Abstract: A distillation tray is described which is suitable for use in a distillation column of a barge-mounted plant. This distillation tray is provided with a plurality of cup-like cavities, each cavity having an apertured bottom for upward passage of vapor and being provided with respective weir means and downpipe means for feeding excess liquid to the tray below. In use of such a distillation tray a body of liquid can be maintained in each cavity for contact with the upflowing vapor and for providing a liquid seal between stages despite tilting of the tray. Each cavity can be provided by an insert comprising an apertured bottom plate, upstanding walls defining together with the bottom plate a cup-like cavity, at least one of the walls being provided with weir means for overflow of excess liquid from the cavity and downpipe means mounted below the bottom plate for transferring excess liquid that has overflowed the weir means to the tray below.