Dumping/weeping distillation

Dumping As gas velocity is lowered below the weep point, the fraction of liquid weeping increases until all the liquid fed to the tray weeps through the holes and none reaches the downcomer. This is the dump point, or the seal point. The dump point is well below the range of acceptable operation of distillation trays. Below the dump point, tray efficiency is slashed, and mass transfer is extremely poor. Operation below the dump point can be accompanied by severe hydraulic instability due to unsealing of downcomers. 

Maximum column capacity is increased since manipulated variables— reflux or distillate, boilup or bottom product—are not changed as much as if unaided feedback controllers were used. Similarly, the column is less likely to weep or dump. 

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