Nitrogen for purging

[frenchc]

I rented an N2 generator thinking I could use it for purging/transfers, purging cans. Then tested the DO on it and it's like 400-500ppb. Curious if that's what others are seeing. That seems a little high to me even for pushing beer. What do others think? I'm using the greenair supply N2 generator. I've read the forums a bit, looking for other practical experiences.

[TGTimm]

I'm interested in this, too. We're contemplating getting one ourselves, but that O2 level is far out of control.

[Weehe]

Are you getting the same O2 results if using CO2?

[TGTimm]

Is that 400-500 ppb what you see in your package, or in the gas itself?

[frenchc]

The DO is of the gas itself. I didn't even want to put it into the beer, but I guess I will test it.

[TGTimm]

We're also looking into an N2 generator. Doing my homework, it looks like 99.5-99.7% N2 purity is the brewing industry standard. I've discussed this with our brewers and they find that acceptable. It's about the same as our beverage-grade CO2.

[frenchc]

The N2 generator is rated at 99.8 (over lifetime). My CO2 purity seems to be much higher as I get DO measurements on it much lower (under 15 ppb). And so is my nitrogen cylinder. I'm looking into the purity specs on my CO2.

[Matter]

Out of curiosity, what instrument are you using to measure the O2 levels in these gases?

[frenchc]

Hach Orbisphere.

[Brewingbrandon]

N2 is lighter than air. Try purging from the top and out of the bottom.
I have never purged with N2 myself but just a thought.

[vinaykumar27]

Most N2 generators only do 99.5% purity under the best case setting, and a lot worse quality at times of big draws. Bottled N2 is typically 99.999%. While not all of the remaining contamination is O2, it likely constitutes the bulk of it.
If you are seeing 500 ppb DO, I would say this roughly corresponds to a gas composition of 0.8% O2 (for temperatures between 32 and 40 F). This quality, while worse than typical, it is totally in line with what I would expect.
If this looks bad for just pushing beer during transfers, it is actually a lot worse when you are trying to dissolve the gas like during nitrogenation, although that may be a longer topic for discussion elsewhere.