Every packed bed needs a support plate that:
- Physically retains and supports the packed bed.
- Has a high percentage of open area to allow unrestricted countercurrent flow of liquid and vapor.
Structured packings allow support by a simple, open-grid structure.
Random packings use a gas-injection support that provides separate passages for liquid and vapor flow so the two phases do not compete for the same opening. Incorrectly designed gas injection support plates can limit the column capacity rather than the random packing limiting the column capacity.