Ok, so I got this idea and thought I would share in a relevant Burton Union thread. I was thinking of hooking a 3 liter pop bottle to my Sanke fermenter as a collection only reservoir (bulk head type fitting with blow off input attached at center bottom of pop bottle), and plumb in a "pressure cooker/canner" steam vent pipe
and multi-weight regulator
through the bottle cap (for a 5-6.5 gallon you could probably use a smaller bottle and use a simple air lock through the bottle cap). Basically, I am thinking that the blow off would go up into the bottle and then everything would fall back into the fermenter just like using a bigger fermenter. Like creating artificial head space, lol. I am not thinking about yeast collection or anything like that with this design, just collecting closer to my fermenter volumes worth of finished beer. Hummm, using pop bottles and the canner/cooker's pressure release system, I could handle 15 psi I need for my pressurized fermentation setup.
Then (for my system of fermenting only), I could just un-tap the fermenting keg and let it self pressure up to 30 psi +/-, crash cool the keg and the device (if there is any liquid in it, if not I would just clean it for next time), and let it go a week. Finally, I guess I could carefully add back the beer (if any) in the device to the serving keg and pressure up the serving keg to the same pressure I have chosen to have the fermenting keg set at. Since my serving keg would be pre-purged of O2 prior to filling with the beer from the device, and re-pressurizing before counter pressure transfer of the fermenter, any O2 would get pushed out once the keg was full of ready to age beer.
The pop bottle is a simple to manipulate media for DIY, and for a (normal) non pressure system and a double hole stopper, I don't see any reason why it wouldn't work wonderfully for a wort recovery device for a carboy brewer. I had to write how I would be using it to kinda think it out loud I am such a nerd/technigeek.