Gas transfer - How much waste?

[djonesax]

Hi,

I want to modify my 15 Gallon speidel so that I can use gas to transfer and not have to lift the thing out of the keezer after cold crash.

I got to thinking about the amount of gas needed to do that. I'm not sure how to do the math but dont want to be wasting too be wasting too much CO2. If that a very wasteful process being that its a 15 gallon space?

Thanks,

David

 

[acidrain]

For liquid Co2 to convert to gas at room temperature, the ratio is about 1000 times in volume.
To make 1 cubic meter of gas, you need 1 litre of liquid.
There are 264 gallons in 1 cu meter.

1 lb of co2 = 8.741 cu. ft. of gas.
8.74 cu ft. = 264 gallons, so 1 lb of liquid Co2 can push 264 gallons.

To push 15 gallons of beer, you would only need .229 lbs. of Co2.

In other words, it won't take much. .

 

[djonesax]

Great, thanks! I have a 20# tank so I think I'm good

 

[FuriousE]

For liquid Co2 to convert to gas at room temperature, the ratio is about 1000 times in volume.
To make 1 cubic meter of gas, you need 1 litre of liquid.
There are 264 gallons in 1 cu meter.

1 lb of co2 = 8.741 cu. ft. of gas.
8.74 cu ft. = 264 gallons, so 1 lb of liquid Co2 can push 264 gallons.

To push 15 gallons of beer, you would only need .229 lbs. of Co2.

In other words, it won't take much. .

This math isn't working for me - wouldn't it take 15/264 = .057lbs of CO2?

 

[Minbari]

it doesnt take much for a liquid to want to come out of a pressurized container. I would think 5-10Psig would be all you would need. since co2 is about 850-900 psig, wont take much.

I agree with the math, should be .057 lbs unless there is something we dont know.

 

[BanditBrewCo]

There are 7.48 gallons in cubic foot... So using your math for C02 conversion would be as follows

1 lb of liquid co2 = 8.741 cu. ft. of gas.
1 cu. ft. (liquid) = 7.48 gallons
8.74 cu ft. gas Co2 = 65.38 gallons, so 1 lb of liquid Co2 can push 65 gallons at zero psi and pure 1.0 volume.

And since we usually have to build back pressure of 1-3psi typically to "push" the beer from one vessel to another we would in fact use approximately 25-30% more gas then our total outcome would be approximately 1 lb Co2 to push 49 gallons beer given above assumptions.

Numbers are kind of my thing and acidrain is still correct in that it will not take much "wasted Co2" at all.

 

[Minbari]

so that would be about 0.3 lbs of co2 for 15 gallons.

you also have to account for the headspace. 1-3 psig would take nearly nothing when it is full and it would take progressively more and more co2 the more empty it got. I am sure there is a calculus formula for this, but I am also sure it has been too many years for me to remember what it is.

still co2 is pretty cheap.

 

[BanditBrewCo]

Thanks correct Minbari and was accounted for in the additional 25-30% Co2 gas needed to back pressurize on top of the initial 8.74 cu. ft./lb.

So in the end based on my local prices 20lb for $20 would cost me close to $.35 per transfer of 15 gallons.

 

[djonesax]

Awesome, thanks for the replies. I am going to try and see if I can rig a carboy cap to fit on the top of my 60L speidel so I can do gas transfers while inside the chest freezer after cold crash. I can lift it out myself but I end up splashing the beer around and stirring up the trub. As a secondary benefit, racking out of the spediel is a PITA anyway and the spigot always fills up with sediment.

David