Abstract: A solid bowl screw-type centrifuge used to continually separate a composition of substances with different densities includes a rotor drum, rotatable about a horizontal axis, with a cylindrical drum section and a conical drum section, and a conveying screw mounted therein, rotating about the same axis, with a helical vane attached to a hollow shaft for transporting the heavy phase to discharge openings in the conical drum section. On a front wall closing the cylindrical drum section, at least one outflow opening for the light phase is provided with a device for setting the fluid level. The device for setting the fluid level is composed of a control element with a system for braking or accelerating the fluid particles of the light phase, which is rotatively driven at a speed different to the drum speed and releases a flow through an annular clearance to the inner wall of the drum.