1 L minicans. The output or outlet of the valve is 1/8" (3.175 mm) so it needs to be adapted to your gas line requirements. Also, keep in mind that they follow the NPT standard for the thread angle (60°) and not the ISO (55°), which matters when buying the next element. NOTE: you can use other valves such as Linde minican valves (e.g. 37610014), but I find Messer's valves more reliable.

2. Minican valve (1/8") to gas line (6 mm) fitting. This piece joins the minican valve with the tubing system of your machine. The tapered version creates a better seal, as explained here. Don't forget that you need to wrap the thread with a bit of teflon tape.

3. Ideally, after the minican valve, you want to have an extra valve, usually known as a shut-off valve. This valve is not that special, usually a ball or bearing mechanism that opens/closes the system. For UHV and typical pressures of up to 12 bar in the gas lines, Nupro valves are usually quite good and already compatible with Swagelok (i.e. they come with Swagelok nuts). Another great alternative, are the swagelok series ball valves.

4. All parts connected with Swagelok pieces must have a set of ferrules to create and maintain the seal between components. These pieces deform the tubing permanently, so be careful where you place them.

5.  The 6 mm tube can frankly be obtained anywhere. It should preferably be stainless steel 304. Same goes for the Swagelok parts (nut–ferrule–fit), although the common steel type is 316. Ultimately, it doesn't matter that much for the type of gases we're using.