Filtering carbonated vs. still beer

[Woolsocks]

Going to try a new trick this week....

Usually we filter our (nearly) still beer with a Velo Horizontal leaf filter and then carbonate it in the bright tank.

I have a beer that's already full carbonated which I would like to now filter. What differences should I expect in the process?

Another change is that usually the source tank is on the first story of the building, along with the filter, while the receiving tank is on the second story. In this instance, both tanks are on the second floor while the filter is on the first floor. What differences can I expect from that?

Thanks!

[Fred Scheer]

Filtering carbonated beer

Woolsocks;
Filtering carbonated beverages is not new.
When you filtering out of Storage tank, your beer ussually has between
1.5 - 2 % CO2. The receiving tank and filter have to have ~ 2/10 - 3/10 CO2 Vol more than the inlet of the filter; otherwise it will NOT work.
As long as you watch the pressure very careful, there should be no problem.
Hope this helps,
Fred

[gitchegumee]

I don't get it. Why would you vent the natural carbonation, filter still, and then carbonate afterward? There certainly are advantages to preserving the natural carbonation and filtering under pressure. Lower CO2 costs, less residence time in the bright tank and less wear & tear on your beer are legitimate concerns. Both the fermenter and the bright tanks should be at the same CO2 pressure during the entire process. Ensure this is the case by running a balance line between the tops of the two tanks. Being on a lower level, the filter will run at a higher pressure--so many feet of beer higher. You could fill the hoses and filter with (ideally deoxygenated) water, add CO2 to make the pressure in the hose at the tank the same as in the tank. Push the water out with CO2, add the beer which will now flow by gravity, filter your beer at a higher pressure than atmospheric, and you're done. Your beer will thank you! Good luck!

[Woolsocks]

Gitchegumee, you may have a point there. Basically I do it because it requires less attention on my part during the latter part of fermentation. Trying to catch it when there's just enough sugar left to carbonate, not enough to set off the PRV, isn't easy. I suppose a smart person, though, could rig up a gadget to relieve pressure once it reaches a certain point. Have you such gadetry?

[grs]

I have one of the ones shown on pages 1 to 3:

http://www.barby-kuehner.de/english/main_e/catalogue.html

[pbutlert]

Woolsocks, I have built some of these for our fermenters with parts from grainger. Stainless t, all thread, a ball valve, and variable pressure relief valve(page 1476). Not as reliable as a barby, but lots cheaper and they do the job. And all our tanks have PRV's as an additional safety. I filter carbonated beer with an erosion dosing DE filter, which has a closed dosing tank, so it doesn't foam. Also the balance lines are key. Good Luck!

[Woolsocks]

<consults zahm chart>

So... if I want to keep my tank pressure under, say 15 PSI, and I want to ferment my ales at, say 68°F, the most CO2 I can get naturally is about 1.5 volumes, right? I guess that's better than nothing, but it's hardly the whole job. Is this something better suited for lager brewing? If I ferment at 50F and allow 20PSI, I can naturally carbonate to 2.7 volumes.

[leechase9]

&quot;Bunging&quot; your fermenter

Naturally-carbonating in the fermenter is often termed "bunging", which refers to sealing the fermenter near the end of fermentation to build head pressure in the tank. You don't need to try to dissolve it at fermentation temperature. If you "bung" the tank to capture 15 psi in the headspace, then proceed to chill the tank, you increase the CO2 solubility significantly. Check out how much CO2 will dissolve in your beer with (15psi) and (at the chilled temperature): This is likely to make your beer overcarbonated (time, temperature, and pressure are the key factors, and surface-area-to-volume ratio is the other big player, as it effects the time function.)

Not knowing much about the system you are using, I'd suggest this: capturing about 5-8 psi in the headspace at the end of fermentation, then chilling when you are ready (don't skip the diacetyl rest if you need it!). Check the condition of the beer when you are ready to filter(or after the filter), and adjust as necessary.


Hope that helps.
Cheers-

Lee

[jarviw]

Sorry if this is completely off topic, but I don't quite get this part...

Wouldn't that also depend on the head space volume??
If the beer is fermented at 68F and capped for 15psi and then chilled to 32F, head pressure will only drop from 14psi (due to temp change, per ideal gas law).

but even under pressure, 14 psi of head pressure only holds about twice the volume of CO2 as the head space... as CO2 dissolves into the beer, the head pressure will decrease until equilibrium point (which may not be the CO2/temp solubility point). Depend on the head space, it may or may not be enough to carbonate the beer to desired carbonation level.

wouldn't it be the case?