Vacuum furnace argon fill system — advice needed

[dudeekeen]

TL;DR Summary

I want to fill my vacuum furnace with argon after pumping down. How to set up valves and regulator to avoid vacuum leaks and gas backflow?

Hi everyone,


I have a vacuum furnace that can reach about 10^-5 mbar. On the KF flange, I currently have a capped tee. I want to build a system that, after pumping down the vacuum, allows me to fill the furnace with argon from a gas bottle through a pressure regulator (e.g., set to 0.5 bar), so the furnace atmosphere is argon instead of air.


Here’s the rough idea for the setup:
vacuum furnace → KF tee → valve (e.g., ball valve) → pressure regulator → argon bottle


I have some questions:

• Will one valve be enough to maintain the vacuum once closed?
• Could the pressure regulator at 0.5 bar cause gas to be sucked back into the bottle due to the vacuum in the furnace?
• How can I prevent the vacuum from pulling gas through the regulator backwards?
• Should I use a check valve or some other type of valve for better protection? If so, which kind?

I’d really appreciate any advice, tips, or experiences with similar setups.


Thanks a lot!

 

[Baluncore]

Could the pressure regulator at 0.5 bar cause gas to be sucked back into the bottle due to the vacuum in the furnace?

If the pressure in the argon bottle remains greater than in the furnace, then argon cannot flow, backwards through the regulator, into the bottle.

 

[Dullard]

You didn't say what you're doing with the furnace. If you just want to 'backfill' the furnace with Argon, your setup will work. Gas won't flow from low pressure (furnace) to high pressure (bottle).
The furnaces that I've been involved with weren't as simple as just 'backfill' - they required a continuous supply of argon - 'flushing' the furnace to maintain composition (melting Titanium, Plasma etching, etc.). In this case (flushing) a mass flow controller and a throttle valve are typically used to maintain target pressure - "fixed flow / variable throttle" or "fixed throttle / variable flow" both work.

 

[dudeekeen]

You didn't say what you're doing with the furnace. If you just want to 'backfill' the furnace with Argon, your setup will work. Gas won't flow from low pressure (furnace) to high pressure (bottle).
The furnaces that I've been involved with weren't as simple as just 'backfill' - they required a continuous supply of argon - 'flushing' the furnace to maintain composition (melting Titanium, Plasma etching, etc.). In this case (flushing) a mass flow controller and a throttle valve are typically used to maintain target pressure - "fixed flow / variable throttle" or "fixed throttle / variable flow" both work.

I produce large single crystals of metals to study the fundamental mechanisms of plastic deformation. The process is carried out in a vacuum furnace, and it works beautifully for most materials — except for high-entropy alloys. These alloys contain a significant amount of manganese, which tends to evaporate excessively under reduced pressure.

My idea was to first create a high vacuum, then backfill the chamber with argon, repeat the vacuum step to further purge residual gases, and finally fill with argon again. However, it’s important for the process to still maintain a minimal underpressure (slightly below atmospheric) during the crystal growth, to limit manganese evaporation while preserving a clean environment.