Unitank pressurized low-oxygen transfer -- with filtering?

[slidingmike]

My first fermentation in the SS Brewtech Unitank of a hazy IPA went pretty well, and I tried to do all the tricks: CO2-purged dry hopping, trub dumping, cold crashing, and carbonation in the unitank. When I was enjoying the benefits of the sampling valve, I noticed that my samples were pretty green with hop matter that hadn't settled in the cold crash (I got it down to 37 degrees, maybe not far enough?). I also found that the transfer from a carbonated / pressurized tank to a pressurized keg was tricky, because with high pressure on both sides, it wasn't obvious to me on how to remove the oxygen from the transfer tubing. So I have a few questions for this learned audience:

1) What is the trick to purging the transfer pathway between the unitank and the corny key's liquid post?
2) Is it likely that I did something wrong that caused the hop matter not to settle decently?
3) Is there a filtering solution that I could use between the unitank and the keg that won't introduce any significant oxygen to the finished beer?

FWIW, the beer is tasty enough from the keg, but it's still got a green murkiness that I'd rather not serve to friends.
Any suggestions or criticisms welcome!

 

[Qhrumphf]

A transfer without ingress isn't possible. Same goes for filtering/straining. Low oxygen purists might still take issue, but between minimizing permeability (ie transfer via stainless piping far superior to silicone tubing) you can still keep it very low.

Assume adding something inline is going to increase ingress. I've used the "Bouncer" inline strainer inline with minimal ill effect.

You can purge transfer lines the same way you would purge a keg- fill it completely with sanitizer, then push it out with CO2 or beer. I'll pack it all, hook it up, and run it to the drain until beer pushes out the sanitizer and the line is all beer. This also lets you clear out any particulate that may have settled in the racking arm. I keg in sanke kegs with a shutoff valve on the coupler that makes it easy. With cornie QDs you could easily use an extra post to flush the line out. Could also just engage the QD by hand and dunk it back in sani afterwards.

Things often settle into the shadows of ports. It's nearly impossible to flush them out completely. If it was still like that after transferring to keg, then yeah, maybe it wasn't crashed cold enough long enough.

 

[Advance]

1) What is the trick to purging the transfer pathway between the unitank and the corny key's liquid post?
2) Is it likely that I did something wrong that caused the hop matter not to settle decently?
3) Is there a filtering solution that I could use between the unitank and the keg that won't introduce any significant oxygen to the finished beer?

1) Sanitized your transfer hose and liquid disconnect. Assemble and secure to the unitanks racking port. Use a plastic dowel or some tool to depress the liquid disconnect poppet. While the poppet is open, open the butterfly valve for the racking arm on the unitank. Allow beer to push through the transfer hose for a couple seconds into a collection vessel to purge the line. Sanitize the disconnect before connecting to the keg, to begin the transfer.

2)What period of time lapsed between the completion of carbonation and the beginning of the transfer to your keg? Carbonating through the stone can cause hop material to be kicked up by creating movement inside the FV. This is especially evident from improper use of the stone. Make sure you are using the carbonation stone correctly and give things time to settle after you finish carbonating. Refer to this post for instructions on proper stone use.
https://www.homebrewtalk.com/threads/carbonation-help.680106/post-8885395
3) For really hoppy beers I usually use this filter gasket between the outside flange on my racking valve, and the TC barb fitting used to connect the transfer hose to this port. It does seem to collect quite a bit of material from time to time:

https://www.amazon.com/Brewery-Gask...child=1&qid=1593273279&sr=8-19&srs=8385887011

 

[slidingmike]

Thank you, Qhrumphf and Advance -- those are great pointers! This forum is great.

 

[slidingmike]

I had ended up waiting a full week after starting cold crashing, and 5 days after carbonating before I did the transfer -- excessive time, I thought!

 

[Advance]

I had ended up waiting a full week after starting cold crashing, and 5 days after carbonating before I did the transfer -- excessive time, I thought!

That seems like more than enough time. I'm not sure why you would have excess hop material during the transfer. Did your head pressure in the unitank remain at the carbonation level or higher during the transfer? The only thing I can think of is if your head pressure dropped enough, it could cause CO2 to come out of solution which would kick your settled hop debris back into the mix. Make sure your head pressure in the unitank stays at or above the pressure that you carbonated at all times.

 

[slidingmike]

The pressure did slowly drop towards the end of the transfer. But the beer is pretty similar to what I was getting just before the transfer straight from the sample tap.