A new approach to ultrasonic cleaning

Traditional ultrasonic cleaning baths are limited in that they cannot clean objects that are too large to fit in the bath, and cannot be taken to objects with complex geometries in order to “clean in place.” Furthermore, the object to be cleaned sits in a “soup” of contaminated liquid, and while cavitation fields can be set up under test conditions, immersion of the object to be cleaned can significantly degrade the bath’s performance by disrupting the sound field. An alternative technique, which does not use ultrasound is the commercial pressure- or -power washer, where high speed jets of water and cleaning agent are pumped onto a surface. Although these can “clean in place,” they pump large volumes of water, and produce significant volumes of contaminated run-off and contaminated aerosol, both of which are hazards for secondary contamination of users and water supplies. The momentum of the water and pump requirements mean they are difficult to scale up. This paper presents a low volume flow technique for ultrasonic cleaning in place, benefits being that it operates with low flow rates (1–2 L/min), and there is no need to expend energy on heating the water.