Carbonation @ 6000 Feet
I have aquired a carbonation chart to use at 6000 ft which is appropriate for our brewery here in the mountains. We use it to determine the volumes of CO2 in our beer. It is similar to the sea level carbonation chart but slightly different in numbers. I have been using this sheet since I began here and I am wondering if anyone knows anything about correction factors and elevation involved in carbonation. At the top of the sheet it reads:
Atmospheric Pressure 11.69
Correction Factor 3.01
Now, I know that atm pressure at sea level is 14.7. So this makes sense that 11.69 plus 3.01 equals 14.7. How then is 3.01 a function of 6000 feet above sea level?
What I am trying to do is to expand and redevelope the sheet for reading vol CO2 at certain pressures and temperatures. I currently have only 45F up to 20 psig. This is for Zahm Nagel testing. Sometimes our beer reaches 50 F and then I begin guessing at the vol CO2. I have tried to enter the data into a spread sheet, however it does not understand the sequence of numbers as they are not consistant. If I understood the method behind the madness then I might be able to design the sheet myself. All comments would be helpfull.
CO2 Elevation Chart
Well, as far as extrapolating the ZahmNagel chart I don't have much to offer. I used to brew in Telluride (9750' elevation). I utilized the traditional CO2 volumes chart with success. I found that when I got the product down to temp (36 degrees F), the desired volumes were achieved. I often wondered if due to the "closed" nature of the carbonating tank, if altitude mattered to CO2 volumes. It seemed to me that even if one began (with "flat beer") at 9750', the beer would essentially have a to compensate for the reduced initial volume/pressure but after X amount of CO2 was introduced for time, Y, the desired volumes could be achieved no problem. I'll be curious to see what other responses you get.
carbonation way up there
If I understand your question right (which I may not), I think GlacierBrewing is right. As long as you're talking about carbonating and serving beer at your elevation, a standard CO2 chart (without correction) should work fine for you since it's relative pressure that determines carbonation (absolute pressure in bright tank - atmospheric pressure at time of pour).
The only time this would not hold true is when your beer's going to be served at some other much lower elevation (like a competition). Assuming the competition is at sea level, you should just be able to add 3.01 psi to your standard carbonation table to compensate for the change in elevation.
If you use nitrogen to dispense, you would also need to make some corrections on your mix since many of these calculations are based on absolute pressures to determine dissolution ratios (what pressure for N and CO2 to get 80% of your dissolved gas as CO2, 20% as N, etc.)
I hope that the real scientists chime in hear if what I've said is wrong.
Hope this helps.
One more thing...
Forgot to include in my first reply;
Check out http://www.mcdantim.com/
This company may be able to help you.
I believe I have the chart you need, please email your fax # and I'll send it.