Method of Application

Immersion Cleaning. When an alkaline cleaner is applied by immersion, the parts to be cleaned are immersed in the solution and allowed to soak. As the alkaline cleaner acts on the parts, convection currents (due to heating or mechanical agitation) help to lift and remove soils from the metal surface. The efficiency of removal by the soak cleaner is greatly enhanced by agitation.

There are several approaches to immersion cleaning:

• Barrel cleaning, in which small parts are agitated inside a barrel that rotates in the cleaner solution

• Moving conveyor cleaning, in which solution flow is created as parts are dragged through the cleaner

• Mechanical agitation, in which the cleaner is circulated using pumps, mechanical mixers, or ultrasonic waves

• Mechanical contact, in which the cleaner is applied with external forces such as brushes or squeegees

Spray Cleaning. The effectiveness, low cost of equipment, and high degree of flexibility associated with spray cleaning has made this method popular for many years. Specialized methods of spray cleaning include steam cleaning, in which the cleaning solution is injected into a stream of high-pressure steam, and flow cleaning, in which the cleaning solution is flooded onto the part at high volume but at relatively low pressure.

Spray cleaning is accomplished by pumping the cleaning solution from a reservoir through a large pipe ("header"), through a series of smaller pipes ("risers"), and finally out of spray nozzles onto the part to be cleaned (Fig. 1). The pressure at which the solution is applied to the part can vary from as low as 14 kPa (2 psi) to as much as 13,800 kPa (2,000 psi). On a typical cleaning line the application pressure will range from 70 to 210 kPa (10 to 30 psi). In general, higher spray pressure produces greater mechanical forces for removing soils from a metal surface. Mechanical effects are especially important for the removal of insoluble particles such as dust, metal fines, and carbon smut.

Fig. 1 Equipment for spray cleaning operation

Spray cleaners are prepared with low foaming surfactants that minimize foam formation, even at high spray pressure. Over the last few years, low-foaming surfactants designed for spray cleaning have achieved cleaning performance comparable to that of surfactants used for immersion cleaning.

While spray cleaning is effective on most parts, certain parts, such as the interior of an enclosed section, have soiled areas inaccessible to the sprayed cleaning solution. In these instances, immersion cleaning is more effective because all surfaces of the part can be brought in contact with the cleaning solution.

0 0

Post a comment