Abstract: A method and a control system for controlling the height level position and horizontal movement of a suction device which is vertically movably suspended from a horizontally movable supporting device according to variations of the inclination, or angular velocity, of a flexible suspending element in relation to the vertical, on which element the suction device is suspended.

Abstract: This invention is directed to an apparatus comprising a suction device having at least one nozzle for sucking suspendible material as a suspension from a bed of said material, means for producing suction in the nozzle and means for moving the nozzle horizontally and vertically in relation to said bed, and the invention relates more particularly to a method of controlling the horizontal and vertical movements of the suction device by utilizing as control signals the variations of the solids concentration and volume of suspension sucked through the nozzle per unit of time, and the invention also comprises an apparatus having means for carrying the method into effect.