Oxygen regulator flow rate

I'm using 0.5 liter per minute for 2 minutes. That's with a 0.5 micron stone on the bottom of a 6.5 gallon bucket, stirring the wand around a bit. The wand is a spare dip tube from a keg.

At higher flow rates I see bubbling on the surface which is likely for the most part oxygen that didn't make it into the beer. I try to limit seeing those.

 

Looks interesting. If the formulas are correct it can help calculate dissolved O2 in a wort with a certain SG. Vessel geometry and height play a role as well, don't you think?

I use 6.5 gallon (25 l) fermentation buckets with 5.5 (21 l) gallons of wort. I run O2 through a 0.5 micron stone on a wand at the bottom at a rate of 1/4 liter per minute for 4-8 minutes.* Any higher flow rate and I see lots of surface rippling, which is O2 escaping that didn't get dissolved. At the 1/4 liter rate I get some rippling but also a lot of foaming, which I guess is good.

A tall narrow vessel would give higher efficiency. Or even better yet, inject into the wort stream on her way to the fermentor.

Without Google translate it's all Greek to me.

* I previously mentioned running O2 at 1/2 l/m for 2 minutes. I've gone to using lower flow rates trying to get more O2 into the wort, while there's less escaping from the surface (rippling). My flow meter goes down to 1/32 l/m, but it would take an extraordinary long time to get to 10 ppm O2 that way.

 

Thanks for the update! Much clearer now.

Even at 1/4 l/m I see some rippling (and foam). It makes me wonder where the rule to oxygenate for 1 minute at 1 l/m came from. Obviously oxygenation efficiency at that pace is far from ideal with small 5-10 gallon batches in small, relatively shallow fermentors. I have the feeling only 1/4 of that gets dissolved, if that, which means one would need to apply for a longer time, wasting even more gas at that rate.

I don't need visualization at the top of the wort/beer. I see the stone foaming when I pull it up, that's enough feedback for me. Seeing rippling and bubbles doesn't excite me, instead it makes me wonder how much O2 didn't make it into the wort.

BTW, I oxygenate for 1 minute, then pitch the yeast, stir and continue oxygenation for 4-8 minutes ay 1/4 l/m. I believe stirring may remove some of that dissolved O2 out of solution, so all that hard work goes partially out the top.

Inline injection is another can of worms. Not worth the effort for small homebrew sized batches, if there are decent (but not perfect) alternatives. Just getting the wort flow to be stable is a major task. Plus more equipment to clean and sanitize.

 

I think you've got the wrong regulator, or reading something incorrectly.

3 cu ft/min (?) is an astonishing flow rate! My tank is 40 cf, at that rate it wouldn't last even 14 five gallon batches, less than a year for me. At 1/4 l/m for 10 minutes I'd use 2.5 liter of O2. Say 3 liters, with purging/cleaning. At that rate, the 40 cf tank will last 28x40=1120 batches. At 20-25 batches per year, I won't live long enough to use it up.

 

Are you using the disposable red O2 tanks from the hardware store? Those regulators don't have an adjustable flow rate. I would turn it open just enough to see some thick foaming develop around the stone when first immersed, then pulled out a Starsan container, or your wort/beer.

Note, with those tanks, close the valve all the way after use. They are notoriously slow leakers. Someone here claimed to get 20+ batches out of that small tank, which seems about right.

Shamelessly copied from here:
Bernzomatic = 1.4 oz. of O2 = 40 grams = 1.25 moles O2 (40 g/32g/mole of O2) = 28 liters of O2 at STP (1 mole of a gas is 22.4 liters at STP - standard temp & pressure)

28 liters of O2 dispensed at 1/4 liter for 4 minutes (1 liter) per batch is 28 batches! At twice the usage per batch, 14 batches. Use frugally at slow flow rates.

My regulator/flow meter looks similar to the one in the OP's picture, except it's green and goes all the way down to 1/32 l/m.

As with CO2, there is no O2 blanket covering your wort/beer after applying O2. It may be a bit richer in O2 for a short while, especially in a narrow carboy neck, but will equalize soon with the atmosphere. In an open bucket, it flows right out. Unless you oxygenate under pressure (e.g., in a keg) there's no way to get that O2 that bubbled out, back in there.

 

If you see large bubbles escaping to the surface, that's O2 that didn't make it into your beer, so turn it down. A little rippling is probably inevitable. Ideally none should reach the surface.

You could measure the flow rate with an inverted graduate or marked beaker in a bucket of water or Starsan, and make corresponding markings on the regulator valve. At least you get some idea what you're supplying.

I'd go for 1/4 liter/minute for 4-8 minutes depending on your gravity and yeast.

 

More O2 in the solution is better (although there's a limit to usefulness) but running it faster doesn't mean more gets dissolved. Running longer at slower rates gives it more opportunity to dissolve, IMO.

Well sure, lower temps slow the growth/lag phase down.

My Belgian IPA at 1.074 was bubbling away happily within 8 hours at 65F => 68F. I used a large fresh starter of WY3522.

Last night it was down to 1.024 already after 48 hours! A little faster than I had anticipated, I wanted to ramp up the temps a bit more around 50% attenuation. The sample tasted awesome! I then added homemade candi syrup dissolved in some extra wort I had saved out, about 3 quarts in total. Chugging away at 75F now.