Tank Venting and Gas Filtration

Air is one of the main potential sources of contamination in your production environment. If the air used during your process is contaminated, it will be a threat for your product quality and potentially reduce its shelf life.

Millipore offers a range of vent filters that will help you to ensure the protection of your beverage production while meeting your tough regulatory requirements.
Due to their robust design and the ability to withstand multiple steam cycles, our vent filters have a long service life, thus improving your process economics.

Tank venting

Air flows in and out of a process tank for two reasons. The first is to replace a volume of liquid as it is pumped in or out of the tank. The second reason air will flow into a process tank is to compensate for the volume change associated with steam condensation.

The goal of the tank vent filter is to maintain near ambient pressure in the tank while ensuring sterility in the tank and consequently protect your beverage. Hydrophobic sterilizing-grade filters are commonly used as air vents on processing tanks to remove microorganisms.

Filter requirements

• Sterilizing-grade PTFE membrane
• Integrity testable and bacteria retentive
• Robust construction validated for multiple SIP cycles
• Delivers high flow rates
• 100% integrity tested to ensure quality

Sizing your tank filter

Case 1: Air used to replace a volume of liquid

Sizing the tank vent filter for pump-out or fill rate is relatively simple. The air flow rate will be equal to the pump-out or fill rate. With flow rate and pressure determined, a flow/ΔP curve can be used to determine sizing.

Case 2: Air used to compensate for the volume change due to steam condensation

At the end of a tank steam-in-place procedure, steam in the tank will cool and undergo a phase change to liquid water. There is over 1,000X difference in volume between an amount of water in gas phase vs. liquid phase. During cooling, sterilized ambient air must be allowed into the tank to prevent vacuum. Sizing the vent filter for steam collapse requires knowing the vacuum rating of the tank and its volume. These can be calculated based on the tank dimensions including height, diameter and wall thickness. Millipore has developed a computer program to facilitate these calculations.

Improper tank vent sizing can result in low pump-out rates, loss of sterility due to rupture disk or filter failure, or worst case, tank implosion. Fortunately, proper sizing is not difficult as long as the flow requirements and driving force are understood. To ensure your sizing, we recommend you to contact your local Applications Specialist or Technical Service for advice.

Gas filtration

The air used to blow the bottles as well as the CO₂ or any other gases injected in certain process steps must be free of microorganisms.

Where to use a gas filter

CO₂ injected

Carbonation is the step of adding carbon dioxide to a drink. The CO₂ you inject in your beverage must be free of particles and microorganisms. Carbonation step is present in the processing of sparkling water and sparkling soft drinks.

Carbon Dioxide Adjustment is specific to beer processing. It is not just the addition of carbon dioxide; it is more adjusting the level of carbon dioxide as gas is already present in beer due to the fermentation process and yeast propagation.

Bottle Blower

Sterile filtration of Air/Nitrogen ensures the microbiological quality of the air used in the bottle blower to turn the pre-forms into the final PET bottle. Bottle blowing is done in any process using PET bottles.

Bottle Filler

You can also use gas filtration during the filling process of carbonated drinks. In order to make the filling possible the filler bowl has to be pressurized and it is essential that the gas used here is microbiologically stable.

Sizing your gas filter

In most gas systems the gas is dry and oil free. Therefore, the filtration system is simply sized according to flow rate. The maximum allowable differential pressure is used to size a final filtration system. Gas face velocity in the pipe should be between 15-30m/s for acceptable noise level.

Fermentation or higher pressure gas filtration is sized using the Ideal Gas Law and the flow rate versus pressure drop curves for hydrophobic cartridges. Gas inlet pressure, temperature, flow rate, and pressure drop information are required to size a filtration system economically. Typical gas systems are sized at 85 Nm3 /h (50 SCFM) per 10 in. cartridge and an initial differential pressure of 0.07 – 0.15 bar (1 – 2 psi).

Gas Filtration Selection Guide

• Beer production
• Bottled water processing
• Soft drink processing
• Wine processing

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