To minimize possibilities of clogging and damage in the fuel system, the fuel should be filtered very well. Bad filtration results in problems like increase in fuel consumption, decrease in the engine performance, malfunctions in the operation of engine and reduction in the lifetime of engine. Fuel filters ensure cleaning of fuel from solid particles which are very dangerous for fuel systems and the engine.
Injection motors, fuel pumps, carburetors are very sensitive to foreign particles in fuel. In one liter of fuel, there can be foreign particles of upto 1 mm at most. The filters mounted on the fuel system of automobiles should be in such a way to increase the efficiency of the engine and to prolong the lifetime of parts of the motor. The fuel filter not only prevents solid particles from getting into the system, it also stops water, paraffin and organic material residues (bacteria living in water mixed with fuel), too.
The efficiency of a fuel filter depends on the quality of the fuel used and the general condition (abrasion) of the engine. Fuel filters in carburetor engines can clean the particle upto 8 micrometers with an efficiency of 99%. In injection motors, this ratio decrease uptı diameters of 2-3 mictometers.
The pore size of the paper used in fuel filters is smaller than that of other filters. The reason for this is higher fuel viscosity and need of very good filtration of the fuel. If the pore size of the paper is larger than required, very small grained foreign particles will not ve filtered and this will cause clogging in the fuel system or some other damages.
The filtration element should have the filtration area sufficient to answer the need of the motor. This is ensured by considering the motor specific values during the design of filter element. Depending on the motor it is used, again in some fuel filters, there is a drain plug for the mounting of dirtiness sensor and water drainage. In fuel filters, by-pass systems and return systems are not used because they are not needed.
Substantial cleaning of the fuel and prolonging the filter lifetime can be achieved by means of multi-stage filters. In fuel systems, as the whole fuel going to the cylinders passes through the filters, it is cleaned. Oil coming from the fuel tank of the motor passes through at least one filter and sometimes, the number of filters can increase to three.
The fuel in the refinery gets dirty during fuelling, fuel dumping and transport. In order to increase the efficiency of the motor and to ensure operation at desired power, filtration of fuel is very important. In cases where the filter is not replaced for a long time, the fuel will not be strained enough and sufficient amount of fuel will not enter the motor. This is the main reason of pinking in the motor.
Filters are divided to the following subgroups:
Auxiliary filters: These filters are generally like a screen. Their function is separating large and solid particles, mixed dirt, organic waste and water from the fuel.
Prefilters: The portion of filtration is specially developed and made of unwoven material (tissue), they ensure cleaning of medium scale solid particles.
Water separators: They can be separate elements of fuel systems or can be placed in filter. Separation of water from the fuel is made by chemical reaction of sedimentation.
Auxiliary filters: Their volumes are generally larger and their surfaces are made of paper. They guarantee a more effective filtration.
Fuel filters are divived into three groups according to their structure and cleaning method:
Linear filters: They are used in carburetor and injection cars. Outer coating is metal and inner filtration part is composed of paper pleats. The outer part of some others can be made of plastic. The characteristic of this type of filters is very large filtration surface and these are especially used in gasoline engines. In modern diesel engines, filters whose filtration parts are made of paper pleats resistant to high pressure are used. As their surface is much larger they ensure more effective filtration and even after long time of use, they keep their absorbtion capability.
Dismountable filters: They are mostly used in construction equipment. When the period of use is ended, the outer (metal) part is kept and the inner part can be replaced. The advantage of this kind filters is that they are quite cheap and easy to replace. But it should be remembered that during these replacements, there is risk of entering of dirt to the fuel system.
Filters that can be mounted by rotation: Their structure is similar to oil filters but these filters are fixed with spirals to minimize the mounting time. Used filters can be dismounted and new ones can immediately be mounted. This type of filters generally have a water separation camera, too.
Fuel filters are divided into three according to the place they are used:
Gasoline Filter: In this type of filters wire or paper filters are used. The wire filter is mounted on gasoline tank, gasoline pump and gasoline inlet of the carburetor. The paper filter is placed between gasoline pump and the carburetor. This kind of filters are used in gasoline injection systems, too.
Diesel fuel Filters: In diesel motors, cartridge type filters are used generally. In production of these filters; cotton yarn, low twisted cotton yarn, accordion shape pleated paper, cellulose disks, bags woven with wool yarn and dense knit filter bags are used. In order to clean the diesel fuel, a very good filter is placed to the inlet of the high pressure pump, first. Also it might be necessary to place filters between the tank and the machine or between the transmission pump and high pressure pump or in both positions.
Gas (LPG) Filter: It is a fuel filter started to be used with the increase of LPG vehicles in recent years.
We can divide filters into following subgroups according to elements used inside them:
Metal element filters
Paper fiber filters
Felt fiber filters
Drum type filters
Cloth fiber filters
Clay fiber filters
Cotton fiber filters
Filter Maintenance:
Suitable maintenance of filters in good time decreases the malfunctions of parts in the fuel system and ensures their long life. For all maintenance process, instructions of the machine producer firm should be followed. Cleanin process is made from the flug at the bottom of the filter vessel with desired periods. Filter element or elements are cleaned, replaced. Because of the excessive water in the system, in some cases nonmetal filter element swells and the filter does not let appropriate amount of oil pass, the motor thrust decreases. When this situation is realized, the element should be immediately replaced.
Source: AFM Filtration, manufacturers of Atom brand of filters
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