CO2 Woes. There's got to be an easier way!

[peebee]

So, after making a few plumbing changes and chasing a couple of leaks down, I managed to fill the internal mylar balloon with air while venting the barrel space. Connecting the balloon to a King Keg full (5 gallons) of water I was able to pressurise the barrel up to 7 psi and consequently pressurised the King Keg up to 6 psi (gauges were not calibrated to each other) and water was dispensed from the King Keg beer out line. Managed to dispense over half of the King Keg. Next step (in a couple of weeks) is to see if I can fill the internal mylar balloon with fermentation gas from the fermentation bucket with actual beer being fermented . Watch this space.

Cor, I hadn't really noticed I was recommending a solution that was converging with yours, even after @Sadfield had suggested I switch my thinking to be effectively in line with what you were doing.

Beer bag would need to be oxygen impermeable. Otherwise beer will oxidise in the bag.

True, but would like to think a bag intended for storing beer would be impermeable to O2...but worth checking out.

I believe you are right. Those bag solutions are fairly impermeable to O2, unlike polythene "Polypins" which are permeable (not that I can convince everyone of that!).

I did look at ways to compress gases like air, such as asked for in the OP. Diving cylinders looked like they'd become an expensive option, air compressors for filling diving cylinders are an expensive option, but compressors for air (to drive tools like nail guns, etc.) are not so expensive (£100ish). I'm sure I had been looking at some cheaper in-line compressors that would more easily adapt to compressing fermentation gases? Note: They'd only compress to modest pressure and nowhere near enough to liquify CO2.

 

[RoomWithABrew]

The fermentasaurus with it's 35 litre volume is running my keg at cask pressure fine. A gas engine for a beer engine.

The keykegs have a foil bag for the beer inside them, but they still tend to be " squeezed " by injected CO2 outside the bag and between the plastic keg.

 

[hoppyscotty]

The keykegs have a foil bag for the beer inside them, but they still tend to be " squeezed " by injected CO2 outside the bag and between the plastic keg.

Yeah, it doesn't have to be CO2 though. Its convenient for bars to use CO2 as its what they've got on hand but for home use if you're looking to save on CO2 consumption then you could use compresses air. If there is a local Scuba dive shop near you, a compressed air fill is dirt cheap once you have a tank.

 

[RoomWithABrew]

@hoppyscotty
Agreed but I'm not totally sure of the gas permeability of those bags. Some bags are double skinned and then you can get the situation where the bag fills with gas between the layers which clearly indicates the layers are permeable and so there will be diffusion.

Completely out of the box option would be to fill with water. This comes out of the tap at more than enough pressure. You heard it here first. But you wouldn't need pressure as it's basically an incompressible volume replacement. So one pint out one pint in.
This might be the best way to go, tiny bit of starsan or even better some ascorbic acid or sodium metabisulphite in the keg space so any oxygen in the water would be inactivated.

 

[peebee]

... Completely out of the box option would be to fill with water. This comes out of the tap at more than enough pressure. You heard it here first. But you wouldn't need pressure as it's basically an incompressible volume replacement. So one pint out one pint in.
This might be the best way to go, tiny bit of starsan or even better some ascorbic acid or sodium metabisulphite in the keg space so any oxygen in the water would be inactivated.

Nice idea. I have heard of bags delaminating this way. @Dads_Ale gave up with them for this reason. I just hope they've got that hiccup sorted by now? (Probably hoping in vain).

But ... won't have heard of using water first here! Although the mechanism will have been different. In Scotland they didn't always go with the "hand-pump" idea but used water pressure and a "tall font" (?). Couldn't dig out anything on t'internet. Would be interesting finding something on that, but it would be wandering well off-subject.

 

[hoppyscotty]

Water sounds like a nice idea but I would worry about buoyancy. Seeing key kegs in operation it always seems to be that the gas, usually CO2, sits on top of the bag and pushes the bag down from the top so the bag of beer occupies the lower part of the keg. If you use water than I would imagine (happy to be proved wrong) that the water might surround the bag, or get under the bag and then that means you can get the bag being squeezed in the middle such that the beer in the lower part of the bag might not scavenge out of the bag...or some strange effect like that. Probably worth a try though.

 

[RoomWithABrew]

The key kegs have a fluted piece of soft plastic that runs down its' length inside the foil bag. This means the bag gets completely emptied. I'll get a picture of it next time I take one apart. This means there isn't any trapping. The water volume and pressure should be balanced or you could force a bit more water in so I don't think the lock will occur. There shouldn't really be any gas above the fluid level in the bag because you fill the bag to the brim. It's in equilibrium in it's filled space so no gas will come out. You then remove beer and replace the space with water. Hence no pressure change and gas still should not come out. There won't be headspace if pressures and balance are right.
I think.
I'm interested in the Scottish font idea but its probably not bag in keg type noodling we have moved onto.