No it won't, simply because so much air will come through the cap that you will never achieve more than a slight vacuum. These caps have a very poor seal, sometimes they leak so badly despite applying 1 bar positive pressure that I've had to re-open them and re-set the cap more than once, imagine what would happen with even the slightest inward pressure.
Does vacuum remove oxygen?
- Thread starter grathan
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No it won't, simply because so much air will come through the cap that you will never achieve more than a slight vacuum. These caps have a very poor seal, sometimes they leak so badly despite applying 1 bar positive pressure that I've had to re-open them and re-set the cap more than once, imagine what would happen with even the slightest inward pressure.
Hermit
fuddle
Well then purging the tank with CO2 is no better as it will also mix. I know this which is why I don't bother purging the keg since bottom filling will push out the air. I'm not sure how you come by these numbers though. A single purge is not a fixed volume. The gas runs when you pull up on the pressure relief.
And what we are talking about in the end is 'good enough'. I've had beer in kegs for over a year that didn't oxidize doing this. This forum seems to be getting overly sensitive about oxygen lately. That's why I stay away for longer and longer periods of time anymore. You listen to the people here and you may as well give up brewing and stick to buying it.
TechFanMD
Well-Known Member
I work with high vacuum systems of all types, and really doubt you could collapse a corny without trying pretty hard.
Vacuum systems work by pumping faster than the system leaks. The fewer leaks you have, and the higher pressure differential rating pump you have makes a greater vacuum. Because on a corny you're probably going to be pulling vacuum through the gas in post, the orifice is very small (and you'd have to have the poppet removed). Your pumping speed will be slowed by this. Even ignoring the lid, the other poppet (liquid out) is going to open with a vacuum in the keg (it is meant to seal the other way) and leak air back in at a rate that you're unlikely to outpace with vacuum on the other side without having something more industrial that what someone doing this is likely to use.
This thread was started in 2013, and much of the information given then clearly wasn't based on experience with vacuum. A vacuum pump doesn't pull all gases out at the same rate. Molecule size matters. Nitrogen pumps out easier (we often pump, purge with N2, then re-pump to have the N2 molecules 'bump' into the other gasses to help get a greater vacuum more quickly) and helium is more difficult to pump out. If you pull a vacuum, oxygen in the vessel will be lowered- but the percentage of oxygen as part of the gas in the container will not still be the same as it was at atmosphere since other gases may pump out more quickly. Then you get into temperature, mean free path, etc. If you really want to purge/pump....Nitrogen is a much better gas to use than CO2.
Long and short...unless you buy a larger lab or industrial grade vacuum pump with a displacement rating much higher than what the other seals will leak (especially considering the small orifice you're evacuating through)....collapse is unlikely.
I kind of agree with @Hermit here. I love this site for debating and discussing science topics and taking some things to the extreme.....but it isn't necessary to worry about oxygen to this level. Some of the posts are so over the top about different impacts to brewing that you'd wonder how anybody makes good beer...including commercial breweries.... if they're all true.
To me, the benefit of using low grade vacuum for transfer is that it doesn't require CO2 .....which for some is expensive, or difficult to get (fill/swaps are far away), and some people may brew in a different area than where their kegs are, so having CO2 in the brewery is going to require a second setup or require taking their CO2 and regulator off of their kegs and into the brewery.
Vacuum systems work by pumping faster than the system leaks. The fewer leaks you have, and the higher pressure differential rating pump you have makes a greater vacuum. Because on a corny you're probably going to be pulling vacuum through the gas in post, the orifice is very small (and you'd have to have the poppet removed). Your pumping speed will be slowed by this. Even ignoring the lid, the other poppet (liquid out) is going to open with a vacuum in the keg (it is meant to seal the other way) and leak air back in at a rate that you're unlikely to outpace with vacuum on the other side without having something more industrial that what someone doing this is likely to use.
This thread was started in 2013, and much of the information given then clearly wasn't based on experience with vacuum. A vacuum pump doesn't pull all gases out at the same rate. Molecule size matters. Nitrogen pumps out easier (we often pump, purge with N2, then re-pump to have the N2 molecules 'bump' into the other gasses to help get a greater vacuum more quickly) and helium is more difficult to pump out. If you pull a vacuum, oxygen in the vessel will be lowered- but the percentage of oxygen as part of the gas in the container will not still be the same as it was at atmosphere since other gases may pump out more quickly. Then you get into temperature, mean free path, etc. If you really want to purge/pump....Nitrogen is a much better gas to use than CO2.
Long and short...unless you buy a larger lab or industrial grade vacuum pump with a displacement rating much higher than what the other seals will leak (especially considering the small orifice you're evacuating through)....collapse is unlikely.
I kind of agree with @Hermit here. I love this site for debating and discussing science topics and taking some things to the extreme.....but it isn't necessary to worry about oxygen to this level. Some of the posts are so over the top about different impacts to brewing that you'd wonder how anybody makes good beer...including commercial breweries.... if they're all true.
To me, the benefit of using low grade vacuum for transfer is that it doesn't require CO2 .....which for some is expensive, or difficult to get (fill/swaps are far away), and some people may brew in a different area than where their kegs are, so having CO2 in the brewery is going to require a second setup or require taking their CO2 and regulator off of their kegs and into the brewery.
I have put a vacuum on pureed fruit to degas it before adding it to the primary. It worked well, and yes, you can see it boil at room temperature which is pretty cool.
I would never consider doing it to purge air from a keg, though. There are much easier ways that work better. And CO2 is cheap. I just emptied first 20lb tank that I use for various things like purging kegs, purging fermenters, cold crashing, partially force carbing, etc. I'm not stingy with it and it lasted about 3 years.
I would never consider doing it to purge air from a keg, though. There are much easier ways that work better. And CO2 is cheap. I just emptied first 20lb tank that I use for various things like purging kegs, purging fermenters, cold crashing, partially force carbing, etc. I'm not stingy with it and it lasted about 3 years.
Your vessel will collapse/implode under a vacuum that is powerful enough to evacuate oxygen. A tank rated for 15 or even 30 PSI would collapse under even a moderate vacuum.
purging kegs is so cheap and easy. i fill a keg completely with sanitizer solution and push it into another keg using the yeast-generated CO2 during fermentation. i can purge several kegs with pure CO2 during a single fermentation.
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The numbers are based on batch purging, not continuous. You could calculate purge rates for continuous if you knew the flow rate but would have to make some assumptions on gas mixing. But yes, at the end of the day we are getting to good enough because even with beverage CO2 there’s still .1% of other gasses mixed in so perfect, or 100%, isn’t even and option.
Don’t kid yourself, many commercial breweries sell beer that’s suffered oxidation, one of the beauties of home brewing is we can dedicate the time and care to make beer that’s better than what you can buy. For some people the small incremental gain is worth it, for others it’s not. That doesn’t make one way better, just better suited for an individuals home brew goals. It’s really no different than all the other things we obsess about like water chemistry, mash temp control with HERMS, keeping hops fresh by vacuum sealing, ferm temp, etc. I go to extraordinary lengths to keep O2 away from my IPAs, less so for many other styles.
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