Trimming beer lines in keezer

Lots of good technical info in this post, but I believe this statement to be incorrect.

The effective beer-line length does not change with the level of the beer in the keg. This is because the length over which restricted flow (of the beer) occurs is always the same -- from the bottom of the dip tube to the tap. The static pressure behind the beer remains the same whether the keg is full or near empty, so the flow should remain independent of the level of the beer.

Cheers!

 

Have to agree with the Disciple from New York on this one. Yes, the static pressure never changes, and the restriction from the beer line is constant. But the 0.45 figure is a result of gravity fighting against beer being delivered. Imagine if the keg was very tall, say about 100 feet. If you pressurized to 10 psi the beer would dispense normally when the keg was full just like a normal keg. But at some point the meager headspace pressure would be insufficient to push the beer up the 100' of diptube (weight of beer exceeds pressure in keg). If your faucet was below the level of the beer it would have the opposite effect, gravity would actually be accelerating the beer flow and effectively be reducing resistance.

You see this with pumps all the time. Typically they are rated at XX gallons per hour, but the caveat is that figure is based being level. Once you start pumping uphill the output is measurably decreased . . . it's that darn gravity fighting against you.

For @thebriansmaude . . . have you poured one yet?

 

I don't know anything about kegging, but just as a matter of physics this seems wrong. The pressure at the bottom of the dip tube should be the sum of the gas pressure above the beer and the pressure from the beer itself. The former may be constant, but the latter should be a function of the depth of the beer in the keg.

 

What you have to consider is the lift. The applied pressure, in addition to maintaining vols, must also overcome resistance and lift. Resistance is built in. But lift varies.

It takes more pressure to lift something 12 feet than it does to lift the same object 10 feet.

In a perfect system if the applied pressure exactly measured the resistance in the system the liquid in the tube would get to exactly the top of the tube and no more. If we maintain the exact same pressure but now lower the level of the beer in the keg 2 feet, the liquid in the line is not going to stay the same height. If we slightly raise the pressure to overcome this lift (by 0.45 psi per foot at MSL to be precise), the liquid will again rise exactly to the top of the tube.

Truthfully in a kegerator setup, we , mostly ignore the added pressure needed. It is just not meaningful. The precise resistance needs to be known and the precise temperature needs to be known and maintained, and as the level of the keg varies anyway, it's not possible to get that part of the equation perfect.

Cheers

 

Indeed.

The depth of the pump is irrelevant. The depth to water matters. The pump sees the head from the DTW to the discharge. Not from the depth of the pump intake to the discharge. All the water in the line above the pump is equal to the DTW, and the pump has to lift from that point only.

 

Yes...mostly irrelevant in a homebrew keg system on level ground

 

Yes, of course. I neglected to consider the static pressure contribution from density*g*height differential. Back to teaching introductory physics for me! Cheers!

 

Hopefully not too much of a tangent - Any of you guys use a (modified) chest freezer as your kegerator? I use a 7cu ft. one and keep it at 39-40F. My exact measurements are at home but I believe the kegs' center are about a foot below the taps. I had trouble with a Hefe that I carb'd b/t 3.0 - 3.5 volumes of CO2. I use Brewcipher and it recommended 11ft of line. The resistance multiplier was at 1.00. I only had 10ft of line at the time and used that. It wasn't too bad but I did have more foam than I wanted for pours. Do you guys use more than 10ft of line for some of your beers (i.e. Hefes)?

I can't find this line over 10ft. I love this line. It's tough to work with but it's hard and thick and I feel like the beer stays nice and "clean" running through it. Like it's "inert". Not sure if that's the right word.
https://www.amazon.com/gp/product/B017EA5ST6/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

 

This is what I use, it's available by the foot in many homebrew outlets and I usually buy 50' at a time. If you shop around you can find it for about 50¢/foot. I keep two lines at 12' for my Belgians. I find the line-calculators to be "off" a couple of feet. The extra resistance caused by the height of the faucet can be safely ignored. I regularly replace my lines, so having extra hanging around makes life simple.

 

This is comforting. I thought I was nuts for thinking I needed more than 10ft but style may require we go this long sometimes. Thanks!

I've only ever used the tubing that I linked previously. May be something you don't adjust (assuming all calculators have this) but do you know what "Resistance Multiplier" you use for that tubing? I believe Brewcipher is preset at 1.00. I dropped mine down to 0.75 based on my experience with the tubing I use.

 

I ignore the calc . . . I know that 12 foot'ers work for 16psi and 8 foot'ers work for 12psi in my keezer. The trail and error method is quicker and more reliable.

 

A lot of times I need to take a step back and realize I don't need to get too detailed. @PortLargo makes sense. Based off memory I think my Hefe was at about 17psi and calc'd out that I need about 12ft too. Thanks!

 

Bevlex 200 is supposed to have 2.2 psi per foot of resistance. Calculate accordingly. Safely ignore the resistance needed to overcome gravity. Add 1 psi to account for hardware resistance. That's about as good a formula you need. And if you need less resistance, slice off 6" and try again.

I have no idea what a resistance modifier is. @VikeMan would know.

Beware of any made in China tubing. I just don't trust that it is FDA approved. Unfortunately the industry is plagued with poor quality Chinese material. Bevlex 200 is very good. Wholesale is $26 per roll of 100' or $0.50 per foot in 1 foot increments. So if you can find it retail at $0.50 per foot but more than you need. You'll always use it.

Cheers.

 

From the mouseover popup hint in BrewCipher (on the Brewhouse Parameters tab):
"Keg Line Resistance Multiplier: This multiplier increases or decreases the line resistance assumed by the kegging beer line length calculator. The calculator uses a standard resistance per length value for each line type, but actual restistance can differ between brands of line, age of line, and cleanliness levels. If you tend to get too much foaming, slightly decrease this multiplier value, which will cause the calculator to recommend a longer line to compensate for the lower resistance. If you tend to get not enough foam, slightly increase this multiplier value, which will cause the calculator to recommend a shorter line to compensate for the higher resistance. Note: increasing line length does not really fix a foaming problem caused by warm lines/faucets (aka "first pour" foam). It can compensate somewhat, but the best fix for that problem is to keep the lines and faucets closer to the temperature of the kegs."

 

Do they state what the standard resistance is? 2.2 psi is accepted as industry norm these days, I assume that is "1" and the modifier is used to change that number.

Anyway, line resistance calculations are not an exact science, and the values most people are getting is designed to get an 8 second pint which is not a requirement. Nobody really needs to be exact here. Just slow it down enough to be manageable imo.

 

BC uses 1.8 for 3/16" ID plastic, based on the experience of Steve Jones here... http://www.franklinbrew.org/wp/?page_id=98

All the more reason to enable the user to be able to modify that with a multiplier parameter, since there are many different "plastic" lines available.

 

First I want to ask did you read my post? Mainly the part about where I said we carry BevLex 200? Then said I also have the info for Bev-Seal handy. I never said we carry it so chill out with your "you are really doing your customers a dis-service if you are selling Ultra for a kegerator application." Because I never said we carry that line.

Please do not conflate what I said with something else.

But the "truth is" you need to be accurate enough to not over/under carbonate your beer. After that we care.