Micrometric cleaning of steel tubes through ultrasonic cavitation

A series of 0.8 mm Inox steel tubes were clean so that no debris with dimensions equal to or greater than 0.1 micrometers remained. The gas flow into the tubulation is used in spectrophotometric analysis of engine exhaust gases to attain the mentioned values. The piping presented lengths between 17 and 20 meters, with many bends and curves, making impossible an ultrasonic cleaning by the classical methods. The problem was solved by sending a continuous flow of isopropyl alcohol through the piping and applying high energy ultrasonic vibration in the outer surface of the pipes while the solvent flows. After the cleaning, the filters used were observed in a microscope, showing no debris outside the specified range.