Pulling a Vacuum on a Keg?

Anybody ever try pulling a vacuum on a soda keg for filling? I’m concerned about the o ring around the lid. It is designed to be under pressure not a vacuum and I don’t know if it will hold. (all of my brew stuff is temporarily in storage so I can’t just “try it”). Thanks in advance!

Why?

If anything, you would want to flood the keg with CO2 before filling it.

I use a vacuum pump to rack / transfer / bottle all the time. I can only gravity feed or siphon if my source vessel is above the receiving vessel which is not always the case. Pulling a vacuum takes away the elevation issue.

OK.

Wouldn’t the keg be at 0 pressure and the negative pressure be in the fermenter?

I’m guessing you would draw the O2/CO2 out the gas post. The beer from the fermenter would be going into the keg from the liquid post. And the fermenter would be under the vacuum, or the liquid is replace with O2?

I have no experience with vacuums. How do you do it and at what psi?
TIA[quote=“DLV”]I use a vacuum pump to rack / transfer / bottle all the time. I can only gravity feed or siphon if my source vessel is above the receiving vessel which is not always the case. Pulling a vacuum takes away the elevation issue.[/quote]

Actually the vessel you are filling is under vacuum. The vessel you are drawing from is at atmospheric. Vacuum pump is connected to the gas inlet of the sealed soda keg. The liquid line of the soda keg would be connected to a dip tube in whatever the liquid is storded in (conical, carboy, drum, etc). The vacuum pump creates a negative in the keg and draws the liquid into it. You can also put filters in line between the two vessels and filter that way as well. BTW I left out some stuff to keep it simple - like always use an overflow protection vessel on the inlet to the pump to protect it from getting a slug of liquid.

What are you fermenting in? Bucket? Carboy? Conical? Sanke? I use pressure to (carefully) rack from carboys, conicals and sankes.

Update:
Yes it is possible although I had issues exactly where I thought I would - at the hatch o-ring. I was all set up for filtering and bottling my wine and I figured I would try to use the vacuum pump for the cider as well. The cider I keg not bottle. So I used the vacuum pump to pull a vacuum on the keg, then pull the cider from the conicle thru a 5 and a .5 micron filters. It worked but you could hear leaks around the o-ring. If I wasn’t pulling thru the filters it would have worked like a champ.
Normally I use the CO2 to push the cider from the conicle thru the filters and into the kegs but I was already set up and thought I would experiment.