Apparatus for controlling the operation of fractionation columns to avoid column flooding is described. The apparatus uses mass flow meters to measure the mass flow rates of the receiver vapor, and the stripper hydrocarbon liquid stream or the stripper reflux and the stripper net overhead liquid. The water from the receiver can be measured with either a volumetric flow meter or a mass flow meter. The apparatus also includes at least one computer in communication with a molecular weight analyzer or specific gravity analyzer; an overhead vapor line pressure gauge; an overhead vapor line temperature gauge; a hydrocarbon liquid outlet line temperature gauge; the stripper hydrocarbon stream mass flow meter, or the stripper reflux hydrocarbon liquid mass flow meter and the stripper net overhead hydrocarbon liquid mass flow meter; the vapor mass flow meter; and the water flow meter.