"Cavitation" is the rapid formation and implosion of millions of steam bubbles generated by the alternation of high- and low-pressure waves generated by high-frequency sound waves (ultrasound). During the low-pressure phase the bubbles form and grow in size, collapsing in the high-pressure phases.
"Degassing" is the initial removal of gases dissolved in the washing solution. The optimum cavitation values are obtained after all gases have been expelled.
How can I obtain the best performance with ultrasonic washing?
There are many parameters that contribute to obtaining the best cleaning result. The best wash is obtained by optimizing these variables. The most important are the type of detergent, temperature, treatment time, and types and dimensions of the ultrasonic tank.
With appropriate applications, ultrasound can be considered safe on many articles. It is very important, however, to take mechanical and chemical steps to prevent the ultrasound from damaging delicate materials such as zamak, aluminum, etc.
Contaminants adhere to the surface of the pieces, and water alone does not have good cleaning power; for this reason it is useful to use a detergent. The purpose of the ultrasound (cavitation) is to help the detergent remove the contaminants; detergents that lower the surface tension of the fluid increase the cavitation levels.
When is it necessary to renew the washing solution?
The solution should be renewed when there is a visible drop in the cleaning action, or when the solution is visibly dirty or exhausted. A change of the solution at every wash is not usually necessary.
From a few seconds for the removal of oil to dozens of minutes for washing molds and cleaning carbon-based residues. Depending on the degree of cleanliness desired, several ultrasonic treatments may be necessary, with different types of detergents.
How do I know if the ultrasonic waves are working well?
Most poor washing results are due to a wrong detergent product, wrong temperature, insufficient time, or ineffective ultrasonic waves. If you suspect your tank is not working efficiently, you can test it either with sheets of aluminum foil or, more objectively, with a cavitation power meter.
Cut three small pieces of food-grade aluminum foil, measuring approximately 10 x 20 cm each. Prepare the ultrasonic tank (degassed, at the proper temperature, and with the proper quantity of detergent). Immerge the first little aluminum sheet into the center of the tank and the other two 5 cm away from the sides. Turn on the ultrasound for ten minutes. Remove the aluminum sheets and examine them: all three should be perforated and “curled” in the same way if the ultrasonic waves are functioning correctly.
The cavitation meter is an instrument that enables you to measure the cavitation in a univocal manner, and thus makes it possible to check the efficiency of the ultrasonic waves.
There are numerous working frequencies for ultrasonic transducers; the most commonly used in the industrial sector are 25 kHz, 33 kHz, and 40 kHz. Both noise level and effectiveness are inversely proportional to the working frequency. High frequencies are suitable for treating delicate pieces or removing very small particles, almost never found in normal washing applications.
To correctly dimension the tank, add to the measurements of the piece 250mm on the sides and 300mm in height. This is a common and quick dimensioning procedure that enables you to qualitatively understand the correct dimensions to use.
How many ultrasonic transducers should be installed?
Usually the dimensioning of the ultrasonic transducers is made in W/l of degreasing solution. The specific values vary from producer to producer; if you check various Internet websites you can find an interval spanning from 5 W/l to 12 W/l. We do not agree with this; our dimensioning is made on the basis of the area of the tank to be put into vibration. In any case, for the sake of similitude, we install 2-3 W/l.
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