There is an old Turkish saying that roughly translates: If the mountain won't come to you, you must go to the mountain. That’s the challenge many microbreweries face in their tasting rooms: the kegs are in one place and the taps are in another…often a far away place.
There are two keys to optimizing your long draw lines for the perfect pour.
As most brewers know, at any temperature, a specific pressure must be applied to a keg to maintain desired carbonation levels. If the temperature or pressure varies, carbonation levels in the beer will change which can adversely affect the characteristics of the beer.
Long-draw lines can pose specific challenges in maintaining the optimal carbonation levels. Beer pump setups require two operational pressures: pressure on the keg or tank to maintain beer carbonation and a separate pressure to pump the beer to the tap.
Designing Long Draw Systems for Resistance
Resistance is determined by all of the components in a beer delivery system. Couplers and faucets have specified resistance values and beer lines provide a certain resistance for each foot the beer must travel. The diameter and type of beer line, whether it is vinyl, barrier tubing or steel, will affect resistance. For instance, if you are using 3/16 inch vinyl tubing you will have resistance of 3 pounds per foot at a volume of 1/16 oz. per foot. You will want to get the values for your particular equipment from your manufacturer.
While any draught system can be designed to operate under a range of applied pressure values, it can get more complicated for long draw lines. Consider the impact on resistance for a line that needs to climb two floors. Even with low resistance components, the applied pressures required will often exceed levels needed to maintain desired beer carbonation levels.
Mixed Gas for Long Draw Lines
To push beer across the distances found in long draw systems usually calls for gas pressures well above the levels needed to maintain beer carbonation levels. Most long draw systems employ a special blend of nitrogen (N2) and carbon dioxide (C02) to prevent over carbonation of the beer while insuring that the beer is delivered in its purest form to the tap.
Nitrogen Gas (N2) is blended with C02 to aid in dispensing beer in systems requiring delivery pressures above CO2 equilibrium. As an inert gas, N2 is not easily absorbed by beer so it does not degrade the flavor of the beer. The exact blend needed can depend on the system parameters and operating pressure. The optimal blend can be purchased in a pre-mixed blend or mixed onsite from separate nitrogen and carbon dioxide sources.
While using carbon dioxide (C02) alone in your beer pumps will create over carbonated, foamy beer, using the wrong combination of CO2 and nitrogen (N2) on ales and lagers can make them flat. The key to the perfect pour is a precise blend of carbon dioxide and nitrogen gas that is delivered at the optimal pressure. Ideally, a pint of beer will consist of 13.5 ounces of beer with a ¾ inch/ o.5 ounce head of foam.
Getting your brew to the tap, no matter how far, does not need to compromise beer quality. With the right piping design and gas mixture, microbrewery owners will reduce waste and insure that customers get a better-looking and better tasting pint.