Ultrasonic cleaning baths are widely used in industrial production for cleaning and degreasing metal components, and are also available for domestic use for cleaning jewellery and spectacles. The cleaning process is based on cavitation generated by ultrasonic waves in the cleaning medium (water, possibly with cleaning additives): high acoustic pressure fluctuations cause vapour bubbles to form, which collapse either spontaneously or after several oscillation cycles. The resulting pressure waves and flows dislodge dirt particles from the surfaces being cleaned. Furthermore, cavitation promotes the distribution of contaminants within the cleaning medium; for example, it is also possible to produce stable oil-in-water emulsions.

In the ZIM-funded research project ‘Mobile ultrasonic cleaning unit for conveyor chains’, a collaboration with two industrial companies investigated whether conveyor chains – which are mounted on factory ceilings in industrial settings and used to transport suspended goods – can be cleaned more efficiently using an ultrasonic recirculation process than with conventional systems such as high-pressure or steam jet cleaners.

The cleaning process depends largely on the intensity and distribution of the sound field within the process chamber. Other parameters include the gas content of the cleaning medium, the frequency of the vibrations and the temperature. To achieve an optimal cleaning result efficiently, these factors must be taken into account when designing the process chamber. The transducers must be tailored to the process and, where possible, operated under controlled conditions. This can be achieved using various modelling approaches and simulations, as well as by validating these against experimental data.

Individual heavily soiled chain links were successfully cleaned in the prototype that was built; however, industrial implementation did not ultimately take place due to excessive investment costs.