Oil bath air filters contain a steel mesh element that is wetted with oil. When dust-laden air flows through it, the filter traps dust particles with an approximate diameter of 3 – 5 µm. The particles stick to the oil-wetted steel fibers and are flushed back into the filter body by the oil. The filter body is regularly cleaned to remove the dirt, typically once a year. The specific oil type recommended by the combustion engine manufacturer must be used.
Oil bath air filters are characterized by their robustness and long service life. Their maintenance-free design is a major advantage, especially in poorly accessible areas, as no spare parts such as filter elements are required. With regard to its disposal, the oil in the oil bath air filter is subject to the same regulations the engine oil. The size of the filter is based on the intake air flow to the combustion engine. The nominal air resistance (delta p) is approx. 15 – 20 mbar. The resistance decreases under partial load. However, the separation efficiency of the filter also decreases – therefore the oil bath air filter must be correctly designed to ensure optimum performance.
Applications for oil bath air filters
Oil bath air filters were developed around 70 years ago as air filters for internal combustion engines. Today, they are only used as the main filter in robust, air-cooled engines in very hot and cold countries, especially in North Africa and Siberia. They are also used as pre-separators, especially in machines exposed to high dust loads, such as material handling machines and dumpers. Their separation efficiency in accordance with ISO 5011 is typically about 99% (SAE coarse).
When used as the main filter, an oil bath air filter functions like a standard air filter. Oil bath air filters are also used as pre-separators to significantly extend the service life of the main filter under extreme dust loads.
Oil bath air filters – properties
Oil bath air filters are suitable for low to medium dust loads. In combination with a Pico single-stage air filter, however, they are often used as pre-separators for extremely high dust loads, for example in construction and agricultural machinery as well as mining and tracked vehicles.
This highly robust filter type is also used on the railroads. In particular, piston compressors and oil-flooded screw compressors are often equipped with oil bath air filters in cold countries due to their longevity and virtually maintenance-free operation.
Oil bath air filters are also used as pre-filters in forklifts. The oil bath air filter achieves a separation efficiency of approx. 99%, the main filter achieves >99.9% (test dust: SAE Coarse).
In forklifts with internal combustion engines, oil bath air filters are used as pre-separators to prevent extreme engine wear in foundries and other areas where sand or other very small but hard particles are present.
Structure of an oil bath air filter
An oil bath air filter has a sheet metal housing, which consists of an upper and lower part as well as the insert. The sheet metal is painted black. The insert contains a steel mesh element. In addition, the insert has both an inner and an outer gasket – the small inner gasket creates a seal between the raw and clean side; the outer gasket seals the housing against the environment.
Spare parts such as filter bodies and inserts, as well as accessories including clean-air pipes and hoses, holders, and rain caps, are also available in our store.
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