Another BBT purge question

[Gbbc]

Hi,

After reading most of the BBT purging procedures, I'm still worried that we are not purging our BBT properly. I'll explain our method and would like to know what you think. We don't have a way to measure the DO in the tank (not that I'm aware of, could you use a Hach HQ 30d DO meter?). We are using 20BBL Premier Stainless Bright tanks and purge through the carbonation stone:

Fill the tank to 5PSI with CO2, close the CO2, open CIP arm with a hose connected into a bucket of sanitiser, discharge slow-medium until tank is empty. We will do this twice and fully discharge the CO2 pressure from the tank, fill again with CO2 to 5PSI and start the transfer.

Any feedback appreciated.

Cheers

[TL Services]

The only guaranteed way to be certain that a tank purging procedure is effective is to use a DO2 meter to measure it. The meter you mention is designed for use in water-courses, etc. so is not really ideal for tanks (you really need a meter that can be connected to a sample point).

During years in brewing QA, the best way I ever found for purging was to fill the tank with deaerated water, then push that out with either N2 or CO2.

Given that deaerated water isn't available, bleed CO2 gently into the tank at the lowest point possible and monitor gas exiting at the highest point. Although the incoming CO2 will mix with air in the tank, the highest CO2/lowest air concentration will be at the bottom, so as the nett amount of CO2 increases the DO2 will drop.

You can use either a dual-phase DO2 meter (ie. one that can measure in liquids and gases) or a standard liquid-phase unit; the maths is simple to give a good guide.

Hope that helps!

Tim Lawrence EngTech MInstMC
TL Services

[patbrewer]

We curently have no DO meter as well, hope to have one soon. Our process is similar to yours Gbbc. We hook up our co2 to the lowest port on the tank and pressurize to 10 psi, hook up a garden type hose with a TC fitting venting out doors then drop the pressure fairly quickly while keeping the co2 pressure on. Do this twice then rack beer. We had one keg of our first batch IPA from late July go on at a bar recently and no oxidized flavors just a little hop drop. I have no analytical data to prove the method, will soon, but it has to be better than the co2 "blanket" method. There is a lot of info on in the forum on this as well as cleaning brites and kegs under co2 pressure.

[indyGold]

We have a Hach Orbisphere 3100 and have used it to validate our processes. There are several threads on PB that mention rules of thumb for purging that are very much true. It's ~20 minutes/10 bbl of bright tank volume from the bottom valve. That will allow final DO post transfer to be 10-20 ppb or less if the beer is brought into the tank slowly so it doesn't fountain in the middle of the dish bottom. For can batches we purge longer so our package TPO can be as low as possible.

Pressurizing a BBT multiple times as described in the initial post might leave as much as 1-2 ppm in the final beer. CO2 blankets are a myth. The atmosphere will become homogeneous and the beer will become oxidized quickly.

[beerbeer95648]

When I worked for a larger regional brewery we always had the best luck with three 5 psi purges. This was the Zahm Co2 tester that uses caustic as a catalyst. 2 purges were not enough, and 4 plus purges were diminishing returns.

[Gbbc]

We have a Hach Orbisphere 3100 and have used it to validate our processes. There are several threads on PB that mention rules of thumb for purging that are very much true. It's ~20 minutes/10 bbl of bright tank volume from the bottom valve. That will allow final DO post transfer to be 10-20 ppb or less if the beer is brought into the tank slowly so it doesn't fountain in the middle of the dish bottom. For can batches we purge longer so our package TPO can be as low as possible.

Pressurizing a BBT multiple times as described in the initial post might leave as much as 1-2 ppm in the final beer. CO2 blankets are a myth. The atmosphere will become homogeneous and the beer will become oxidized quickly.

Thank you for all the replies. indyGold, when you say 20min/10BBL, would I be correct by purging our 20BBL tank with CO2 from the bottom dump valve, not through the carb stone situated in the lower 1/3 of the tank, for a minimum of 40min? At what pressure would I set my regulator for this?

[indyGold]

We're using a 500 lb Dewer with regulator set at 40 psi for our CO2 distribution. Purging from bottom valve with CIP arm valve open for 40 mins. Feels like a light "push" out of the CIP arm on our 22 bbl BBTs.


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[Gbbc]

We're using a 500 lb Dewer with regulator set at 40 psi for our CO2 distribution. Purging from bottom valve with CIP arm valve open for 40 mins. Feels like a light "push" out of the CIP arm on our 22 bbl BBTs.


Sent from my iPhone using Tapatalk

Thanks indyGold, just trying to work out what the best PSI setting for each tank when purging. Each of the two 20BBL BBT's we have has its own regulator coming off the same gas manifold. Each regulator only goes up to 15PSI. Going by other post it seems like the range is anything between 2 and 5PSI for a "continuous" purge. I suppose it is really hard to say and only a guess when you don't have a way of testing the DO in the tank. We are starting to can our product in the coming weeks and I just want to make sure we are doing it the right way.

Cheers and thanks for the help