Using Sanke Kegs For Homebrew?
TroubleShooting
Robert Pritchard — Bridgewater, New Jersey asks,
I am trying to determine if I should be using a Sanke keg instead of a regular pin-lock keg for a beer gas mixture (75% nitrogen / 25% carbon dioxide) that I am pushing at about 50 PSI. Although I have not checked every weak point in my system, I have replaced all the O-rings, bought a new lid, and have a new gas line. But I do have a gas leak somewhere. Are Sanke kegs inherently more reliable when it comes to leaking gas?
One feature of reliable designs is the minimization of the number of parts that may fail and result in a problem with the device in question. The Sanke keg valve (from “sanitary key”) assembly has two elastomeric parts that are on the keg side of the system, and the Sanke coupler/tap that connects to the keg has five elastomeric parts (combination of O-rings and special seals).
The Cornelius-type (Corny) keg used by so many homebrewers has a total of eight O-rings on the keg side of the system and two O-rings on the coupler side. Yes, Corny kegs have more elastomeric parts than Sanke kegs, but two versus eight is a manageable difference, especially since the most important O-rings on a Corny keg are visible and easy to inspect. However, Corny kegs have a removable lid that is sealed to the opening in the keg by an O-ring, and this seal can be compromised if the lid or the shape of the sealing surface of the keg become damaged. My view on these designs is that they are both robust when viewed from a gas leak perspective.
Sanke kegs are designed to be cleaned without disassembly and require special cleaning equipment for this type of service. Some Sanke kegs do have threaded, removable spears that make disassembly and cleaning easier than the more common design of spear that is secured to the keg with a special split ring. Sanke spears must never be removed when a keg contains pressure because the spear can be shot out of a pressurized keg, resulting in severe bodily injury or death. The Sanke design is terrific for breweries with the correct cleaning systems, service tools, and training required to properly clean and maintain these kegs. However, very few homebreweries are equipped to clean Sanke kegs without disassembly; for this important reason, homebrewers are really best served, no pun intended, by Corny kegs.
Also remember that the opening on the top of Corny kegs can become bent, so you should inspect the uniformity of the lip.
OK, now onto the fun part of your question; leak testing! Keg leaks are fairly easy to identify in a binary manner because a leaky keg will eventually lose all of its pressure. Leak rates are very difficult to measure unless you conduct your test in a temperature-controlled environment where any change in pressure is due to gas loss, versus temperature change. Once you check the keg, you can begin expanding the size of the system to help identify what part of the system is leaking. Connections are the most common sources of leaks. And don’t forget to test your gas regulator assembly for leaks around all the threaded ports and connections to the regulator using soapy water or you could try submerging the regulator in a water bath to spot leaks. Also remember that the opening on the top of Corny kegs can become bent, so you should inspect the uniformity of the lip.
Replacing gas and beer lines is definitely a good start. You should also check the size of the hose barbs in your system to verify that all hose and barb connections are properly coupled. And then you want to ensure you have a secure fit. The clamp of choice among draft techs are so-called stepless, ear-type clamps. This clamp type was invented by Hans Oetiker in 1979 and named the StepLess® ear clamp. Trivia time! Oetiker founded his company in 1942, developed the first ear clamp in 1951, and his name is associated with his clever and reliable inventions. There are many other clamps based on Oetiker’s design used in a variety of industries.
The StepLess® design evenly reduces the clamp diameter when tightened with a crimping tool, while creating no sharp protrusions that can cut the tubing wall. The major downside of the design is that the clamp is not designed to be used more than one time; once an ear clamp is connected it must be destroyed to remove. Although the clamps are not expensive, they are a bear to remove. I am an optimist and view this as a good thing as it encourages the use of proper connections, like stainless steel, flared fittings with free-spinning nuts, in areas where tubes need to be attached and removed.
For what it’s worth, 50 psig (gauge pressure) is a much higher dispense pressure than the 35 psig of 70% N2 /30% CO2 suggested by Guinness for their quintessential nitro stout. Find those leaks and enjoy a nice pint of your nitro brew!
