Process Equipment and Plant Design
In seive plate column, holes are drilled or punched in sizes ranging from 2.5 to 12 mm (5 mm being widely used). The hole pitch is normally __________ times the hole diameter to give the required hole area.

2.5 to 4.0
10 to 15
5 to 10
0.5 to 1.5

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Process Equipment and Plant Design
Weep holes provided in the plates of a distillation column

Must be large enough (usually 1/4" to 5/8" dia) to prevent plugging but should not deliver excessive amount of fluid during operation
All of these
Are normally located near the overflow weir so that any delivery of liquid during operation follows approximately the same path as the overflow fluid
Facilitate draining out liquid from a tray when the unit is not in operation

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Process Equipment and Plant Design
Pick out the wrong statement about the design of a sieve plate column.

Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds
Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger diameter columns
For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design
An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure above atmospheric and 6-12 mm for vacuum columns

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