Keg beer

In the dispense of keg beer, the relationship between gas content, temperature and pressure is very important. If for example a beer at 10 C (50°F) has to have a carbon dioxide content of 2 voL, the equilibrium pressure is 0 7 bar over-pressure (or 10 5 psig). Were the temperature to fall to 4 4 C (40°F) and the pressure maintained, the content would rise to 2 4 vol. so that the beer may be difiScult to dispense. On the other hand if the temperature rose to 15 5 C (60°F), the gas content would fall to 1 65 vol. at the dispense tap and the beer would foam uncontrollably. Fobbing of this kind is usually a result of having an incorrect balance of temperature, pressure and carbon dioxide content. However, compensation has to be made when gas pressure has to force beer along long runs of dispense pipe or up a vertical pipe. Thus for every horizontal metre an additional 0 011 bar is required and for each vertical metre, an extra 0 108 bar. If, however, the pressure required to take the beer to the dispense tap is, because of height or distance, in excess of the equilibrium pressure then a pump must be installed. 

Microaerophilic strains of acetic acid bacteria may develop in some instances during fermentation. More commonly, however, they multiply during racking, and subsequently the most striking growth is when air is allowed to accumulate above the beer, for instance when casks stand partly-emptied for some time. Infection may occur in keg beers if the keg or its component spear is not sterilized effectively. Contamination of cask and keg beer may also be caused by lactic acid bacteria and by Zymomonas mobilis. The possible results as already mentioned include turbidity, acidity, off-flavours, and ropiness. 

To prevent contact with oxygen, the beer in the pressure tanks is exposed only to a carbon dioxide atmosphere. The pressure must be higher than the saturation pressure for carbon dioxide. Infection in the brewery is prevented by daily cleaning and disinfection of all equipment in contact with the beer. In the past, almost all the beer left the brewery in kegs, but today most beer is bottled or caimed. The ratio is different from country to country. The growing share of beer in bottles or cans has provided a great need for filling machines with capacities of up to 100,000 bottles or cans per hour. 

The process of fermentation gives off heat, and the tanks may need to be cooled with chilled water coils, with jackets, or by cooling the cellar in which the tanks are located. When fermentation is complete, many beers are now pasteurized, in the same manner as milk (see Section 17.1). The beer is then cooled to just above freezing, filtered and left to age . Before final bottling, kegging or canning it will undergo a fine filtration to improve the clarity. 

The self cooling beer keg is based on the principle of closed sorption systems shown in chapter Y2 Figure 8. Figure 244 shows the beer keg from the outside and the inside. 

During the adsorption—the discharging—cold is produced in the evaporator. In the beer keg the evaporator is located in the lower part of the keg and is in contact with the beer. As soon as the valve is opened the water in the evaporator will evaporate and starts getting cold. The heat of evaporation will be extracted from the beer and by this process the beer will be cooled. Figure 2 shows the falling temperature of the beer down to 8 °C. The process can be stopped and restarted by closing and opening the valve. 

Looking at the beer keg sorption system as an indirect heat storage, the system would look like Figure 246. The first part of Figure 3 shows the charging... 

The lower part of Figure 246 shows the discharging process, where the heat for evaporation is taken from the beer and the heat of adsorption is released through the surface of the keg. 

Figure 245. Temperature during the adsorption/discharging of the self cooling beer keg...

Figure 246. Self-cooling beer keg as an indirect heat storage...

Samantha was in her freshman year of high school and had decided to throw a party at her house while her parents were out of town for the weekend. Samantha invited everyone, including upperclassmen, to her house on Saturday night. Some of the upperclassmen brought a keg of beer, and everyone was drinking and dancing. 

The kegging operation is concerned with filling carbonated pasteurized beer into sterile aluminium or stainless steel containers. In British practice. 

Some breweries deliver pasteurized beer, similar to that dispensed into kegs, in tanker wagons directly to the point of sale. The beer is pumped through a hose from the wagon into cellar tanks in the inn cellar. Such cellar tanks (usually about 8 hi or 5 brl) may be aluminium or stainless steel and may be equipped with cleaning-in-place facilities and also with means of maintaining constant pressure. Other cellar tanks of similar size are of mild steel construction and the beer is filled into a disposable plastic bag which acts as a liner to the tank. In such tanks, the beer may be emptied from the bag by applying gas pressure (usually air) within the top of the tank upon the plastic bag. It is not normal to use tank beer systems unless the beer within the tank is likely to be held for 4 days or less. 

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