BUYER’S GUIDE FOR INDUSTRIAL PLEATED CARTRIDGE FILTERS

Cartridge filters are available in a variety of media types, each tailored with specific characteristics to trap distinct types of dust particles.

• Cellulose: A conventional filter medium, cellulose is economical and suitable for numerous standard tasks. These cartridges typically have a MERV rating of 10-12 (see below). However, they might not be the top choice in terms of efficiency or durability, especially for intense industrial uses.
• Cellulose-Polyester Blend: Combining cellulose with synthetic fibers boosts the filter’s resilience, structure and strength. These filters often offer enhanced filtration efficiency (higher MERV ratings) and better performance for small particulates.
• Spunbond Polyester: Renowned for its durability, this filter medium stands up well against various challenges, including certain chemicals, elevated humidity, and higher temperatures. Additional coatings can further amplify its efficacy. Some spunbond polyester filters are also washable for a limited number of times under some usage scenarios.
• Nanofiber: Constructed from exceedingly fine fibers, nanofiber filter media is generally a slender layer atop a foundational material, such as a cellulose polyester blend or 100% polyester. While the nanofiber stratum ensures efficient small particle capture, the foundational layer offers the necessary structural integrity. Nanofiber is a great choice when high filtration efficiency is needed, especially for submicron particles.

In addition to the base filter medium, cartridge filters may come with various coatings or other special properties. Here are some specialty cartridge filter coatings and features to look for. 

• PTFE-Coated: PTFE (Polytetrafluoroethylene) is a type of plastic that can be formed into a thin membrane with very small pores. PTFE-coated filters provide high filtration efficiency and excellent moisture and chemical resistance. They also improve the filter’s ability to shed dust (including moist or sticky dust), which extends filter life. PTFE-coated filters may be recommended for moist, oily, sticky particulate. 
• Oleophobic media: Used for moist or oily dust, oleophobic filters are treated with special coatings or chemicals designed to repel oil and other hydrophobic substances, such as a fluoropolymer, silicone or nanoscale coating. These treatments allow the filter to repel oil and shed oily particulate more easily. Note: Oleophobic cartridge filters are used in applications when particulate is mixed with a small amount of oil; an oil mist collector must be used for applications producing significant mist from metalworking fluids (MWFs) or lubricants. 
• Anti-Static Filters: These filters are designed to reduce the buildup of static electricity, which can be a concern in applications involving combustible dust. They typically feature a special coating or are made from conductive fibers. For example, cellulose filters may be carbon impregnated, while spunbond polyester may be carbonized or aluminized.
• Flame retardant: Flame-retardant cartridge filters are usually impregnated with a chemical that inhibits the combustion process to slow the spread of a fire within the dust collector filter chamber. They may be recommended when working with combustible or flammable particulate or in environments where there is a high risk of a spark entering the filter chamber. (Note: filters are fire retardant, not fireproof.)

Filtration efficiency refers to a filter’s ability to capture and retain particles from the air passing through it. It represents the proportion of particles (of a particular size) that the filter can remove from the air. The higher the filtration efficiency, the better the filter is at capturing smaller particles. Dust collector cartridge filters are usually rated using the MERV (Minimum Efficiency Reporting Value) rating system, which classifies filters based on their ability to capture particles in different size bands (3 to 10 microns, 1 to 3 microns, and 0.3 to 1 microns). The higher the MERV rating, the better the filter is at capturing smaller particulate. 

Industrial cartridge air filters are usually rated between MERV 11 and MERV 15, with some as high as MERV 16. The recommended MERV rating for industrial air filtration depends on the particle size distribution (large, coarse particles vs. submicron particles) and air quality requirements for the application. 

• MERV ratings of 11-12 are suitable for larger particle sizes and less toxic applications (e.g., woodworking, manual metal grinding or cutting, abrasive blasting, non-toxic powder & bulk applications). 
• For submicron particles produced by thermal processes like welding, a cartridge filter with a MERV rating of 15 or higher is usually recommended.
• Note that as a dust cake builds on the filter media, all cartridge filters will approach a filtration efficiency of MERV 16. However, when filtering fine and potentially hazardous particulate, it is important to choose a filter that will provide an appropriate level of filtration across the entire filter life. 
• Applications with very fine submicron particulate, fumes or vapors and/or highly toxic materials may require a HEPA or activated carbon after filter. 

When choosing a MERV rating for an industrial cartridge filter, always consider the specific dust challenges of your environment. Additionally, while a higher MERV rating means better filtration efficiency, it can also result in increased airflow resistance, which can impact energy consumption and filter lifespan. Therefore, it’s essential to balance efficiency with operational costs and filter performance.

The end cap for a cartridge filter helps to ensure cartridge integrity and shape. The end cap generally has a gasket, which provides a seal within the collector, preventing any bypass of unfiltered air. The top cap may be circular, oval or another shape. Some cartridge dust collector filters also have a flange. When purchasing aftermarket replacement cartridge filters, you will need to get the exact dimensions of the flange if one is present. 

It is important to choose the right end cap configuration for your cartridge dust collector. Common configurations include: 

• Open/Open (OO) End Caps: Both ends of the cartridge filter are open. This configuration allows air to flow through both ends.
• Open/Closed (OC or CO) End Caps: One end of the cartridge filter is open, allowing airflow, while the other end is closed, typically with a solid metal or plastic cap. It is common in many dust collector systems where air enters from one end of the cartridge and exits out the other.
• Open/Threaded (OT) End Caps: One end of the cartridge filter is open, and the other end is threaded. The threaded end allows the filter to be screwed into or onto a fixture.
• Conical: The conical cartridge filter usually tapers from a larger diameter at one end to a smaller diameter at the other.