When air moves across a surface, such as a high-speed web, a boundary layer is formed. This layer can build to substantial thickness, trapping and carrying particles with a diameter less than the boundary layer thickness. A web moving at 1500 ft/min for example can form a layer larger than 1 inch, allowing even large particles to remain trapped.

Typical vacuum systems are not able to break up or penetrate this layer and thus cannot remove the smaller particles.

Conventional air knives can reduce the thickness of the boundary layer by directing high velocity air along the substrate. This method, however, has severe limitations, since in the process of overpowering the web’s boundary layer, the air knife creates a new thinner boundary layer, perhaps 50 to 100 microns thick. Larger particles can be removed, but small particles are still trapped in this newly created boundary layer.

The only effective solution to removing the trapped fine particles is to utilize an agitating method to disrupt or penetrate the boundary layer. The dual ultrasonic nozzles of the Ultra Cleaner superimposes high frequency pulses over a high pressure, high velocity flow to impart very high energy levels to the substrate. These pulses knock the trapped particles out of the boundary layer so the vacuum, without any damage to the substrate, can remove them.