DIY Hop Torpedo

So, after having ruined several batches of beer with dry hopping and having hop particles fall out of the bag, making the beer bitter and grassy, I decided it was time to make a change. I had always been curious about recirculating while dry hopping, and the benefits I would think could be made from this. Sierra Nevada has perfected the system using their “Torpedo.” This is more like a Hop espresso machine-- they compress hops together and force the beer through it at 50 PSI. While my DIY hopback could handle the pressure, I don’t have the technology to compress the hops, nor to generate that kind of pressure gradient across the hops without having to do a LOT of work. So, rather than do this, I thought it would be much easier to just make a recirculation dry hopper. I already had my hopback, which is designed to work perfectly in this situation, as well, and so I just needed a very slow pump and some connectors to make this work. I figured the easiest way to do this was to dry hop straight from a cornelius keg, so I could keep things sterile, and it already has a dip tube and a return tube (the gas inlet), making construction MUCH easier.
Here’s what I did. I bought a single speed peristaltic pump (Anco 907-058 pump) that was rated for continuous use (very important that it is rated for continuous use). At 58 RPM using 1/4” ID tubing, it pumps about 3.5 ml per second, or about a gallon every 18 minutes. I attached this to some 3/16” beer line on both ends of the peristaltic tubing with a 1/4” stainless hose splice, then to a black (liquid out) ball lock quick disconnect. On the other side of the pump’s peristaltic tubing, I connected 3/16” beer line to a 1/4” to 1/2” hose adapter into a 1/2” female stainless disconnect. Another cord was made with 3/16 beer line with a gray (gas in) ball lock quick disconnect, and on the other end another 1/4” to 1/2 inch hose adapter to a 1/2” female stainless quick disconnect. My Hopback has been fitted with male 1/2” stainless disconnects, so it can clip between the two cords.

Here is how it is used:

I fill a Cornelius keg with at least a gallon of Starsan. I then plug both of the quick disconnects onto the keg, place a hopback bypass connector in place of the hopback, and start circulating the Starsan through the tubing. In the meantime, I place the stainless hopback into the oven at 350 to sterilize it, and I let it cool, and fill it with hops (up to 5 ounces).

Flushing lines with CO
After recirculating Starsan for a while, I remove the quick disconnects from the keg, and place the “gas flush input” on the liquid out quick disconnect, and the “gas flush valve” on the gas in quick disconnect. The crummy thing about this setup (with my pump, at least) is that in order to force the stars an out, the peristaltic tubing needs to be removed from the machine. This means I have to unscrew the cover, and screw it back in once the tubing is replaced, making it more of a pain to use. I close off the gas flush valve, set the CO
2 pressure on my regulator to 5 mmHG, then plug the gas flush input into the CO2 quick connector. I then slowly open the needle valve and slowly drain the liquid out of the lines until CO2 flows out, then I close the valve and disconnect the CO2.

Flushing hops with CO
Once all the lines are clear of Starsan, I replace the hopback bypass with the sterilized and filled hopback, and reconnect to CO
2. I open the gas flush valve a bit more and let CO2 vent to the atmosphere for a few minutes. This purges all the air from the hops and hopback.

When air is purged from the hopback, I spray Starsan over the gas in and liquid out posts of the keg to dry hop to sanitize it. I disconnect the gas flush input and place the quick disconnect gas flush valve on the keg. I also remove the gas flush valve and place the gas in quick disconnect onto the keg’s gas in port. I replace the peristaltic tubing into the pump, and then turn it on. My plan is to recirculate for a total of 3 days, and no more.

I am running a test right now, with the first sample running. I have a Bavarian Hefeweizen that I brewed 2 years ago, is not very good and has been filling a keg. I’ll probably never drink it but don’t have the heart to throw it away. Instead, I will sacrifice it to science! I am currently dry hopping it with 4 ounces of citra… not the most normal choice for a bavarian hefeweizen, but something that will definitely be noticeable, and with the light flavor of the hefeweizen I think this will be a good test of what the process does. I’ll let it run for a few days, and report back.

Parts List: Number
Cornelius Gas In Post 2
Cornelius Liquid Out Post 1
Cornelius Gas in post to 1/4” NPT female adapter 1
Cornelius Gas in Post to 1/4” NPT male adapter 1
Cornelius Liquid Out Post to 1/4” NPT female adapter 1
Noshok 1/4” Male NPT Needle bleeder valve 1
1/2” NPT stainless mail to male quick disconnect 4 (2 for hopback bypass, 2 for hopback)
1/2” FPT stainless female quick disconnect 2
3/16” beer line 10 feet
Ball lock gas in quick disconnect (w/ swivel adapter) 1
Ball lock liquid out quick disconnect (w/ swivel adapter) 1
1/4” stainless steel hose splicer 2
Hose Clamps 8
Peristaltic pump with rate of approx 2-3 ml/sec 1
Hopback 1

Update 2/18/13: The hefeweizen took on a huge flavor and aroma of Citra. The project is a success!