Tray deck upset

Most often, tower packing supports are dislodged, or distillation trays upset, when a tower is operated with an excessive bottom liquid level. Forcing heat into a tower when the liquid level is several feet above the bottom tray deck often results in dislodging the bottom few trays. Occasionally, trays are mis-assembled during a turnaround. The results of either of these misadventures is diminished fractionation efficiency. 

Although trays can corrode through, a more common cause of damage is unit upsets. A high liquid level, above the flash zone, will cause the trays to be bumped by the up-flowing vapors. Slugs of water can dislodge tray decks when the water suddenly flashes. 

It seems that many tray upsets occur during short unit outages. At such times steam may back into the fractionator and form pockets of water. Also, any operating malfunction that causes a pressure surge in the overhead or flash zone (check (he pressure recorder) can disrupt tray decks. If the operating engineer sees a loss in fractionation following such incidents, he should proceed as follows ... 

Reduced ASTM gap Flooding Upset tray decks Pumparound rate too high Top trays corroded Water in reflux Downcomer Installation... 

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