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  1. #21

    On Beersmith, what units are you using? What value are you using for resistance in that equation?

    In my experience the tube that we normally use and the vinyl tubing used in the states are vastly different animals. The tubing mostly available here are meant to be used for beer and it has a super low resistance. Most equations don't work for us.

    Save yourself some trouble and get a compensator/flow control tap. They negate the need for long tubing.

  2. #22
    Quote Originally Posted by getack View Post
    On Beersmith, what units are you using? What value are you using for resistance in that equation?
    I was using the required units, so feet and PSI and from the website I took the value beersmith gave so a loss of 3psi per feet for the 3/16" tubing. But it makes sense that if our tubing is different the equation wont work.

    I will look into the flow compensator tap once I have some money saved up.

    Thanks for the feedback everyone, I would have used a 4m beer line and would probably have issues, think I will start with a 2m or 1.5m beer line and reduce the length if needed.

  3. #23
    Senior Member
    Join Date
    May 2014
    Bredell Rd Somerset West
    That sounds a good length. If the beer line is too long the flow rate will be slower, if it's too short the beer will foam and therefore will be flat. Err on the side of caution and use 2m you can always cut it shorter but not so easy to make it longer.

    7C is quite warm but 2.7 volumes of CO2 is quite high, what beer is it?

    Flow compensator taps are for tweaking the flow rate and cannot fix overcarbed beer. It's better to understand the principles like you are doing.
    I spent 90% of my money on brewing and drinking beer and the other 10% I wasted

  4. #24
    I cut my 6m off beer line into a 2m and 4m section, so have some options now. I connected the 2m beer line and will test it out this evening.

    Beer in the keg is a wheat beer so the 2.7 vol CO2 fits there, my keezer struggles to go much colder than 7 degrees unfortunately so not much I can do there, saving up for a better fridge.

    Thanks for the feedback guys

  5. #25
    Senior Member
    Join Date
    Dec 2014
    Hartbeespoort/De Wildt
    Here's a recent article by Brad the Beersmith himself:

    This week we take a look at the science behind designing a good draft beer system for your kegged homebrew. Everyone loves draft beer, and I consider my keg system to be one of the best purchases I've made in my brewing career. Kegging makes everything easier, and if you want to start kegging, please read my earlier article on how to keg. This week we're going to look at the more advanced topic of balancing your keg lines.
    In my previous article we covered how the temperature of the beer and carbonation level desired in volumes of CO2 drives the overall carbonation pressure - a number you can also calculate easily using BeerSmith. You will need to know your keg pressure as a starting point for designing your overall system. However this is not the complete story - as the lines of your keg play a very important role. In general the longer your keg lines are, the lower the serving pressure at the tap. If the tap pressure is too high or too low, the overall system is said to be out of balance and your beer will either foam or be flat.
    Line Resistance is Not Futile

    So how does one design a draft beer system to maintain proper balance at the tap? The pressure drop depends on resistance in the beer line. Beer lines have two types of resistance - one due to elevation change (i.e. the keg being higher or lower than the tap), and a second due to the beer lines themselves which generate friction as the beer flows through the lines.
    Lets look at resistance first to keep things simple. Here are some sample resistance ratings for various popular beer lines:

    • 3/16" ID vinyl tubing = 3 psi/ft
    • 1/4" ID vinyl tubing = 0.85 psi/ft
    • 3/16" ID Polyethylene tubing = 2.2 psi/ft
    • 1/4" ID Polyethylene tubing = 0.5 psi/ft
    • 3/8" OD Stainless tubing = 0.2 psi/ft
    • 5/16" OD Stainless tubing = 0.5 psi/ft
    • 1/4" OD Stainless tubing = 2 psi/ft

    Generally plastic tube of smaller than 3/16" ID is not recommended - it provides too much resistance for practical use!
    So now that we have the resistance factors how to we go about designing a keg system that is in balance? For the purpose of our example lets assume that you have pressurized your kegging system at a nominal 12 psi, which at a 40F refrigerator temperature represents a mid range carbonation level of about 2.5 volumes of CO2 - typical for an average American or European beer.
    At the tap end of our balanced keg system we want a slight positive pressure to push the beer out, but not enough to foam. Generally this would be between less than 1 psi. So let's target a tap end pressure of 1 psi. The math from here is pretty easy to calculate the balanced line length (L):

    • L = (keg_pressure - 1 psi) / Resistance

    So starting with our example of 12 psi keg pressure, and some typical 3/16" vinyl keg tubing (which loses 3 lb/ft) we get L= (12-1)/3 which is 3.66 feet. So a 12 psi kegging system would provide 1 psi of pressure at the tap with 3.66 feet of tubing.
    Note that some authors leave out the 1 psi tap pressure (i.e. use zero tap pressure) and simplify the equation to L= (keg_pressure/Resistance) which makes the math even easier (the simplified equation would give you 4 feet of tubing vs 3.66 ft). The truth is that you can target anywhere between zero and 1 psi at the tap and still be in balance - the difference is relatively small, though a slight positive keg pressure will give you a better flow rate.
    The four foot example with 3/16" ID vinyl is great if we only have a few feet to go (i.e. in a fridge) but what if one needs to go further? A simple switch to 1/4" ID vinyl tubing will get us there - looking at the same 12 psi keg system we get: L = (12-1)/0.85 = 12.9 feet. So with the larger tubing we can deliver our beer to just under 13 feet. For other applications we can consider polyethylene or stainless. However if going a long distance one needs to also consider refrigeration - as you don't want a large volume of warm beer in the lines.
    Beer Line Length and Elevation

    Changes in elevation also come into play if you design a more complex serving system. The rule of thumb is that your beer loses 0.5 psi/foot of elevation gain. So if your tap is 1 foot higher than the keg it loses 0.5 psi, and conversely if it is lower than the keg it will gain 0.5 psi per foot of elevation.
    So if we roll this into our equation, we get the following for a given height (Height - in feet) of the tap above the keg itself:

    • L = (keg_pressure - 1 - (Height/2)) / Resistance

    So lets go back to our original example of a 12 psi keg pressure, 3/16" ID vinyl tubing and this time put the tap 2 feet above the keg itself. We get L=(12-1-(2/2))/3 which is 10/3 or a line length of 3.33 feet.
    Another example with longer lines: 12 psi keg pressure, 1/4" ID vinyl and a tap four feet above the keg gives: L=(12-1-(4/2)/0.85 which is 9/0.85 or 10.6 feet of line length.

    Using the above equations, it is pretty easy to calculate the ideal line lengths for a given keg system operating at pressure. Hopefully this will help you properly balance your own keg system for home use. I intend to roll the line length calculator into a future update for BeerSmith.

  6. #26
    Thank you for the info, using the equation (L = (keg_pressure - 1 - (Height/2)) / Resistance) I get a length of 1.5m, using two at the moment.
    My beer has been sitting at 6 degrees (16PSI) now for over two weeks and it is still not carbonated, the beer comes out flat and really foamy plus it dispenses really really fast ( when I drop the pressure to 12PSI).
    I have even increased the pressure to 30PSI for 48 hours to boost carbonation, but that also made no difference to the carbonation levels.

    I did check for leaks and could not find any. What reasons could there be for foamy flat beer? Could my beerline be to long (2m instead of 1.5m) or could my regulator be faulty, or are there perhaps some not so obvious places to check for gas leaks that I could have missed?

  7. #27
    Senior Member
    Join Date
    Dec 2013
    Cape Town
    I use the same beerline, even with short as 1 meter still get nice carbonation and foam thickness. With party taps.

    Disconnect the CO2 from keg and release some of the CO2 from keg. Try pouring small sample.

    Keep on releasing gas till happy with pour.

    Turn down your regulator close to zero. Reconnect to keg. Slowly open regulator pressure adjustment, on my reg you can hear gas starting to flow. Check what the gauge shows.

    Otherwise get a seperate air pressure gauge and compare

  8. #28
    Senior Member JIGSAW's Avatar
    Join Date
    Jul 2013
    Cape Town
    Had that same problem in the beginning ... the beer is actually carbonated (might even be over-carbonated) ... but because you only pour foam, that foam will in fact be flat beer once it convert back into liquid form. These days I carbonate at 30-40PSI for 36Hrs ... disconnect gas and release excess pressure .... turn regulator down to zero ... reconnect and only turn gas on till i hear it flow ... usually 3PSI ... and that's how I pour .... sometimes I have the gas completely turned down and I easily pull beer at a good rate and carb level for up to 3 days before needing to up the gas again and give it a little boost

    These figures and equations they have on paper only work in classrooms ... each guys setup is different so he must fiddle till it works for him
    Last edited by JIGSAW; 20th October 2017 at 16:08.
    The Problem With The World Is That Everyone Is A Few Drinks Behind.!

  9. #29
    Super Moderator AtronSeige's Avatar
    Join Date
    May 2013
    Blog Entries

    Quote Originally Posted by DR_Beer View Post
    So I am a bit confused, there is a massive difference between 1.1m and 4.3m of beer line, so how do I know what to use?
    A bit late to the convo, but here is my my 5c (after spending loads of money and time on getting my taps to work).

    Does your tap have flow control? If so, then do not worry about line length! I have my keg in a the fridge at 7C. 1 bar CO2. Beer line around 15cm. No issues.

    Currently I keg my beer, put it in the fridge, connect CO2, wait a few days, and beer is ready.

    If you do not have a flow control, then you need to do magic math and a lot of swearing. One trick I heard of is inserting fishing line into the beer line as this causes friction and thereby slowing the beer.
    It's not the size of your equipment; it is what you brew with it.

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    April, June and November;
    All the rest are thirsty too
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