Hoppers and silos
Silo
Also known as silos, storage silo.
A silo is a large vertical vessel for storing bulk solids — cement, fly ash, lime, biomass pellets, fertilizer granules, food powders, mining concentrate. Silos range from a few cubic metres to tens of thousands of cubic metres and are typically cylindrical with a conical discharge bottom feeding into a single outlet or a cluster of outlets.
Why silos bridge
Most bulk solids show some degree of cohesion. Under the gravitational load of metres of stored material, the cohesive bond is enough to form a stable arch above the discharge outlet (bridging) or a narrow flow channel surrounded by a hardened mass (rat-holing). The longer material sits in the silo, the more it consolidates and the harder it is to restart flow.
Sonic horns as flow aids
Sonic horns installed at the silo discharge cone provide continuous low-amplitude vibration that prevents cohesive structures from forming. A single horn typically covers the discharge cone and the lower 2–5 metres of the silo wall. Multiple horns address larger silos or persistent rat-holing zones.
Compared with air cannons and bin vibrators:
- No structural impact on the silo
- No discrete blast moments that introduce air pockets into the discharge
- Lower total air consumption per unit cleaning effort
- Single mounting versus arrays of cannons
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.
- Bunker (coal bunker)A coal bunker is an intermediate coal-storage vessel that feeds pulveriser mills. Bridging in coal bunkers interrupts mill feed and forces unit derates; sonic horns are the standard flow aid.
- Bridging (bulk-solids)Bridging (also arching) is the formation of a stable arch of bulk solids above the discharge outlet of a hopper or silo, stopping material flow. The universal failure mode of bulk-solids storage.
- Rat-holingRat-holing is a flow pattern in which material discharges through a narrow vertical channel above the outlet, while the surrounding material remains stagnant and consolidates.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.