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Types of Filters

9/9/2013 8:23:02 AM | by The Green Book


The definition of a filter is a porous device that allows small liquid or gas particles to pass through it, but traps the larger solid particles. There are many different kinds of filters for different uses in various industries, such as electronics, computing, chemistry and photography. This article shall focus on the types of filters that are meant to separate mixtures. Some of these include air, oil, water and paper filters.


Air Filters


An air filter is a device which is made up of fibrous materials. These materials remove dust, pollen or solid particles from the air. A chemical air filter is specifically designed to remove airborne molecular contaminants from the air as it consists of an absorbent. Air filters also make use of foam, fiberglass or pleated paper to filter the air.


The application of air filters is usually in places where the quality of air has to be good, for example in hospitals or office buildings. Air-conditioners are pre-fitted with air filters to ensure the quality of air is not compromised. Air filters made of stiff filter paper are also used in internal combustion engines to keep particles from entering the cylinders of the engine, because the abrasiveness of the particles might damage the engine through wear and tear.


Using air ionizers is another method of air filtration as it makes use of static electric charge that is applied to fibers or elements that attract the dust particles.


Oil Filters


The function of an oil filter is to remove impurities from engine, transmission or lubricating oil. The engines of motor vehicles, light air planes and naval vessels make use of these filters in order to attain good quality oil for combustion. Just like the air filter mentioned above, the filter filters the oil to keep particles out of the cylinders of the engine. The particles might also reduce the efficiency of the engine because the presence of the particles lowers the efficiency of the way the particles are burnt.


They can be used in various types of hydraulic machinery. An example of a type of oil filter would be the mechanical oil filter. These designs make use of a large quantity of material such as cotton waste or filter paper that entraps the impurities and filtering the oil. However, as the sediments build up on the filter, it requires frequent cleaning so that oil can flow smoothly.


Oil can also be filtered in a variety of other methods. Using magnetism to remove magnetic particles has been employed in automatic transmissions in some vehicles. Sedimentation is where gravity will cause the particles denser than oil to settle at the bottom of it. Using centrifugal force is also another method.


Water Filters


Water filters serve the same purpose as any other filter which is removing impurities. They do this by using a physical barrier or a chemical process. Water filtration is one of the most important forms of filtration to humans as without it; we would not get clean water to drink. The way and level of the filtering differs. Some processes remove harmful particles, bacteria and other impurities, while other remove those as well as certain minerals. In large water treatment plants, the water can go through a variety of processes, not just including filtration but also treatment, such as having fluorine added and being passed through ultraviolet light in order to kill bacteria. People at home can also purchase their own water filters to further filter their tap water. There are also portable water filters.


There are other purposes that water can be filtered for, such as irrigations, swimming pools or aquariums. Some examples of water filters are screen filters, disk filters or sand filters.


Filter Paper


Filter paper is semi-permeable and it allows small fluid particles to be separated from larger solid particles. The types of filter paper there are usually depend on its application. Filter paper is used to filter things in two ways – surface and volume. In surface filtration, the particles are trapped on the surface of the filter paper. In volume filtration, the particles are caught in between the filter paper(s).


Filter paper has a large majority of everyday uses, such as coffee filters, tea bags, oil filters. Filter papers are also used in the laboratory, usually along with a filter funnel.

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