Help - Nitro / Beer Gas / Relocation - Now Foam Problems

[homer4111]

I really need some help - I have been reading and trying things for weeks and I can't figure out what is going on. I'll try and be as brief as possible.

I have a nitro kegerator setup. Lived in Florida for 2 years, in a high-rise (500 feet up), ran 16 kegs (14 kilkenny(50L) and 2 guinness(50L)) through it - perfect pour until the end of the keg. 75/25 beer gas, 33psi, and estimated 40 degrees (I say estimated becuase it worked so well, I didn't feel the need to calibrate). Life was good.

Moved to the carribean a few months ago, and brought my kegerator with me. Grabbed beer gas, and a keg of kilkenny(50L). Normal routine, just hooked up beer gas and good to go.

Beer was great until last 3rd of keg - then progressively more and more foam. After reading online, it seemed like beer gas was the culprit. The supplier apologized and refilled my tank assuring me it was correct.

Guinness keg(50L) next, with "fixed" beer gas. Exact same problem. Great for first 2/3 of keg, then becoming more and more foamy - like 3+ inch head.

There are only 2 things that have changed, keg supplier, and gas supplier. There is a small restaurant down the street that serves guinness. I asked the bartender about his kegerator setup (looks just like mine - mini fridge with draft on top). He said he has the same problem - they just toss the keg when it hits the 1/3rd mark. Only difference between us is he is using 70/30 mix. We both get our kegs from the same distributor, and our gas mix from the same shop.

Rather than filling this post with all my crazy thoughts and things I have tried - I'm hoping someone can shed some light on what might be going on. So much of what I have read comes from people just starting out, whereas my system was running fine for years.

Thank you so much for any help!

 

[Spikybits]

You can try to turn down the gas pressure as the keg gets low. see if the reduced pressure helps with the last 1/3 of the keg.

 

[homer4111]

You can try to turn down the gas pressure as the keg gets low. see if the reduced pressure helps with the last 1/3 of the keg.

I've tried that, but I'm guessing the beer is over carbonated already. So I have also tried de-carbing (shaking, releasing gas, repeating over and over) the keg and trying again at varying lesser pressures. I have read a few things here and there regarding the co2 level increasing as the beer is removed from the keg, but I don't understand - simply because it has worked fine for 2 years without any adjustment.

 

[doug293cz]

At 40°F, 33psi, and 25/75 (CO2/N2) beer gas the equilibrium carbonation level is 1.1 volumes. This doesn't seem excessive. Equilibrium level means the beer will shift towards this level with time and more gas headspace.

If your beer gas isn't really what you think it is, then all bets are off. Higher CO2 to N2 ratio will lead to higher carbonation over time.

Brew on

 

[homer4111]

At 40°F, 33psi, and 25/75 (CO2/N2) beer gas the equilibrium carbonation level is 1.1 volumes. This doesn't seem excessive. Equilibrium level means the beer will shift towards this level with time and more gas headspace.

If your beer gas isn't really what you think it is, then all bets are off. Higher CO2 to N2 ratio will lead to higher carbonation over time.

Brew on

I was hoping to hear from you Doug! I've read a lot of your posts on gas - thanks so much for chiming in!

Ok, so can I make the assumption that my beer gas is definitely not 25/75? The shop doesn't have a CO2 tester to verify it for me - they just assured me it was right. 2 quick follow-up questions then:

1) Could this be anything else? Could my old keg distributor have been pre-carbing my kegs? If that is even a thing. Or could my current keg distributor be doing something different? My old keg distributor kept the kegs cold. My new one, only chills them before I pick them up. They have both been cold when I put them in the kegerator, and I leave them in for 24+ hours before tapping to make sure they are cold enough. If it more-than-likely IS the gas...

2) I have looked into purchasing a 25/75 blender - when I suggested this to my keg distributor, they said they wouldn't recommend this as "there’s a smaller chance of it affecting the pour due to the short distance pushed". Does this make any sense? Would I be safe purchasing a blender, or should these only be used by long-haul installations?

Thanks again for any help!

 

[doug293cz]

Not enough evidence to say it's definitely an incorrect gas mix. If the keg were incorrectly carbed initially, you would have issues immediately after tapping, not after serving 2/3 of the keg.

Can't see why tubing run length would affect how a gas blender worked (although I have never dealt with blenders.) Long runs are on the beverage side, not on the gas supply side. I think your gas supplier is worried about reduced revenue.

Brew on

 

[homer4111]

ok, thanks! I know you can't be 100% sure, but do you feel like we are above 80%? It is really difficult to get stuff here, and I have a trip to the US coming up - so trying to figure out if I try a blender, or if I need to look at some other option? thanks again!

 

[doug293cz]

Sorry, can't really put a confidence level on this. I can do the gas science part, but don't have any experience with actual dispensing systems using beer gas.

Brew on

 

[homer4111]

One last question - and I will post back here with any good news / solutions for anyone else having this issue.

Can I assume that if I am dealing with a higher CO2 content in the gas, I can raise the temperature on the keg (after degassing) to try and help? If so, should I attempt any pressure changes in addition?

I realize that getting the mix right is the ideal solution, but if that is not an option, I'm trying to find ways to enjoy the whole keg with what I have. Routine for first 2/3 of keg, then some combination of temp/pressure/degassing to make it through the last 1/3.

thanks again!!

 

[pigroaster]

One last question - and I will post back here with any good news / solutions for anyone else having this issue.

Can I assume that if I am dealing with a higher CO2 content in the gas, I can raise the temperature on the keg (after degassing) to try and help? If so, should I attempt any pressure changes in addition?

I realize that getting the mix right is the ideal solution, but if that is not an option, I'm trying to find ways to enjoy the whole keg with what I have. Routine for first 2/3 of keg, then some combination of temp/pressure/degassing to make it through the last 1/3.

thanks again!!

Keep posting I am really interested in this topic!

 

[doug293cz]

One last question - and I will post back here with any good news / solutions for anyone else having this issue.

Can I assume that if I am dealing with a higher CO2 content in the gas, I can raise the temperature on the keg (after degassing) to try and help? If so, should I attempt any pressure changes in addition?

I realize that getting the mix right is the ideal solution, but if that is not an option, I'm trying to find ways to enjoy the whole keg with what I have. Routine for first 2/3 of keg, then some combination of temp/pressure/degassing to make it through the last 1/3.

thanks again!!

Raising the temp can have a beneficial effect. As noted above, 33 psi of 25/75 gas at 40°F gives you 1.1 volumes of gas. At 50°F and 33 psi, you need 30/70 gas to get the same 1.1 volumes. The other thing you can do is reduce the pressure (as long as your stout tap still pours ok.) If you reduced the pressure to 25 psi at 50°F, you could use 36/64 gas and have the same 1.1 volumes.

Raising the temp of the keg will cause some of the CO2 in the beer to come out of solution, raising the CO2 concentration in the headspace. Venting the keg after the keg has been warm for a couple of days (it takes time for the excess CO2 to come out of the beer) will reduce the excess CO2 in the headspace.

Another thing you could do is serve about 1/3 - 1/2 the keg on beer gas, and then switch to pure N2. Then the excess CO2 that built up in the beer will slowly come out of solution. In this case, I wouldn't recommend venting the headspace before or after changing to N2. Doing so would cause the beer to lose carbonation too quickly.

Brew on

 

[homer4111]

This is GREAT information! After 2 weeks of banging my head, I'm finally feeling better about managing this issue.

The nitrogen-only swap sounds like the best approach! Final question, I hope - when making the decision on when to swap to N2, can I use the head-size (when poured correct) as a gauge? As in, once I notice the head getting significantly bigger, perform the swap then? I realize this is probably trial-and-error, but this is my first thought on how to know when to switch. If you would advise otherwise, I would love to hear so.

Thank you again so much for all the help! I will report back here on how things are going - really would love to help out anyone else having this issue.

 

[doug293cz]

This is GREAT information! After 2 weeks of banging my head, I'm finally feeling better about managing this issue.

The nitrogen-only swap sounds like the best approach! Final question, I hope - when making the decision on when to swap to N2, can I use the head-size (when poured correct) as a gauge? As in, once I notice the head getting significantly bigger, perform the swap then? I realize this is probably trial-and-error, but this is my first thought on how to know when to switch. If you would advise otherwise, I would love to hear so.

Thank you again so much for all the help! I will report back here on how things are going - really would love to help out anyone else having this issue.

Yes, it's trial and error. Your change in head size sounds like a reasonable place to start.

If you notice the beer starting to go flat after being on pure N2, you can switch back to beer gas at that time.

Brew on

 

[Bobby_M]

You can check your beermix against the tare weight of the tank. If you have a TW of 8LB and it reads 2 pounds full, you know you have 75/25. It sounds to me like your mix is a bit CO2 heavy or your gauge is reading vastly lower than actual.

 

[homer4111]

Wow - also great to know - so it sounds like I can just bring my scale to the gas supplier and call them out on the ratio?

My second tank, which they said was filled at 75/25, has the following weights:

Total Weight: 9.72 pounds (kitchen scale)
Tare Weight: 8.06 pounds (imprinted on tank)
Difference: 1.66 pounds

So I am right in saying that this is roughly an 80/20 mix? If not, how are you calculating it?

If this is that straightforward, then it sounds like I can just keep having them fill the tank until it is right.

thanks!

 

[doug293cz]

You can check your beermix against the tare weight of the tank. If you have a TW of 8LB and it reads 2 pounds full, you know you have 75/25. It sounds to me like your mix is a bit CO2 heavy or your gauge is reading vastly lower than actual.

Wow - also great to know - so it sounds like I can just bring my scale to the gas supplier and call them out on the ratio?

My second tank, which they said was filled at 75/25, has the following weights:

Total Weight: 9.72 pounds (kitchen scale)
Tare Weight: 8.06 pounds (imprinted on tank)
Difference: 1.66 pounds

So I am right in saying that this is roughly an 80/20 mix? If not, how are you calculating it?

If this is that straightforward, then it sounds like I can just keep having them fill the tank until it is right.

thanks!

It seems to me that you would also have to look at the pressure in the beer gas tank as well as the weight. Otherwise a short fill would make a high CO2 ratio look like a lower CO2 ratio.

Brew on

 

[Bobby_M]

Wow - also great to know - so it sounds like I can just bring my scale to the gas supplier and call them out on the ratio?

My second tank, which they said was filled at 75/25, has the following weights:

Total Weight: 9.72 pounds (kitchen scale)
Tare Weight: 8.06 pounds (imprinted on tank)
Difference: 1.66 pounds

So I am right in saying that this is roughly an 80/20 mix? If not, how are you calculating it?

If this is that straightforward, then it sounds like I can just keep having them fill the tank until it is right.

thanks!

The rationale is that CO2 is liquid at those pressures and nitrogen is all gas. While the nitrogen will contribute a little weight, it's negligible. That's to say that a 5LB CO2 tank, when full of CO2, weighs 5 pounds more than the tare weight of the tank.

Doug made a good point that it could have just been a short fill across the board.

 

[doug293cz]

The rationale is that CO2 is liquid at those pressures and nitrogen is all gas. While the nitrogen will contribute a little weight, it's negligible. That's to say that a 5LB CO2 tank, when full of CO2, weighs 5 pounds more than the tare weight of the tank.

Doug made a good point that it could have just been a short fill across the board.

With beer gas, if you increase the pressure to where some of the CO2 liquefies, then the CO2 to N2 ratio of the gas phase changes so that it contains a lower fraction of CO2, thus changing the gas mix. I have always assumed that beer gas cylinders where filled to pressures below the liquefaction threshold.

Anyone know what pressure beer gas cylinders have in them when "full"?

Brew on

 

[homer4111]

I just got ahold of my old gas distributor, where the mix was perfect. He said the pressure when full should be 1800 PSI.

So 2 questions:

1) If my second tank is at 1800, does this confirm it is 80/20?

2) To determine the tank pressure on my second tank, can I just hook my regulator up to it (with valve closed) and turn on the gas (the gauge goes past 2000 PSI). If so, then is there a formula I can use where I plug in my tare weight, the total weight, and the tank pressure, to get the ratio in the tank?

thanks!!

 

[doug293cz]

I just got ahold of my old gas distributor, where the mix was perfect. He said the pressure when full should be 1800 PSI.

So 2 questions:

1) If my second tank is at 1800, does this confirm it is 80/20?

2) To determine the tank pressure on my second tank, can I just hook my regulator up to it (with valve closed) and turn on the gas (the gauge goes past 2000 PSI). If so, then is there a formula I can use where I plug in my tare weight, the total weight, and the tank pressure, to get the ratio in the tank?

thanks!!

1) No.

2) Probably, but I don't know what it is yet, but may be able to derive it. The boggy is that tare weights are not usually very precise, and any uncertainty in the tare weight will have a larger effect on the determined gas mixture. This is due to the well known issue of the difference of large, similar numbers.

Brew on

 

[homer4111]

Got it. Ok, so then if I completely empty the tank, and measure the weight myself (using the same kitchen precision scale as measuring it full), we should have an apples-to-apples comparison (between empty and full weights), removing the uncertainty? Or am I missing something?

 

[doug293cz]

Got it. Ok, so then if I completely empty the tank, and measure the weight myself (using the same kitchen precision scale as measuring it full), we should have an apples-to-apples comparison (between empty and full weights), removing the uncertainty? Or am I missing something?

You got it.

Brew on

 

[homer4111]

Awesome! So final question then before I start posting results (new gas and new keg coming next week):

Given the tare weight (kitchen scale) and the filled weight, plus the pressure on the full tank - how do I calculate?

thanks!

 

[doug293cz]

I forgot, one other piece of information needed to do the calculation is the actual (not nominal) internal volume of the cylinder.

Brew on

 

[homer4111]

Well you got me there. I've gone through all the tank markings, found the company in China (Zhejiang Winner Fire Fighting Equipment Co. Ltd)
, but I cannot find any specs related to it. So I'm guessing my only option is to purchase a new tank and make sure I have the internal volume prior? I found a few tanks that were close in specs with volume (207.5 cu in / 3.4 l) - but no exact match. So before I buy a new tank, am I correct in saying that we can figure out the mix if we have TW, Filled-Weight, Pressure, and Internal Volume?

thanks!

 

[doug293cz]

Theoretically we can figure out the mix, but I suspect the uncertainty in the calculation may make the result unusable. There are a lot of places for small measurement errors to create large errors in the outcome.

I think you're better off trying to dial in a gas swap protocol.

Brew on

 

[FloppyKnockers]

You mentioned going from a 500' high-rise to the Caribbean. My experience with CO2 with moving to a different elevation definitely had a part to play in bubbles. I went from 150' to 600'+. Took me a bit to rebalance my system. It's been a while from the last time I had something on nitro at 150' to recently at 600', so I couldn't tell you my differences.

 

[doug293cz]

Standard air pressure at 150 ft elevation is 14.6 psi (vs. 14.7 psi at sea level.) Pressure at 600 ft is 14.4 psi. So the pressure difference between your two locations was only 0.2 psi. You can't even read your pressure gauge that close. Something else was causing your issues. Move to Denver (12.1 psi) and we'll talk.

Brew on

 

[homer4111]

update! I'm about 1/3 of the way through the new keg. 10 days ago I noticed the head/foam creeping up - so I swapped it out for pure N2 like you suggested. Good news is that it hasn't gotten worse - but it also hasn't gotten better. Like I said, I'm 10 days in, and I've gone through about 15 pints - still no change. I did NOT vent the headspace either, as you suggested. Maybe vent is slightly and give it a day to try and remove some of the CO2? Or do you have another recommendation? Maybe I just need to wait longer?

thanks!

 

[doug293cz]

You could try a slight vent. After all, you are in experimental territory here.

If you lose to much carbonation after a while, you can swap back to the "beer gas" again, and in this case I definitely think you need to vent.

Brew on

 

[homer4111]

update! ok, so I've finished the keg. the swap to straight nitrogen did a great job in keeping the head from becoming too much. it didn't seem to lessen though, just remained about the same. I performed the slight vent - then went another week - then a larger vent - and went another week, but still roughly same size head. but this did allow me to drink the entire keg, which was great!

I was able to get some more details from the gas company, and they were filling it with some variation of exactly the calculation we were trying to work backwards from - they were going off TW, filling with liquid CO2 to certain weight, then filling rest with N2. They clearly are not as knowledgeable as Doug, because they can't seem to get it right. One of the local bars has been trying to correct this problem over the course of 20+ tanks - they were so frustrated that they just purchased a gas blender and now are extremely happy.

So that is the route I'm going now. Thanks for much for all your help everyone - I'll do a last follow up post once I have everything settled and the beer finally pouring perfectly!

 

[homer4111]

final post! thanks so much for all the help everyone! Doug, your method was the next best option before biting the bullet and getting a blender. Would definitely recommend that to anyone else having foam gas mix issues - swapping to pure N2 when foam starts to creep in. While my setup is now a bit bulkier - the blender is brilliant - perfect pint every time now.

thanks again everyone!