This impact air velocity can range from a gentle breeze to greater than Mach 0.6 (40,000 ft/min) to alter the surface of a product without mechanical contact.
In most hot dip applications both top and bottom coated surfaces can be independently controlled by computer via feedback loop as accurately as plus or minus 5 grams/meter squared.
[1] Blower-powered air knife systems came of age with the advent of the 1987 Montreal Protocol, which started the clock on the worldwide phase-out of atmospheric ozone depleting CFC’s (chlorofluorocarbons) then used as cleaning agents in many industries.
Although the printed circuit board industry was still in its infancy, it was among the first to initiate the conversion to aqueous and semi-aqueous-based parts cleaning systems.
Additionally, the conversion to water-based inks, paints, coatings, adhesives and other solutions used in various manufacturing sectors has resulted in the need for air knife dryers where none had previously existed.
Air knife designs today have evolved to where some manufacturers produce a very efficient “teardrop” shape with a .95 coefficient of discharge.
With construction ranging from 1⁄8 in (3.2 mm) thick aluminum extrusion to 11 gauge fabricated stainless steel, air knives can weigh 1 lb/ft to 25 lbs/ft.
The applications include drying bottles and cans after filling and rinsing, printed circuit boards following the conveyorized wash to remove solder paste and flux, metals castings after automatic machining and many more.
These range from “garage built” devices with a low level of precision to the most exotic metals of construction used in air knives for class 100 clean rooms.
These enclosures keep water contained, reduce the amount of air knife noise and even eliminate any liquid that could create safety concerns.
Information is needed regarding the Occupational Safety and Health Administration (OSHA) and their standards and directives on Compressed Air, especially when used for cleaning.