Process Equipment and Plant Design
Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger

Permits the use of less tubes in a given shell diameter
Both B and C
Facilitates comparatively easier external cleaning because of large clearance
Permits the use of more tubes in a given shell diameter

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

All of these
Must be large enough (usually 1/4" to 5/8" dia) to prevent plugging but should not deliver excessive amount of fluid during operation
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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