Abstract: Hydrodynamic data of sieve trays with hole diameters of 5, 10, 15, 20 and 25 mm were experimentally obtained and studied. A set of equations to correlate pressure drop, weeping velocity, entrainment and froth height was established, and was considered precise enough for design requirements. The performance and operating flexibility of large-holed sieve trays were studied and discussed. It can be shown that for properly designed sieve trays, operating flexibility can be achieved with a loading ratio 2 to 4, which is adequate for fluctuation of commercial-scale columns.