The choice of cartridge filters depends on the specific application. Cartridge filters are ideal for systems with less than 100 ppm of contaminants (i.e. less than 0.01% by weight of contaminants).
Cartridge filters can be either surface or depth filters: depth filters capture particles and contaminants through the entire thickness of the media, while surface filters (usually made of thin materials such as paper, woven wire, cloth, etc.) hold particles at the filter surface.
Surface filters are the best choice if you are filtering a deposit of particles of similar size. If all particles are 5 microns in size, a 5 micron pleated filter will work best because it has more surface area than other filters. Depth filters have limited surface area compared to pleated surface filters, but their depth advantage is significant.
Generally speaking, the larger the filter area, the greater the flow rate, the longer the filter life, and the greater the dirt holding capacity. Filter cartridges are usually designed for single use: this means that when the filter becomes clogged, the cartridge must be replaced.
Bag filters are often used for industrial dust removal. The airflow can flow from outside the filter to inside (i.e. particle separation occurs on the outer surface of the filter) or from inside to outside, depending on the application. Particles are usually captured on the inner surface of bag filters.
Bag filters are usually designed not to need replacement when clogged, but some bag filters for gas applications (such as dust removal) can be cleaned by mechanical shaking or backwashing with compressed air (so-called reverse flow bag filters).
Bag filters are mostly surface filters. Surface filters are easier to backwash and clean, while depth filters usually need to be discarded after use.
Differences in filtration rate:
Bag filters are usually designed for applications with filtration rates from 1 to 1000 microns.
Cartridge filters have filtration rates from 0.1 to 500 microns.
