A centrifugal separator

The invention refers to a centrifugal separator and a method of separating a product to a heavy phase and light phase. A centrifuge rotor (1) encloses a closed separation space (8), which has a radially outer part (11) for the heavy phase, a radially inner part (12) for the light phase and a central gas-filled space (13). The radially outer part is separated from the radially inner part by a interface layer level (14). An inlet (21) extends into the separation space (8) for feeding the product. A first outlet (22) extend from the radially outer part for discharge of the heavy phase. A second outlet (23) extends from the radially inner part (12) for discharge of the light phase. A control equipment permits control of the interface layer level to a desired radial position. A sensor (51) senses a parameter related to the gas pressure in the central space. The control equipment controls the counter pressure in the first outlet in response to the sensed parameter for controlling the interface layer level to the de