Function, set-up The filter element is the central component of a filter. The actual filtration process takes part in the filter element. The main filter variables, such as retention capacity, dirt holding capacity and pressure loss are determined by the filter elements and the filter media used in them. Rexroth filter elements are used for the filtration of lubricants in wind turbines. The series elements cist of two separate filter elements which are flown through one after the other and a bypass valve. In order to achieve the cleanliness class, the outer filter element made of non-woven glass fiber media (1) serves as the main filter. The inner filter element (2) made of wire mesh serves as a protective filter in case of a cold start. The outer filter element (1) cists of a multi-layer combination of star-like pleated filter media which are laid around a perforated support tube. The bypass valve (3) is located in the cover of the filter element. The bypass valve has a cracking pressure of 4 bar The inner filter element (2) is set-up in the same way, except for the filter element mat.