Pressure Transfer - Equalize Between Two Corny Kegs?

[John Spiegel]

Just got a spunding valve and am planning on fermenting my next beer under pressure in a corny keg set to around 10 psi. For pressure transfers, I've heard you need to equalize pressure between the two kegs, and that you can do this by hooking up the Serving Vessel (SV) to a regulator set to the same pressure that the spunding valve on the Fermentation Keg (FK) was set to. From there, use a jumper cable (liquid/liquid disconnect) to hook up the two kegs and release the PRV in the SV to begin the flow.

My two questions regarding the process:
1. Do I need to have the PRV continually opened/a gas disconnect hooked up to allow gas to continually flow out of the SV? Or once the flow goes, can I let the PRV close again and it will continue?

2. This is the one I'm more uncertain of. To equalize the pressure between the two kegs, rather than using my tank, is it possible to use a second jumper cable (gas/gas) to connect the two kegs and allow the pressure between the two to equalize that way? In my head, the pressure in FK would drop to fill SV; from there I could purge SV to remove the oxygen from the system. Because I wouldn't have hooked up liquid/liquid line yet, no liquid should transfer over. From there, I could connect the liquid jumper, open up the PRV on the SV to start the flow, but because the gas lines are connected, wouldn't that cause the CO2 from the SV to be transferred back to the FK, thus continuing the process? I've read a few posts/watched a few videos, but haven't seen anybody do it this way, so I'm not sure if it doesn't work that way or if I just seriously misunderstand the concept here and should instead keep the FK hooked up to a regulator to keep the pressure transfer going. Or maybe it's just a bad idea to purge SV this way but would a doable way of transferring once the two kegs are already equalized? Any clarification would be helpful.

 

[sibelman]

1. Purge Serving keg
2. Add CO2 to serving keg at or slightly above FV pressure;
3. Move spunding valve to serving keg gas post. This will
4. Attach CO2 to FV, set to spunding pressure.
5. Jumper from FV outlet to serving keg liquid post.
6. Reduce spunding valve setting so that transfer gently begins.

 

[John Spiegel]

1. Purge Serving keg
2. Add CO2 to serving keg at or slightly above FV pressure;
3. Move spunding valve to serving keg gas post. This will
4. Attach CO2 to FV, set to spunding pressure.
5. Jumper from FV outlet to serving keg liquid post.
6. Reduce spunding valve setting so that transfer gently begins.

Ok. This seems like it takes a lot of CO2. Would jumping gas/gas not do the same thing after purging?

 

[Dgallo]

2. Add CO2 to serving keg at or slightly above FV pressure;

If the op is transferring from the fv to the serving keg, the op would not want the serving keg at equal or high pressure. That would prevent transfer. In order to move liquid from the fv to the serving keg he would need less pressure so that the liquid would actually leave the fv to serving keg

Also while transferring the op would need to continuously release pressure from the serving keg so that the transfer would continue

 

[bracconiere]

Ok. This seems like it takes a lot of CO2

2-4ozs.... (best gues on my part i'm working on similar right now, haven't actually had an oportunity to watch my scale go down yet)

 

[bracconiere]

3. Move spunding valve to serving keg gas post. This will

If the op is transferring from the fv to the serving keg, the op would not want the serving keg at equal or high pressure. That would prevent transfer. In order to move liquid from the fv to the serving keg he would need less pressure so that the liquid would actually leave the fv to serving keg

Also while transferring the op would need to continuously release pressure from the serving keg so that the transfer would continue

i think he just had a brain fart or something?

 

[sibelman]

No, or probably not brain fart but possibly misguided. I just wanted to avoid any initial foamy burst. Then adding the spunding valve (and decreasing its setting) will drop the pressure so flow can start. There could be better advice (ya think? ) from someone who has done more of this.

 

[sibelman]

Ok. This seems like it takes a lot of CO2. Would jumping gas/gas not do the same thing after purging?

Hopefully the pressure difference will reduce (eliminate?) the flow of CO2 from your tank. But I recommend having it hooked up so you can give the prices a boost if needed. Especially if the serving vessel is not below the fermentation vessel.

 

[bracconiere]

No, or probably not brain fart but possibly misguided. I just wanted to avoid any initial foamy burst. Then adding the spunding valve (and decreasing its setting) will drop the pressure so flow can start. There could be better advice (yes think? ☺) from someone who has done more of this.

good thinking!

 

[k-daddy]

I pressure ferment @ 8-10psi and use the fermentation gas to purge my 2, 2.5 gallon kegs. Once fermentation is complete, I disconnect the keys from the system while I wait to transfer. When ready, I purge a jumper from my still pressurized conical to the kegs gas post to equalize pressure between the two vessels. I then connect the racking tubing to the conical and slowly fill my hydrometer tube to purge the line of any debris and get a sample for testing. I then connect to the outpost of the keg, slowly open the ball valve and begin the transfer. Works like a charm for me. Good luck.

 

[John Spiegel]

I pressure ferment @ 8-10psi and use the fermentation gas to purge my 2, 2.5 gallon kegs. Once fermentation is complete, I disconnect the keys from the system while I wait to transfer. When ready, I purge a jumper from my still pressurized conical to the kegs gas post to equalize pressure between the two vessels.

I think this is closer to what I was thinking of doing - connecting the two via gas posts to equalize pressure rather than filling with CO2 from my tank.

If the op is transferring from the fv to the serving keg, the op would not want the serving keg at equal or high pressure. That would prevent transfer. In order to move liquid from the fv to the serving keg he would need less pressure so that the liquid would actually leave the fv to serving keg

Yeah, I get that part. I'm thinking after that. Once the two kegs are equalized and connected, one needs to decrease the pressure in the vessel being filled. My question is, if I were to decrease the pressure in SV using the PRV, could I then hook up a second line via gas posts between the two vessels in order to get a continual flow of beer to SV and also a continual flow of CO2 to the FK to keep the transfer continuous?

 

[Dgallo]

I think this is closer to what I was thinking of doing - connecting the two via gas posts to equalize pressure rather than filling with CO2 from my tank.



Yeah, I get that part. I'm thinking after that. Once the two kegs are equalized and connected, one needs to decrease the pressure in the vessel being filled. My question is, if I were to decrease the pressure in SV using the PRV, could I then hook up a second line via gas posts between the two vessels in order to get a continual flow of beer to SV and also a continual flow of CO2 to the FK to keep the transfer continuous?

So essentially you want to transfer without using any regulator. Let me see if I have this straight;

FV to SV

Liquid post of FV to liquid post of SV
Co2 post of SV to Co2 of FV.

The problem with this is that everything would be equilized so no flow would occurs with out a pump or positive pressure.

You’ll need to go regulator to fv gas post. Fv liquid post to Sv liquid post. Then either SV prv left open or SV co2 post to a spunding valve or to a hose in a bucket up starsan

 

[John Spiegel]

So essentially you want to transfer without using any regulator. Let me see if I have this straight;

FV to SV

Liquid post of FV to liquid post of SV
Co2 post of SV to Co2 of FV.

The problem with this is that everything would be equilized so no flow would occurs with out a pump or positive pressure.

Even if I were to pull on the PRV of the SV a few times before connecting the gas posts? That wouldn't get the flow started?

 

[Dgallo]

Even if I were to pull on the PRV of the SV a few times before connecting the gas posts? That wouldn't get the flow started?

Where would the positive pressure come
From to move the liquid originally? You have to get the syphon to start some how

 

[John Spiegel]

Where would the positive pressure come
From to move the liquid originally? You have to get the syphon to start some how

From the PRV. Maybe I'm not explaining myself well.
1. Equalize pressure via gas post
2. Unhook gas posts
3. Connect liquid posts
4. Pull PRV on SV to create initial flow
5. Connect gas posts again

 

[JJinMD]

Also, keep in mind, since you are fermenting in the keg, you could easily purge your SV during fermentation with a jumper and putting your spunding valve on the SV you would essentially purge and have both the FV and SV at 10 psi (or whatever you reasonably want) prior to transfer. Then you might not have to hook up to your tank at all when time to transfer.

 

[Dgallo]

From the PRV. Maybe I'm not explaining myself well.
1. Equalize pressure via gas post
2. Unhook gas posts
3. Connect liquid posts
4. Pull PRV on SV to create initial flow
5. Connect gas posts again

Yeah I’m def confused then. You need constant positive pressure being placed on the vessel you are transferring out of. If there is not constant pressure both vessels will eventually meet equilibrium and stop the transfer. So unless the FV has your co2 tank connected to it. Or the liquid line is connected to a pump, flow will not be continuous

 

[eric19312]

1. Purge Serving keg
2. Add CO2 to serving keg at or slightly above FV pressure;
3. Move spunding valve to serving keg gas post. This will
4. Attach CO2 to FV, set to spunding pressure.
5. Jumper from FV outlet to serving keg liquid post.
6. Reduce spunding valve setting so that transfer gently begins.

This is pretty much exactly what I do except the FV is a conical. I purge my kegs using CO2 starsan push and they are pressurized a bit higher than the conical. I take the spunding valve off the conical, put it on the gas post and let the purged kegs reach same pressure as the conical. Then I pressurize the conical head space about 3-4 PSI above where it was. Then connect conical to the liquid out port on the keg. Works just fine. If I want a faster flow I may give the spunding valve a quarter turn. I could save a bit of CO2 with a closed loop like described above but I've got three kegs to fill off that conical and that seems like too much fussing around. Buy CO2 by the 20# tank and don't worry about using a few ounces to push the beer around on kegging day.

 

[Climb]

John S., if you want to do a closed transfer as you describe in post #15, once the beer starts to transfer (step 4) you will need the SV lower than the FV and before you connect the gas posts together (step 5). Once you connect the gas posts, both vessels will equalize in pressure and the beer will stop flowing as mentioned. You need the pressure difference to start the the beer flowing. I would call this a pressurized transfer. When the SV is lower than the FV and you connect the gas posts, you are know doing a siphon transfer.
One other thing to keep in mind is that you want the pressure in FV and SV to be close, may be only a few PSI different. Otherwise you could get foaming during the pressurized transfer stage. Its also a good idea to have the FV and SV at the same temperature to help prevent foaming.

 

[John Spiegel]

John S., if you want to do a closed transfer as you describe in post #15, once the beer starts to transfer (step 4) you will need the SV lower than the FV and before you connect the gas posts together (step 5). Once you connect the gas posts, both vessels will equalize in pressure and the beer will stop flowing as mentioned. You need the pressure difference to start the the beer flowing. I would call this a pressurized transfer. When the SV is lower than the FV and you connect the gas posts, you are know doing a siphon transfer.
One other thing to keep in mind is that you want the pressure in FV and SV to be close, may be only a few PSI different. Otherwise you could get foaming during the pressurized transfer stage. Its also a good idea to have the FV and SV at the same temperature to help prevent foaming.

That's the explanation I was looking for. Thanks for clarifying.

 

[JJinMD]

Yeah, just make sure you fully empty the FV by keeping the bottom of the FV diptube higher elevated than the ball lock on the SV. I just put my FV on the counter and SV on the floor. It does take a while though sometimes (probably because I use the 4mm ID evabarrier tubing in my jumpers). To speed it up, I do pull the prv every now and then during the process.

 

[sibelman]

... It does take a while though sometimes (probably because I use the 4mm ID evabarrier tubing in my jumpers). To speed it up, I do pull the prv every now and then during the process.

I got some 5mm ID EVAbarrier tubing to help with transfer speed. Still takes about 20 minutes.

Instead of PRV, I use spunding valve (for carbonated beer) or a tube into a water bucket (for flat beer) to release pressure via the gas post on the serving keg.

When the pace of bubbling decreases I add some pressure to the fermenting vessel. Gravity (FV above SV) would reduce or eliminate that need, but my setup (and physical strength limitations) argues for leaving the FV low.

Sounds like OP @John Spiegel is ready to rock and roll. Cheers!

 

[Dgallo]

I just need someone to now explain this to me because I’m having such a hard time understanding this transfer without being the FV being constantly connected to the co2 tank and regulator.

What I’m gathering is the fv is set to, let’s say 5 psi, and the SV is at 0 psi. The fv will be disconnected from the regulator, and then only connected from Liquid post to liquid post to the SV. Once the transfer begins, then you are connected the SV co2 post to the co2 post of the fv closing the loop. is this correct?

 

[Eltes]

I just need someone to now explain this to me because I’m having such a hard time understanding this transfer without being the FV being constantly connected to the co2 tank and regulator.

What I’m gathering is the fv is set to, let’s say 5 psi, and the SV is at 0 psi. The fv will be disconnected from the regulator, and then only connected from Liquid post to liquid post to the SV. Once the transfer begins, then you are connected the SV co2 post to the co2 post of the fv closing the loop. is this correct?

And you need to make sure the FV is higher than the SV. Once the transfer begins and you equalize the pressure gravity will take care of the rest (you're basically siphoning from FV to SV, just in a closed system).

 

[Dgallo]

And you need to make sure the FV is higher than the SV. Once the transfer begins and you equalize the pressure gravity will take care of the rest (you're basically siphoning from FV to SV, just in a closed system).

Gotcha. I didn’t see anyone mention the drop in gravity (could have just missed it) so I was having such a hard time grasping how equilibrium wouldn’t be met and flow would continue

 

[JJinMD]

Gravity is the only reason you don't need to keep the FV hooked up to the pressure. Make sure the elevation of the bottom of your FV diptube is above the elevation of the ball lock on your SV and the siphon action created from your FV liquid line to your SV liquid line will fully empty your FV.

 

[John Spiegel]

Gotcha. I didn’t see anyone mention the drop in gravity (could have just missed it) so I was having such a hard time grasping how equilibrium wouldn’t be met and flow would continue

After some more digging, I found a video detailing the process. Begins at the 12:40 mark in the video. Thanks again for the input everyone.

 

[Carolina_Matt]

Thanks for sharing the video - that's probably the best video I've seen that details the process.

One question on purging the keg with fermentation co2, for those who have tried. How long does this take? I tried doing it for the first time this week and it didn't seem too successful, but maybe I wasn't patient enough.

I use a blowoff tube for the first 3 days of fermentation, then I set up a spunding valve once the bubbling starts to die down. Once it got around 10 psi, I hooked the gas line from the FV (keg) to the starsan-filled SV (keg). It pushed out less than a gallon, then stopped. The next day I tried again, and it pushed a little and then stopped. As I thought about it, it makes sense - there's only a little bit of co2 in the headspace, and it doesn't seem like enough to fully purge a keg. But it seems to work for others somehow?

 

[sibelman]

Gotta start early in fermentation to get the full benefit.

 

[Bobby_M]

My two questions regarding the process:
1. Do I need to have the PRV continually opened/a gas disconnect hooked up to allow gas to continually flow out of the SV? Or once the flow goes, can I let the PRV close again and it will continue?

You need a PRV on the gas port of the receiving keg set to 10psi and then push about 15 psi into the donor keg to make the transfer happen in good time.

2. This is the one I'm more uncertain of. To equalize the pressure between the two kegs, rather than using my tank, is it possible to use a second jumper cable (gas/gas) to connect the two kegs and allow the pressure between the two to equalize that way?

You could jump the two gas ports together but then the kegs will need a decent height differential to have the beer siphon properly since both headspaces will be equal.

I personally prefer letting the pressure differential move the beer even though you use a bit more gas doing it that way.