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NorvilleBarnes
02-22-2017, 09:31 AM
Does anyone measure the DO levels of clean, unfilled kegs? I'm looking for a baseline level to judge whether or not our keg washer is performing to specification. I've increased our number of CO2 purges from 2 to 3 times, but I am still seeing a DO content of 1500-2000 ppb. The CO2 leading into the keg washer is reading around 12.5, and although relatively high, wouldn't have a significant impact. A freshly filled keg is measuring between 50-120 ppb, with the brite tank level of about 25 ppb.
I managed to lower the DO level to about 100 ppb by manually pressurizing the keg to 30 PSI and blowing down twice. We've had troubles in the past with the keg washer over pressurizing kegs, causing blow-back into the brite when kegging. The current washer purge cycle is set at 13 PSI, and I'm hesitant to increase it further.

TL Services
02-27-2017, 11:08 PM
If you are measuring the level of O2 in gases using a DO2 meter then you need to look at converting the readings to % O2 to get a truer picture.

Typically a dissolved meter will read 8-9000ppb in air, which is 20% oxygen so:

Around 800ppb = 2% O2
80ppb = 0.2% O2
Etc.

So the 12.5ppb you mention on your CO2 works out at around 0.03% oxygen, is. 99.97% oxygen-free, which is fine.

The problem with straight gas purging is that the purge gas just mixes with the air so if you fill at 14psi you'll have (roughly) twice as much CO2 as air. Vent that back to atmospheric pressure and the O2 level will still be around 1/3 of the start level, so 7%. Repeating this cycles will drop it to 2-3% O2.

Would it be possible to fill your kegs with water then blow out with CO2? That is by far the most effective way to reduce remaining oxygen.

Hope that helps!