Centrifugal separator

In a centrifugal separator, the combination of a rotor having a separation chamber (4) and an inlet (9) for supplying to said chamber a mixture of light and heavy liquids and solids, the rotor being operable to form in said chamber an interface layer between a radially inner layer of separated light liquid and a radially outer layer of separated heavy liquid, the rotor having three outlets, namely, a first outlet (23a) for separated light liquid and situated at the central part of the separation chamber, peripheral outlet means (12) for separated heavy liquid and solids and situated at the periphery of the separation chamber, and a second outlet (35) for light liquid and situated radially intermediate said first outlet and said peripheral outlet means, means (13-21) for intermittently opening said peripheral outlet means (12) during operation of the rotor, stationary recirculating means (31-33) through which the liquid discharging from the motor via said intermediate outlet (35) is returned to the rotor, a sensing device (38) associated with said recirculating means (31-33) for sensing when said interface layer has moved radially inward to a predetermined level, control means (39) coacting with said sensing device (38) and said opening means (13-21) to emit a signal to the opening means in response to said movement of the interface layer to the predetermined level, and throttle means (37) for limiting the flow through said stationary recirculating means (31-33) and formed in the rotor between said radially intermediate outlet (35) and said recirculating means, the throttle means (37) having less throughflow capacity than said recirculating means.