Ultrasonic cleaning is a purification method based on the use of non-linear effects arising in the liquid subjected to ultrasonic vibration. Among these effects, perhaps, the most significant one is cavitation; however, there is also a range of ‘additional’ effects to point out, such as acoustic flow, sound pressure and acoustocapillary effect.
Cavitation is the process of formation of cavities and bubbles in an ultrasonic field during the phase of stretching, available in varying sound pressure. During the compression phase, these cavities and bubbles collapse. Cavitation accelerates the course of a number of physical and chemical processes. The reason for the exceptional efficiency of cavitation is that the bubbles starts from the slamming of the surface being cleaned. Cavitation is accompanied by the appearance of a very high instantaneous hydrostatic pressure that comes off sticking to the surface being cleaned dirt particles.
Ultrasonic cleaning in the laboratory
Cavitation can be heard as hissing noise generated in the liquid at a certain value of the intensity of the ultrasonic field. The Introduction of ultrasonic oscillations in the washing solutions can not only speed up the cleaning process, but also to obtain a higher degree of surface cleanliness. In most cases, attempts to eliminate flammable and toxic organic solvents and aqueous solutions used exclusively technical detergents. This undoubtedly leads to improved working conditions, higher production standards, and also allows to partially solve the issues of environmental safety.
The ultrasound is used for removal of contaminants arising during production of parts and products, as well as during their operation. Ultrasonic cleaning is particularly useful in the preparation of ultrasonic cleaning surfaces prior to coating and cleaning complex cavities and channels in the products. Much depends on the equipment – thus, the innovative ultrasonic cleaner devices by Hilsonic, a seasoned UK-based manufacturer with years of experience, will demonstrate way better performance in an average cleaning case.
Ultrasound is widely used for cleaning wire, metal strip, nozzles, cable, and others. The specific application of the technology of ultrasonic cleaning includes cleaning powders, radioactively contaminated surfaces, the regeneration of ceramic filters, etc.
Ultrasonic cleaning efficiency depends on the choice of many parameters, ie. physico-chemical properties of the liquid detergent. For the right choice of solutions must take into account the nature of contamination: the degree of adhesion to the surface to be cleaned, the chemical interaction with the detergent solution, the ability to withstand stress microshock (cavitation resistance). Preclassification of contaminants is better to be conducted beforehand to increase removal efficiency. Given this feature, you can choose the right technology of ultrasonic cleaning (the environment and sound field parameters).
Given the nature of the contamination and the nature of their relationship with the surface the following types of pollution are distinguished:
- inorganic contaminants – mechanically weakly coupled with the surface (dust, debris, metal and nonmetal chips, black and so on. n.);
- overact in mechanically surface (abrasive grains, particles of mineral or metal);
- deposited on the surface (salt cake after treatment in salt baths, scum and so on. n.)
- Pollution and organic nature of the coating or resin bonds:
- mechanically weakly coupled with the surface (dust, plastic swarf and dust, carbon black, coal, coke);
- having a small degree of adhesion to the surface (grease and oil film and lubricants, grinding, polishing and lapping pastes);
- firmly grip (resin, varnish, glue, paint and so on. n.).