weird force carb question

[Aschecte]

Ok I may be over thinking this but, let me paint a scenario here. Lets say I have a red ale for examples sake that I want to carbonate to 2.39 volumes of co2 at 40 degrees so I set my regulator to 11PSI. now that part is easy to figure out based on charts. So, I leave my beer on 11 psi for 2 weeks and there we have it carbonated beer. Next I cut my co2 regulator down to serving pressure of 8 psi and start drinking away. Now I know it's not a huge leap from 11 psi to 8 psi but, over time wouldn't the beer become uncarbonated as it is being left on 8 psi until the keg is done ? wouldn't periodically you need to bump to pressure back to 11 to maintain the proper volume level or am I over thinking this ? thanks for the input. you would think that being I've been kegging for over a year I would have thought of this before.

 

[Yooper]

Ok I may be over thinking this but, let me paint a scenario here. Lets say I have a red ale for examples sake that I want to carbonate to 2.39 volumes of co2 at 40 degrees so I set my regulator to 11PSI. now that part is easy to figure out based on charts. So, I leave my beer on 11 psi for 2 weeks and there we have it carbonated beer. Next I cut my co2 regulator down to serving pressure of 8 psi and start drinking away. Now I know it's not a huge leap from 11 psi to 8 psi but, over time wouldn't the beer become uncarbonated as it is being left on 8 psi until the keg is done ? wouldn't periodically you need to bump to pressure back to 11 to maintain the proper volume level or am I over thinking this ? thanks for the input. you would think that being I've been kegging for over a year I would have thought of this before.

Yes, it would. That's why I don't think there is any such thing as "serving pressure" and "carbing pressure".

My regulator for almost all of my beers and kegs is at 12 psi at 40 degrees.

I can't imagine changing it back and forth! I'd have to say, "Well, I want to drink from keg A" and so purge and reset my regulator. But then, if I wanted to drink from keg B, I'd have to mess with that. Or keg C. And then turn them all back up? Or down? And then back up? No way! My regulator is almost never messed with. If I want a lower carbed beer, I have that on a different regulator, but I rarely use that.

 

[JRems]

You are correct, that's why your serving pressure should be the same as your carbonation pressure. That's why you balance your draft lines, so you can serve at the proper pressure to keep the proper carbonation.

 

[Aschecte]

Ok I was right I'm not crazy !!! well maybe a little. Ok so that's where beverage line extention comes into play as the restriction from the longer lines negates the foaming and blasting out of the faucets. ok I know there must be a chart out there to calculate the length of beverage line needed to reduce foaming at "x" psi@tmp. thanks for conforming my suspicions.

 

[Yooper]

Ok I was right I'm not crazy !!! well maybe a little. Ok so that's where beverage line extention comes into play as the restriction from the longer lines negates the foaming and blasting out of the faucets. ok I know there must be a chart out there to calculate the length of beverage line needed to reduce foaming at "x" psi@tmp. thanks for conforming my suspicions.

There are calculators- but I've never found them to be accurate in the real life home setting.

I'd rather go with long lines and not worry about it. Then you can serve beers carbed at 4 volumes, if you want, as well as beers carbed at 1.5 volumes, all with the same beer line/tap.

I started with 6' of line, then went to 8', and then to 10'. I'd say that 10'-12' would be a good place for the majority of homebrewers in their kegerators as a good guess to start.

 

[BansheeRider]

Or just use these....https://www.homebrewtalk.com/f35/cure-your-short-hose-troubles-100151/

 

[Brewerforlife]

Most calculators are meant to balance a commercial bar system so that it pours as fast as possible without foam loss. A rate of 1gal/min is the standard.
The rest of us at home don't need to worry about serving a bar 4 deep, so speed is not a big issue. I would listen to Yooper and the other's who advocate
8-12 feet of 3/16th ID tubing, the only thing this causes is longer pour times, but
a beer with proper carb vol. and low foaming issues, and the easier ability too carb beers even higher volume's, like yooper said!! Hope that made sense!!!

 

[Aschecte]

no the longer lines make perfect sense...... it's just such a PITA to get the 3/16" lines onto the barbs that's the only dreaded part.

 

[Brewerforlife]

Just put the hose in a cup of almost boiling, or really hot water for a few seconds just before you slide them over the barbs!! Should go on really easy, if were talking about vinyl hose, not poly!!!

 

[Yooper]

Just put the hose in a cup of almost boiling, or really hot water for a few seconds just before you slide them over the barbs!! Should go on really easy, if were talking about vinyl hose, not poly!!!

Exactly. And, if I can do it, anybody can! Even the more rigid tubing I got for soda from McMaster-Carr finally submitted to the boiling water treatment.

What I did was dip the tubing into boiling water, smush it on, wait until it stopped, pulled it off, and then redip. Finally it went on and stayed. (Don't forget the hose clamps!)

When I put the tubing on the quick disconnects, I stuck the barb portion of those in boiling water as well, so the metal was hot and so was the tubing. It took about three rounds of "smushing", but it went on.

But...........when you change the lines out, it's a real pain getting them off!

 

[Yooper]

Most calculators are meant to balance a commercial bar system so that it pours as fast as possible without foam loss. A rate of 1gal/min is the standard.
The rest of us at home don't need to worry about serving a bar 4 deep, so speed is not a big issue. I would listen to Yooper and the other's who advocate
8-12 feet of 3/16th ID tubing, the only thing this causes is longer pour times, but
a beer with proper carb vol. and low foaming issues, and the easier ability too carb beers even higher volume's, like yooper said!! Hope that made sense!!!

By the way, how long are your serving lines at the brewery? I just realized that I don't even know where your serving tanks are but assume they are in the basement from what I saw of your brewery.

(Please don't tell me they are behind the bar in plain sight, as I'd feel even more stupid! )

 

[AnOldUR]

I have a red ale for examples sake that I want to carbonate to 2.39 volumes of co2 at 40 degrees

2.39 . . . hmmm, missed your OCD meds I see. :cross:

 

[Brewerforlife]

By the way, how long are your serving lines at the brewery? I just realized that I don't even know where your serving tanks are but assume they are in the basement from what I saw of your brewery.

(Please don't tell me they are behind the bar in plain sight, as I'd feel even more stupid! )

Your right!! Their right below the bar. I'm running 25-28 Feet of 1/4" vinyl at 12 feet of elevation, from tank bottom to tower shank directly, no 3/16th choker line. This equals a total resistance of 28.4 psi if you go by Foxx equip. numbers of .80psi/ft of resistance for bevlex 200 1/4" vinyl hose.
This is why I don't trust the calculators at all. I am pushing my beer at 11-15 psi@ 38-40F and it is still almost pouring too fast!! It does'nt make any sense at all, it seems to defy the law's of physic. It shoud'nt flow at all or very slowly!!
I trust the laws of physic's on the .5psi/ft resistance per foot of elevation, so this only can leave me to not trust the stated resistance per/foot that the manufacturer's state for the various type's of hose in their different diameter's. I hope this makes sense!!!

 

[Yooper]

Your right!! Their right below the bar. I'm running 25-28 Feet of 1/4" vinyl at 12 feet of elevation, from tank bottom to tower shank directly, no 3/16th choker line. This equals a total resistance of 28.4 psi if you go by Foxx equip. numbers of .80psi/ft of resistance for bevlex 200 1/4" vinyl hose.
This is why I don't trust the calculators at all. I am pushing my beer at 11-15 psi@ 38-40F and it is still almost pouring too fast!! It does'nt make any sense at all, it seems to defy the law's of physic. It shoud'nt flow at all or very slowly!!
I trust the laws of physic's on the .5psi/ft resistance per foot of elevation, so this only can leave me to not trust the stated resistance per/foot that the manufacturer's state for the various type's of hose in their different diameter's. I hope this makes sense!!!

It does.

I know the calculators seem to work for some, and I'm not sure why unless either they got lucky, or they happen to have hit the right resistance in their guestimate. That's why I asked you- I wanted to hear of your experiences with a 12' rise because I assumed they were downstairs.

Thanks!!!!!!

 

[Brewerforlife]

I have install draft system's at local bars/restaurants as a side job over the years. Vangos,Stucko's,L'atitude,Blackrock's,Aubree's,etc, and have found that i need to build 22+ psi in any system I set-up, whether i'm running off straight CO2 or using a gas blender. It still seems to be running too fast at 12-14 psi @ 38F. The macro beer's are the worst, especially Labatt, this beer, I swear has the upwards of 2.9+ vol. of carbonation, that's 17 psi@ 38-39F to keep the vol. in solution. That's the borderline of using straight CO2.
I have had to go back and un-wrap a trunkline to add 3 more ft of 3/16th choker at the tower side to get just enough resistance to pour reasonable. This is now over 30 spi resistance, according to the calculator's. A really pain in the a**. Now I alway's build at least 22 psi in any system I design.
See, our theory of 10 ft of 3/16th vinyl @ 2.2.lb/ft= 22 psi of total resistance. Same as i'm doing with longdraw system's!!

 

[Demonantis]

I have read about these beer line calculations and none of them make sense to me from my fluid dynamics education. You do calculate a friction loss and a gravity loss, but completely ignore fitting losses.
There should be a pressure loss in every fitting in the system from the dip tube opening to the actual faucet(that is why the epoxy mixer helps so much). Plus, friction losses are dependent on the velocity of the fluid through the tubing I have no idea how the manufacturer reports that number.
That is why when you use long lines(should be a negative pressure according to the calculator) beer still flow out of the system unless it can't overcome gravity albeit extremely slowly. The calculator probably gives an okay estimate, but it would always need fine tuning. I think I went off on a tangent, but I hope that helps someone.

 

[JuanMoore]

Most calculators are meant to balance a commercial bar system so that it pours as fast as possible without foam loss. A rate of 1gal/min is the standard.
The rest of us at home don't need to worry about serving a bar 4 deep, so speed is not a big issue. I would listen to Yooper and the other's who advocate
8-12 feet of 3/16th ID tubing, the only thing this causes is longer pour times, but
a beer with proper carb vol. and low foaming issues, and the easier ability too carb beers even higher volume's, like yooper said!! Hope that made sense!!!

Yep, exactly. The other huge difference is serving temperature. As I'm sure you know, the companies that train commercial installers insist on beer temps below 38°, and many distributors and breweries demand similar temperature restrictions. One of the main problems for homebrewers using these calculators and equations is that they tend to have higher beer temps, and the warmer the beer is the slower/gentler the pour needs to be to prevent the CO2 from coming out of solution. Same goes for higher carb levels. If you try to serve a hefe or Belgian carbed to 4.0 vol at 1gal/min it's going to result in a foamy mess not matter how cold it's stored.

This is why I don't trust the calculators at all. I am pushing my beer at 11-15 psi@ 38-40F and it is still almost pouring too fast!! It does'nt make any sense at all, it seems to defy the law's of physic. It shoud'nt flow at all or very slowly!!
I trust the laws of physic's on the .5psi/ft resistance per foot of elevation, so this only can leave me to not trust the stated resistance per/foot that the manufacturer's state for the various type's of hose in their different diameter's. I hope this makes sense!!!

It doesn't defy the laws of physics, but that doesn't mean the manufacturer figures are wrong either. The main problem is that all of those calculators and equations assume that line resistance is a fixed figure for a specific line, but it's not. One of the basic concepts of fluid mechanics is that line resistance is a function of flow rate (among other things also not accounted for in those equations), so the slower the flow rate, the lower the line resistance is. The tables and manufacturer figures for line resistance are not only somewhat variable between production runs, but also only valid at one particular flow rate, typically 1gal/min. As soon as you change the flow rate even a tiny bit, the equations are no longer even close to valid.

I've been taking fluid mechanics classes recently towards my engineering degree, and thought about creating a calculator that accounts for varied flow rates, but somebody beat me to it. It allows the user to input a pressure and desired flow rate (in terms of the time it takes to fill a pint), and then gives you the line length required for that flow rate. Now all we need is to figure out the flow rate that won't cause foaming for every combination of carbonation level, temperature, and SG.
https://docs.google.com/spreadsheet/ccc?key=0ApGb-vIKLq7FdGtzN3BrY2xZSldORzQ2bHVVX0hzaEE#gid=0

 

[Brewerforlife]

Great answer!!! That makes sense!! Thanks!!