Using Keg CO2 and Gravity for Closed Transfer

[troglodytes]

This topic has probably been talked about ad nauseum, but I had the most horrible time the first time I attempted to do a closed transfer. Nothing moved. It could have been the hop debris or the pressure of the keg vs lack thereof in the fermenter, or some combo of both. Either way I'm kegging tonight and don't want to go through the nightmare again. and here's the thing, I find that people talk about the gadgets and connections and hoses to attach on the fermenter side, but don't discuss what to do with the pressurized keg on the receiving side. I'm very new to kegging so please forgive any ignorance.

Background: I have a speidel with stock spigot on top and stainless spigot on bottom. I pulled me hop bag after dry hopping and everything is compacted after a cold crash so debris should not be an issue. I have a clean/sanitized/pressurized keg awaiting the beer.

Process: I was going to use the CO2 in the clean keg to create a loop. Keg gas into fermenter head space, pushing liquid out the bottom spigot into the liquid in post of the keg. My thinking is that initially the pressure in the keg will fill the headspace with CO2 and push the beer out of the fermenter oxygen free.

Issues:??
As the fermenter empties the pressure will decrease as headspace increases and the keg will do the opposite as it fills with liquid its head pressure will increase. How do you get the beer to flow? Wouldn't the pressure increase in the keg to the point where the beer will stop flowing all together. Do I pull the PRV at a certain point to remove keg pressure down to atmospheric levels, but then wouldn't oxygen just be introduced into the keg, or is the PRM a one way valve? Also, with a speidel I can give the headspace some pressure, but not much, maybe 5 psi max...should i just pressurize the fermenter to 5 psi, seal the top and transfer that into my keg at atmospheric pressure without creating a loop (albeit wasting some CO2)?

 

[Carolina_Matt]

Wouldn't the pressure increase in the keg to the point where the beer will stop flowing all together.

That hasn't been my experience. As beer flows into the keg, the CO2 in the headspace should be forced out of the keg via the gas disconnect. Assuming you have a closed loop, it will flow through the tube and back into the fermenter headspace, which should help push it down. If you have one tube going from the spigot to the liquid disconnect, and another tube going from the gas disconnect back to the top of the fermenter, then everything should keep flowing well.

The only issue I've had is when my fermenter had too much trub so it got clogged, but that shouldn't impact you if debris isn't an issue.

 

[troglodytes]

Ok, so I don't need to keep open the PRV to release keg pressure, then. I just wanted to make sure. Hopefully all my issues were due to debris last time and I have that fixed. Thanks.

 

[brewbama]

I do not open the PRV.

 

[troglodytes]

Success! My problem last time had to have been entirely due to debris. I transferred last night and the closed loop worked perfect. Slow and steady transfer took about 15 minutes, no bubbles in the lines and fermenter was definitely pressurized with the CO2 when I finished. Looks like I got the process down, now I just need to find a solution for filtering dry hops in the future if I want to not use a hop bag.

 

[brewbama]

Congratulations!

 

[bairsbrewing]

I do not open the PRV.

I have the same fermenter! Love it! What did you use for the lid? A rubber stopper? Also, what pressure did you pressurize the keg to?

 

[brewbama]

The return hose has a drilled stopper attached. I use the same hose for blowoff — just remove the QD.

To purge, I completely fill the keg to the rim with sanitizer by fill a bottling bucket attaching the liquid out hose and open the PRV. The keg is full when it comes out the PRV. I use Iodophor. To force the sanitizer out of the keg into a bucket very little pressure is required. I use ~2-3 psi. Once the keg is blowing bubbles vs sanitizer, I remove the liquid out QD (black), turn the keg upside down over the now full sanitizer bucket, shake it a bit to pool any last remnant of sanitizer into the lid and pull the PRV to push it out.

To answer your question the keg is pressurized to ~2-3 psi.

Once the keg is purged, I connect the liquid out QD, and while CO2 is flowing push it onto the spigot to purge the line. I then connect the gas in QD and let the remaining CO2 flow out while pushing the hose into the blowoff port of the fermenter.

 

[Brian66]

The return hose has a drilled stopper attached. I use the same hose for blowoff — just remove the QD.

To purge, I completely fill the keg to the rim with sanitizer by fill a bottling bucket attaching the liquid out hose and open the PRV. The keg is full when it comes out the PRV. I use Iodophor. To force the sanitizer out of the keg into a bucket very little pressure is required. I use ~2-3 psi. Once the keg is blowing bubbles vs sanitizer, I remove the liquid out QD (black), turn the keg upside down over the now full sanitizer bucket, shake it a bit to pool any last remnant of sanitizer into the lid and pull the PRV to push it out.

To answer your question the keg is pressurized to ~2-3 psi.

Once the keg is purged, I connect the liquid out QD, and while CO2 is flowing push it onto the spigot to purge the line. I then connect the gas in QD and let the remaining CO2 flow out while pushing the hose into the blowoff port of the fermenter.

question on the timing and/or connecting the CO2 tube to the fermenter. Are you saying let CO2 out as (or before) connecting to the fermenter? Last time I did this the CO2 rushed into the fermenter and I had a very hard time getting anything to flow at that time.

 

[Sammy86]

Wouldn't the pressure increase in the keg to the point where the beer will stop flowing all together.

I had this happen the first time i did a closed loop transfer...well semi closed I have a big mouth bubbler so I'm sure there is some CO2 escaping...anyway it equalized and the beer stop flowing. I had to hit the PRV 2-3 times and it started up again.