Characteristic of a hydraulic fluid to separate from contamination by means of rising (air) or sinking (solids).
- Air separation capability: Characterises the ability of a hydraulic fluid to separate out undissolved air (air bubbles). Undissolved air can primarily enter the pressure medium due to leaks, turbulence in the tank or due to cavitation in the hydraulic fluid. It must be separated out again before the fluid is drawn in again by the pump, as free air has a very negative effect in hydrostatics installations. The air separation capability is primarily dependent on specific fluid characteristics, the operating viscosity, contamination and the bubble size. It is determined according to DIN 59 381.
- Contamination separation capability: Characteristic of a hydraulic fluid to separate out foreign particles of varying density, above all water and foreign particle contamination. In mineral oil the water collects at the bottom of the tank due to the higher density, in HFD fluids at the surface due to the low density. It is also important here to separate out solids in the tank or in the filters before they are drawn in again with the fluid. Dispergent oils.