A centrifugal separator includes a frame and a rotating part including a spindle and a centrifuge rotor enclosing a separation space. An inlet channel provides fluid communication into the separation space and includes a rotary channel part, a frame channel part, and a first seal at the interface between the rotary and frame channel parts. An outlet channel provides fluid communication out from the separation space and includes a rotary channel part, a frame channel part, and a second seal at the interface between the rotary and frame channel parts. The inlet and outlet channels are arranged concentrically with each other. A forcing device is provided to generate a leak flow through one of the first and second seals in a first direction from the outlet channel to the inlet channel and to counteract leakage in the opposite direction.