Does vacuum remove oxygen?

[grathan]

I was thinking about beer and wort transfers with a vacuum pump. This would be ideal if it could remove the oxygen from my fermenter(steel) and kegs before filling?

I could avoid having to sanitize a plastic auto-siphon with hidden crevices this way, but something tells me that breweries don't do it this way for a reason...

 

[Golddiggie]

I wouldn't do it. If you're fermenting in stainless, why not just fit it with some corny posts (gas and liquid) and use a CO2 push to move the finished beer? I do that with every batch. No lifting, sanitizing an autosiphon or anything like that. I have liquid dip tubes cut to lengths to leave a certain amount behind in the fermenting vessels. Makes it damned easy. Especially since I fill the kegs via the liquid post.

 

[grathan]

How do you know co2 is pushing out the oxygen and not just releasing the co2? besides that, vacuum costs less than co2 refills.

 

[billl]

The keg isn't going to hold a vacuum. The lid is designed to seal with pressure pushing up on the lid and compressing the o-ring. If the vacuum is "pulling down" the lid, it will leak.

 

[Golddiggie]

How do you know co2 is pushing out the oxygen and not just releasing the co2? besides that, vacuum costs less than co2 refills.

The O2 was removed during the fermentation process. I purge the keg it's going into as well. I have zero O2 issues in my beers with this method.

As for the cost of CO2 refills, I typically pay $10 for a 5#, $12 for a 10# and $17 for a 20# refill. I also pay $2.99 for paintball tank refills up to 16oz and $3.99 for refills up to 24oz. Requiring ZERO power to move the finished beer is another huge benefit, since it means I don't need to think about where I'm doing this. Or run extension cords of any kind.

I might be exchanging my 2.5# CO2 tank for either a 5# or 10# tank today. Depends on the cost difference. Since refills on the 2.5# tank normally run about $7, I'd rather have the larger tank. Besides, the regulator is a bit too heavy for the 2.5# tank (got it as a backup originally).

Do what you want, but don't mislead yourself into thinking that a vacuum pump is a better method. Or that it's going to be cheaper. Since I can push a lot of beer per CO2 tank/bottle, the cost per batch is very low.

Plus, as bill posted, using pressure will be better for actual use. Unless you plan on modifying a serving keg to seal with a vacuum. In which case you'll need to reverse that in order to use it for serving. Seems like a huge PITA to me. Which is probably why you don't see people mentioning doing this, or vendors selling hardware to do this all over the place.

 

[BadNewsBrewery]

Additionally, you're never going to get a 'true' vacuum... And if you could, I'd wager the pressure differential would crush whatever you're trying to use as a vacuum chamber. You can get some vacuum to form, no doubt - but you'll still have O2 left behind, in which case you've gained nothing for your efforts.

 

[grathan]

So vacuum does remove 02? What about 20hg or the opposite of 20 psi whatever. Would that have much oxygen left?

 

[BadNewsBrewery]

Vacuum removes the contents of the vessel, which in your case would be air. Air contains about about 21% O2 by volume. So, whatever air you pump out of the vessel to create vacuum, 21% of that will be O2. 20hg (I think you mean 20mmhg) is not the opposite of 20PSI, and I'm not sure where you're coming up with these numbers... A true vacuum is 0 PSI which also happens to be 0 mmhg, 0 kpa, and 0 anything else, because it's a vacuum.

 

[grathan]

Ahh I see, thanks.

 

[ruralbrew]

One thing no one has mentioned is that a vacuum will also degas your beer. So you end up having to use more CO² or priming sugar to carbonate it.

 

[ReddHead]

You can boil water at room temperature with a vacuum.

 

[Golddiggie]

One thing no one has mentioned is that a vacuum will also degas your beer. So you end up having to use more CO² or priming sugar to carbonate it.

That would suck even more.

I can't imagine that a pump capable of creating an actual vacuum (to the level needed) would be all that cheap. Then there's the additional stress it creates on the kegs/vessels connected to it. IMO, there's a LOT of design/engineering that would need to go into such a system in order for it to be safe for use. If you have that much free time to spend, and deep enough pockets, you might be able to get it to work. Although I can't see any actual benefit over just using a CO2 push. A couple of purge cycles (at ~5psi) of the destination keg puts enough CO2 in the bottom to blanket the beer going in. Which then makes it easier to purge the O2 from the headspace of the filled keg.

 

[zachattack]

I think everyone has good points re: expense (you'd probably want an oilless diaphragm vacuum pump which might be a couple hundred bucks) and the fact that corny keg lids aren't designed to handle negative pressures.

But just for the record a full vacuum is only -14.7 psig. That's absolutely not going to destroy a stainless steel keg rated for 160 psi. The lid would need to be replaced with one meant for vacuum, and if you're really interested (and already have a vacuum pump lying around) you can buy lids that are rated for vacuum. I'm not sure what size you'd need for a corny keg, but at work I use corny-like pressure vessels from Alloy Products Corp, they sell vacuum lids that look like this, but they're around $50:

You will lose CO2 as you transfer the beer, but with a standard (rough) vacuum pump and a quick transfer you probably won't lose all of it. You can always use the vacuum pump to empty the keg and/or prime the siphon, that would probably do a great job eliminating all the O2. But it's really not worth the cost, time, trouble, etc. when siphoning then purging a couple times works just fine. Is it really that hard to sanitize an autosiphon? It really just takes a second.

 

[Golddiggie]

Is it really that hard to sanitize an autosiphon? It really just takes a second.

You can use a wallpaper tray, or even dip it into a bucket of Star San and get it to sanitize. I've simply pumped Star San through mine (when I was using them). I sanitize the dip tubes I use for the transfers either with a dip, running Star San through them (with another fitting) or spraying the insides with Star San. Takes very little time no matter which, and very little effort.

 

[zachattack]

Word. Yeah it really only takes a few pumps to get the star san completely through it.

 

[Golddiggie]

Word. Yeah it really only takes a few pumps to get the star san completely through it.

Two pump chump??

 

[zachattack]

 

[grathan]

I think everyone has good points re: expense (you'd probably want an oilless diaphragm vacuum pump which might be a couple hundred bucks) and the fact that corny keg lids aren't designed to handle negative pressures.

But just for the record a full vacuum is only -14.7 psig. That's absolutely not going to destroy a stainless steel keg rated for 160 psi. The lid would need to be replaced with one meant for vacuum, and if you're really interested (and already have a vacuum pump lying around) you can buy lids that are rated for vacuum. I'm not sure what size you'd need for a corny keg, but at work I use corny-like pressure vessels from Alloy Products Corp, they sell vacuum lids that look like this, but they're around $50:

You will lose CO2 as you transfer the beer, but with a standard (rough) vacuum pump and a quick transfer you probably won't lose all of it. You can always use the vacuum pump to empty the keg and/or prime the siphon, that would probably do a great job eliminating all the O2. But it's really not worth the cost, time, trouble, etc. when siphoning then purging a couple times works just fine. Is it really that hard to sanitize an autosiphon? It really just takes a second.

Hey, thanks for posting that. I really don't think it's hard sanitizing an auto-siphon, I do use a wallpaper tray thanks.

I have used a lot of vac pumps in the past and was mainly just curious. I don't even know if I have problems with oxygen in my beer and doubt the autosiphon is a major bacterial contributor. I may pursue this further one day. It's just a seed for thought for now.

Losing CO2 while transferring? You would put the vacuum on the empty vessel you are transferring into then open a valve on the vessel the wort/beer is coming from, closing off the transfer before empty and not transferring any air.

 

[zachattack]

Losing CO2 while transferring? You would put the vacuum on the empty vessel you are transferring into then open a valve on the vessel the wort/beer is coming from, closing off the transfer before empty and not transferring any air.

Well, the transfer would stop as soon as the pressure in the receiving vessel returned to around atmospheric, if you pulled an absolute vacuum this would mean when the keg was full but that's not going to happen with this system (plus there's air in the lines, etc.). So you'd need to keep at least a slight vacuum on the receiving end to keep pulling it in. And if you maintain vacuum over a liquid, you're going to degas the liquid at least a little.

 

[AlCophile]

grathan:
At work, we evacuated a 55gal drum.....behind blast doors. In a FRACTION of a second it collapsed into an hourglass shape. After that, as shall be your keg, it was good for scrap. You're likely to hurt yourself. Some tips: CO2 is 50% heavier than air. If you run some into bottom of keg, it will stay put. If it is cold, it is heavier. As I siphon, I put some CO2 into bottom of vessel, start siphoning, and, if you keep flowing CO2, the bubbles show you exactly where it is. By moving the (CO2)gas inlet tube around, you can make a layer of CO2/bubbles to seal off the liquid from the air. All of this can be done at atmospheric pressure. It you're REALLY worried, sparge(flow CO2 thru a gassing stone well beneath surface of beer) w/ CO2; this may replace any O2 present. Maybe not. If you're PARANOID, you can blast those bubbles right out the top of vessel. You can make a temp bladder out of a poly bag, to see how much gas is being delivered. Do as Golddiggie suggests: use existing tubes-you paid for them. Get some poly fittings, play, experiment!

 

[helibrewer]

I saw a DIY vacuum pump built from a bike pump in Winemaker Mag. It works well but only with rigid containers...can't do it with a Better Bottle.

I was my wine transfer pump to move all my beer, using corny keg connections. I purge the receiving keg with CO2 and use the beverage side as the input.

 

[zachattack]

grathan:
At work, we evacuated a 55gal drum.....behind blast doors. In a FRACTION of a second it collapsed into an hourglass shape. After that, as shall be your keg, it was good for scrap. You're likely to hurt yourself. Some tips: CO2 is 50% heavier than air. If you run some into bottom of keg, it will stay put.

Again, I agree that this is impractical. But I think you're being a little extreme.

What was the pressure rating on your 55 gallon drum? Was it anywhere near that of a Corny keg? Was it metal or plastic? You can completely evacuate a simple glass vessel and it won't collapse (I worked with a few bell jar ultra high vacuum systems in grad school), and like I said, there are plenty of corny-like vessels out there that are fully rated for vacuum. I don't know if a proper Cornelius keg is (they look almost identical to the ones I use at work), but I really don't think such a sturdy vessel is going to collapse from a partial vacuum. It's not like he's going to be going down to 10^-7 torr here, it's going to be a partial vacuum for a few seconds just to roughly evacuate the vessel and prime a siphon.

I'm all about lab safety (and I'll admit I wear safety glasses even while pressurizing/purging a keg), but I don't see anything dangerous here with a cheap vacuum pump and a stainless vessel.

Also, CO2 may be heavier than air, but it's definitely not going to stay put. Gases readily mix (see kinetic theory of gases).

 

[Chris Freitag]

I’m interested closer transfer from a fermenter bucket and in oxygen removal in kegs prior to transfer.

First, some thoughts about vacuum vs star-san flood and CO2 purge.

Evacuating a vessel to 10-3 torr and refilling with CO2 ~three times will purge 99.9xx% of the oxygen. This is the method chemists use to remove oxygen from vacuum glove box chemical handling chambers (see https://www.mbraun.com/products/glovebox-workstations/unilab-glovebox). We used these with oil pumps and evacuated and refilled the air lock chamber with nitrogen 3 times to prevent explosions when working with with oxygen sensitive chemistry and pyrophoric catalysts at my company.

Oil vacuum pumps can get to 10-4 tire. A good diaphragm vacuum pump may get to 10-2 or 10-3 range. So maybe one extra evacuate and refill cycle. Diaphragm pumps are not cheap. I’m in the shadow of a large a semiconductor company, and the local surplus store sells used pumps for ~$150. BUT, they are likely contaminated with all sorts of nasty heavy metals, so I would have to convince myself of how to decontaminate one.

The concern over a Corny keg buckling in from the vacuum would could be proven with a test, or I can volunteer to run some rough calculations. Does anyone know the wall thickness of a Corny Keg?

The vacuum level for metal stress isn’t much different for 1 torr as 10-4 torr, out of 760 torr (1 atmosphere, or 14.7 psi absolute pressure). The real difference is the Lower the vacuum level, the fewer remaining gas molecules.

Now the cost of 3 or 4 volumes of CO2 plus the vacuum pump has to be weighed against the cost of Star San. Of course, you can use the Star-San over again. Or use boiled water.

Hmmm, maybe liquid flood and purge looks pretty good. But if I had a clean, free pump capable of sub-1 torr levels, it would be kinda cool . . . .

 

[Hermit]

I seriously doubt you can collapse a keg with your pump. You are however WAY over concerned about O2. The keg fills from the bottom pushing out air as it goes. After you seal the keg a short blast of CO2 and purge will clear the little remaining air head space. You can do this a couple of times if it makes you feel better but it really isn't needed as the volume of CO2 in even short burst is substantial compared to the remaining head space in the keg.

 

[speavler]

Why need a pump? My occasional process uses the vacuum created in my fermenter after a cold crash to suck in the CO2 from a connected corny keg which simultaneously pulls in the beer from the fermenter. closed loop transfer.

 

[seatazzz]

When I read the thread title I honestly had a vision of a vacuum cleaner....sucking up o2 from the top of a fermenter. I'm tired.

 

[GPP33]

After you seal the keg a short blast of CO2 and purge will clear the little remaining air head space. You can do this a couple of times if it makes you feel better but it really isn't needed as the volume of CO2 in even short burst is substantial compared to the remaining head space in the keg.

A single purge at 2x atmospheric pressure, so ~15psi, will remove exactly 1/2 the air in the head space. CO2 doesn’t somehow magically push the air out, it mixes and what comes out is the same homogeneous blend as what is left. At 30psi it takes about 15 purges to clear out enough O2 to get to get down to the purity level of your CO2.

Higher pressures will remove more of the original gas in the head space but you’ll never get to one and done.

 

[Cool_Hand_Luke]

The concern over a Corny keg buckling in from the vacuum would could be proven with a test, or I can volunteer to run some rough calculations. Does anyone know the wall thickness of a Corny Keg?

I took a stab at this math for a different thread a while back. There’s some guesswork with thickness, but relatively close to being able to take some decent vacuum. Haven’t tested one yet. Sorry for the units...

“So a cylindrical tank's (or pipe's) capability of withstanding external pressure is dependent on four things: Length without reinforcement (in this case the height of the keg), diameter, wall thickness, and the material properties.

I ran the math using ASME BPVC VIII UG-28. If you assume the corny keg has a wall thickness of 1 mm (0.039 in) the code allowable external pressure is ~11.6 psi. At sea level this would equate to an internal absolute pressure of 3.1 psia which is 23.6 in Hg vacuum.There is some innate safety factor in that code as well. That's actually better than I thought. But that is assuming the wall thickness is 1 mm which seems thicker than they are to me.

Another thing to consider is how the lid seals on a corny keg. It utilizes the internal pressure to help the gasket seal the keg. So you may have difficulty pulling a vacuum since it might bleed air in.”

Original post:
Creating an NA (Or...how I neutered my beer)
https://www.homebrewtalk.com/forum/index.php?posts/8225776/

 

[AkTom]

I have the allinonewinepump that I use. Typically I ferment in a glass carboy When ready to bottle, I add priming sugar (simple syrup if you will) into a sanitized carboy. Vacuum rack from fermenter into bottling carboy. The racking cane goes all the way to the bottom. It self mixes with the priming sugar. This carboy is lower than my counter where I bottle. Of course I vacuum up to the bottles. I love it.

 

[shortyz]

lol vacuum on a corney keg, the baby will buckle like when u step on a popcan. and leak like hell through the cap thing, like many people have said.

i work in the food industry and for products that are highly oxidized you usually pump them into a tank at at high vacuum (callled a deaerator) , this removes any entrained air and prevents oxidation. Just remember if your wort has any CO2 left from fermentation it will go crazy.

most vessels for vacuum will have external banding to prevent implosion.

 

[Vale71]

lol vacuum on a corney keg, the baby will buckle like when u step on a popcan. and leak like hell through the cap thing, like many people have said.

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]

A single purge at 2x atmospheric pressure, so ~15psi, will remove exactly 1/2 the air in the head space. CO2 doesn’t somehow magically push the air out, it mixes and what comes out is the same homogeneous blend as what is left. At 30psi it takes about 15 purges to clear out enough O2 to get to get down to the purity level of your CO2.

Higher pressures will remove more of the original gas in the head space but you’ll never get to one and done.

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]

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.

 

[kevink]

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.

 

[Jayjay1976]

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.

 

[speavler]

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.

 

[GPP33]

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.

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.