Hold Down Grids (Bed Limiters)
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For columns where pressure or flow surges can occur across a bed of random packing, a packing hold down grid (bed limiter) is recommended.
The hold down grid is made from a wire mesh (or expanded metal) screen attached to an annular frame. Free area for vapour and liquid flow is normally greater than 85% of the column cross sectional area.
For small columns one piece construction is used (Model nos. 300 & 301). Segmental construction is used for large diameter columns (Model nos. 310 & 311).
For random packing beds:
- Perforated plate or mesh type
- Separate or integral with liquid distributor
- Plastic or metal construction
For structured packing beds:
- Bar / angle construction
For catalyst beds:
- Perforated screen type