---
title: "Fluidisation pad / aeration pad"
description: "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."
canonical_url: "https://sylio.co/glossary/fluidisation-pad-aeration-pad"
last_updated: "2026-06-28T02:29:32.915Z"
---

**Fluidisation pads** (also *aeration pads*) are porous ceramic, sintered-metal or fabric panels mounted in the lower wall of a [hopper](/glossary/hopper) or [silo](/glossary/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](/glossary/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](/glossary/sonic-horn) 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

- [Hopper](/glossary/hopper)
- [Silo](/glossary/silo)
- [Anti-bridging device](/glossary/anti-bridging-device)
- [Geldart classification](/glossary/geldart-classification)