A method for controlling operation of a fractionation column comprising: measuring a molecular weight or a specific gravity, a temperature, and a pressure of an overhead vapor stream from the fractionation column to a receiver; measuring a temperature of a stripper hydrocarbon liquid stream from the receiver; measuring a mass flow rate of the stripper hydrocarbon liquid stream, or measuring a mass flow rate of a stripper net overhead liquid stream and a reflux hydrocarbon liquid stream; measuring a mass flow rate of a stripper vapor stream from the receiver; measuring a flow rate of a water stream from the receiver; determining a total overhead flow using the flow rate of the water stream from the receiver; the mass flow rate of the stripper vapor stream from the receiver; and the mass flow rate of the stripper hydrocarbon liquid stream, or the mass flow rate of the stripper net overhead hydrocarbon liquid and the mass flow rate of the reflux hydrocarbon liquid stream; determining a total overhead moles from the total overhead flow; determining a total moles of water from the measured water flow rate from the receiver and the measured temperature of the hydrocarbon liquid stream from the receiver; determining a partial pressure of water in the overhead vapor stream from the total moles of water, the total overhead moles, and the measured overhead pressure; determining a dew point temperature at the determined partial pressure of water; determining the dew point margin from the determined dew point and the measured overhead temperature; comparing the calculated dew point margin with a predetermined minimum dew point margin; initiating an alarm or changing an operating condition of the fractionation column or both when the calculated dew point margin is less than the predetermined minimum dew point margin. measuring a molecular weight or a specific gravity, a temperature, and a pressure of an overhead vapor stream from the fractionation column to a receiver; measuring a temperature of a stripper hydrocarbon liquid stream from the receiver; measuring a mass flow rate of the stripper hydrocarbon liquid stream, or measuring a mass flow rate of a stripper net overhead liquid stream and a reflux hydrocarbon liquid stream; measuring a mass flow rate of a stripper vapor stream from the receiver; measuring a flow rate of a water stream from the receiver; determining a total overhead flow using the flow rate of the water stream from the receiver; the mass flow rate of the stripper vapor stream from the receiver; and the mass flow rate of the stripper hydrocarbon liquid stream, or the mass flow rate of the stripper net overhead hydrocarbon liquid and the mass flow rate of the reflux hydrocarbon liquid stream; determining a total overhead moles from the total overhead flow; determining a total moles of water from the measured water flow rate from the receiver and the measured temperature of the hydrocarbon liquid stream from the receiver; determining a partial pressure of water in the overhead vapor stream from the total moles of water, the total overhead moles, and the measured overhead pressure; determining a dew point temperature at the determined partial pressure of water; determining the dew point margin from the determined dew point and the measured overhead temperature; comparing the calculated dew point margin with a predetermined minimum dew point margin; initiating an alarm or changing an operating condition of the fractionation column or both when the calculated dew point margin is less than the predetermined minimum dew point margin.