oxygen cylinders

[Crackin]

What size medical cylinders are people using? I want to get the smallest possible, that will still last 2 years + (50 batches). I suppose I could figure it out depending on the liters it holds, but what flow rate is most common? A M6 tank holds 165 liters, so at 2 liters / minute, averaging 1.5 minutes a batch, that would give me about 55 batches. Correct?

[Crackin]

Thanks to beltbuckle in the other thread for posting this link

http://www.byo.com/component/resource/article/147-are-welding-oxygen-canisters-safe-for-homebrewing-aeration

I got an M6 Oxygen cylinder, good for 165 liters, and a 0-4 lpm regulator, that includes settins for 1/32, 1/16, 1/8, 1/4, 1/2 lpm - all the way up to 4. From the BYO article, it appears that if I can set it at 1/8lpm setting and run it for 1 minute without any oxygen escaping from the surface, I should be about right. If oxygen is escaping (bubbeling out), I can reduce the flow, and go for longer times accordingly.

Seems like if I can dissolve .1 liters of O2 into the wort, without any escaping from the surface, that little tank will last forever.

Doug

[beltbuckle]

Yes if you do the math, a little oxygen will go a long way. Here's some sample math from a 6 gallon batch.

6 gallons of wort = 22.7 liters

Now we want an ideal oxygen concentration of 8 ppm (8 mg/ L).

22.7L * 8 mg/L = 181.6 mg of O2 are needed

.1816 grams * 32 grams/mole of O2 = 0.005675 moles of O2

0.005675 moles * 22.4 L/mole = 0.12712 Liters of O2



So I need 0.12712 L of O2 assuming 100% transfer which the article says is realisttic with a fine (.5 micron) stone and a low flow rate (this is why you need a very low-range flow meter).

I adjust the flow to .1 LPM with my flow meter, and keep the O2 flowing for 1.3 minutes (78 second) to yield .13 L of O2 (I rounded up a tad).

A bernz-o-matic has 1.1 cubic feet of O2, which is 31.15 Liters. Assuming zero waste, this would be enough O2 for 239 injections of oxygen for a 6 gallon batch (remember .13L of oxygen per injection).

Now even including waste, there is still plenty for 100+ batches. You guys that are only getting 5 batches per bottle are using WAY too much oxygen and either over-oxygenation or oxygenating in a very inefficient manner. Again, this is why you need a very low-range flow meter!

[beltbuckle]

What size medical cylinders are people using? I want to get the smallest possible, that will still last 2 years + (50 batches). I suppose I could figure it out depending on the liters it holds, but what flow rate is most common? A M6 tank holds 165 liters, so at 2 liters / minute, averaging 1.5 minutes a batch, that would give me about 55 batches. Correct?

2 L/minute for 1.5 minutes? That's 3 liters of oxygen!! Read that article again. That is WAAAAYYY too much! You only want 8 mg/L, or 0.13 Liters for a 6 gallon batch!

I've done the math for the small 1.1 cubic foot bernzomatic bottles, so might as well crunch the numbers for this one too.

165 Liters / 0.12712 Liters per 6 gallon batch = ~1298 6 gallon batch injections.

BTW, here is a picture of what I use. It's range is 0-1.2 LPM. You can pick these up on ebay for $45. Make sure you get the model WITH the valve.

[Crackin]

Per the BYO article, I also realize I was probably using way too much O2! The 0-4 lpm regulator I picked up, which regulates down to .03125 lpm, was only $25 off Ebay.

[beltbuckle]

Nice, that sounds like it should work fine. If you want to give your yeast plenty of O2, you are better off giving them maybe 2 doses of the proper amount of oxygen 2-6 hours apart at the beginning of fermentation rather than one big blast that is way too much. But that's a great article BYO had that really breaks it down into detail and explains why a flowmeter is so important.

[bluelou6]

which month's BYO was the article in?

[Crackin]

Thanks again for posting that article beltbuckle! You might have just solved my lager fermentation issues. I can't wait to get my tank and flow meter and brew a tasty helles!