Electrostatic precipitators
Tumbling-hammer rapper
Also known as tumbling hammer, European-style rapper.
A tumbling-hammer rapper uses a horizontal shaft fitted with weighted hammers that strike anvils attached to the collecting-electrode frame. As the shaft slowly rotates, each hammer falls under gravity onto its anvil, transferring an impact pulse along the plate row. It is the dominant rapper design in European-style ESPs from suppliers such as ALSTOM, FLSmidth, Hamon and SHU Power.
Strengths and weaknesses
| Strength | Weakness |
|---|---|
| Robust mechanical design | Shaft and hammer fatigue under continuous service |
| Even distribution along long plate rows | Risk of hammer-shaft breakage during outages |
| Tunable by hammer mass and shaft speed | Difficult to retrofit additional intensity |
| Low electrical infrastructure | Cannot easily target individual plates |
Why sonic horns are common on European-style ESPs
Sonic horns installed on the ESP penthouse complement tumbling-hammer rappers by reaching the upper plate area and the discharge electrodes, neither of which the hammer can clean effectively. They also reduce the duty cycle on the hammers themselves, extending shaft and hammer life.
Related terms
Related terms
- ESP rapperAn ESP rapper is the mechanical hammer or magnetic impulse device used to dislodge accumulated dust from ESP plates and discharge electrodes. Sonic horns complement and partly replace this duty.
- Magnetic-impulse-gravity rapperA MIGI rapper lifts and drops a steel plunger by electromagnet onto an anvil rod connected to the ESP collecting plate. Standard design in American-style ESPs from B&W, Mitsubishi and Hamon.
- Electrostatic precipitatorAn ESP removes particulate from flue gas by charging dust and collecting it on plate electrodes. Sonic horns are widely used to dislodge ash from plates and to keep hoppers from bridging.
- 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.