3. Tubes are fixed to the tube sheet (a thick circular metallic plate) by the method of tube rolling and brazing (non-removable) or ferrule connection (removable). Thickness of the tube, sheet is normally __________ the outside diameter of the tube but in no case it should be less than 22 mm (7/8").
5. Liquid gradient over a tray can be minimised by
Options
A. providing a higher skirt clearance or a higher weir.
B. decreasing the number of rows of caps through which the liquid flows or by decreasing the velocity of liquid flow past the caps or by reducing the distance along the tray through which the liquid must flow.
C. using split flow, radial flow or cascade flow for column diameter large than 4 ft.