But then how do you get the hops in there without letting any oxygen in?
I think there are two issues here: 1) what’s the best way to sani-purge and leave no sani in the keg? See immediately above. 2) what you just said. To which there’s no perfect solution, but at least you won’t have sani in there too. Here are two approaches I have, first one somebody mentioned before. a) Open the purged keg, pop the hops in, close up fast, and do a few purge cycles through the liquid side, then closed-transfer the beer onto the hops in the keg. You’ve done your best. b) same as (a), but toss in a small amount of sulfite (~10ppm) with the hops to scavenge O2. If you’re really paranoid. (Which I sometimes am. ;) )
I think a person needs to make decisions about what is important. So if crazy high hop aroma is number 1 on the list then quit worrying so much about O2 and plan to drink the beer fast. If you can’t get through a keg before oxidation starts destroying it, then maybe you need to consider getting dry hop aroma some other way than the keg.
I’m lucky. I get all the hop aroma I personally need from whirlpool. And through closed transfer to a properly purged keg, and keeping that keg always cold, I’m able to preserve that aroma quite a while.
Think a hop aroma version of the tortoise and the hare
^^^^
I prefer dry hopping (when I do it) in the fermenter with a little yeast activity left to scour the O2. But I totally agree, if you want to dry hop in the keg, you probably are going for extreme freshness, so drink quickly and enjoy the unique moment. When you think dry hopping (ok, when I think dry hopping) what comes to mind is British cask beer that goes in 2 or 3 days at the pub. The candle that burns the brightest burns the fastest. That said, this thread is about those who want to keg hop and may take some time to consume the beer. I’d forgotten, went back and re-read from the top, some interesting conversation. Why I hang around.
not perfect but i hook up co2 to the liquid side at about 4 psi and gas while i dump hops into the bottom of the sani purged keg (with sure screen). close back up, and rack beer in through liquid line. let sit 3-5 days then cold crash under pressure for 2 days and jump to a new keg.
I’m currently drinking an IPA that is about 5-6 months old, dynamite hop aroma and minimal to no oxidation notes (i.e. i don’t feel its oxidized at all). i have another (Different recipe) IPA on tap that is about 2 months old - also excellent, same intensity.
i personally like the aromas doing this versus in the fermentor. Also, i like that the hops in this method are free balling within the entire keg versus a bag or SS canister - with the amount of hops i use, those vehicles were always crammed and often the middle of the hops was still dry.
I also whirlpool but the hop aroma is just not enough for me, which is why I’m looking for different ways. 
. I’ve also had oxidized beer within a couple of weeks of kegging.
Here’s what I’ll try for my next batch. Once fermentation starts and krausen starts to build up I’ll purge the keg as described by Robert, open the keg up, toss the dry hops in and seal the keg. Then I’ll connect my 7G Fermonster from the blow off tube to the beer line in, and hook up the gas disconnect to a jar of sanitizer. Put everything in the temp controlled chest freezer and let it go until fermentation slows down. Once heavy fermentation is done connect the fermonster back to the jar of sanitizer (or an airlock) and give it a few days for the yeast to clean up. Then CO2 transfer to the dry hopped keg for a few days until I transfer to the serving keg and chill.
I wonder about a CO2 purged Randall between the primary and the keg, with a slow closed tesnsfer.
Are you guys purging the receiving keg at the start or just suggesting those steps noted? I think either approach would work, but could be enhanced or helped by starting with a purged keg to keep the O2 goblins at bay (at least a tiny bit better).
Hmm. I’m intrigued. How slow would that transfer have to be? Anybody have actual experience? (Fermenter ==> dry hop in purged keg ==> jump to another keg is essentially this idea with a reallllly slooowww transfer, right?)
See my post above
I’m just wondering if there’s a reasonable flow rate that would get any effect from using a Hop Rocket as a Randallizer in the transfer. Like taking an hour to jump 5 gal, or something on that order. (My next variation to try is crashing in fermenter, then dry hopping in my cold-conditioning keg for a few weeks, before filtering. Because that’s a dry hopping variant I haven’t tried, but standard procedure for treatment of the beer otherwise. I’ll just be moving the dry hop to post-fermentation. Like the Blatz Method, but cold and slow.)
Gotcha. My transfers take about 15 min currently. I can’t imagine you’d extract enough with just an hour passage/contact time (ie without letting sit 5 days or whatever) would give you enough aroma to last through the life of the keg but I’d be interested in hearing others trials.
I have used a hop rocket to do that, excellent results.
15-20 minutes to transfer. You can the go back to the original keg by swapping the fittings. Pour a sample, evaluate, repeat. I think I did it 4 times.