5　Design

5.1　Design Principles

5.1.1　Trays may be designed in a single-pass structure or multi-pass structure as per process requirement.Where a multi-pass structure is applied，similar effective flow area shall be ensured for each pass.

5.1.2　Each tray pass shall be provided with a hatchway，and in the shell with same diameter，the hatchways between adjacent manholes shall be in vertical alignment.The minimum size of hatchway opening shall be 380mm×450mm.

5.1.3　Where the space between bottom of support beam and the lower neighboring tray is less than 380mm，hatchway shall be provided for the trays at both sides of the support beam.

5.1.4　Trays should be designed to minimize welding work inside of the tower.

5.1.5　Both tray floor and hatchway shall be removable.Except for large-size trussed beam，tray floors，hatchways and other removable component parts shall be able to pass through manholes，and the weight of each item should not be heavier than 30kg.For large-size trussed beam，removable structure is preferred.

5.1.6　All removable component parts shall be able to be dismantled and assembled on the top of tray，but hatchway shall be designed to enable dismantling on either side of tray.