Pressure in keg falling off at start

[bracconiere]

Of course, since I panicked after that initial fast drop by turned off the CO2; took the keg apart and checked all the connections; swapped out the posts, poppets, and lid; and re-applied keg club, and more, I'm not completely sure which, if any of those, changed the situation or if there really wasn't a leak in the first place.

i'm so paranoid of co2 leaks, i keep my tank ona scale acurate to the 1/10th ounce, just caught one after losing 8 oz's....in my case it was a cheapo pin lock gas connector, thankfully it was a flare one, and i had a spare to swap it with....

 

[Tobor_8thMan]

Beer absorbs CO2 more slowly at colder temps, not the other way around. Even if you don't chill the beer but the beer is not saturated for the temperature/pressure combination you leave it at you will see a pressure drop as beer will still absorb some if not most of the CO2. That's how forced carbonation works, as a matter of fact.

This assertion really makes no sense. Use any brewing software or online carbonation tool. We need less CO2 when the beer is cold to carbonate to the desired level vs needing more CO2 when the beer is warm (warmer than the cold beer) to get the same level of carbonation.

For example.

My uncarbonated beer is at 38F. I want it carbonated to 2.3 levels of CO2. At 38F I set the CO2 regulator to 9.15 PSI

However, if my uncarbonated beer is at 68F, then I'll need to set the CO2 regulator to 24.51 PSI to achieve the same 2.3 volumes of CO2.

 

[Tobor_8thMan]

Pressure was back to zero this morning. On close inspection, the rubber housing on the top of the keg, which I thought was just wrinkled, is pulling away from the keg all along the beer out disconnect.

I’m pressure testing another keg right now and if that holds for a few hours, I’ll transfer the beer to a new one.

By "the rubber housing on the top of the keg" do you mean the handles? If so, these are for lifting convenience and will not cause a leak.

 

[Tobor_8thMan]

Because I turned off the CO2 at that point, the beer just continued to absorb CO2 overnight until the pressure was zero.

Don't turn off the CO2 until the desired levels of CO2 are reached. Once this happens, the beer will pour with the CO2 off or set to a lower setting. If the CO2 is off the pour will eventually slow or stop. The beer in the keg is carbonated, there is just nothing to push it out. Give the keg some CO2 and you're good for some more pours.

 

[Tobor_8thMan]

I was always told to turn off the CO2 tank when not in use (please realize I'm not writing about carbonating). Pour a few, give a shot of CO2 to push out the carbonated beer and turn off the CO2 tank until the next time it's needed. Why? Prevents leaks in the system (tubing, CO2 on/off knob, etc).

 

[johndan]

The black rubber cap, which includes the housing. The portion around one of the posts was cracked. I've never taken one apart so I wasn't sure whether cracks in that might cause leaks. I guess if it's only there to create a handle, you're right--it's not going to have anything to do with leaking.

Keg's still holding pressure after several days, so I think I'm out of the woods (for this specific problem, anyway…).

By "the rubber housing on the top of the keg" do you mean the handles? If so, these are for lifting convenience and will not cause a leak.

 

[Tobor_8thMan]

Oh, the post gaskets? Is this a ball lock keg or pin lock keg?

 

[day_trippr]

Pretty sure the "black cap" reference is indeed the top keg rubber, and the focus was on that rubber cracking around the base of the posts.
Which happens, and obviously is of no functional concern.

Turning off a CO2 cylinder obviously doesn't "prevent leaks". If there is gas pressure in the otherwise closed system that pressure will find those leaks, and when the cylinder is turned back on it will have to bring the system back up to pressure, meaning the loss would be the same either way...

Cheers!

 

[bracconiere]

Pretty sure the "black cap" reference is indeed the top keg rubber, and the focus was on that rubber cracking around the base of the posts.
Which happens, and obviously is of no functional concern.

Turning off a CO2 cylinder obviously doesn't "prevent leaks". If there is gas pressure in the otherwise closed system that pressure will find those leaks, and when the cylinder is turned back on it will have to bring the system back up to pressure, meaning the loss would be the same either way...

Cheers!

but at least you'd know when you turn it on you had a leak from the fact the reg was making noise.....

 

[Tobor_8thMan]

Turning off a CO2 cylinder obviously doesn't "prevent leaks".

I mentioned as I was advised by the CO2 fill shoppe to turn off the CO2 when not in use.

 

[johndan]

Ball lock.

- Johndan

Oh, the post gaskets? Is this a ball lock keg or pin lock keg?

 

[Tobor_8thMan]

Was the post gasket cracked/leaking or just the rubber/plastic handle (near the post) on top of the corney keg?

 

[doug293cz]

This assertion really makes no sense. Use any brewing software or online carbonation tool. We need less CO2 when the beer is cold to carbonate to the desired level vs needing more CO2 when the beer is warm (warmer than the cold beer) to get the same level of carbonation.

For example.

My uncarbonated beer is at 38F. I want it carbonated to 2.3 levels of CO2. At 38F I set the CO2 regulator to 9.15 PSI

However, if my uncarbonated beer is at 68F, then I'll need to set the CO2 regulator to 24.51 PSI to achieve the same 2.3 volumes of CO2.

You are confusing rate of absorption vs. maximum amount absorbed. The rate of CO2 absorption is lower at lower temps because diffusion is slower at lower temps. The maximum amount absorbed is higher at lower temps for any given CO2 partial pressure, because the CO2 solubility is higher at lower temps.

Brew on

 

[Tobor_8thMan]

You are confusing rate of absorption vs. maximum amount absorbed. The rate of CO2 absorption is lower at lower temps because diffusion is slower at lower temps. The maximum amount absorbed is higher at lower temps for any given CO2 partial pressure, because the CO2 solubility is higher at lower temps.

Brew on

No one goes by higher temp maximum amount absorbed. Please see

https://www.homebrewtalk.com/threads/pressure-in-keg-falling-off-at-start.690417/post-9071265

 

[doug293cz]

No one goes by higher temp maximum amount absorbed. Please see

https://www.homebrewtalk.com/threads/pressure-in-keg-falling-off-at-start.690417/post-9071265

That has nothing to do with the physical chemistry of the process.

If someone wants to force carbonate at room temp (because they have no room available in a cooler), then they absolutely go by the maximum absorbed at room temp vs. pressure.

Brew on

 

[VikeMan]

You are confusing rate of absorption vs. maximum amount absorbed. The rate of CO2 absorption is lower at lower temps because diffusion is slower at lower temps. The maximum amount absorbed is higher at lower temps for any given CO2 partial pressure, because the CO2 solubility is higher at lower temps.

Could you please provide some Minkowski diagrams for photons emitted from CO2 molecules in each case? I think that would clear it up nicely.

Also, you're right.

 

[Tobor_8thMan]

I do believe we're messaging about 2 different topics.

 

[doug293cz]

I do believe we're messaging about 2 different topics.

Aren't we talking about CO2 absorption in beer, and how under some circumstances absorption can look like a CO2 leak to someone who doesn't adequately understand the science?

Brew on

 

[jddevinn]

Despite it's name volumes of CO2 is the space that the CO2 would take up at standard pressure (one atmosphere about 15 psia / 0 psig) and at standard temperature (32 °F). Essentially this unit is a mass.

The CO2 Volume per pressure and temperature table essentially shows the saturation amount (amount that can be absorbed) of CO2 in beer in Volumes at a specific temperature. At a steady pressure amount (Volumes) of CO2 that can be absorbed raises as the temperature falls.

Like almost every reaction the diffusion rate (time for absorption of that CO2) into the beer decreases as the temperature falls.

So in context of this conversation assuming the beer is not already saturated a small amount of CO2 at 15psig will absorb down to ~0psig quicker at a warm temperature than at a colder temperature, but it will happen at any temperature.

 

[doug293cz]

Despite it's name volumes of CO2 is the space that the CO2 would take up at standard pressure (one atmosphere about 15 psia / 0 psig) and at standard temperature (32 °F). Essentially this unit is a mass.

...

It is more correct to say "CO2 Volumes" is a density (mass/volume) unit. 1 volume of CO2 is 1.977 g/L or 0.264 oz/gal.

Brew on

 

[johndan]

Was the post gasket cracked/leaking or just the rubber/plastic handle (near the post) on top of the corney keg?

Just the rubber/plastic handle near the post.

 

[jddevinn]

It is more correct to say "CO2 Volumes" is a density (mass/volume) unit. 1 volume of CO2 is 1.977 g/L or 0.264 oz/gal.

Brew on

By essentially a mass unit I mean vs a volume unit, it does not have to be accompanied by a pressure & temperature to determine it's affect in calculations. So in 'thought math' it can be considered as a mass. But yes it is more accurate a density

 

[doug293cz]

By essentially a mass unit I mean vs a volume unit, it does not have to be accompanied by a pressure & temperature to determine it's affect in calculations. So in 'thought math' it can be considered as a mass. But yes it is more accurate a density

If you have 2.75 oz of CO2 in your beer, how many "volumes" of CO2 is that?

Brew on

 

[jddevinn]

If you have 2.75 oz of CO2 in your beer, how many "volumes" of CO2 is that?

Brew on

Of course you know the answer. Depends on how much beer. 10.4 Volumes/gallon. Assuming 5 gallons 2.1 Volumes.

But I didn't need to know the pressure or temp to know that. Similar to say volumetric flow of gas given in SCFM, not really a mass but in terms of your variable set can be treated as a "mass unit" not a "volume unit." Maybe referring to design variables that way is industry specific. If someone wants me to design a condenser and gives me volumetric flows I'm going to approach it one way; if someone gives me SCFM, mass flows, partial pressures, molar ratios, ect. I'm going to approach it another.

In the context of this thread I was stating that a small headspace at a higher pressure may absorb quicker than a large headspace at lower pressure because there is less mass even the the volume at lower pressure is larger. And with the name "Volumes" it's easy to confuse and think that Volumes is a volume CO2 to volume beer ratio that is dependent on the pressure/temp that you carbonate at, not that the pressure/temp is a saturation point. I think confusion over this is why there are so many variations of burst carbonation around.

 

[doug293cz]

Of course you know the answer. Depends on how much beer. 10.4 Volumes/gallon. Assuming 5 gallons 2.1 Volumes.

But I didn't need to know the pressure or temp to know that. Similar to say volumetric flow of gas given in SCFM, not really a mass but in terms of your variable set can be treated as a "mass unit" not a "volume unit." Maybe referring to design variables that way is industry specific. If someone wants me to design a condenser and gives me volumetric flows I'm going to approach it one way; if someone gives me SCFM, mass flows, partial pressures, molar ratios, ect. I'm going to approach it another.

In the context of this thread I was stating that a small headspace at a higher pressure may absorb quicker than a large headspace at lower pressure because there is less mass even the the volume at lower pressure is larger. And with the name "Volumes" it's easy to confuse and think that Volumes is a volume CO2 to volume beer ratio that is dependent on the pressure/temp that you carbonate at, not that the pressure/temp is a saturation point. I think confusion over this is why there are so many variations of burst carbonation around.

Now, if I tell you you have 0.686 oz/gal of CO2, how many "volumes" of carbonation do you have?

Brew on

 

[jddevinn]

2.598 Volumes

 

[jddevinn]

If I say I have a bottled pint of beer at 2.2 Volumes you'll know the mass of CO2 (other than arguments over pint vs pint)in solution, but you won't know the actual volume of the CO2 in solution without also knowing the internal pressure and temperature.

 

[bracconiere]

2.598 Volumes

are you calculating residule co2 from fermentation? i'm curious, does co2 have calories? i try to calculate to the nearest 10, but now i wonder if i'm burst carbing...if maybe i need to compensate for the co2?

 

[day_trippr]

 

[jddevinn]

are you calculating residule co2 from fermentation? i'm curious, does co2 have calories? i try to calculate to the nearest 10, but now i wonder if i'm burst carbing...if maybe i need to compensate for the co2?

Total CO2. We're just talking about my use of 'mass unit'. You will have residual CO2 from fermentation but it will be process and equipment dependent. It can't have much calories because it doesn't contain much energy.