Multipass crossflow trays
A reexamination of Figures 2.3e2.5 shows that liquid flowing across a one-pass
tray eventually encounters an outlet weir having a limited horizontal length. At
high liquid rates, such an outlet weir sometimes proves to be insufficient. For
high liquid rates, two-pass, three-pass, and four-pass trays are employed, as shown
in Figure 2.8. Every two-pass tray has two outlet weirs; every three-pass tray,
three; every four-pass tray, four. As the number of liquid flow passes increases,
the total outlet weir (horizontal) length increases, and liquid has more outlet
weir to flow over.