Glossary
Hoppers and silos
Fluidisation and aeration pads
Also known as fluidisation pad, aeration pad, air slide pad, aeration nozzle.
Fluidisation pads (also aeration pads) are porous ceramic, sintered-metal or fabric panels mounted in the lower wall of a hopper or silo. Low-pressure air admitted through the pad permeates upward through the material, partially fluidising the bed and restoring flow towards the outlet.
Where they work
- Dry, fine Class-A powders (see Geldart classification) — cement, fly ash, alumina
- Continuous-flow applications where some bed aeration is acceptable
- Vessels where wall access for pad installation is straightforward
Where they don't
- Wet material — moisture blocks the pad pores or channels the air
- Hygroscopic material — added air picks up moisture and worsens cohesion
- Class C powders in some conditions — air channels through rather than fluidising
- Vessels where downstream equipment cannot tolerate aerated discharge
Fluidisation pads vs sonic horns
Both are continuous-operation flow aids. Fluidisation pads add air to the material; sonic horns add vibration to the material. Pads suit a narrower range of materials (dry, fluidisable) but consume more compressed air over time. Horns suit a wider material range, are simpler to retrofit, and do not aerate the discharge.
Related terms
Related terms
- HopperA hopper is an inverted-pyramid or conical vessel for storing and discharging bulk solids. Bridging and rat-holing are the universal failure modes; sonic horns are a clean, low-maintenance remedy.
- SiloA silo is a large vertical bulk-solids storage vessel. Cement, fly-ash, lime, biomass, fertilizer and food-powder silos all bridge and rat-hole; sonic horns are the leading flow aid.
- Anti-bridging deviceAn anti-bridging device is any flow-aid hardware installed to prevent or break material bridging in a hopper or silo: sonic horns, air cannons, vibrators, fluidisation pads.
- Geldart classificationThe Geldart classification groups powders by particle size and density into A, B, C and D classes. Predicts fluidisation, bridging and discharge behaviour.