pre purging recieving tank

[dick murton]

CO2 DOES sink to the bottom of an enclosed space. Ask the widows of three guys at one of the breweries I worked at - not while I was there I hasten to add, but a few years before. Unfortunately I have also worked in another where someone took his last drink in a full FV, not a pub (his own choice, not an accident). And I have know of other deaths, animal and human due to CO2 in enclosed spaces - FVs, effluent chambers

Point I'm making is - ensure you have adequate low level ventilation and ensure if you go into aan enclosed space, it is checked thoroughly for CO2 content (not more thn 0.5% for more than 10 minutes) and Oxygen content (> 19 % I seem to remember - need to check the exact figure though)

And an enclosed space can be your fermenting room, it doesn't have to be a tank, or drainage pit

[Larry Horwitz]

I don't need other posts (although they exist). All I need is a DO meter. Try it out. pressure up you tank w/co2 and then rack your beer and throw the meter on it. There is no science that shows the program you're speaking of. This is a common brewing fantasy. Sure CO2 is heavier than some other gases and all other things being equal will sink...but it itsn't displacing enough air to keep from oxidizing your beer. Purge your tank from the bottom for about 20 mins per 10 bbls THEN you'll have luck reducing the O2. Don't be fooled, just 'cause some guru says it doesn't make it so. Ted is a friend (hey Ted) but there isn't a scientific study out there showing the magic CO2 covering your beer thing. Saw Bamforth talk about this topic, ask him if you don't want to take my word for it.

Also, just 'cause you see / smell / feel the CO2 coming out of your BBT to your cooler floor doesn't mean there is no O2 there...just to little for you to live on...which is a ton more than it takes to oxidize your beer.

Purge or oxidize. no shortcuts based on wishful science will work

[dick murton]

I'm not disagreeing that purging from the bottom is not necessary - quite the opposite. Its just that I sometimes think that people over purge, and waste gas. The point was made about slow filling at the start, and avoiding the beer forming a fountain - doesn't do the beer CO2 content any good, let alone the risk of DO2 pickup. This is one reason why I would always try to use conical vessels, though they are a pig to get pressure tested for use with bright beer and high CO2 levels, so dish bottom vessels are the norm. The cone quickly damps the fountain.

I think Teds approach is pretty good and not likely to give problems.

The main reason for my comment was the times I have been in small rooms when people have been purging tanks, or fermenting, without adequate CO2 extraction at low level.

Cheers

[jfulton]

Ahem..

Sorry to ruffle the feathers... Merely stating that CO2 does sink.

[RobZamites]

I remember as a newbie pro brewer, almost doing myself in removing an anti-whirlpooling fitting in the bottom of a freshly emptied 60bbl BBT. I reached in the manway to the waist, and almost became a human waste.
Learned a big lesson that day!

[Ted Briggs]

This will also foam the heck out of the beer in the tank. You shouldn't pressurize a full tank of beer through the carbonating stone.
Unless I mis-read your advice...---Guy

Yes, putting in gas too fast will foam the beer. I should have said "very slowly" I put my ear against the tank and open the carb stone valve to where I hear bubbles slowly/gently going into the beer. This will take an hour in a 10bbl tank to reach 15psi depending on the co2 already in solution. Then check w/ your Zahm and/or DO meter if your fortunate enough to have them. This part of the technique is my own devising and results in good carbonation levels for me, with additional carbonating sometimes necessary. But its easier to add co2 than to try to fix over-carbonated beer! You could add top pressure and carbonate from there if that’s more to your liking. The O2 reduction is accomplished mostly by the 2 5psi purges.

LARRY: "All I need is a DO meter. Try it out. ....There is no science that shows the program you're speaking of. This is a common brewing fantasy......there isn't a scientific study out there showing the magic CO2 covering your beer thing.

Larry is correct; you are not 'covering up' the beer. The point is to reduce the overall amount of O2 in the tank which leads to lower DO levels in the product. Don't rely on a 'Co2 blanket' without purging. My post was for the 97% of pub brewers (and probably allot of distributing brewers too) who don't have DO meters and need a reliable technique. I don’t even have a Zahm!!!

DICK- "I sometimes think that people over purge, and waste gas."
The "scientific study" from Weihenstephan I referenced showed that two 5psi purges were best. Beyond this you would be getting little reduction in O2 levels in the tank, thus wasting gas.

I apologize for not being able to cite the publication or author but I stand by its authenticity. (Logic process: W published study = validity, save to memory) It was over 8 years ago and I can still see the graphs in the back of my brain........

[oppigards]

Thanks

Thanks all for your input in this topic. The reason why I started to think about this was that if I filtered to a just emptied bbt, emptied with co2, I got a more tasty and stable product compared with the same beer filtered to a bbt with just a blanket of co2 up to the near half of the tank. I will adopt the 2* 5 psi purging for the couple of next brews and valuate it.

Merry Christmas,

from Oppigards Brewery
Bjorn

[Moonlight]

I am curious about the double 5 psi purge. Remembering back to college days, if you put CO2 into a atomspheric (atmospheric=15 psi "Absolute"; air=20% O2) pressure tank until 5 psi (5 psi "gauge" = 20 psi "absolute"), you should have roughly 25% CO2 and 15% O2. Then vent to atmospheric, leaving the same ratio. Next repressurize to 5 psi with CO2 and you'll get 43.5% CO2 and 11% O2. Venting leaves the same ratios.
I can imagine one could skew the numbers to favor CO2 if you filled the CO2 in the bottom (and gently) and vented out the top. I wouldn't be happy with 11% O2 in my tank atmosphere after filling. Perhaps there was additional purging of the headspace after filling?

[gitchegumee]

Not to segue this thread...

..but replies to my post for nitrogen users have been limited. I've followed this thread and wonder whether someone can direct me to guidelines for purge gas purities? I'm considering a membrane nitrogen generator to replace carbon dioxide for purge gas. 99.8% is a common factory-set purity for these units. It seems that 0.2% oxygen is still high for a product destined to be packaged and put on a warm shelf. Filling slowly from the bottom to eliminate the tank atmosphere, closing the valve on the CIP arm when that is done, pressurizing (again with N2), and then relying on a shallow blanket of CO2 from the transferred beer seems risky. I'm nervous because replacing air with N2 from the bottom has got to be less sure than with the very heavy gas CO2. Actually, a N2 purge would seem to be more effective by slowly purging from the top! And finally, is there an easy way to scrub the remaining O2 from the N2? Surely someone out there has some experience they might be willing to share with me. I could use some help! Thanks!

[Ted Briggs]

...I can imagine one could skew the numbers to favor CO2 if you filled the CO2 in the bottom (and gently) and vented out the top. .....Perhaps there was additional purging of the headspace after filling?

Yes, I do exactly that. But after two purges of an empty tank you are chasing diminishing returns.

[Simha H]

CO2 sinks but needs time for it.

Yes CO2 sinks but first of all it needs some time to do so. Even when you give it enough time to sink what happens when you are purging a tank with CO2 under pressure. Just try the same with two immissicible liquids. The liquids mix in no moment at all. Gases diffuse much more easily than liquids and hence while purging, the gases are mixed. Some initial displacement of air does occur but after some time it is the mixture of the two gases that goes out. Double purging lessens the concentration of air but does not entirely remove it. But again at cost of huge wastage of CO2. If you have enough time and are totally quality oriented then try what I tried with huge success. In an empty tank take enough CARBONATED water (at low temprature as low as you could afford) from bottom displacing air from top of the tank. Give some rest and then using counter pressure of CO2 displace water in the tank from bottom.

SUCCESS is assured.

[Moonlight]

How about if we conclude that CO2 has a propensity to settle in air if it is hasn't yet mixed with the air. After the CO2 is mixed, it will not ever again separate and settle.
If CO2 is about 0.5% of the atmosphere, and if those of us near sea level are in the bottom 0.5% of the atmosphere, why are we not dead of CO2 asphyxiation? With a mixed gas CO2/N2 bottle, why wouldn't the Nitrogen come out first from the top? When the fermenting room is heavy with CO2 near the floor and you turn on a mixing fan, it never re-settles. Why does it take so much skill to make a perfect black and tan?
The exact same issues happen in a beer tank. Unless you can guarantee the CO2 entering isn't mixing with the tank atmosphere, the CO2 really, really never settles into a layer on the bottom.
For a dead horse, this issue is more like a cat with nine lives!

[Simha H]

Low cocentration & mother nature save us.

Constant winds and rain and other atmospheric conditions keep the gases in a constant state of motion. It would take a very calm almost non existant movement in the atmosphere combined with a very long period of time to make our planet unfit for breathing. But in nature there are places were these conditions occur and cause death to wild animals living in the vicinity of such places to die out of asphyxiation when they enter these low lying craters.

[am-brewer]

Where is the "other thread" on this topic ?

[rafters_brewer]

here is a sure-fire way to remove oxygen from your tank- fill the tank with water till it pours out the top. attach a co2 line to the top and blow the water out the bottom... not a bad plan if you have 100 gallon tank. pretty wasteful if it's 1000...