Air Knife Drying on Bakery Lines: Where the Pressure Window Sits

Packaged bakery products leave the wrapping section with moisture and crumbs on the film surface. Downstream operations do not tolerate it.

Moisture on a package is rarely an aesthetic problem. Corrugated cases lose compression strength as board moisture rises. A wet film blocks label adhesion and ink bonding, while water in the seal area weakens the seal. The cost of a wet package appears three stations later.

Removing it is a momentum task, not a thermal one. On a 500 ml container with a 20 micron water film, evaporation removes only a small share of the water in the available exposure time. The rest has to be stripped mechanically by a high-velocity air curtain.

Droplets near 0.5 mm release at roughly 30 m/s impingement velocity. The smaller droplets and thin films that remain on a package surface need 60 to 80 m/s. Allowing for jet decay, this maps to a pressure rise of 15 to 20 kPa. Above roughly 25 kPa, the return falls away.

The GALEX X720 high-speed turbo blower is built for this band. Its 7.5 kW drive covers the pressure rise and air volume needed by an air knife spanning a standard conveyor width.

Mounting distance and exposure time decide the result. Moving a knife from 20 mm to 50 mm from the product cuts impingement velocity by about a third. At 1.5 m/s line speed, a second knife in series doubles exposure and can improve results more effectively than raising pressure.

For continuous blow-off, blower-driven knives replace compressed air at a fraction of the energy, making them particularly effective on lines running several shifts.