O2 Injection question

I made an inline O2 injection tube using Home Depot O2 tank and a diffusion stone.

I use a flow meter and set it for the flow I want. But then, when I pump wort and turn it on, the flow meter seems to go down. I thought my check valve was sticking. Turns out, the setup creates some kind of back pressure. So if I just turn the O2 on in the tube with no wort flowing, it maintains the flow I set.

But when I'm oxygenating wort, the flow meter tend to go down a bit.

Is the O2 still getting where it needs to go? I can see the bubbles in the tube. Anyone have similar issues?

 

Back pressure would cause the rise. I think your actually creating a draw (vacuum) as your wort is flowing by. I think it's ok if it's bubbling it's going somewhere..........my.02

 

Just curious, is the flow meter upstream or downstream of the oxygen stone? If the meter is downstream of the oxygen stone, the addition of lower gravity air in the wort will cause a false decrease in the flow of wort. Try looking at it like this; the flow meter has a vane on it that spins like a paddle wheel, the faster it spins the greater the flow, and you are pumping a high gravity wort through it. Now you start to add O2 to the wort, which has a low gravity, and so you have reduced your overall gravity of the wort which in turn makes the wort less dense. Because it is less dense, it doesn't push as hard on the flow meter vane which shows a decrease in flow. At least that is the way that I see it.

 

I would inject the O2 once the wort is in your fermenter/primary... Give it enough L/minute to get your concentration and then pitch the yeast.

I plan on getting a flow meter before my next batch. This will go between my O2 regulator (I have a tank from my welding rig, with a dual stage regulator) and stone wand (picked up from Williams Brewing Supply)... With the stone on the wand, I can just put it into the fermenter, turn on the gas, and get it to oxygenate from the bottom up. Has already done really great things for me.

Oh, and those small O2 tanks from HD/Lowes/hardware stores, are ok to start. You'll probably want to upgrade to a larger tank at some point though. Especially something where you can actually SEE how much gas is left in the tank.

 

Here's a pick of my setup.



O2 goes from bottle to flow meter, to manifold with O2 stone in it. Wort is pumped into the end with the stone, out the end with the thermometer. I pump from my kettle to a sanke with a modified coupler. I then have to bleed pressure from my sanke.



My guess is that the wort being pumped thru the O2 injection manifold is creating a draw on the flow meter. But this should have no effect on the amount of O2 being injected, but will affect the flow meter when wort is pumping. So I'll likely just set up the flow meter to the right rate and ignore it when it falls slightly.

The fall in the meter must be due to the vacuum sucking the O2 out a little faster than the tank is delivering it. Just a guess, really.

 

Yeah, this is a good way to go. But then I have to open up the fermenter, which is a bit of a pain since mine has a sanke ring and a dip tube to remove and keep sterile. But 9/10 times I have to remove it to pitch yeast anyway.

Inline injection is very streamlined and cool. My guess is that mine is working fine. Yeast took off in about 12 hours so I assume the O2 injection was working fine.