Tank vent filtration helps protect food and beverage products, ingredients, CIP chemicals and other processing fluids from airborne contamination while maintaining airflow into and out of storage and process tanks. Properly selected tank vent filters help maintain equilibrium pressure during filling, storage, emptying and sterilisation while providing a barrier between tank contents and the surrounding environment.
What does a tank vent filter do?
A tank vent filter supports three important functions:
- Protects tank contents from airborne microorganisms, viruses and physical contaminants that could affect product quality
- Helps protect the surrounding environment from aggressive tank fluids or aerosols escaping from the tank
- Maintains equilibrium pressure to help protect the tank from overpressure or vacuum damage
During filling, air is forced out of the tank as the incoming liquid displaces the air inside. During emptying, surrounding plant air is drawn into the tank to replace the liquid volume. The vent filter must allow this airflow while continuing to provide the required filtration barrier.
A tank vent filter protects product from airborne contamination during filling, storage and emptying while helping protect the surrounding environment from aerosols released from the tank.
Why is tank vent filtration important?
Storage and processing tanks are exposed to the surrounding environment whenever air moves into or out of the tank. Tank vent filtration helps maintain a barrier between tank contents and the surrounding environment while supporting the airflow needed during normal operations.
Tank vent filtration supports:
- Product protection: Helps protect tank contents from airborne microorganisms, viruses and physical contaminants
- Environmental protection: Helps limit the release of aggressive tank fluids or aerosols
- Pressure management: Allows air to move into and out of the tank during liquid transfer
- Tank protection: Helps protect tanks from overpressure or vacuum damage
Where is tank vent filtration used?
Tank vent filtration can be used with storage and processing tanks containing:
- Liquid food and beverage products
- Food and beverage ingredients
- CIP chemicals
- Other food processing fluids
Tank vent filters protect contents during filling, storage and emptying. They are also particularly important in applications involving sterilisation in place with steam.
How do tank vent filters help prevent microbial contamination?
Filters selected for tank vent applications are typically sterile air and gas cartridge filters. The filter should retain airborne microorganisms and viruses, including bacteriophages, while allowing the required volume of air to pass into and out of the tank.
The filter should also be hydrophobic. Exposure to surrounding humidity or steam can wet an unsuitable filter and impede airflow into and out of the tank. It is important that tank vent filters continue to support the required airflow while providing protection from airborne contamination.
How is airflow maintained during tank filling and emptying?
When liquid is pumped into a tank, the incoming volume forces air out. When liquid is removed, surrounding plant air is drawn into the tank to replace that volume.
The tank vent filter must support airflow in both directions without upsetting the equilibrium pressure inside the tank. For these applications, the filter is sized using the higher of the pump fill rate or pump draw-down rate, with an equal airflow rate.
Consider these operating conditions when reviewing a tank vent application:
- Pump fill rate
- Pump draw-down rate
- Required airflow in both directions
- Exposure to humidity or steam
- Tank sterilisation conditions
- Direct or indirect food contact requirements
Why is correct tank vent filter sizing important?
Correct sizing is particularly important for tanks that are sterilised in place with steam. After sterilisation, steam cools and condenses rapidly. This creates an immediate volume change and negative pressure inside the tank.
There is more than a 1,000-times volume difference between water in the steam phase and water in the liquid phase. Air must enter the tank quickly enough to replace the volume lost as the steam condenses. If the vent filter restricts that airflow, the rapid pressure change can put the tank at risk.
Improperly sized tank vent filters can result in:
- Low pump draw-down rates
- Restricted airflow
- Loss of protection following filter collapse or rupture-disc activation
- Tank implosion or deformation in the most serious cases
How do you select the right tank vent filter?
| Selection Consideration | What to review |
|---|---|
| Contamination control | The airborne microorganisms, viruses or physical contaminants that must be retained |
| Filter media | Whether hydrophobic media are required to resist wetting from humidity or steam |
| Airflow demand | The higher of the pump fill rate or pump draw-down rate |
| Flow direction | The need to support airflow both into and out of the tank |
| Sterilisation conditions | Whether the tank undergoes sterilisation in place with steam |
| Food contact | Whether the application involves direct or indirect food contact requirements |
National and international regulations may apply depending on whether the filter is used for direct or indirect food contact.
Which Air Filtration Approach Is Right for Your Application?
Different air and gas filtration solutions support different stages of contamination control in food and beverage processes. Depending on where contamination risks exist in your process, you may need pre-filtration, sterile filtration or both.
Need help selecting a tank vent filtration solution?
Correct filter selection and sizing depend on tank operating conditions, airflow requirements, sterilisation processes and food contact requirements.
Pall has more than 60 years of experience specifying tank vent filtration products for food and beverage applications, including sterile and final air filters.
Get Help Selecting a Tank Vent Filter