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Thread: Line Length, Pressure, and Carbonation Question

  1. #1
    Join Date
    Jan 2016
    Location
    Manitowoc, WI USA
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    14

    Line Length, Pressure, and Carbonation Question

    Hi -

    I'm trying to balance my new draft system that uses kegs. The formula I'm using is:

    Length of Line = (Pressure - 1 - (Height/2) / Resistance

    Because of my setup, I have to have 12 foot runs. The height from the middle of my keg to the tap is 4.5 ft. I have purchased 3/16 ID beverage tubing, so I'm using a resistance of 3.

    With all of this in mind, that tells me that my pressure needs to be at 39.25 to be balanced. That seems insanely high to me. Will my beer will eventually be severely overcarbonated and eventually pour with a lot of foam? What recommendations might you make? I'm stuck with 12 feet of line. Use tubing with a greater inside diameter?

    Thanks

  2. #2
    Join Date
    Jun 2007
    Location
    Jacksonville FL
    Posts
    85
    Yes that pressure is too high and will over carbonate your beer. You either need blended gas or beer pumps. Also remember you need to chill that conduit your lines are running in, a 12' run will need a glycol system running through it or the beer in the lines will warm up and you will never get things to pour correctly. Read the BA draft manual if you haven't already: http://www.draughtquality.org/ and if you haven't installed a draft system before, consider calling a good professional installer (if you can find a competent one...).

  3. #3
    Join Date
    Sep 2015
    Location
    San Francisco, CA
    Posts
    45
    Without putting too fine a point on it, you're thinking about this backwards.

    From a quality perspective, you can't afford to overcarbonate your beer when it's sitting in the cold box, and you also haven't even built the draft lines yet. Totally solvable problem.

    I assume you're going to carb most of your beers at 2.4 to 2.7 volumes. Depending on your coldstorage temperature, this implies that you will have to keep your kegs on draft pressurized at 12 to 16 psi to avoid over carbing your kegs or allowing gas to escape and undercard the beer.

    Thus, you have to size the lounge according to that target +\- 14psi. Normally, one can change both the line length and the line size to hit that target. Since you have to have 12' runs, this means you will have to use a nitrogen/co2 blend to pressurize the lines - a 25/75 mix of co2/n2 is commonly available because of Guinness. For these purposes, 25% co2 gas at 40 psi is a good approximation of 100% co2 gas at 10 psi. Thus, make your lines such that the restriction numbers add up to 50 to 60 psi of total resistance and use a Guinness gas supply of 25:75 blend ratio. Please check these rough numbers with your own calculations.
    Last edited by theomuller; 08-21-2017 at 08:27 PM.

  4. #4
    Join Date
    Jan 2016
    Location
    Manitowoc, WI USA
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    14
    Thanks you two...I didn't even think about blended gas. That's probably the answer.

    However, I'm wondering....what if I used 1/4 beer lines (.85 resistance) instead of 3/16? Using the 1/4 lines at .85 resistance at 15psi (2.7 volumes) then comes back saying that I need 14 feet of line, which is getting my closer to 12. Possible solution? Seems like an easy fix, but I must be missing something.
    Last edited by petskullbrewing; 08-21-2017 at 09:08 PM.

  5. #5
    Join Date
    Jul 2004
    Location
    MO.
    Posts
    8

    beer pumps

    The person suggesting a 25% CO2/N2 gas at 40 PSI is right about the carbonation issue, but.......... I wouldn't want to work around bright tanks at 40 PSI when their manufacturers don't want to guarantee them above a working pressure of 15-20 PSI. A 200 square inch door at 40 PSI means there is going to be 8000 pounds of force pushing on that door!

    Go with beer pumps.

    Carbonation levels then are a simple balance of CO2 pressure and beer temperature. Easily pegged to exactly where you want them to be. And the flow rate to the taps is determined by the pressure sent to the pumps.

    CO2 is a lot cheaper in the long haul than are the blends, nitrogen tanks, blenders, etc.

    The BA draft book, or companies like micromatic, can help you determine the proper line sizing, and also help you with determining the best methods to keep the beer lines properly temperature controlled. Having your lines properly sized, cooled, and insulated, with no "dead spots" will save many headaches.

  6. #6
    Join Date
    Oct 2013
    Location
    Dallas, Bangalore and soon Goa
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    223
    Quote Originally Posted by brewingpro View Post
    The person suggesting a 25% CO2/N2 gas at 40 PSI is right about the carbonation issue, but.......... I wouldn't want to work around bright tanks at 40 PSI when their manufacturers don't want to guarantee them above a working pressure of 15-20 PSI. A 200 square inch door at 40 PSI means there is going to be 8000 pounds of force pushing on that door!

    Go with beer pumps.

    Carbonation levels then are a simple balance of CO2 pressure and beer temperature. Easily pegged to exactly where you want them to be. And the flow rate to the taps is determined by the pressure sent to the pumps.

    CO2 is a lot cheaper in the long haul than are the blends, nitrogen tanks, blenders, etc.

    The BA draft book, or companies like micromatic, can help you determine the proper line sizing, and also help you with determining the best methods to keep the beer lines properly temperature controlled. Having your lines properly sized, cooled, and insulated, with no "dead spots" will save many headaches.
    Having used both, I prefer the blended gas. Both work. With kegged product, I wouldn't worry about the 40psi since they are rated to 60psi (in most cases). Serving vessels with a long run, I'd opt pumps. It also depends on how many taps you have. One blended gas tank & regulator/generator, or 6, 8, 10, more pumps?

    Last generator I got at a good discount, but the savings on buying co2 was actually pretty significant. I projected a break even before two years, and we planned to be open for longer than that. Also, I needed all the co2 I could get for production side (large canning runs).

    Again, pumps work good too. Look at ROI and if you plan to grow for the best plan. 1/4" lines may give you good resistance, but will they pour your needed volume in a reasonable time?

  7. #7
    Join Date
    Nov 2010
    Location
    Newtown, PA
    Posts
    32

    Pumps or 1/4

    Long draws I certainly prefer pumps. I just did our cold box with 1/4" lines with 14 beers on tap. I chose a long length of hosing to allow tapping the kegs that are farther away so no one would have to move a keg if they need a new tap. Based on the length I wanted 1/4" was the way to go and its all pours nicely. If I did it again I would prefer the cleaner look of shorter lines and only do a few with 1/4".

  8. #8
    Join Date
    Apr 2015
    Location
    Lakewood, CO
    Posts
    23
    Rule of thumb we use is 1.5 psi per foot of 3/16" tubing. Which means 18 psi or so for 12 feet. Your height difference is minimal, so I wouldn't even bother correcting for that. Based on 18 psi, you'll have to go with beer gas to avoid overcarbing in the keg. Any local gas supplier should be able to provide 50# tanks of food-grade 75/25 N2/CO2 mix, so you shouldn't have to worry about blending. The only issue you may encounter is that the partial pressure of CO2 in the keg as it empties may fall below carbonation pressure, which may cause the last gallon or so to be pretty flat. We used beer gas for our previous setup, which was 35 feet of run, but our new 6 foot runs only needed 12 psi, so we had the partial pressure problem until we switched back to CO2.

  9. #9
    Join Date
    Jan 2016
    Location
    Manitowoc, WI USA
    Posts
    14
    Thanks for all the advice, folks. I picked up a 50# 75/25 N2/CO2 tank. Our taproom is opening this weekend, so I'll follow up and let everyone know how it went. Thanks again!

  10. #10
    Join Date
    Aug 2010
    Location
    Enterprise, Oregon
    Posts
    1,602
    Why didn't you simply use larger ID tubing for the long run? AFIK, it's pretty much standard to use a 3/16" choker line to reduce pressure at the faucet end of the line, and 3/8" to get to the choker.

    I don't know how much gas you actually get with a 75/25 mix, as N2 is a non-condensing gas, while CO2 becomes a liquid at around 500-800 psi at ambient temps. You can pack a heck of a lot of CO2 in a can at 800-1,200 psi, but not so with N2--most straight N2 cans run at 4,000+ psi.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

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