« on: July 18, 2014, 04:57:20 PM »
This is probably overkill but this is what I know. no i know this is overkill
There are 2 types of draft systems remote and direct.
1.Remote systems are those that basically require insulated lines.
2. Direct draw systems are those that are self contained and temp controlled such as in a walk in cooler, jockey box, keggerator or refrigerator.
Balancing a direct draw system allows for
1. Eliminating waste
2. Protecting the beer against microbs needs to be at or below 38F
3. Dispensing an industry standard flow of around 1 gal a min. Ya I know that is a bit much, 128oz per min.
I think 1 Gal a min for pouring a beer is to fast personally but that’s what the industry standard is I am told That’s about 1 pt of beer in 7.5 sec. I shoot for 10sec and vary the angle to tailor the foam/head to my preference.
There are 2 pressures in a draft system Gauge pressure and restriction pressure.
1. Gauge pressure is obviously the actual PSI applied to the keg.
2. Restriction is the resistance the beer encounters as it flows to our glass which comes from 1. system hardware. 2. gravity and 3. beer tubing.
Each of the above restrictions has a known measurable PSI value.
System Hardware: tailpieces, faucets, shanks and couplers. Each piece acts as restriction as beer passes. If one has a tower assembly it can easily give 3PSI restriction. I have 4” 3/16 ID shanks with Perlick 525ss faucets
Gravity: vertical lift or drop either above or below the keg. One has to take into account the height of the keg from the bottom some measure from the middle but the bottom seems to be the best. So the vertical distance is measured in feet and has a PSI value of about .5 per foot. My collared kezzer measures from the bottom of a 5 Gal keg to the middle of the shank at 2.67’. To determine the gravity restriction portion of the equation I do this. 2.67’ x .5 = 1.33PSI for mine.
Beer Tubing: I really don’t know the correct number/restriction value but most say 3PSI of 3/16ID” vinyl tubing. I use 2.7 PSI just because “brewers friend” says so☺ and it works for my system.
So this is what I do and it works for me.
Determine my Gauge Pressure: I want my beer to be at 2.3Vol Co2 at 38 F. This means I need to have gauge pressure at 9PSI however, I live at 4781’ elevation and for every 2000’ above sea level I need to add 1 PSI. This adds 2.4PSI to my 9PSI but I round down so I set my gauge to 11PSI to maintain 2.3 Vol in solution.
Now I need to determine my Restriction sources: I have 2.67’ of vertical lift from the bottom of my 5 gal keg. I have a 4” shank of 3/16” ID resistance. I have 3/16” ID beer tubing at 2.7 PSI.
So I know I have to keep my Co2 vol at 2.3 at 38F and 11PSI. This 11PSI is required and will not change so I must determine the resistance of each.
Gravity (Vertical lift form bottom of keg to middle of shank of 2.67’) x ( Standardized gravity per vertical foot of .5) = 1.33 PSI resistance.
Shank is the same ID as my beer line so I add the 4” of shank length into my beer line equation.
Beer line length: I know I have to have 11PSI and I have to subtract gravity (1.33PSI) which gives me 9.7 PSI restriction required to balance the system which must be made up with by the length of beer tubing. So 9.7PSI/2.7 PSI of 3/16”ID= 3.6’ of beer line needed. Now this length is for pouring at the standard 7.5 sec per pint which I know is just to dam fast in my book So I was a little pissed that I just wasted beer line and was at a stand still and had to order more! So I had to determine at what rate I wanted my beer to pour and that is 10 sec with a beer line length of 4’ 8”. Dam did I ramble or what? I could have just said I keep mine at 4’ 8” and get a nice ½” head.