Keg Setup - Foamy First Beer - Possible Solution?

[brocasarea]

So I just set up my keg system. Everything works well except for one thing - the first beer is too foamy. After that it's all good. Now I put this down to the shanks in the fridge door. They're quite long because i put wood panels on the front to make it look all pretty not thinking of the effect it would have.

Now the long shank will have warm beer down the end right? Would I be correct in saying that a heatsink of some sort would counteract this problem? I was thinking of getting a brass or copper bush from a plumbing store and putting it all together with some thermal paste I have. I'm relying on the extra surface area and the better thermal properties of the brass to cool the shanks.

Are there any physics heads here that can tell me yea or nay? Would I be running fool's errand?

 

[pcqypcqy]

I just let the first bit of the pour drop into a drip tray and then put my glass under. I haven't been measuring but I don't have to empty my drip tray too often and I'd guess I wouldn't even lose a whole glass over the course of a 19l keg.

This is what they do at my local craft beer bar as well, and I assume they have properly cooled fonts as well. I reckon it's inevitable that some beer will be a bit too warm, no matter what you do.

 

[brocasarea]

Yeah, I've been letting it drop but it's too much. Especially when I'm drinking on my own (not as bad as it sounds) and the tap has time to warm up again.

I used to work in bars - too many. It depends on what type of system you have as to whether you need to do a drop or not. The glycol systems will cool the tap so you don't need a drop - these are the ones that freeze up. They have cold glycol circulating around all the lines to keep them cold. The ones that don't freeze up are probably a temprite system and they face the same problem we have here. They're just a liquid heat exchanger and a fridge smooshed into one under the bar. They have an unrefrigerated riser on the bar with warmer than desirable beer in it.

 

[crowmanz]

I suggest a fan to circulate the cold air better. I find my taps don't take much of a draw to cool down the taps, so I will pour less than 1/4 of the glass then top up once I see condensation on the taps which is usually pretty quick.

 

[brocasarea]

Definitely the right idea Crowmanz, but there's already a fan in there right at the top that blows onto the front door. I just need that little bit extra. Just wasting a little too much beer.

 

[peteru]

You should be able to estimate where physically the foamy beer comes from by measuring the volume of dispensed foamy beer and then estimating how far back that amount of foamy beer would reach in the dispensing system. If it looks like it's just the tap, then cooling the shank will probably have minimal effect. If it looks like the beer in the shank is involved too, then you may be able to reduce the problem with a heat sink. Of course, before you go into the trouble of installing a heat sink, you should make sure that your fridge has a good fan that circulates the air well.

 

[Dan Pratt]

turn down the serving pressure. the shank has about 20mls of beer which doesn't equate to the entire serving to be too foamy.

 

[pcqypcqy]

I have a similar set up to you, but with my long shanks going through a wood collar on a freezer. I wouldn't even let a second's worth of beer drop, and it takes me about 10 seconds to fill a schooner, so talking 40 mL wastage per glass maximum. Hasn't been a big enough deal for me to change it, but I understand that it is for you.

If you really want to minimise it, could you cut out some insulation from around the shank, and tighten the nut up against the back of the metal of the fridge wall? Coupled with a fan like others have suggest, this would allow the circulated air to get as far forward as possible. Slightly less efficient to run the fridge this way, but we're talking a few square cm of fridge door that's uninsulated so I can't imagine it'll have an appreciable effect on the power consumption of your fridge.

If you didn't do this, there'll be a thermal gradient with the shank at the inside of the door being near the fridge temp and the tap on the outside being near the ambient temp. No amount of fan blowing will change that because the shank is insulated.

 

[GalBrew]

I find whatever has been sitting in the lines in between drinking sessions doesn't taste all that great anyway, so I always let about 1/4 of pot through just to clear out that beer. What you've got happening is a classic issue with keggerators that have the shank running through the door. That being said it shouldn't take a whole glass of beer to cool the shank/tap down.

 

[pcqypcqy]

The other thought I had was that if you were having a few beers of an evening and didn't want to have the tap warm up between each glass would be to pour yourself a jug.

 

[pcmfisher]

If you have 2metres of 5mm id beer line the total volume in that line would be 40ml. Less than a tenth of a glass.

So if you look at your line before you do your first pour and you can see any beer, even if you pour whatever is in the line away you are not losing much.

If there is a big bubble behind you tap, it could be partly a warm tap and partly the highest point, but most likely a ballancing issue.

Once again, either you have too much gas in your beer or not enough serving pressure to hold it in there.

 

[brocasarea]

I have a similar set up to you, but with my long shanks going through a wood collar on a freezer. I wouldn't even let a second's worth of beer drop, and it takes me about 10 seconds to fill a schooner, so talking 40 mL wastage per glass maximum. Hasn't been a big enough deal for me to change it, but I understand that it is for you.
If you really want to minimise it, could you cut out some insulation from around the shank, and tighten the nut up against the back of the metal of the fridge wall? Coupled with a fan like others have suggest, this would allow the circulated air to get as far forward as possible. Slightly less efficient to run the fridge this way, but we're talking a few square cm of fridge door that's uninsulated so I can't imagine it'll have an appreciable effect on the power consumption of your fridge.

If you didn't do this, there'll be a thermal gradient with the shank at the inside of the door being near the fridge temp and the tap on the outside being near the ambient temp. No amount of fan blowing will change that because the shank is insulated.

@pcqypcqy - I'm getting like half a glass of foam. I have thought about removing insulation but i want that to be a later option. I'm thinking it may be another issue at the moment.

 

[brocasarea]

You should be able to estimate where physically the foamy beer comes from by measuring the volume of dispensed foamy beer and then estimating how far back that amount of foamy beer would reach in the dispensing system. If it looks like it's just the tap, then cooling the shank will probably have minimal effect. If it looks like the beer in the shank is involved too, then you may be able to reduce the problem with a heat sink. Of course, before you go into the trouble of installing a heat sink, you should make sure that your fridge has a good fan that circulates the air well.

@peteru - Good thoughts. I'm getting like half a glass of foam - maybe a bit more. That's like the shank and all the line. I think I may have another problem.

 

[brocasarea]

If you have 2metres of 5mm id beer line the total volume in that line would be 40ml. Less than a tenth of a glass.

So if you look at your line before you do your first pour and you can see any beer, even if you pour whatever is in the line away you are not losing much.

If there is a big bubble behind you tap, it could be partly a warm tap and partly the highest point, but most likely a ballancing issue.

Once again, either you have too much gas in your beer or not enough serving pressure to hold it in there.

@pcmfisher - I have 3m of 4mm line. It was at 10psi for the last beer at 2 degrees. I made it 3m so I could chop it back but this is happening.

This is my first go at balancing a system so I'm going to go through everything again.

 

[pcmfisher]

Was that 10psi left to carbonate over a week or so or forced?

 

[klangers]

The volume in the line is mostly irrelevant for this discussion.

How much beer it takes to flow through the shanks to cool them AND the taps depends on:

• Initial temperature of the tap and shank (lower is better)
• Thermal mass of the tap and shank (lower is better)
• Thermal conductivity of the tap and shank (higher is better)
• Temperature of the beer (lower is better)
• Flow rate of the beer (higher is better)

Where better = faster cooldown of shank and tap. You'll never achieve a zero-time cooldown with this type of font. To avoid first-pour issues altogether you're going [to need your] taps/shanks at a lower temperature than what your kegs are stored at.

The issue here, as outlined above in regards to comparison with glycol-flooded fonts, is that the lowest possible font temperature is the same as the equilibrium temperature for that particular carbonation (assuming your kegs have been sitting in there for long enough to equilibriate). This is because your fridge is the same temperature as the "cold" that you're trying to transfer through to your taps, but the taps are outside and warmer. This will always be the case; it's only a matter of to what degree.

For arguments' sake, if you make it -18 inside, the tap will be colder outside than before but still warmer than -18. Assuming your beer is insanely alcoholic and won't freeze, then it will get more carbonation due to the lower temperature (assuming again you keep the pressure the same). Since it then equilibriates to -18, as it hits the shank/tap (which is going to be above -18 since part of it's outside and transferring heat, and heat transfer requires a temperature differential), it will warm up and some CO2 will come out of solution (foam).

Therefore, the font will always cause foam initially - how much is what you want to optimise.

Foam will continuously form too - it's not quite right to say "measure back" and say that's where it's coming from. It will form as long as the pressure/temperature suddenly shifts out of equilibrium. So if your tap takes a long time to cool, then it will keep forming foam until the conditions stop forcing CO2 into gas phase.

Check for kinks in the hose as the door closes. These create a zone of low pressure just after the kink and this will cause in-line foaming.

 

[brocasarea]

Was that 10psi left to carbonate over a week or so or forced?

Yep, 10psi all the way through.

 

[brocasarea]

The volume in the line is mostly irrelevant for this discussion.

How much beer it takes to flow through the shanks to cool them AND the taps depends on:

• Initial temperature of the tap and shank (lower is better)
• Thermal mass of the tap and shank (lower is better)
• Thermal conductivity of the tap and shank (higher is better)
• Temperature of the beer (lower is better)
• Flow rate of the beer (higher is better)

Where better = faster cooldown of shank and tap. You'll never achieve a zero-time cooldown with this type of font. To avoid first-pour issues altogether you're going [to need your] taps/shanks at a lower temperature than what your kegs are stored at.

The issue here, as outlined above in regards to comparison with glycol-flooded fonts, is that the lowest possible font temperature is the same as the equilibrium temperature for that particular carbonation (assuming your kegs have been sitting in there for long enough to equilibriate). This is because your fridge is the same temperature as the "cold" that you're trying to transfer through to your taps, but the taps are outside and warmer. This will always be the case; it's only a matter of to what degree.

For arguments' sake, if you make it -18 inside, the tap will be colder outside than before but still warmer than -18. Assuming your beer is insanely alcoholic and won't freeze, then it will get more carbonation due to the lower temperature (assuming again you keep the pressure the same). Since it then equilibriates to -18, as it hits the shank/tap (which is going to be above -18 since part of it's outside and transferring heat, and heat transfer requires a temperature differential), it will warm up and some CO2 will come out of solution (foam).

Therefore, the font will always cause foam initially - how much is what you want to optimise.

Foam will continuously form too - it's not quite right to say "measure back" and say that's where it's coming from. It will form as long as the pressure/temperature suddenly shifts out of equilibrium. So if your tap takes a long time to cool, then it will keep forming foam until the conditions stop forcing CO2 into gas phase.

Check for kinks in the hose as the door closes. These create a zone of low pressure just after the kink and this will cause in-line foaming.

You got it mate - kink in the hose. Somewhere along the line it was kinked and this has created a spot of turbulence. Cut him out and now all good.

 

[peteru]

Why did a kink affect only the first beer?

 

[brocasarea]

I'm guessing it would be a combo of warm shank and the kink.