Specially designed Parker Maxam coalescing and carbon filters are specified for the Air Separation Systems assembled by Kenilworth-based Airpacks Limited for Messer UK, industrial gas suppliers to industry, in general, and the beer dispense sector, in particular. The Messer dispense gas system includes a specially designed 'separator' which produces nitrogen directly from clean compressed air. The system, installed in more than 12,000 pubs and bars throughout the UK and the Republic of Ireland, provides a mixture of carbon dioxide and nitrogen in a range of ratios to suit different beers.
The mixed gas helps beer retain its head and improves dispense pressures and the speed of dispense over carbon dioxide only systems.
Carbon dioxide is the most obvious choice for use as a dispense gas for keg products, being a natural product of fermentation, and the gas which is in the beer to form the head and give the beer life.
Carbon dioxide can only be held in solution using a top balance pressure of carbon dioxide.
The correct balance pressure required depends on the ambient temperature and the desired level of carbonation of the beer.
If the top pressure is higher than the balance pressure, the beer absorbs additional carbon dioxide and becomes over carbonated.
If the pressure is lower, the beer loses some of its dissolved carbon dioxide and the beer appears flat.
However, the gas pressure required to 'lift' the beer from the cellar to the bar taps means that with 100% carbon dioxide as the top pressure, pressures higher than the balance pressure have to be used.
This then means that beer will absorb the excess carbon dioxide resulting in product variability, dispensing problems and beer wastage.
The addition of nitrogen, an inert gas that is not readily absorbed by beer, provides the correct carbon dioxide partial pressure on the keg (to maintain the desired carbon dioxide content) and yet has the improved motive power for dispense purposes.
Different gas mixes are used for the two main groups of beers: 50/50 or 60/40 for lagers; and 30/70 for ales and stouts.
This enables the high dispense pressure (typically 38 psig) to be used for all products.
The Parker Maxam coalescing and carbon filters specified for the Messer Air Separation System are important elements in the system to ensure that the mixed gas is free of hydrocarbons and smells which could taint the beer.
The coalescing filter element removes particles, both solid and liquid, down to a size of 0.01 micron.
The carbon filter element relies on carbon absorbtion techniques using selected grades of activated carbon to remove vapours.
Filter bodies are manufactured from aluminium and then anodised for increased corrosion protection.
Airpacks assemble the complete system, which also includes a compressor, air filter, the special membrane separator and controls, nitrogen storage and gas mixers or blenders.
The system is fully automatic, generating nitrogen and shutting on or off as gas is used and demanded.
With the widespread use of mixed gas have come more and more products which need it for dispense.
In the same way that stouts have a creamy texture, an excellent lasting head and a good appearance other products ã bitters, lagers, Irish ales, etc, have all come on to the market in the wake of mixed gas usage.
The availability of clean, dry nitrogen in the cellar has other advantages: weekly beer line cleaning; gas pump operation; and the blanketing of cask conditioned beers.