A system includes a hermetic centrifugal separator, a recirculation system, a first monitoring system, a first control system, a pressure monitoring system, and a pressure control system. The separator includes a rotor, a separation chamber, an inlet channel for separating components, a first outlet channel for receiving separated light components, and a second outlet channel for receiving separated heavy components. The recirculation system recirculates the separated heavy components from the second outlet channel to the separation chamber. The first monitoring system monitors density and/or flow rate of the heavy components in the second outlet channel. The first control system controls flow rate in response to a control signal from the first monitoring system. The pressure monitoring system monitors pressure in the second outlet channel. The pressure control system controls a back pressure valve in the second outlet channel in response to a control signal from the pressure monitoring means.