Sieve tray design hole size

Sieve Tray Design Perforations usually are in the range of 0.125 to 0.25 in (0.32 to 0.64 cm) in diameter, set 0.5 to 0.75 in (1.27 to 1.81 cm) apart, on square or triangular pitch. There appears to be relatively little effect of hole size on the mass-transfer rate, except that with systems of high interfacial tension, smaller holes will produce somewhat better mass transfer. The entire hole area is normally set at 15 to 25 percent of the column cross section, although adjustments may be needed. The velocity through the holes should be such that drops do not form slowly at the holes, but rather the... 

A valve tray is shown in figure 6.12. Each hole contains a valve and the extent of opening varies with the vapour flowrate. Thus these trays can be operated over a wider range of flowrates than sieve trays of a similar size. They are said to have a high turn-down ratio which means that they can be operated at a small fraction of design capacity. A figure of 10 1 has been quoted for valve trays, while the turn-down ratio of sieve trays is less than 4 1. 

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