Guinness shrinking head!?!?

[ChookieBaby]

setup:
I have a home bar setup with 3 kegs, none of which is refridgerated. I am using a Gamko cooler and a Cornelius Flash Cooler with cold water recirculation to the tap so all beers are served at the same temperature. The Guinness setup has it's own cooler and Mixed Gas bottle (22#) with it's own (new) regulator set for about 2.4 bar (35psi) and dispensed through an official Guinness tap using 3/8" lines and mostly J.Guest fittings.

problem:
when i tap a new keg, the head acts as is is suppose to, but about 1/4 way through the keg (30L) the head gets smaller and smaller. it has the correct density, but is quite small - less than a centimeter - like 1/4 inch thick only (or less). i get my kegs from the same supplier as all the irish pubs in Amsterdam (Netherlands), and the same gas supplier, the same regulator, the same everything.
What i'm wondering is if it is because i am using a flash cooler instead of cooling the keg itself, though all evidence says that i should have the opposite problem. i have talked with the barmen at various pubs and nobody has any idea why i get less and less head on my pints.
There are no leaks in my system, and i use it every day, usually 4-8 pints depending on who comes around!
I have not tried a different tap, but i have tried 2 different keg connectors, an InBev one and an InterBrew connector. the #25 creamer plate is in place and all o-rings are new. i have tried 6 different spouts, all the same result. the tap works perfectly, but the guinness seems to get less and less head on it. (the lager, bitter and pilsners all act properly)

Summary:
How can i get more head (on my guinness pints). do i need to shake up my kegs, do i need to chill them? do i need to replace my lines, do i need to try a different regulator, gas mix, connector, hang from the ceiling, dress in a chicken costume?

any help is greatly appreciated.

cheers from Amsterdam.

Chookie Baby.

[TheSlavik]

Interesting problem. I had a similar issue, however, I froze the last 1/3rd of my keg. Being yours is not refridgerated (did I read your post right?) I dont have a clue.

[ChookieBaby]

Thats correct. the kegs are stored inside the bar, but not cooled. they are at room temperature, 18c? not sure of the conversion, but around 75F degrees? and there is no way they could have been damaged by freezing. i unloaded them off the truck from Ireland myself. this is the 4th keg that has done this same thing.
i suspect my equipment. i may start with replacing the tap, then the coupler, then the regulator, then the gas bottle.

without these troubleshooting steps, i don't have a clue what is could be either.

any ideas? anyone?

[TheSlavik]

What is really odd is how it starts fine, but then degrades as your kegs becomes more depleted. That makes me think it wouldnt be hardware, as in; your stout faucet doesnt know how full the keg is. Maybe pressure? Do you have any leaks in the system? You said you were at 38 psi right?

[ChookieBaby]

Yes, that's right. i just did a re-conversion and bled off the pressure and it does the same thing.

here's the strangest thing. when i start to pour a pint - usually the first one of the day, like breakfast...opps, no, um, it starts out pouring very creamy and then slowly becomes more clear - the stream from the spout that is, and if i watch it carefully, it fluctuates between slightly creamy and clear (as in as if it is coming out completely flat.)

i turned the keg again tonight to make sure it isn't settling, and untapped it and re-coupled it and the same thing.

i'm completely out to sea here. i just haven't a clue on why it's doing this. i can't even think what to try now.....

sooo... ummm... no idea. any help is greatly appreciated.

[BrewGuru]

I'd try the chicken costume!

Luckily this is an easy problem to fix!

The problem is that you are not putting enough pressure against the beer to maintain the (very low) level of carbonation in the beer.

35 PSIG is enough to maintain a 1.2 v/v beer Such as Guinness, but only at 38 Deg F, at your temps, the pressure needs to be much higher as CO2 is less likely to stay in solution at higher temps.

18C is actually 64.4F - let's just assume you're working with a baseline 'room temperature' of 21C or 69.8F

At this 'room temperature', using a 25% CO2 / 75% N mixed gas, you would need a whopping 70 PSIG to mantain 1.2 volumes of CO2 - DO NOT SET YOUR REGULATOR TO THIS SETTING. This exceeds the 60 PSI that most kegs are rated for and would be a VERY BAD IDEA.

If you can get the 30%/70% mixed gas, you can run at 54 PSIG, and this will maintain the proper level of carbonation in your Guinness - this is borderline the limit that kegs are made to withstand, so be very careful if you like to rap on your kegs with a ball peen hammer or whatnot.

The reason that the beer in your chiller appears to pour properly at first is that after getting cold, the liquid is more readily able to absorb the CO2 that is present in the pressurized line, and it is re-carbonating while sitting there cold. As soon as you start dispensing, the higher carbonation beer comes, out, quickly followed by beer at a lower dissolved level of CO2, which causes turbulance and the oscillating effect you observe. I would wager that the longer you wait to pull a pint, the 'better' the first portion pours.

Short answer here is to raise your pressure, and look into the gas you are using. You may need to add quite a bit of choker line to get your system to be balanced, if you need more help with this, let us know. Depending on how committed you are to properly pressurized and dispensed Guinness, you could look into a custom mix blender and do a 42% CO2 blend...

Good luck!

[TheSlavik]

^
And that is why I am a member of this forum!

[BrewGuru]

Another point to be considered is that the higher pressure will be resident in the line as was the pressure that was too low.

The low temp area of the system holding beer in may allow the small amount that is in there to carbonate up to 2.1 v/v This may cause you to have a slightly different occurrence when tapping the first pint of the day, instead of a small amount of correct beer and then a bunch of under carbonated beer, you will have a small amount of overcarbonated beer, and then the rest correct beer...

Unfortunately dual temp systems such as this are very difficult to balance, but a rule of thumb is balance towards the majority of the beer, that is, keep the beer in the keg at the right level of dissolved CO2.

Chances are the first pour of the day (that has been sitting in the chiller lines overnight) will have a higher level of dissolved CO2, but the subsequent pours should be at the right pressure and temp, but not have enough time at the low temp to really gain an appreciable level of carbonation.

Good luck!

[Misterworst]

At these temperatures i would use a 60/40 blend and set my psi at 34. Just because i like to hit my kegs with ballpeen hammers so 54 is a little unnerving.

[ChookieBaby]

The chicken costume worked, but only while hanging from the ceilng

I am using the standard 30/70 gas mix. i have turned up the pressure to 4.5 bar as suggested. the room temperature of the keg is around 18c now, so everything looks good. i will now wait a moment and let the gas dissolve since i have a full pint of nearly headless guinness already.

it's just really strange to see it oscillate between creamy, then clear, then creamy again, then back to clear.

i will post a followup in the next few minutes on what is happening.

thanks for the super-technical advice. this is why i love this forum, and hope that some day i can be a beer guru also!

chookie

[BrewGuru]

Misterworst:
60/40 mix is almost always 60% CO2 and 40% N. and I'm not aware of a supplier of this mix in cylinder, it is generally produced by a gas blender system with either cylinders or extractors / generators attached, and is typically used to push ales in long draw systems.

Also, this mix would be inverse for the application, at the stated temp and pressures, 34 PSIG of 60% CO2 / 40% N, would result in a carbonation level of 1.7 v/v - quite over carbonated for Guinness.

If one could find a 60% N / 40% CO2 blend, the correct pressure would then be 38 PSIG for 70F.

chookiebaby:

Please do bear in mind that it takes some time for gas to enter or leave solution, just as a bottle of beer does not go flat immediately after opening, your keg will not come back up to the desired level of gas in solution for some time, quite likely 3 or 4 days depending on the volume of beer left in the keg, also, at the higher temperature it will take longer for the gas to enter. Imagine that putting a higher pressure against the top of the beer is akin to creating a slow moving wave that will take several days to get to the bottom of the keg (where the draw tube is).

So don't be discouraged when it's not different immediately, depending on how fast you drink, the keg will balance itself out or expire, and your next keg should be ideal.

Also, the oscillating effect you observe is due to thermal and pressure differences in the multiple areas of your system, the fluid flowing through it is subject to the laws of physics, always trying to balance itself out, thus causing the visible turbulence while dispensing.

Good luck!

[BrewGuru]

Whoa there, I just realized you said 4.5 bar!!!

That's way too high and outside of the safety range! 4.5 bar is equal to 65 PSI.

The correct setting at 18C is 3.44 bar - this will maintain the 1.2 v/v that is normally in the Guinness.

As you are technically UNDER sea level, so no adjustment for altitude there.

Also - the higher pressure may help to give a boost to the what might normally take days process of forcing the gas back into solution, but NEVER exceed 60 PSI or 4.13 bar applied pressure.

[Misterworst]

Sorry about that I did have the Co2 and N backwards BrewG, but i'm still thinking the 60Co2/ 40N mix would be the way to go. At 70F you would need 20 PSI to maintain 1.2 v/v a little more reasonable pressure for system in my mind. I was always told that a couplers pressure relief valve will start blowing off in the 50 PSI range...never tested it though.

[ChookieBaby]

Phew! caught it before it exploded, or started leaking!

Ok, it didn't explode, though i *DID* have the pressure a few clicks too high. i immediately turned it down after reading your reply. Sure don't need to blow a gasket! It would be the worst type of crime against beer, and Ireland.

So now i have the pressure set at 4.13 bar and will see if the system stabilizes a bit over the next days. as of last evening, there was no noticeable difference yet so we will see if it actually absorbs more gas as it sits a while.

Plan B will be adding 3 small keg coolers to the inside of the bar where the kegs are being stored!

I will update this tonight and tomorrow as things progress (or not)

thanks again for all the super-technical information, that's exactly what i need!

[ChookieBaby]

reply about line pressure.

Sorry about that I did have the Co2 and N backwards BrewG, but i'm still thinking the 60Co2/ 40N mix would be the way to go. At 70F you would need 20 PSI to maintain 1.2 v/v a little more reasonable pressure for system in my mind. I was always told that a couplers pressure relief valve will start blowing off in the 50 PSI range...never tested it though.

You are correct! I had to remove the in-line pressure relief valves to get the pressure that high. the one on the regulator will let it go a bit higher, but not the in-line ones. they started bleeding off at just under 3.5 bar, or around 50psi.

Also, getting custom blended gas will be a big problem here, so for now, will try to work with what i can get, which is the 70n/30co2 foodmix gas.