Draught Equipment and System Configuarations > Essential Draught System Components > Gas Source
Draught systems depend on gas pressure to push beer from the keg to the faucet. To achieve this, kegs should be pressurized with carbon dioxide, or a carbon dioxide and nitrogen mix.
Gas selection and purity affect the freshness and quality of the beer served through the draught system. Remember: The gas you use fills the keg as the beer drains. Thus, off-flavors or impurities in the gas quickly migrate to the beer to spoil its freshness and flavor. Compressed air should never be used to pressurize a keg as the oxygen in the air generates stale flavors in beer within just a few hours. All gas used for beer dispense should meet the specifications of the International Society of Beverage Technologists or the Compressed Gas Association (See Appendix A).
Direct-draw applications use straight CO2 except for the dispensing of “nitro” beers where an appropriate nitrogen/CO2 mix must be used. Nitrogen is available in cylinders or can be generated on site.
Gas used for draught dispense should be “beverage grade.” Retailers may purchase this gas in cylinders that will be delivered by the gas vendor and swapped out when empty. Such cylinders are filled, maintained and inspected by the vendor. High volume users may purchase a bulk gas vessel known as a Dewar that will be filled on location from a bulk gas truck. Bulk tanks can provide CO2 for both soda and beer.
CO2 tanks contain both liquid and gas phases. The tank pressure is dependent on ambient temperature and—regardless of tank fill level—will vary from 600 – 1200 psi until empty. CO2 tanks should never be located inside the refrigerator or walk-in cooler. A gas filter may be installed to help reduce the likelihood that any contaminants in the gas reach the beer.
| No Air Compressors, Please! |
| Systems that use compressed air as a dispense gas expose beer to oxygen, which produces stale paper- or cardboard-like aromas and flavors in the beer. Brewers go to great lengths to keep oxygen out of beer to avoid these undesirable stale characteristics. Air compressors also push contaminants from the outside atmosphere into the keg, increasing the chance of beer-spoiling bacteria and off-flavors. For these reasons, compressed air should never be used in direct contact with beer. |
Note: Breathing high concentrations of CO2 can be deadly! Take care to prevent CO2 buildup in enclosed spaces such as cold boxes. System leaks or beer pumps using CO2 can cause this gas to accumulate in the cooler. To prevent this, beer pumps driven by CO2 must be vented to the atmosphere. CO2 warning alarms are available and recommended for installations with enclosed areas such as cold boxes containing CO2 fittings and gas lines.
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