Knocked Into Shape With The Pneumatic Knocker

Online Editor

Adrian Grüninger details the requirement profile and use of the pneumatic knocker

Pneumatic knockers are mostly used in rough environments. Wet conditions and temperature fluctuations are factors that can affect the beater. This often makes the use of an electric vibrator more difficult.

Pneumatic interval knockers are used for bulk materials with material flow disturbances when high frequency vibrators with sinusoidal vibrations are not effective. Other applications are to remove sticking or adhering materials on silos, pipelines and bin walls and to prevent bridging.

In most cases, they replace the previously used knock-off hammers in a more personnel- and material-friendly way.


Findeva’s pneumatic knocker is delivered with a base plate, which is used for mounting the knocker and transmitting the impact pulse. The knocker housing and base plate are made of aluminium. The impact plate (integrated in the base plate) is made of an impact-resistant special polymer.


The piston is pressed against a preloaded spring by compressed air. When the piston chamber is quickly vented, the piston impacts against an impact plate. The force is given by the piston weight and the preload of the compression spring. Impact energies of 1-280Nm (kinetic energy) and impact pulses of 1 - 80.5Ns are achieved.

Interval impact mode: the impact depends on the interval time, which is set by a throttle valve. The force is adjusted by the three control bores 1-3.

Single impact mode: the impact is triggered immediately after switching the 3/2-way valve. Several knockers can be connected in parallel. The impact force is continuously adjusted with the pressure. The valve is controlled by a PLC or similar.

The knockers can be operated with dry compressed air and thus without lubrication. If oil-containing compressed air is selected to operate the knocker, this must also be kept, as the basic lubrication of the knocker is washed out by the oil-containing air.

The cycle time is a maximum of 10 strokes per minute for each knocker.

The knocker can operate in a temperature range of -20°C to 120°C in the standard version. Special versions are available for temperatures down to -40°C or up to 150°C. The range of pneumatic knockers covers wall thicknesses from 2 to 20mm.

All knockers can be used in explosive environments of levels 1/21 and 2/22.

Examples of applications

The range of application of pneumatic knockers is very wide. They are used in coal-fired power plants to knock the coal dust from the silo walls. In the food industry, they are used in milk powder filling plants to prevent bridging and to keep the container walls clean. In basalt stone plants they are used for the same function, and also in chemical plants where sticky powder with poor rubbing properties is used.

Adrian Grüninger is managing director of Findeva