Also called the real dirt holding capacity. This provides information on the quantity of dirt that a certain filter can hold before a reference pressure (normally the response pressure of the bypass valve) is reached. Therefore the dirt absorbing capacity of a filter is also a measure of the service life of that filter element.
The dirt absorbing capacity of a filter can be calculated to a high degree of accuracy using the α-value. Its size depends primarily on the filter element used and –– when using a bypass valve –– its initial differential pressure Δp A (Figure S 30). The test for the dirt absorbing capacity is performed in accordance with ISO 4572 (Filter cumulative efficiency). ISO 3968 contains the tests to determine the pressure difference.
Figure S 30: Dirt absorbing capacity of two filters with different filter cartridges