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Vent & Process Gas Filters Protect Product Quality

In addition to filtering liquids during chemical processing, tank vent filters are used to protect liquid raw ingredients, intermediate solutions and finished products from airborne contaminants while they are stored in tanks. Process gas filters are used to remove potential contaminants from bulk gases used during the manufacturing and formulation & filling processes. More information is presented below on vent and process gas filters, or you can go to the product selection table at the bottom of this page to explore specific filter options.

Tank Vent Filters

Controlling the contamination of ingredients, intermediate products, water and the final product while they are in a tank is critical to the quality of finished products from bulk chemicals to ink jet ink. Adding a liquid to a tank forces air out, just as emptying a tank draws outside air into it. Since the air around tanks is full of dust, airborne bacteria, mold spores and other contaminants, filters (housings marked 4) are used to prevent those contaminants from reaching the contents of the tanks. Consideration should be given to the temperatures that the vent filter will be exposed to. Long durations at elevated temperatures or repeated steaming may accelerate oxidation of many filter materials.

Sizing a Vent Filter System
In many systems, the tanks used are sealed. That makes sizing a vent filter system critical. A filter system that overly restricts the flow of air in and out of a tank may result in the tank being over-pressurized (possible seal damage) or a vacuum being created in the tank (potential tank collapse). Critical Process Filtration has years of experience sizing filter systems and can help you design your system to avoid such issues. Click here to try our filter system sizing calculator for guidance on the number of filters required for your system.

Filtering Process Gases
Gases may be used during production to prevent product contact with normal atmosphere. Normal air may be replaced in tanks and/or containers with inert process gases – possibly nitrogen, argon or carbon dioxide. Tanks are filled with the gas as liquid is removed and the gas is allowed to escape when the tanks are filled. During final packaging, as containers are filled, a process gas ‘blanket’ may be injected into the container to displace air before container closure. These process gases are usually filtered (housings marked 4 in the figures below) to prevent potential contaminants from entering the production system. If a gas is used as a raw ingredient in chemical production, then it could be filtered for particle removal in the same way as liquid ingredients.

Common Filtration Steps in Chemical Processing
Particle Filtration in Reprocessing
Common Filtration Steps in Ink Jet Ink Formulation

Choosing the Right Filters

The level of filtration required is different with each process. Larger particles (larger than 1 micron) are most often removed using depth filter media. Smaller particles (smaller than 1 micron) or airborne bacteria (as small as 0.2 microns) will often require more complex membrane filters.

Pleated media filters are most often used for tank vent filtration. Their relatively low pressure drop allows the use of fewer filter elements than required for standard depth filters. Pleated depth media filters, made using polypropylene or fiberglass, have the advantage of a large surface area that can hold a higher quantity of particles, but are not usually used to remove very small particle or airborne bacteria.

In pleated membrane filters, hydrophobic materials are used to prevent wetting of the membrane by water droplets. If the membrane becomes wet, then the air flow is reduced and pressure drop goes up, dramatically increasing the risk of tank overpressure or vacuum. Hydrophobic media include hydrophobic polyvinylidene fluoride (PVDF), polypropylene and polytetrafluoroethylene (PTFE).

Our filter media are available in multiple filter formats for all gas and air flow ranges. Disc filters support small scale flows in test and research laboratories. Small capsule filters are available for low flow applications such as bench scale systems or small product development systems. Our large disposable capsule filters and cartridge filters are used for larger flow applications ranging from pilot production to full scale operations.

Custom systems are designed for new applications and to solve challenges in existing processes. Critical Process Filtration will work with you to design, build and install a cost-effective system that delivers the results you need. Contact us or visit our custom filtration systems page for more information.

The table below shows the filter media in cartridge, capsule and disc filter configurations. We also have housings for filter cartridges. Click on the PDF Files in the appropriate location to download a data sheet for the filter media and configuration that fits your needs.

Media Code
Filter Media
Filter Grade
Cartridge Data Sheet
Capsule Data Sheet
Disc Filter Data Sheet
Pore Sizes Avail. (µm)
Pleated Polypropylene Depth Media
0.1, 0.22, 0.45, 0.65, 1.0, 3.0, 5.0, 10, 20, 30,40, 60, 100
100% polypropylene construction for high purity.
Pleated Fiberglass Depth Media
0.22, 0.30, 0.45, 0.65, 1.0, 2.0, 3.0, 5.0, 10, 20, 30
High capacity filters for clarification and prefiltration applications.
Hydrophobic Polyvinylidene fluoride Membrane
High capacity hydrophobic membrane for economical bacteria control in vent filtration
Polypropylene Membrane
0.10, 0.22
Hydrophobic membrane for process gasses. Excellent material compatibility.
PTFE Membrane
0.1, 0.22, 0.45, 1.0
Highly hydrophobic with superior air flow rates for vent filtration