Unique New Membrane Process allowing draught carbonation and dispense from Bag in Box

• Pre-set Carbonation; within the range from 3 to 12 gm/l
• Silent, 100% gas-efficient operation
• Normal dispense, best retention of carbonation in the glass

The technology behind the innovation: Hollow fibre membranes

Carbonator modules in draftstream systems use polysulphone hollow fibres with graded porosity culminating in a thin, “defect-free”, outer skin which is hydrophobic and gas-permeable.

Permeation, governed by this outer skin, is uniform over the whole surface – indistinction from the microporous types which give localised high-flux passage of gas via through-holes or slits in the fibre wall. Such differences are key in gas / liquid applications, since liquid must be prevented from entering fibre bores and stopping gas transfer. 

Even under controlled conditions, microporous fibres become less hydrophobic with prolonged use and repeated cleaning. When this happens, liquid can easily seep back through individual pores. Skinned fibres are far less prone to that effect; gas permeates evenly to the whole external surface to dissolve in surrounding liquid. 

At a given temperature, carbonation level is simply proportional to the absolute pressure of CO2 gas applied to the fibres. Each draftstream module contains an axial fibre bundle with a seal separating the liquid-contact region (at outer fibre surfaces) from the gas feed (to one end of the fibre bores – they are sealed at the remote end). 

Twin liquid feed and outlet ports at each end of the liquid region, combined with the selected number of fibres and module dimensions, provide high efficiency gas / liquid transfer helping provide accurate and best retention of carbonation in glass.


While skinned polysulphone fibres have big advantages for carbonation, it has only recently been understood exactly why the stop / start nature of practical beverage dispense makes special demands on the system’s controls in order to maintain long-term reliability and efficiency.

All draftstream systems therefore include a unique control unit (patents pending) which sets carbonation level and dispense rate and also manages the pressures of liquid and gas inside the membrane module –during both dispense and standby periods. These new features automatically keep the carbonator module operating under ideal conditions for its fibres and include an exclusive facility preventing gas breakout from those beverages which are normally prone to foaming in the dispense line.