Incipient flood equation

Equation (14-142) permits finding the pressure drop curve in Fig. 14-55 or 14-56 at which incipient flooding occurs. 

Equation 1 above stales that a tray will become less efficient due to incipient jet flood when the pressure drop per tray, expressed in inches of liquid, equals 22% to 25% of the tray spacing. The inches of liquid term assumes the liquid is deaerated. Of course, the liquid in the downcomers and on the tray decks is closer to a froth than to a flat liquid. The more highly aerated the liquid is (i.e. the more foamlike it becomes), the greater will be the depth of liquid corresponding to a measured external pressure drop. Hence, liquids which foam in distillation columns (such as dirty amine and ethane-rich fractionators) reach their incipient jet flood point at pressure drops below the 20% indicated in Equation 1. 

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