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#101 malt junkie

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Posted 20 May 2017 - 08:23 AM

1m = 10kpa... luck with that



#102 wynnum1

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Posted 20 May 2017 - 10:09 AM

So is that plus atmospheric pressure and its measured with  atmospheric pressure as zero on the pressure meter



#103 pcqypcqy

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Posted 22 May 2017 - 11:50 AM

So is that plus atmospheric pressure and its measured with  atmospheric pressure as zero on the pressure meter

 

No, the keg with nothing on it has atmostpheric pressure pushing on the outside of it (and the inside).  So all you're measuring is the additional pressure over that (often called gauge pressure).

 

3.4 metres to get 5 psi, so maybe not practical.

 

On the other hand, if you used mercury, it would be liquid at room temperature and you'd only need 258mm of it!  :D  (link)



#104 malt junkie

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Posted 22 May 2017 - 11:58 AM

Interestingly the pressure would directly relate to the Gravity of the liquid.



#105 klangers

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Posted 22 May 2017 - 12:07 PM

Yes, static pressure is height (m) x density (kg/m3) x acceleration due to gravity (m/s2) = Pa (N/m2)



#106 Hpal

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Posted 22 May 2017 - 05:05 PM

This one is pretty munted. It is the one that looks like an A type but isn't so I am going to put a corny top on it

at least you can get your arm in to clean then, it's the way to go.

#107 peteru

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Posted 23 May 2017 - 01:46 AM

Yes, static pressure is height (m) x density (kg/m3) x acceleration due to gravity (m/s2) = Pa (N/m2)

 

Taking that info down the practical path, you could use a piston with a weight on it. Hydraulics, here we come! :super:



#108 wynnum1

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Posted 23 May 2017 - 04:24 AM

No, the keg with nothing on it has atmostpheric pressure pushing on the outside of it (and the inside).  So all you're measuring is the additional pressure over that (often called gauge pressure).

 

3.4 metres to get 5 psi, so maybe not practical.

 

On the other hand, if you used mercury, it would be liquid at room temperature and you'd only need 258mm of it!   :D  (link)

Pvc pipes  come in 6 meter lengths  so 3.4 meters is not a problem .



#109 pcqypcqy

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Posted 23 May 2017 - 12:02 PM

Pvc pipes  come in 6 meter lengths  so 3.4 meters is not a problem .

 

Pics or it didn't happen :D

 

I'd be keen to see how it goes.  You doing this outdoors?  Tall shed?



#110 klangers

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Posted 23 May 2017 - 12:50 PM

Taking that info down the practical path, you could use a piston with a weight on it. Hydraulics, here we come! :super:

 

Indeed, this is how a lot of hydraulic accumulators were designed prior to 1950s.

 

Honestly though, it's a shitload easier and cheaper buying a good spunding valve than trying to rig up some hydraulic rig to apply backpressure to your keg. The CO2 needs to be exhausted, so if you were going down a hydraulic accumulator route, you'd need to have enough volume in that water column to take up the exhausted CO2. In addition, it would need to be a closed system (not open to atmosphere). If it's open at the end, CO2 would just bubble up through the water and/or push out the water. If it's closed, then the volume would need to expand. So in order to do this with a water column, you'd have to have a flexible membrane between the keg CO2 and water column. Then the CO2 emerges and pushes against the static water pressure without mixing with it.

 

You'd be better off connecting your full keg gas to an empty keg. Then the CO2 will gradually fill the empty keg and headspace in full keg and increase the pressure in both. It's possible to calculate this extra volume you need.



#111 Mardoo

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Posted 23 May 2017 - 04:16 PM

Indeed, this is how a lot of hydraulic accumulators were designed prior to 1950s.

 

Steampunk pressurised fermenting!



#112 mtb

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Posted 23 May 2017 - 04:26 PM

Steampunk pressurised fermenting!

 

Maybe "Steam Ale" will finally have a basis on which to define itself as an actual style



#113 rude

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Posted 26 May 2017 - 11:49 AM

Looks good Crusty so I've got myself an address in the States through shop mate cheers

 

Carted a  valve , gauge , tee piece all 1/4 npt just need 1/4" npt male to the thread size of gas disconnect female  ????

 

7/16 usf or usn ???

Shop Mate worked but ended up with 2 parcels instead of 1, blew that

 

Had to pay 2 lots of postage as Shop Mate dont repack

 

Expensive valve this one just hope its better than the KK one if not I lose



#114 pcqypcqy

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Posted 26 May 2017 - 12:43 PM

Indeed, this is how a lot of hydraulic accumulators were designed prior to 1950s.

 

Honestly though, it's a shitload easier and cheaper buying a good spunding valve than trying to rig up some hydraulic rig to apply backpressure to your keg. The CO2 needs to be exhausted, so if you were going down a hydraulic accumulator route, you'd need to have enough volume in that water column to take up the exhausted CO2. In addition, it would need to be a closed system (not open to atmosphere). If it's open at the end, CO2 would just bubble up through the water and/or push out the water. If it's closed, then the volume would need to expand. So in order to do this with a water column, you'd have to have a flexible membrane between the keg CO2 and water column. Then the CO2 emerges and pushes against the static water pressure without mixing with it.

 

You'd be better off connecting your full keg gas to an empty keg. Then the CO2 will gradually fill the empty keg and headspace in full keg and increase the pressure in both. It's possible to calculate this extra volume you need.

 

I don't know that it's quite the same as an accumulator.

 

If you had a column of water that was open to the atmosphere, this should provide a constant back pressure on your system.  Gas above this pressure would escape into the water and bubble away.  



#115 klangers

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Posted 26 May 2017 - 01:36 PM

I don't know that it's quite the same as an accumulator.

 

If you had a column of water that was open to the atmosphere, this should provide a constant back pressure on your system.  Gas above this pressure would escape into the water and bubble away.  

 

... but it won't. If the keg was just liquid, then yes it would work. But CO2 is less dense that the water, so all that will happen is either:

  • You put the column of water entering the bottom of the keg (dip tube). All the CO2 floats to top of the keg. Unless you have the perfect amount of sugar, the excess CO2 will build up and displace the water in the column by pushing beer out of the keg up the column. Yes your pressure was constant but now your volume is less
  • You put the column of water entering the top of the keg (no dip tube). All the CO2 (less dense than liquid water) bubbles up and you have flat beer. J

You need to exhaust the right amount of CO2. It's not just about static pressure.



#116 Mardoo

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Posted 26 May 2017 - 05:44 PM

OK, I had mentioned I would post some papers I had saved. Turns out they were on my old computer that died and didn't make it across to the backup in time.

 

However, I've hunted down a few papers on the topic of pressurised fermenting, which I'm currently going through.

 

The TL:DR is that as long as you keep pressure below 20PSI/138kPa, it's been shown in laboratory and actual practice that you will see significant suppression of esters, and be able to ferment at higher temperatures before fusel alcohol production kicks in. This is due to the higher volume of CO2 that is allowed to remain in solution at higher pressures. Yeast growth is inhibited to some degree, but it is said to be likely that it is the cap on yeast growth that allows the suppression of esters and fusels. Many, many major breweries use pressurised fermentation of lagers, so it can't be that much of an issue with the yeast.

 

There is likely some reduction in head formation for beers fermented at higher pressures. I'm trying to chase up a paper on that specific topic, but have yet to track one down that's not behind a paywall. Here's one interesting thing that's referenced. For a given volume of wort, no matter what the gravity of that wort, the amount of head-forming proteins will be exactly the same. 20L of 15P wort will have exactly the same amount of head-forming proteins as 20L of 25P wort. Weird. So, if you brew high-gravity and dilute back to get increased volume, you're likely to see a reduction in head formed.

 

I'm including a very interesting paper on high-gravity brewing, since some folks in this and the pressurised fermenting thread have mentioned brewing high to dilute low.

 

So, here are the papers. I haven't yet finished going through them so there may be more of interest that one of youse wants to point out, as well as any shortcomings in my descriptions.

 

And...GOOGLE SCHOLAR ROCKS!!! If you're into searching out actual research, get on it.

 

Attached File  Improving Yeast Fermentation Performance.pdf   1.07MB   7 downloads

Attached File  CO2 Pressure and Ester and Fusel Formation.pdf   670.64KB   5 downloads

Attached File  Yeast Response to Fermentation Under Pressure.pdf   355.1KB   5 downloads

Attached File  Controlling Yeast Fermentation.pdf   958.98KB   1 downloads

 



#117 pcqypcqy

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Posted Today, 08:23 AM

... but it won't. If the keg was just liquid, then yes it would work. But CO2 is less dense that the water, so all that will happen is either:

  • You put the column of water entering the bottom of the keg (dip tube). All the CO2 floats to top of the keg. Unless you have the perfect amount of sugar, the excess CO2 will build up and displace the water in the column by pushing beer out of the keg up the column. Yes your pressure was constant but now your volume is less
  • You put the column of water entering the top of the keg (no dip tube). All the CO2 (less dense than liquid water) bubbles up and you have flat beer. J

You need to exhaust the right amount of CO2. It's not just about static pressure.

 

OK, I think I'm with you now.  

 

I think in my mind I'm picturing a system where instead of the elastic compression held in the spring to apply back pressure to the valve, it's a column of water.  If you could run it through a one way valve that only opens when the C02 pressure is greater than the water pressure, then you'd have the same effect.

 

If you have this one way valve, then it does become a matter of just maintaining the static pressure inside the fermenter, which is obviously much simpler than designing an accumulator.



#118 wynnum1

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Posted Today, 09:48 AM

At major breweries is there a limit on the depth of tanks to limit pressure at the bottom of the tank.