Oxygenating with flow meter, slowed down by diffusion stone?

[o.m.]

Hi!

I´ve got my 4 liter oxygen flask with flow control (1-15 liters per minute, in steps) about a month ago, and have used it for 2 brew sessions, together with a .5 mikron diffusion stone stone (KEG595 at MoreBeer).

The first brew I used 60 sec. - 1 liter per minute (OG: 1.056), the second got 90 sec - 1 liter per minute (OG: 1.060), but the fermentation have been going a little slow, so I wonder if the diffusion stone slows the flow, and if so, how much I should compensate in minutes or liters per minute?

My batches are 50 liters (13.2 gallons), which I split into 2 fermentation buckets, with different yeasts. I use the MrMalty pitching rate calculator to calculate my stir plate starter size or slurry amount, and the fermentations have been fermenting at 18°C (64,5°F), slowly ramping it up to 20° C (68°F) after a few days.

Beer 1: Christmas ale ("Vienna ale")
OG 1.056
Bucket A: Wyeast 1318 - SG: 1.011 after 2 weeks (as expected, but it took longer time than normal)
Bucket B: Wyeast 1056 - SG: 1.016 after 2 weeks
Oxygen: 60 sec per bucket, 1 liter per minute

Beer 2: Brown porter
OG: 1.063
Bucket A: Wyeast 1098 - SG: 1.024 after 1 week
Bucket B: Wyeast 1318 - SG: 1.023 after 1 week
Expected FG: 1.012
Oxygen: 90 sec per bucket, 1 liter per minute
Here I was pitching a few degrees too cold, as the new superchiller (50 feet, 1/2" from MoreBeer used with the whirlpool option, also bought this fall) was so quick that I didn´t stop it in time. This might have something to do with the low attenuation, but I still suspect the amount/saturation of oxygen beeing to low.

I try to shoot for the oxygenating time (60-90 seconds) Jamil is mentioning in the aeration show on this, but I guess the different diffusion stones will give different flow..., and his batches are a little smaller (6 gallons in one fermenter).

I´d be happy to get your thoughts on this, how to adjust the flow right, and how to help my beers finish the fermentation.

I don´t have a oxygen meter, but I guess it could have help me out. And in that case, when would you measure the saturation in the wort?

Cheers,
Lars,
Norway

[Travisty]

If you are directly measuring O2 flow, then it doesn't matter how much the stone is restricting flow because you will end up adjusting the pressure of the O2 to achieve the flow you are looking for.

[o.m.]

The O2 flow is adjusted out from the O2-flask, instead of an ordinary regulator.. I´m not sure if this will adjust according to the resistance it will meet, but I might be wrong.

[Travisty]

Is the flow of the O2 measured directly? Do you have to turn a dial/valve to achieve the flow rate you want or are there simply preset settings for each flow rate? It seems to me that preset settings would not be very useful for our application since any change in resistance downstream of the regulator would change the flow rate.

[o.m.]

Yes, the flow rate is adjusted stepwise by presets, which in my opinion gives me a very good possibility of repeating the same flow every time, and together with the time factor - a very repeatable amount. Since the diffusion stone will have a pretty constant resistance, I guess it would be possible to dial in the optimal flow rate preset together with 60, 90 or 120 seconds.

The difficult for me, is knowing how much oxygen (the actual flow in liter per minute) I now get out of the diffusion stone, so I can adjust the preset (and time) to that.

If no one knows, I guess I should try to borrow a oxygen meter (can´t afford one at the moment). And if so, when and how do I measure the saturated oxygen in ppm? Will I get the same numbers if I do the same experiment in (boiled) water, or does the gravity count here?

[Gahr]

Hi, Lars. You've found your way in here too!

I use a dissolved oxygen meter to measure the ppm directly after adding the O2. Or, rather, I start measuring the P2 concentration at the same time as I start adding the O2. I have found that since there's a slight delay in the DO meter's measurements, I have to stop adding O2 a little before the readings reach the O2 level I'm shooting for (which generally is around 12 ppm). I don't have a flow meter like you have, but I set the regulator to a pressure of 1 bar (roughly 14 psi) and find that adding O2 for about 30-45 seconds (through a diffusing stone) usually does it.

I don't think adding O2 to boiled water would be of much use, since the sugar concentratian in the wort has a direct effect on how much O2 can be dissolved in the liquid (and hence the time it will take to reach your target saturation level).

I bought my DO meter (a pretty decent Milwaukee meter) at ebay for 1056 NOK. Ask your wife to pitch in for Christmas!

Take care,
Gahr

[o.m.]

Hi Gahr,
nice meeting you over here/there/everywere as well.
Thanks for filling me in on your measuring, I didn´t think of the different wort compositions as an important factor.

I´ve been reading topics in here for a while, and thought that asking my questions in different forums/to different brewers, would improve my chances of getting the necessary feedback.

I will definately add a dissolved oxygen meter to my wish list, as I´m not sure when I´ll be able to spend more money on beer related equipment for a while.. Also, having a (less expensive) flow meter, measuring the actual gas flow, would also help me out. And I´ve also been thinking of filling a plastic bag with oxygen for 1 minute, sinking it in a bucket of water and then measure the volume. It could be one way to approach the problem, when I´m home again, and have some time to spend.