Unitank Questions

[PDore]

We are a small brewery using two 7 barrel conical; fermenters. Our process has been to ferment, cool, dump yeast, condition and carbonate all in the same tank. What we have noticed is that when we cool there is often a vacuum created in the tank from the cooling process. Has anyone else experienced this? I have spoken to a couple of people who have told me it was imposssible. Obviously not the case. How can this be prevented?

My other question is if during the conditioning process anyone has ever tried a gentle circulation ( gentle whirlpool) in the tanks to remove any yeast that may be clinging to the sides of the tank, helping the beer drop brighter?

[Matt Dog]

You can create a vacuum if you dont have any pressure on the tank when you chill it. You should have at least 5psi before you chill. If you are carbing in the unitank why wouldnt you be bunging near the end of the active ferment to capture all that CO2 and get some nice natural carb. I would think in your case you would want to have as close to 15Psi or whatever the max pressure rating on the tank is when you crash it. Never heard of anyone whirlpooling a fermenter but I know guys will gently pound the cone or sides in hopes of getting yeast to slide down. Do you have racking arms or just racking ports. With arms you dont really have to worry about yeast sliding down the walls during transfer.
Remember that vacuum is more dangerous than over-pressurization in regards to tank integrity. you should really have a vacuum relief somewhere on the tank.

[dick murton]

Even if the vacuum relief is simply the sprayball supply open to atmosphere.

Re whirling - I also have never heard of that. I strongly suspect that you would have to get a very high speed for it to have any effect, to scour it off the walls and compact it in the centre, and the pumping / stirring mechanism would cause far more damage to the yeast and beer. A gentle circulation will simply stir up the yeast, and it will still setlle on the cone.

Depending on the slope of your cone, you either pull off the yeast very slowly, and when it runs thin, leave for 24 hours or so to slide down / resettle, or you need an upstand of some sort (racking arm) or racking take off point, as already mentioned.

But if a racking arm causes high losses, why not try the whirling and leave for 24 hours or so afterwards to stand. Providing you don't introduce oxygen, it may just work. There is a first time for everything.