Foreline valve and trap - what is neccesary?

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.
Post Reply
User avatar
Dennis P Brown
Posts: 3160
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Foreline valve and trap - what is neccesary?

Post by Dennis P Brown »

Until you get a proper valve, the simple solution is to leave the mechanical pump running - turn off the turbo; then allow it to spin down (assuming you have no mid-point vent built into the turbo body.) After it stops, turn off the mechanical pump and let air into the system. No oil vapor back flow issues (just water vapor but for most fusor's, that issue isn't too big a problem if you first run the system down to the 10^-5 torr range before opertaion.)
ChristofferBraestrup
Posts: 131
Joined: Sat Apr 11, 2020 9:47 am
Real name: Christoffer Braestrup

Re: Foreline valve and trap - what is neccesary?

Post by ChristofferBraestrup »

Okay so this is exactly what I wanted to do in the first place. I thought the higher vacuum once the turbo slows would 'suck' oil back from the roughing pump even though it kept running.

And I do have a mid-point turbo vent valve, both solenoid and manual.
John Futter
Posts: 1848
Joined: Wed Apr 21, 2004 10:29 pm
Real name: John Futter
Contact:

Re: Foreline valve and trap - what is neccesary?

Post by John Futter »

you should also have an activated alumina trap in the roughing line to stop oil vapor from the backing pump backstreaming into the turbo wwhen at high vac with no leaks
ChristofferBraestrup
Posts: 131
Joined: Sat Apr 11, 2020 9:47 am
Real name: Christoffer Braestrup

Re: Foreline valve and trap - what is neccesary?

Post by ChristofferBraestrup »

I should, yeah, but that is less critical as far as I know. The magnitude of oil is a trillion times lower than sucking half a litre oil back into the pump!

I wouldn't be terrified about pumping down the system without a foreline trap.
Post Reply

Return to “Vacuum Technology (& FAQs)”