I am the GM of a restaurant and I, along with the people who service my draft beer system are stumped. Every keg I have is going flat when it gets down to about 5-10% left in the keg. There is no drop in pressure to the kegs when this happens. Temperature in the keg cooler is consistently 34-37 degrees. Pressure on all my kegs is between 18-22 lbs. We use a nitrogen generator and a blend box that puts out 60/40 blend to the kegs. We have had the same temps, same pressures, same blend for as long as I've been here (5 years) and this only recently started happening. I would really like to figure out what is going on so I can stop losing beer!
If your 60/40 is 60% nitrogen and 40% carbon dioxide you shouldn't be having any flat beer. The math: 20psi (your average) x 0.40 (percentage of CO2) will give you a partial pressure of 8psi for your carbon dioxide. At your temps that's about 2.3 volumes which is a touch on the low side but nothing weird. If pressure/blend-percentage/temp figures are accurate, the beer should be carb'ed if keg is full, or half, or one drink left. The most logical answer is one of the settings are off. Temp is easiest to measure, probably figure it's correct. Pressure gauges do fail, good news is they are easy/cheap to replace. Or if could be the blend box is mis-calibrated. If the beer is pouring at the same rate as before, the pressure is probably okay. Makes me think Mr blend box is lying to you (putting out something close to pure nitrogen). On a new keg this isn't immediately noticed, only when quantity is lowered and the beer has largely off-gassed all of it's CO2 into the headspace. In my area the distributors tweak the blend . . . I would ask them to troubleshoot. If it's a rental maybe have the owner switch out to a new unit. A quick fix (to save the beer) would be to vent the near-empty keg, then shoot with pure CO2 at around 10 - 12psi, let it sit overnight, then sample . . . should be re'carb'ed.
Everything Largo says x100. Site unseen, tell me if any of this is true. You have Guinness on draft. You have a direct draw system. That is to say the kegs are in a cooler directly behind the faucets. OR you have a very short draw system, that is the kegs are only a few feet from the faucets. NuCO2 installed your system and maintains your leased blender. Some or all of this is true, and it will help us to diagnose the problem. First thing we need to determine is what gas blend you need. 60/40 is not one size fits all but it is often installed that way. Cheers.
Turns out my system is set up for 70/30 blend. We recently change CO2 companies and my old box was 70/30 and the new box is 60/40. CO2 company is coming out to change it back to 70/30 and I believe that will fix the issue.
Not to be a pain in the ass, although that's what I usually do, this does not make sense. If "We have had the same temps, same pressures, same blend for as long as I've been here (5 years) and this only recently started happening." then there's something other than the gas blend at the heart of the problem. My guess is that you're talking only about kegs that have been on tap for way too long. Can you corroborate that?
Yeah but to be fair the vendor did not tell them they changed blends. 60/40 is used way to often as the universal blend but it really does not fit into the sweet spot very easily. 70/30 is often times a better choice in my experience. I'm happy the vendor realized the mistake because that too is not common. Cheers.
A simple flogging and return to duty seems in order. But more to the point . . . if the beer went flat at 60/40 does anyone really think 70/30 will fix anything? A touch under-carb'ed maybe, but flat? The OP is probably gone for good, but I see more unbalanced beer waiting on him. For @billandsuz , I haven't tinkered with blend boxes much, but don't they have a clear display of what ratio is dialed in?
The blender will have each outlet labeled. At least it should. We have ordered special blends and not had the outlet labeled but that is well, special. Once upon a time McDantim sold a tool that allowed for field adjustments but no more. How I wish. Now you're on the phone with Helena. But you will talk to someone who really really knows their shit inside out. They pretty much invented this stuff. And they make the black box Micromatic blender. It's just more expensive. The McDatim blend calculator app is cool, and something only a beer gas nerd might find interesting (know of any?) I think the 10% difference is significant enough to make a difference. Especially if the kegs don't turn over quickly. Losing carbonation is much more of a problem than over carbing, all things equal. Pour a 2.5 at 2.2 vol and its noticeable. Pour it at 2.8 and it's a lively beer but not a disaster. I lose sleep worrying about 60 40. The 60 40 blend is usually a bit too much on the under carb side in most applications, and it's easier to reduce pressure than it is to crank it up. Cheers
