View Full Version : Question on beer transferring in the context of open top fermenters

01-02-2015, 05:31 AM
So I've been operating a nano system for the past 2+ years. All is fine with the product with the exception of the batches being too small. So now I'm building a larger system - 10 barrel, but am considering using a few horizontal dairy tanks to ferment in.

I use Stout conical fermenters with the nano system, and move beer out of the fermenters by pushing it out with co2 - with the goal to limit exposure to oxygen (to avoid oxidation obviously).

I've come up with a plan on moving beer out of the horizontal tanks to get the beer off of the yeast. But I don't know if the technique of pushing the beer out with co2 will work, since I'm not sure if these tanks will hold any kind of pressure (the main access entries have weird lids that clamp down).

I just recently ran into a tank that would work well as an open top fermenter, which got me wondering about a few things.

When using open top fermenters, and the beer is drained off from the bottom (and oxygen is hovering over the beer) does this create a risk of oxidation? I know the beer will have a protective blanket of co2 over it, but wouldn't that be disturbed when the beer is drained off from the bottom? Do brewers who ferment with open top systems have problems with oxidation in general? I figure it would be similar to draining from a cask, and beer at the end of a cask gets oxidized.

I would think that draining off from a horizontal tank would be very similar to draining from an open top - if the beer was not being pushed out with co2. In fact, wouldn't the same holds true for any fermenter?

I am curious what people think? Pushing out with co2 is obviously good insurance against oxidation, but if it's too difficult - how much of a risk is oxidation by simply draining off into say another vessel that is filled with co2?

dick murton
01-12-2015, 01:17 PM
Open fermenters were, and still are very common in the UK, now mainly, but my no means exclusively, amongst the micro fraternity. Emptying an open FV is absolutely no problem until the vessel is nearly empty, when there is the risk of vortexing if the tank is emptied too quickly. As long as you do not allow a vortex to be created, and stop the runoff before any gas (mainly air) is drawn into the runoff pipe, then the oxygen pickup is minimal.

This is one very good reason for having conical bottomed vessels, as they tend not to create such vigorous vortices and the volume of residual beer is much smaller. But loads of people, biggish (e.g. 120 hl brewlength) brewers included used to, and still do (e.g. Black Sheep, Theakstons) use open "squares" (term includes rounds, ovals, and almost triangular vessels - basically anything virtually flat bottomed and open or non sealed covered vessels). My experience is that dish bottomed vessels vortex more than flat bottomed or conical vessels. Horizontal vessels, admittedly based on observations during CIP cycles are the worst of the lot, and you have to be very careful during final runoff, and tend to leave lots of beer there is a CO2 or nitrogen blanket.