pre purging recieving tank

[oppigards]

I use to fill the recieving tank (BBT for example) with co2 until I can sniff a strong odour of co2 from the sample valve (40 % up on the side of the tank.) of the tank with no pressure. Is this a good enough or is the co2 gas in the bottom of the tank still to mixed with air?

[jfulton]

CO2 is a dense gas and will gather at the bottom of the tank, creating a more defined "layer" when under even slight pressure. The surface of the beer will be in contact with mostly CO2 when it fills the tank.

Jamie

[gitchegumee]

Also, be sure to fill the tank slowly from the bottom.

[Moonlight]

There was a long thread on this a couple months ago.

[Dave Suds]

I purge my horizontal tanks (10 hl bierdrive)with about 5 PSI and then totally release it up through the release valve. Because Co2 settles at the bottom of the tank I believe that when I release the gas from the valve at the top of the tank until NOTHING comes out of the tank, then there must be NOTHING in the tank. RIGHT? Then by purging again I am certain that the beer flowing in is under a nice bed of Co2 and will push out the remaining air whilst filling.
It may be a slight waste of Co2 but I have gotten good results doing this. Better safe than sorry.
Skål ta me fan
David Meadows

[Woolsocks]

I get out a Zippo lighter, light it, and hold it under my CIP arm as I'm purging. If it doesn't immediately go out, I know there's still some air in the tank. I also use a Zippo to test for air in the dose tank on my DE filter.

[RobZamites]

In the other thread on this, I referred to my "burning nose hair" method!

[Dave Suds]

Ah yeah.....i´d much rather inhale nitrous oxide than carbon dioxide . I used to do the lighter thing but I burnt my finger once and after that I devised the method I use now. Works well for me. What I need to do is get an O2 meter or send some samples to a lab to check O2 level. Expensive toys like o2 meters I like to call "nice to have" items.
David Meadows

[Larry Horwitz]

see the other post, but the "CO2 sinks" thing is a fallacy. There is no science to back up this theory. If you don't purge all the way you WILL oxidize your beer.

[Ted Briggs]

I posted this the last time this question came up but here it is again:
A Weihenstephan study showed that a tank, no mater its size, will be adequately purged if filled from the bottom to 5psi and vented from the top twice. The study indicates to then fill to counter pressure the transfer and after transfer completely vent the head space and re-pressurize though the carbonating stone. This will give low DO levels. A 3rd though 5th purge showed limited results, and were not recommended. I have used this process for years with good results, although I've never owned a DO meter.....
I swear the study was published in "Brewing Techniques" but could not find it in their on-line index. Maybe it was MBAA T.Q. ?

[RobZamites]

Ted, thanks for that tidbit; I'm going to try it today!

[pennbrew2]

I posted this the last time this question came up but here it is again:
A Weihenstephan study showed that a tank, no mater its size, will be adequately purged if filled from the bottom to 5psi and vented from the top twice. The study indicates to then fill to counter pressure the transfer and after transfer completely vent the head space and re-pressurize though the carbonating stone. This will give low DO levels.

This will also foam the heck out of the beer in the tank. You shouldn't pressurize a full tank of beer through the carbonating stone.

Unless I mis-read your advice...

---Guy

[Dave Suds]

I usually counter pressure only to seal the manhole. My tanks require this. Then as the beer is gently pumped into the tank so as not to create "shear forces", the pressure in the tank rises faster and faster as the beer nears the top of the tank. This requires repeated venting through the valve. I am certain that this vents out any air that may be left in the tank. I do not repressurize after filling because the tank already has adequate pressure. I usually wait until the beer has settled and then give it gas until equilibrium is reached.
David Meadows

[Dave Suds]

Oh yeah!!!! NO FOAMING
David Meadows

[jfulton]

When CO2 is forced into an area at higher than atmospheric pressures it will accumulate below other gases normally present in the atmosphere. Drop down to the bottom of your coldroom and take a whif after letting it out of a tank, open the bottom of a fermenter after its empty...it comes GUSHING out! I've never heard anyone doubt this... A CO2 molecule is heavier than nitrogen and oxygen, with comprise the majority of the atmosphere...What is the other post where people talk of this Larry? I couldnt find it...

Jamie