Material separation does not occur in the same way in every filtration system. Membrane filtration systems use media to trap contaminants as they pass through the filter. When foams or other material are used, similar techniques are used. Other filtration options use centrifugal force, gravity and even biological agents or electrically charged particles. Hydrostatic or rotational pressure can be employed in a filter to remove heavier particles.
Chemical filters dissolve contaminants by pulling them out of the solution as it flows through the filter. A biological filter can be used to remove organic compounds, but this function is less common.
Two different types of filtration systems use an electrical charge to cleanse air or fluid. The first type, an electrodialysis system (ED), has membranes that allow either negatively charged or positively charged ions to flow through, but not both. The second type, an electrolysis reversal system (EDR), works in a similar way. However, an EDR periodically reverses the current in order to generate a fresh flow.
Other less common types of filters are reverse osmosis (RO), ultrafication (UF), and electrodeionization (EDI). Although these are all less common than ED or EDR systems, they are just as efficient and come with their own distinct advantages.
In complex industrial systems, the filters mentioned above are often used together to maximize the purifying power of the system. By using multiple filters in a flow, particles can be separated and removed several times over. Not only will this improve the quality of the product, but it allows the filters to function with more efficiency since they are not being regularly clogged with large particles.
In industries where solid recovery is a priority, progression filtration is used because it helps to sort contamination based on their size. The particle size and type of slurry are both important when considering what type of filtration system should be used for a given application.
Aluminum, plastic, steel, stainless steel, carbon, Teflon, resin, nylon, sand, and synthetic fibers are all commonly used to manufacture filters. Material choices affect variables like filter location, filter rate, load capacity, absorption, and so on.
The filtration rate is the rate at which a stream can move through a filter as it provides maximum particle separation/removal. A filter may be placed at the intake, inline, or exhaust of a system. Sometimes they are incorporated at all of these points.
The goal of a filtration system is to cause the air or fluid being processed to be as pure as possible. Sometimes the idea is to suspend solids or clarify air. Most industrial operations and machinery require filtration systems to keep their performance clean and consistent. Gasoline, oil, diesel, hydraulic fluid, water, exhaust air, and more all require filters to process them and keep the flow up to industry-specific standards or regulations.
The ISO’s Technical Committee 131 maintains regulations as they pertain to filtration. Regulations aside, filters play a critical role in health and safety in commercial, residential and industrial settings.