OK, admittedly the answer is probably ‘You can’t,’ but we’re a creative bunch.
The specific issue is that I recently bought a stainless conical from Stout Tanks. I have always used gallon marks on my Better Bottles or my Speidel fermenter to see when I need to shut off the transfer from the fermenter to the keg so as to not have beer bubble out of the pressure relief valve on the corny keg. The issue is that I want to do all my transfers with no exposure to air, so I can’t just look inside.
So now as I see it, the only way to be sure of that is to watch the volume going into the conical from the boil kettle - one step removed hence a greater chance of mistakes.
I know this isn’t a critical issue, but I have some time to work out the details of using the conical since I can’t use it until I purchase an upright freezer for a fermentation chamber. How do you all make sure of the volume going into your keg from a conical?
I purge my kegs with CO2 before filling. Then my fill hose is inserted to the bottom of the keg being filled and I gradually raise it keeping about 1 inch of the fill tube below the level of the beer. When it looks like I am about 2.5 inches from the lip of the opening I shut off the flow, withdraw the tube, and put the lid on the keg. Two inches from the lip is about 5 gallons in a ball lock corny.
How about filling through the liquid out tube (fill from the bottom) then hook up a tube to the gas in post (to release pressure as it fills). Put the tube in a glass and stop transferring when beer comes out.
You could probably cut those things in two or three pieces so you can use one gauge for two or three kegs as you probably are not that interested in knowing how empty the keg is. Essentially you could do the same thing by feel or if the air is humid enough looking at condensation. This all assumes that the beer being transferred at normal refrigeration temperatures.
I think Mort’s scale idea is a good one too.
My first thought was a flow totalizer but that is probably expensive.
Another possibility is to rig up a circuit tester like one built into a multimeter and when the beer closes the circuit you know to turn the beer flow off. This is how many simple level alarms work. You would have to remove the pressure relieve valve to do this unless you are willing to put a bulkhead fitting into your corny. This would greatly reduce but not eliminate exposure to air.
I’m thinking that Mort’s idea of the scale may be the cheapest and easiest. Just weigh a corny filled with water, then sit the empty keg on the scale and watch until it hits the right weight. I like it.
WHy dont you calibrate a stick or some such on your BK to know how much is in it before you chill? then just calculate how much wort you lose to hoses etc with water and you are there.
I like to do closed transfers with CO2 as well. I just chill the beer down to near freezing, then when I’m filling the keg, I just follow the condensation on the side of the keg up to the top (or almost, I stop at that weld line). If you don’t have a way to chill the beer first, I would try the scale method.
if i understand the question about guessitamating the vol.
a cyl you take ID sq x length in inches x .7854 divided by 231 will give you gal in cyl.
Then the cone is ID Sq x 1/3 length in inches times .7854 divided by 231 wlil give the gal in the cone and add the two together.
–ie-- look at sweat mark the liquid has made on the outside and get tape measure out and you can figure how many gal you have.
This is essentially how I fill kegs at the brewery. The main difference is it is through sanke fittings and the beer is carbonated so I am looking for foam coming out. It is also chilled, so I can feel the side of the keg and feel the liquid level.
I have done it with a scale as well, but don’t prefer that method.
By the way, I have a thing similar to the keg gauge you saw, it is for propane tanks. It works the same way and would work on a keg, although the magnet probably won’t stick. Even if it did though, I think they are too annoying to use and would not buy another one. http://www.amazon.com/GrillPro-00030-Magnetic-Level-Indicator/dp/B000FHZ33C/