A guide to Counter Pressure (Isobaric) Filling

The filling moment

• At this time the bottle is filled by practically only pressurized CO2 at, let’s say, 2.2 to 3.0 bars of pressure.
• Gas has been pumped into the bottle to fill it with CO2 and we have removed harmful oxygen.
• The valve at the top of the filling tank is vented to allow oxygen to escape.
• This also pressurizes the bottle to the filling pressure. The CO2 input is then closed.
• The filling valve is opened, allowing beer to flow into the bottle. Pressure is slowly released by the vent allowing CO2 to escape and beer to flow in and replace CO2 into the bottle. Because the bottle remains pressurized during the fill, foaming is kept to a minimum. When the bottle is filled, the infeed liquid drink valve is closed.
• Remaining pressure is released from the vent and a cap is put on the bottle. For some products a small foaming before capping (for example when bottling beer) is induced by way of a fine warm water spray. This little head of foam displaces any Oxygen that may have settled in the neck of the bottle between filling and capping.
• Once capped bottles are generally washed externally with a fine water spray when exiting the filler to remove any sugary or sticky residue that may have settled on the outside surface of the bottle. If not removed these sediments would soon become dry and sticky and discolor the bottle and the label.
• Because the bottle is filled at this point, only a small amount of foaming occurs as the cap is put on and sealed.

Chilling product to avoid foaming while filling in counter pressure (isobaric)

Any variation of pressure in any carbonated product, while it is being filled in a bottle or other container, will inevitably cause an expansion of any gas contained in it and the creation of foam (bubbles of gas in the product). The warmer the product the more severe the effect of foaming will be.

Some products are more sensitive than others to the creation of foam, in general the higher the level of proteins in a drink, the higher the sensitivity to the creation of foam. Beer is more sensitive than carbonated water, some beers are more sensitive than others, again depending on the level of proteins contained in the beer. This is one of the main reasons why micro brewers have initial difficulties in stabilising the filling conditions of their products when they begin to bottle their products, as artisanal batches of beer often vary in level of proteins from one formulation to the next and from one batch to the next.

Also high sugar content non-alcoholic drinks suffer from the same condition, for example Cola products are notoriously sensitive to the creation of foam due to their high sugar content, and Kvass in Eastern Europe is also a malted rye drink that is high in proteins and subject to foaming easily during filling.

The answer to foaming while filling is two fold:

• Chill the product more if you get foam. Most beers are best filled at 2 C from the storage tanks and reaching 3-4 C in the bottle.
• Stabilize the oscillations of pressure variations between storage tank, carbonator unit (if used to carbonate the product) and the filling machine.
• In order to do that we use two classes of tools either fitting a modulating valve inside the infeed connection of the filler to adjust constantly the pressurized flow of product to the filler (this method is however reserved for the higher end of high speed filling machines as it is expensive) or a pneumatic product feeding pump which ensure a smooth and pressure constant feeding of beer or other foaming product to the filler. This is also a rather expensive solution (typically a pneumatic pump costs up to 7 times a centrifugal screw pump of equivalent capacity) but solves a lot of headaches and allows ease of production to inexperienced operators or beginners of the filling process.
• Adding a non-return valve at the infeed of the filling machine to avoid “waves” of product oscillating back and forward from  the carbonator to the filler.

De-aeration of water prior to producing carbonated soft drinks or water

Not to be confused with the pre-evacuation of air from bottles prior to filling, the de-aeration of water is an essential part of the carbonation process of most water-based drinks.

While beer, wine and cider are all saturated to a lesser or greater degree with CO2 as part of their production process (wine, beer and cider produce alcohol from sugar fermentation and release CO2 carbon dioxide in the air) soft drinks or carbonated water are not saturated with CO2.

Water is normally saturated with air.  If you don’t believe me boil some water for cooking rice or pasta. The bubbles you see coming out is not steam but bubbles of air that expand and escape the water. Try boiling again the same water the next day and there will be no bubbles coming out, you will see just the normal thermals of the hot water. The air is gone forever.

Therefore, if you tried to carbonate water straight away as it comes out of a tap or a spring, you would have a very poor result.

The water in this case is already saturated with air (which is dissolved in it, the colder the liquid the more gas it will accept before becoming saturated) and as you know when a liquid is saturated with a gas, if you put extra gas in it, the gas does not dissolve - it is rejected.

De-Aerator and Carbonator with 1000 litres per hour capacity

So, what happens when you open a bottle of water that has been poorly carbonated without prior de-aeration? You will have a flash of CO2 and then the water will go rapidly flat. Not a great result for your marketing efforts and for your customers!

To remedy this situation any water that is to be carbonated, either on its own or in preparation to mixing it with fruit and other ingredients to produce a soft drink, needs to be treated to first extract the air dissolved in the water before you can carbonate it.

This is done by adding a second column before the carbonating column unit.

This preparation unit is called a DE-AERATOR UNIT and it consists of a column that will extract the air in the water by means of a vacuum pump

The water is showered down from the top inside a perforated stainless-steel tube, housed inside the main column, in a doughnut (tube in tube) configuration and the vacuum pump, positioned at the top of the de-aerator column takes out the air from the water, which is then sucked out of the column by a secondary pump, and sent to the carbonating unit.

Your water is now ready to be mixed with other ingredients and carbonated and chilled to make your favorite soft drink.

Cheers!

Giovanni Solferini

Managing Director, IC Filling Systems

Useful Links:

• Automatic Beer Bottling Machines
• Semi-Automatic Beer Bottling Machines