Bag in a Keg.

[foxy]

I wrote some time ago about using a 10 litre keg with a bag inside. Decided to go with the 19 litre bag in a keg. So while cask beers do taste superior the shelf life isn't so good. Yes one can fill the vacuum of a cask with gas from the bottle and prevent air getting in but it's a lot of mucking around.
I have today brewed an Extra Stout which I will be transferring into the bag in the keg to condition adding sugar to the brew to encourage further fermentation.
I have a couple of inline pressure valves one is a $2.00 white plastic one which I doubt will be accurate enough, the other is a factory set valve this one is set to 6 PSI and is spot on but I will get a 5 PSI version so won't have to rely on a gauge. I am hoping after a few weeks conditioning I will be able to draw a cask style beer from the keg with the use of a picnic pump and a stout nozzle on my tap. I will not have any worries about having to finish the cask quickly or playing about with a CO2 bottle.

The cheap one on the left and the factory set on the right.

I will put a blow off tube on the keg while conditioning before attaching the inline pressure valve.

 

[MashBag]

I do like the idea of being gas free. Watching with interest.

 

[floydmeddler]

Very cool. Watching with interest, too.

Can you put a link to your original post? I think I remember seeing something like this a while back. Ringing a bell. Cheers.

 

[Sadfield]

A keykeg.

https://www.keykeg.com/?utm_term=ke...Cwb5Rgw7q07MV6yxyvQlDc54VWTGzB0caAqG3EALw_wcB

 

[foxy]

Very cool. Watching with interest, too.

Can you put a link to your original post? I think I remember seeing something like this a while back. Ringing a bell. Cheers.

I think they are more popular in the UK, I saw a video of a pub and it seemed that is all he used, he had an air pump servicing all the kegs. In saying that the beer he had in the kegs would have been carbonated to whatever volume and just served. What I am trying to achieve is conditioning the beer and serving it hopefully with the advantages of a cask but without the disadvantages.

 

[Pennine]

What happens when the pressure runs out before you are done with the keg? Add more sugar?

 

[foxy]

What happens when the pressure runs out before you are done with the keg? Add more sugar?

It shouldn't run out, the CO2 is dissolved in the beer at around 5PSI it is the air between the bag and the keg which is under pressure forcing the beer out, when that pressure drops then add more air with the picnic pump.

 

[Pennine]

It shouldn't run out, the CO2 is dissolved in the beer at around 5PSI it is the air between the bag and the keg which is under pressure forcing the beer out, when that pressure drops then add more air with the picnic pump.

Ahh yes so simple and the purpose of the bag... Sorry a bit slow today.

 

[foxy]

Ahh yes so simple and the purpose of the bag... Sorry a bit slow today.

The bag holds the beer, like those bags that hold icing sugar squeeze the bag and the icing sugar comes out. The air in the keg squeezes the bag and the beer comes out.

 

[hoppyscotty]

Have been thinking about something similar but for carbonated beer or a reusable key keg.

How are you planning on connecting the bag to the liquid out post or however you are pulling the beer?

 

[foxy]

Have been thinking about something similar but for carbonated beer or a reusable key keg.

How are you planning on connecting the bag to the liquid out post or however you are pulling the beer?

I have an Ultra Twist tap with a stout spout, it is on the 10 litre keg in the photo.

 

[foxy]

My beer is just about ready to transfer, there has been something niggling me about my method with the King Keg, I was thinking I will transfer the stout into the keg and add a syrup of sugar to prime and let it vent while I am away. Then I realised there isn't a way of venting!
The liquid post is for the liquid obviously and the gas post is for outside of the bag. it has a spear inside the bag should I have put a blow off tube on the liquid post it would make a right mess.
So how to get around it? Trial and error with the priming sugar, don't prime and hope there is enough volume of CO2 in the beer, or tip the keg upside down and vent it that way. Going to have to make a decision soon.

 

[RoomWithABrew]

@foxy
I've thought about this as well and have been using the key kegs with the bag removed as a keg for a while.

If the key keg had a solid tube for the liquid you could spund off the gas post by changing the connector to a liquid ball lock and Inverting the keg. Many disposable kegs do have a solid liquid tube, but they tend to be the ones without a bag in. The key keg has a plastic fluted liquid exit system so this won't work for you.

If you slightly underfill the bag and put the spunding on the gas post as the bag fills with a bit more gas from your priming it will squeeze out the last of the air in the surround. Then you will have CO2 in the top part of bag and might be able to spund on the liquid post?

Then change to the liquid line and pour the beer pumping air in as you need.

I do worry that the bag isn't going to be fully impervious to air but they do say they are.

I'm watching to see how it goes.

 

[foxy]

@foxy
I've thought about this as well and have been using the key kegs with the bag removed as a keg for a while.

If the key keg had a solid tube for the liquid you could spund off the gas post by changing the connector to a liquid ball lock and Inverting the keg. Many disposable kegs do have a solid liquid tube, but they tend to be the ones without a bag in. The key keg has a plastic fluted liquid exit system so this won't work for you.

If you slightly underfill the bag and put the spunding on the gas post as the bag fills with a bit more gas from your priming it will squeeze out the last of the air in the surround. Then you will have CO2 in the top part of bag and might be able to spund on the liquid post?

Then change to the liquid line and pour the beer pumping air in as you need.

I do worry that the bag isn't going to be fully impervious to air but they do say they are.

I'm watching to see how it goes.

Its a solid spear so the only way I can spund is upside down. They do come with pressure in so the bag is completely deflated. It is a bit of a problem filling there is a PRV on the air side so I am hoping I can gravity fill by opening the PRV and just slowly letting it fill. I cant put any pressure on the liquid as that will be just getting absorbed by the beer. I can get a few to play with so I may just take a punt with 10 gram of priming sugar to start with and see how that goes. That's if I can get it in by gravity. First go so it will be a learning curve.

 

[Sadfield]

Surely, this can all be calculated in the same way as bottle conditioning, if you know the volume and what temperature the beer is at?

 

[foxy]

No, it is a rough estimate that a keg is generally half to that of bottles, cask even less. Dennis King told me years ago when I got a beer engine one level tea spoon for a 21 litre cask, which turned out about right. And that was at ambient temperature.

 

[Sadfield]

You can calculate what's already in the beer instead of hoping. You can also calculate how much CO2 is produced by the sugar addition.
Theoretically the bag never has any headspace, even when serving. Or, can be controlled with external pressure. Shouldn't that be enough?

With normal kegs vs bottles, the headspace is increased in one and removed in the other when serving. Cask is different as beer is racked before fermentation is completed.

 

[foxy]

You can calculate what's already in the beer instead of hoping. You can also calculate how much CO2 is produced by the sugar addition.
Theoretically the bag never has any headspace, even when serving. Or, can be controlled with external pressure. Shouldn't that be enough?

With normal kegs vs bottles, the headspace is increased in one and removed in the other when serving. Cask is different as beer is racked before fermentation is completed.

As I said, first time trying this so just going to play around until I get a satisfactory outcome. In a brewery the beer will be carbonated to a set pressure and the bag filled. The result I am looking for is a cask beer from a keg so carbonation will be very low.

 

[Sadfield]

As I said, first time trying this so just going to play around until I get a satisfactory outcome. In a brewery the beer will be carbonated to a set pressure and the bag filled. The result I am looking for is a cask beer from a keg so carbonation will be very low.

But you could still calculate it, knowing how much is already in solution and how much CO2 you are adding via sugar.

 

[foxy]

But you could still calculate it, knowing how much is already in solution and how much CO2 you are adding via sugar.

No you can't, if it was under pressure then yes you probably could but there are other factors to take into consideration. How long does it take to fill a keg through a 4 mm ID tube? How much will the temperature go up during that time? Does the bag restrict the flow being it has had all the air squeezed out of it? How quick does the air evacuate the cavity? Best way to tackle these unknowns is by trial and error. No other way around it.