The “Sieve tray” is a perforated plate type tray, with holes punched into the deck-plate that typically measure from 3/16” up through 1” in diameter. Typically, a standard hole size can measure 0.5” OD. Vapor comes out of the holes which in turn, keeps the liquid from weeping through. The vapor and liquid then, create a mix on the tray deck. The liquid will then leave the tray, via the down-comer. As the vapor continues to the tray above.
A sieve tray has a higher entrainment than a standard valve type tray. For efficient operation, hole velocity must be sufficient in order to balance the head of the liquid on the tray. It is used when turndown is limited to 2:1 and fouling is not a concern. The sieve tray is and remains, one of the most economical trays because it does not contain separate valve assemblies.