Another Air Compressor question.

[CharlosCarlies]

Well I read through all the other threads I could find, but I'm still not sure exactly what route to go.

After debating back and forth, we decided to go w/ compressed air for wort aeration. I saw a lot of recommendations for oil-less, but rotaries are out of our price range (for now) and I can't seem to find a big enough oil-less otherwise. FWIW, we aren't packaging and will need air for our keg washer as well (Premier 3-head).

My thoughts right now are to use a regular piston compressor, but get some food grade oil and do the best we can to filter everything down-stream. What are yall's thoughts? Will this be acceptable or should I push the investors to just spend the money on a rotary?

Thanks!

[Natrat]

If it's JUST for aeration, then I'd recommend getting a scuba tank and first stage regulator....the air is pre-compressed and filtered for breathing, the reg is adjustable (just get a tech to pre-set the intermediate pressure to what you want to use) and you can have it refilled anytime for about $5.

IF you use a compressor, oilless is the way to go. Perhaps look at small breathing air modules, such as a RIX oil-less compressor. But maintenance on those is also expensive, especially in time.

Then you can get a big reciprocating compressor for all your other needs. Having said that, our big recip only cost about $2000 less than the big screw compressor we have (both Ingersoll-Rand)

Good Luck!

[CharlosCarlies]

Thanks Nat...gives me even more to think about!

What about using a small oil-less just for aeration and having a separate reciprocating for keg washing, etc? I might try and persuade the investors to spring for the rotary though. If we did go that route, do you have any recommendations as far as filtering goes?

Seriously thanks again!

[TGTimm]

Why not just use straight O2 for aeration? It comes in handy tanks which last a long time, and is completely free of any any contamination, so you won't need a micro-filter. We get several hundred barrels (300+) per 50 lb tank, and our gas supplier brings filled tanks right to the brewery!

Caveat: If you have any color-blind brewers (we have two), be sure they're extra careful when using CO2 in the 50 lb tanks. The O2 cans are green, the CO2 cans grey--the same to a CB person. An O2 regulator will not fit on a CO2 can, but a CO2 reg. will work fine on an O2 can.

[OneMoreBrewer]

Why not just use straight O2 for aeration? It comes in handy tanks which last a long time, and is completely free of any any contamination, so you won't need a micro-filter. We get several hundred barrels (300+) per 50 lb tank, and our gas supplier brings filled tanks right to the brewery!

Caveat: If you have any color-blind brewers (we have two), be sure they're extra careful when using CO2 in the 50 lb tanks. The O2 cans are green, the CO2 cans grey--the same to a CB person. An O2 regulator will not fit on a CO2 can, but a CO2 reg. will work fine on an O2 can.

You can over oxygenate your wort with pure oxygen.

You may consider a simple double diaphragm air pump and simply place a sterile air filter in line post pump. Maybe even a check valve for good measure. Your air would be free, the pump is much cheaper than a compressor, but you have filter costs. Since the average o2 in air is like 18-20% I think you would not risk over oxygenating.

I have used a number of compressed gas devices and so forth and would not recommend using an oiled compressor, fwiw. If you had to, then I would use a handful of air line dryer type devices, either silica gel or other medias.

[Natrat]

Since the average o2 in air is like 18-20% .

Where, exactly, is air LESS than 21%? (ok, 20.947% for nit-pickers)

[OneMoreBrewer]

Where, exactly, is air LESS than 21%? (ok, 20.947% for nit-pickers)

Well I would suppose that air is usually 100% everywhere.

If you mean oxygen, I couldn't remember its content. I could only remember that nitrogen was about 78%. Also having used gas detectors quite extensively in a variety of industrial work situations, I can tell you from verified results that air is not consistent in work environments. Anyone who thinks so has done too much reading and not enough measuring.

A work environment that uses a lot of compressed gasses, is likely to displace a significant amount of oxygen. I have personally witnessed this at the largest brewery in existence.

Regardless, I think the point stands.

[Natrat]

Fair enough, I wasn't challenging your point...a diaphragm air pump WOULD probably do just fine at injecting air into wort.

And I concede that what we breathe in many industrial environments is often enriched with elevated levels of CO, CO2, N2, etc.

I was just being pedantic...

[Bainbridge]

The question occurs, that while a compressor might be fine for standard strength worts, what happens when you decide to make a barleywine, or some high-teens ABV monster? I seem to remember that is was hard to get more than 8ppm O2 with just air, though maybe an industrial compressor could push a little more in?

If the answer is, "well then we'll just goose it with some pure O2" then why bother with the compressor? A tank of O2 lasts us several months, costs like $60 to fill and a small lease fee. Add on a $120 medical-grade reg and some hosing. Set it to the right LPM and you can oxygenate at the right level for each beer. If you brew something big you can put a carb-stone in the tank, roll the cylinder over, and goose it for a couple minutes during high kreusen.

[OneMoreBrewer]

The question occurs, that while a compressor might be fine for standard strength worts, what happens when you decide to make a barleywine, or some high-teens ABV monster? I seem to remember that is was hard to get more than 8ppm O2 with just air, though maybe an industrial compressor could push a little more in?

If the answer is, "well then we'll just goose it with some pure O2" then why bother with the compressor? A tank of O2 lasts us several months, costs like $60 to fill and a small lease fee. Add on a $120 medical-grade reg and some hosing. Set it to the right LPM and you can oxygenate at the right level for each beer. If you brew something big you can put a carb-stone in the tank, roll the cylinder over, and goose it for a couple minutes during high kreusen.

I agree with this line of thought in general. Measure your oxygen correctly and you have no worry of over oxygenating. I think if you have a good method of diffusion, that the regular air can reach above 8ppm if you simply run your air longer. The ppm of oxygen in air is well above your targets, it's just a matter of getting it to stay in the wort.

The problems come with the dissolution of the oxygen. The LPM measurement gives you an exact measure of your oxygen, however it does not tell you the dissolved oxygen content of the wort. I personally assume that the dissolved oxygen content of the wort is the only measurement that matters, not the amount of oxygen we put into the tank. (I don't measure DO prior to fermentation, it's just my theory) It shouldn't matter how the oxygen is introduced as long as it diffuses in the wort to provide a good ppm of oxygen. A straight hose of oxygen in may not provide as high ppm levels as regular air through a diffusion stone for example.

We would regularly adjust our aeration to support higher gravity worts, or to suppress krausen when brewing a double batch of a fast fermenter. Personally, I would prefer to have the oxygen apparatus even if I wasn't using it. It's always better to have something and not need it.

[Bainbridge]

Exactly. Just because your reg is dialed to 3 LPM or whatever doesn't mean it's going in 100%, so a DO meter would be just the thing to help you check what you need to set the reg at. Or just trial and observation. 1 LPM: slow krausen, 2 LPM: reasonable lag, 3 LPM: insta-krausen, 4: insta-krausen and overattenuation, and so on.

FWIW our wort flows into a T on the middle of the T, with a carb-stone stuck in there on one end of the T so the wort makes a hard corner while being hit with the O2 before heading towards the tank, and later we go from a 1.5" to a 1" sight glass to a 1.5" again at another bend for a little more turbulence. Works for us, YMMV.

[dereknobleluke]

Nitrogen is extremely hard to dissolve in water/beer--hence why you need larger ASME rated tanks to nitrogenate something. CO2 and O2, to my understanding, are relatively close in saturation levels in warm water/beer. CO2 is a tad easier than O2 to saturate in cooler beer/water and can get a higher ppm. Using air compressors will never be able to get O2 levels higher than 8 ppm in "normal" exchanged wort at ~ 65 degrees using "normal" brewing equipment and hoses. Pure O2 can get up to 18 ppm in a large 18 plato wort (mind you that using 15 LPM is a waste of O2 at lower plato beers, but necessary for higher plato beers. If 15 LPM was used in water only I read it can get as high at 38 ppm...the lesson here is that more sugar means less ppm O2 possible). You can never "over oxygenate" wort to my understanding, please provide some new data to correct me if you contradict the statement. Yeast cells will uptake the O2 at the fastest rate they can and if there is more O2 around, less than 1 generation of yeast cell growth will eat all that up. So "over-aeration" would simply mean more yeast cells than usual (and yes, this can become autolytic, in which case detrimental beer flavor) OR a waste of O2...

long story short. do yourself a favor and get O2 in bottles. Unless you live in the fricken boonies or on an island and can't get reliable O2 bottles, you'd be a fool to use an air compressor, especially if you plan on brewing anything over 12 plato...