Air release time

The air release time of an oil is the time it takes to remove air that was dispersed earlier. This is particularly relevant for turbine and hydraulic oils, as the air release time changes during oil lifetime.

Air is forced into the oil through a standardised nozzle at a defined pressure over a certain period of time. Subsequently, the time span in minutes is measured until the dispersed air in the oil is separated again down to a residual content of 0.2 vol-%.

The determination is made according to DIN ISO 9120 or ASTM D3427.