Bubble cap tray is a flat perforated plate with risers (like pipes) around the perforations, and caps in the form of inverted cups over the risers.The caps are usually equipped with slots or holes through which vapor comes out. The cap is mounted so that there is a space between riser and cap to allow the passage of vapor. Vapor rises through the riser and is directed downward by the cap passing through slots in the cap, and finally bubbling through the liquid on the tray. As vapor has to pass through many passages this lead to higher pressure drop and lower capacity than other conventional trays. Liquid and froth are filled on the tray to a depth at least equal to the weir height or riser height, giving the bubble-cap tray a unique ability to be used for reaction applications.      

Bubble cap tray is a flat perforated plate with risers (like pipes) around the perforations, and caps in the form of inverted cups over the risers.The caps are usually equipped with slots or holes through which vapor comes out. The cap is mounted so that there is a space between riser and cap to allow the passage of vapor. Vapor rises through the riser and is directed downward by the cap passing through slots in the cap, and finally bubbling through the liquid on the tray. As vapor has to pass through many passages this lead to higher pressure drop and lower capacity than other conventional trays. Liquid and froth are filled on the tray to a depth at least equal to the weir height or riser height, giving the bubble-cap tray a unique ability to be used for reaction applications.