Glossary
Hoppers and silos
Whip hammer
Also known as sledge hammer (silo), manual hammering.
Whip hammering is the legacy manual technique of striking the outside of a hopper, silo or bunker with a sledge or weighted hammer to dislodge material bridges. It survives in many older plants as the first-line response to a stuck discharge.
Why it persists
- Zero capital investment
- Immediate availability when more sophisticated devices fail
- Familiar to maintenance crews
Why it should be retired
- HSE concerns — operators working in confined or elevated spaces, occasionally with falling-material risk
- Structural damage — repeated impacts at the same location dent and crack the vessel
- Local effect only — energy reaches only material near the impact point; deeper bridges unaffected
- Symptom not cause — does nothing to prevent the next bridge
The migration path
Modern plant upgrades replace whip hammering with continuous sonic horns on the discharge cone, supplemented where needed by a small number of air cannons for restart-after-shutdown duty. The combined system delivers vastly better availability, zero ongoing operator exposure, and no structural damage to the vessel.
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.
- 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.
- 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.