Product losses, through drain

Chimney draw-off trays are typically designed to slope toward the draw-off nozzle, thus avoiding a need for drain holes. However, with age, such trays warp because of thermal expansion and pools of water can be trapped. Inspection after water washing will reveal such poorly drained trays and pinpoint the location of required drain holes. But excessive use of drain holes can also be bad. Product losses through the drain holes can be estimated by the following ... 

This is like unsealing a tray s downcomer in a distillation tower. If the bottom edge of the downcomer from a tray is above the top edge of the outlet weir on the tray below, then vapor can blow up through the unsealed downcomer. This will prevent the internal reflux ft om draining down the column. Tower flooding and loss of product separation efficiency will result. This is called liquid flooding or excessive downcomer backup due to loss of the dovmcomer liquid seal. 

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