Long Draw system? Need mixed gas? - Page 2 - Home Brew Forums

 Home Brew Forums > Long Draw system? Need mixed gas?

07-10-2012, 04:12 PM   #11
divi2323
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Oct 2011
Blue Island, IL
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Subscribed to this. You're doing exactly what I'm planning on doing in a few weeks, except I'm fabricating my own trunk line and chiller.

07-10-2012, 04:28 PM   #12
zachattack
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Mar 2012
, MA
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Quote:
 Originally Posted by SpartyParty So if my normal serving pressure is say... 4 or 5psi i would need to add .5psi per foot (lets assume about 10 feet vertical) then another .5psi per foot of line resistance... so I could serve it at say 14 or so? Maybe I'm not understanding the math...? What I'm looking for is it waste of my time to drill a hole in my wall and run line if I'm not willing to spend the money on a gas blender? If there is a chance that i can use only co2 and balnce it out and not have over carbed beer I'm willing to try it and see if i can balance it out. Thanks again!
In a balanced system, your serving pressure should equal your carbonation pressure. For most people this is in the 12-14 PSI range, depending on the beer style, temperature, personal preference, etc. In a proper system there should be no need to change the pressure to serve.

According to the calculations, you should be fine with 1/4 inch tubing and pure CO2 pushing the beer out. I can't promise you it will work in practice... but I'm sure someone here's done it before

07-10-2012, 04:34 PM   #13
carlisle_bob
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Apr 2012
Carlisle, PA
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Quote:
 Originally Posted by SpartyParty So if my normal serving pressure is say... 4 or 5psi i would need to add .5psi per foot (lets assume about 10 feet vertical) then another .5psi per foot of line resistance... so I could serve it at say 14 or so? Maybe I'm not understanding the math...? What I'm looking for is it waste of my time to drill a hole in my wall and run line if I'm not willing to spend the money on a gas blender? If there is a chance that i can use only co2 and balnce it out and not have over carbed beer I'm willing to try it and see if i can balance it out. Thanks again!
Hi

There may be a disconnect here:

Your serving pressure (pressure coming out of the faucet) is always going to be 0 psi. The beer is in normal air at that point. You *want* it to get down to that pressure gradualy. Abrupt changes will make it foam.

If your beer is kegged at 4 or 5 psi that's a different issue. That's a very low carb beer. Most commercial beers are up in the > 12 psi range and a few are served as high as 18 psi. At 4 psi, there isn't going to be much carbonation at all...

Bob

07-10-2012, 04:37 PM   #14
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Nov 2011
Cranberry Township, PA
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Quote:
 Originally Posted by zachattack Sorry, but this is wrong. It takes 0.43 PSI per foot to lift water. One inch of water = 0.036 PSI. The rule of thumb for balancing a keg system is to assume 0.5 PSI per vertical foot. That's why above I said that a vertical gain of 12 feet would roughly cancel out half his serving pressure. 1/4 inch ID polyethylene tubing has a resistance of roughly 0.5 psi/foot so with 12 feet of line, 12 feet of vertical gain he's looking at a 12psi drop which should be good to go. In practice things might work a little different, sometimes the resistance is less than you think so he may need more tubing to cancel it out, as Bob mentioned.
zachattack, you are correct. I fail at scrutinizing quick google results. The numbers I grabbed agreed with my gut, so I didn't fact check. Thanks for the correction. My gut still says slow pours and/or higher than desired carbonation is likely, but maybe not to the point where it is a serious problem.

Also, FWIW, the reason that resistance is often different than expected is because the pressure drop due to the tubing itself varies depending on flow rate. Higher flow rates require greater pressure drop. Estimating .5psi per foot of tubing length is a very rough estimate which assumes a certain flow rate. That's why it ultimately takes some experimentation to tweak it just the way you want it.

SpartyParty, please keep us updated for posterity sake.

07-10-2012, 04:58 PM   #15
zachattack
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Mar 2012
, MA
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Quote:
 Originally Posted by adamreef zachattack, you are correct. I fail at scrutinizing quick google results. The numbers I grabbed agreed with my gut, so I didn't fact check. Thanks for the correction. My gut still says slow pours and/or higher than desired carbonation is likely, but maybe not to the point where it is a serious problem. Also, FWIW, the reason that resistance is often different than expected is because the pressure drop due to the tubing itself varies depending on flow rate. Higher flow rates require greater pressure drop. Estimating .5psi per foot of tubing length is a very rough estimate which assumes a certain flow rate. That's why it ultimately takes some experimentation to tweak it just the way you want it. SpartyParty, please keep us updated for posterity sake. Adam
Good point about resistance being a function of flow! I think you're right that OP should experiment. I think this will work, might need a bit of tweaking (increasing/decreasing extra line) but shouldn't require nitrogen.

07-10-2012, 05:09 PM   #16
SpartyParty
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Jun 2011
Cresco, IA
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Thanks for all the help guys! I may have been off with my "4psi serving" I carb most of my kegs between 8-12 psi. A few of you mentioned adding line to balance it out. When or why would I want to add line?

I think what i'm going to do is run about 12 feet of line from a keg full of water to a picnic tap and have the line at a 8 foot vertical. Then try and pour and play with it just to see if it works. If I can pull that off then it should work with the beer and the actual build. Is there any issue with testing using water and not carbed beer? I should have the line at the desried temp when running the test correct?

Thanks again! When I start the build I'll be sure to update the post. I have 6 tap brass tower I snagged from CL for \$25. It was a mess and I cleaned it up and replaced two shanks. I'm pumped to give it some action!

07-10-2012, 05:20 PM   #17
zachattack
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Mar 2012
, MA
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Quote:
 Originally Posted by SpartyParty Thanks for all the help guys! I may have been off with my "4psi serving" I carb most of my kegs between 8-12 psi. A few of you mentioned adding line to balance it out. When or why would I want to add line? I think what i'm going to do is run about 12 feet of line from a keg full of water to a picnic tap and have the line at a 8 foot vertical. Then try and pour and play with it just to see if it works. If I can pull that off then it should work with the beer and the actual build. Is there any issue with testing using water and not carbed beer? I should have the line at the desried temp when running the test correct? Thanks again! When I start the build I'll be sure to update the post. I have 6 tap brass tower I snagged from CL for \$25. It was a mess and I cleaned it up and replaced two shanks. I'm pumped to give it some action!
Measure the flow (pour) rate when you're experimenting. A slower pour rate is what you want, if it comes screaming out of the faucet it means it's gonna be all foam if it's beer. Don't worry about temp, just measure flow rate.

For your other question, sounds like you need to read up on system balancing! This is something you should understand before you take on a project like this, once you understand why we're suggesting these things it'll be pretty obvious. There are some good guides online, here's one:

http://beersmith.com/blog/2011/07/14...of-draft-beer/

07-10-2012, 07:15 PM   #18
SpartyParty
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Jun 2011
Cresco, IA
Posts: 129
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Quote:
 Originally Posted by zachattack Measure the flow (pour) rate when you're experimenting. A slower pour rate is what you want, if it comes screaming out of the faucet it means it's gonna be all foam if it's beer. Don't worry about temp, just measure flow rate. For your other question, sounds like you need to read up on system balancing! This is something you should understand before you take on a project like this, once you understand why we're suggesting these things it'll be pretty obvious. There are some good guides online, here's one: http://beersmith.com/blog/2011/07/14...of-draft-beer/
Great article! If I carb at 12 ... doing the math (line) L = (12-1-(8/2))/.85 = 8.24 feet of lilne to achieve balance. I need at least 12 feet for my run. If I carb at 15 I get L = (15-1-(8/2))/.85 = 11.76 feet of line. Do you think that is too high to carb at 15? If the numbers are right I think I should be able to make this project come together with 12 feet of line and an 8 foot vertical by carbing/serving at 15psi. Of course the numbers might say one thing and the practical application be different. I'll try and run that test using water and measure the flow rate and post the results. Thanks again!

07-10-2012, 11:35 PM   #19
JuanMoore

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Oct 2009
The Old Pueblo
Posts: 22,568
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Quote:
 Originally Posted by SpartyParty Great article! If I carb at 12 ... doing the math (line) L = (12-1-(8/2))/.85 = 8.24 feet of lilne to achieve balance. I need at least 12 feet for my run. If I carb at 15 I get L = (15-1-(8/2))/.85 = 11.76 feet of line. Do you think that is too high to carb at 15? If the numbers are right I think I should be able to make this project come together with 12 feet of line and an 8 foot vertical by carbing/serving at 15psi. Of course the numbers might say one thing and the practical application be different. I'll try and run that test using water and measure the flow rate and post the results. Thanks again!
Your math looks good, but those equations are notoriously inaccurate, and typically underestimate the length of line required to get a good pour. Also remember that they're designed to give the fastest possible pour without creating foam. Since it doesn't sound like you're running a bar or restaurant where the number of pints you can pour in an hour impacts your profit, a slightly slower pour won't hurt anything. Based on my own experiences and long draw projects I've seen on here, I think you'll be fine with pure CO2 and 12 psi. You may even find that you need longer than 12' of line to slow it down a little.
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