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amcclai7
11-05-2014, 07:36 PM
I have heard from many people that the way to go with my serving system is a beer gas blend. This link, http://www.micromatic.com/draft-keg-beer-edu/dispensing-beer-blended-gases-cid-1793.html is just one of the many companies that offer this. The idea is that you serve ALL beers with a bit of Nitrogen. A guiness style beer would be 25% CO2/75% N while any normal beer would be 80% C02/20% N. The idea behind this is the fact the N is heavier than CO2. The top layer of your beer is then only coming into contact with N, which is supposedly even more inert than C02. This is also, although I'm not exactly sure how, supposed to give a more even, less foamy pour with none of the guiness style head or flavor. I've talked to a bar in Knoxville that swears by it. Have any of you had any experience with this and if so, what are your impressions?

Starcat
11-06-2014, 06:07 AM
You can run blended or total straight nitrogen for dispense across the board without any perceptable issues.

monkeybrewer
11-06-2014, 10:31 AM
Gas blends do not separate in your tanks causing N2 to be on top of the beer. Whatever the concentration of the gases going in to the tank will remain constant throughout the head space. The use of blended gases comes into play for long draw draft systems where you need more than 10 psi in order to get the beer to the taps without foaming. If you need 20psi to push to the taps and you used CO2 only you would hugely over-carbonate your beer in short order. If you used the gas blend (75%N2/25%Co2) by the end of the tank your beer will be flat as you have only been giving the beer 5psi of CO2, instead of the 10psi (at 40F) that would maintain proper carbonation. Also in no way does any N2 go into the beer at pressures that would be needed to push beer to the taps. I believe it does not start dissolving in beer until a pressure of 35psi reached at cold temperatures (approximately). Some people may "swear by it" but this isn't a taste question or an opinion question, it is simply math according to the partial gas law. The wrong gas blend, pressure or temperature and you are going to over-carbonate or flatten your beer accordingly.
Cheers

Starcat
11-06-2014, 04:49 PM
Jay, your post sounds pretty good by the theory and well written I might add.
But the idea that you will have flat beer on a long draw system running 20 PSI blended does not work out in practice on our system which is straight nitro, zero blend. This was discovered accidentally.
There are no flat beer issues at the end of the keg.
So, there is a zone where very good theory and practice are shown to be quite different.
Why does it work? Possibly because we are running greater than 20 PSIG.
Might be something to investigate.

panadero
11-06-2014, 05:05 PM
I think if you push from 1/4 or 1/2 bbl kegs you will be fine, but unless you can sell ten barrels from a tank very fast, the CO2 level will fall. The same way head pressure will carbonate, low head pressure will lose carbonation. The length of time will be the determining factor - if you carb with strait CO2 in a brite, and then keg, the last keg will still be fully carbed when hooked up, whereas the last keg worth in a ten barrel tank will be kind of flat.

The percentage of CO2 vs nitro matters, as does the head pressure. If you have a 50/50 CO2 Nitro blend, and go at 20 psi, you will have ten pounds of CO2 pressure - if I read the draft manual correctly - which will give a normal CO2 level for draft beer. Roughly 2.5 volumes, though I am not quoting the manual on that, just my memory.

Starcat
11-07-2014, 09:29 AM
The percentage of C02 to Nitrogen does NOT apparently matter on all configurations.
This is the straight fact and the point of my original post.
To clarify, not everything that appears to be writ on stone tablets is the actual way things are.
What you have stated about using larger serving vessels is noteworthy.

TGTimm
11-07-2014, 10:26 AM
On the other hand, using straight CO2 @ 16psi to push our 2.60 v/v ales, which should have a breaking pressure of around 14 psi at our cooler temp, we do not experience over-carbonation at the end of the kegs, even when they have sat partially full for a couple of days when the pub is closed. Based, of course, on our highly calibrated bio-Zahms.

I think the limited surface area of the beer in an upright keg seriously restricts the exchange of gas between the liquid and the headspace. It would be interesting to compare a half-full keg stored upright with one stored on it's side to see if increased surface area makes much difference.

Theory and practice, practice and theory.....

monkeybrewer
11-07-2014, 01:21 PM
regardless of tank or keg, an improper gas balance will guarantee either a flat or over carbonated beer, given enough time. Time being the key to whole thing. You can push with air if your going to use it all in one night without issue (ie picnic pump) but the principle is still the same. Partial gas law is just that, a law. You can do it wrong and hope the beer goes quick enough to not be affected or you can do it right and know you'll never have trouble regardless of how long the beer is in the vessel. And remember...the more empty the keg is, the less time needed to go out of balance with the wrong gas mix. If you're serving from a serving vessel, the wrong gas mix will surely screw your brew by the end. Again this is all just math, plain and simple.
Starcat - the mix of gas DOES matter to ALL configurations, given enough time, that is straight fact...again partial gas law does not care about how a bar sets up their draft..nothing about being written in stone, just long known gas laws that were and are true, long before craft brewing hit the scene. Curious...how much experience do you have with all of this and what size brewery are working at?
Cheers

panadero
11-08-2014, 08:00 AM
My brewery is in the real world. Not meaning to offend, just adding my experience and understanding. There are plenty of forums to get mad on, please don't do it here, I think we are all in this together, and everyone has value to add.
David

Starcat
11-08-2014, 09:14 AM
My experience is not much on that side actually, but I am making observations and wondering why it works because I want to know the best way which would appear to run blended at the correct ratio and pressure for your given system.
I am strictly having fun looking for answers which some might misread.
The time factor is of interest.
I see the points being made of interest and find them all helpful.

monkeybrewer
11-09-2014, 03:15 PM
Who's mad man? I'm just trying to tell it like it is.... No offense to any one... Just spreading the good word of strong scientific based brewing... This stuff is straight out of the draft line manuals, along with many educational publications about the gas laws. I was taught by scientists and try to share the knowledge I was lucky enough to be given. No beef with any one at all... Just want all of us to be successful. Cheers to everyone

Starcat
11-10-2014, 06:22 AM
MB, the ideal gas law is taught in refrigeration 101. but interestingly enough does not apply to those gases.
I have found this discussion quite interesting.

The other thing is how what should be known envelopes are pushed and things don't quite add up and then work with no problem over time.
In our case we were not trying to cut any corners. Also the Brewmaster is pretty sharp and there are some tricks in the set up that add stability.

Timm, I fully admire your game!

Some other things to note.
We have been and are coming more into a time when many of the seeming laws of physics are being shattered.
The reality field we are in is proving to be more fluid that " believed."
The Meta Sciences will replace the old physics without any doubt.
Did anyone take note of the truck driver who was dead for 45 min and came back the other day?
The experts sure cannot deal with such matters.
There are many other things going on that never see the light of day that are far more bizarre.

Some additional things to consider......

The Observer effect
The Hutchinson effect
Local Field effects


until later

monkeybrewer
11-10-2014, 08:42 AM
Maybe I'm not explaining it correctly. The partial gas law does apply to these gases...as does the ideal gas law.
here's a link about draft beer which includes these gas laws

http://www.draft-beer-made-easy.com/carbonation.html

take it as you will...I can't add any more to this discussion
Cheers

TGTimm
11-10-2014, 10:28 AM
Whoah!

I'm not questioning any gas laws or physical principles. I'm just pointing out that we may operating systems too small for too short of a time for the gas pressures to fully (or significantly) come into equilibrium. We rarely have a keg on for more than two days, which apparently doesn't allow the excess head pressure of CO2 to significantly affect our carbonation.

Going the other way--zero CO2 partial pressure--I'm sure we would experience flat beer within a day or so, because I've witnessed it when using party pumps to push beer with air--essentially no CO2 pp. The beer is definitely flat (and beginning to oxidize) by the next morning.

So I wouldn't worry too much about excess CO2 pp unless storing beer for extended periods of time, or using huge push pressures. I would be concerned about losing carbonation with insufficient CO2 pp in the head space, as in the case of using pure or improperly mixed Nitrogen.

TL Services
11-10-2014, 11:48 AM
Ideally ALL beers should be dispensed with a gas mix that exactly matches the proportions of the same gases that are dissolved in that beer. This will ensure there is no change at all in the level of carbonation or nitrogenation throughout the dispense life.

Clearly in the real world this would be impractical, so the best way to do it is to select a standard gas mix that is closest to 'exact'; that way any changes will be minimal and well within both product specification and palate sensitivity.

The gas laws do apply in this case - and they apply equally for tanks and, indeed, any closed vessel containing beer.

There is a rider to this, which is simply that a keg, sitting quietly with a slight inequilibrium of headspace gases will take time to reach true equilibrium between gaseous and dissolved phases. I did a major amount of work on this some years ago and in this situation we found it takes a keg around 48 hours to re-equilibrate.

Of course any movement - rolling, being shaken about on a delivery truck, etc, etc. - will speed up the time to equilibrium.

On an associated matter, when kegs that have been CO2- or N2-purged to control dissolved oxygen, it is important to ensure filling is 'quiet' to avoid entraining the purge gas into the beer as it fills. What happens in this case - and this was the reason I did all the above work - is that the entrained gas dissolves over time and the beer ends up over-carbonated or over-nitrogenated, leading to dispense problems.