How to assess cleaning? Evaluating the cleaning performance of moving impinging jets

Cleaning of process equipment is a necessity in the pharmaceutical and food industry. Recently, the efficiency of these cleaning processes has come more into focus due to increasing economical and ecological demands. Different approaches to assess cleaning processes in terms of their cleaning effectiveness, cleaning efficiency, cleaning rate and cleaning performance are discussed. Stainless steel sheets soiled with Xanthan gum were cleaned by a moving impinging water jet in a laboratory scale test rig. Different assessment criteria (time, fluid consumption and energy) to determine the related cleaning performance indicators were studied. The influence of operating parameters (nozzle diameter, gauge pressure and jet moving speed) on these performance indicators was quantified. Experiments showed that the cleaned area width, used as a quantitative criteria of cleaning, decreased with jet moving speed. The influence of the three operating parameters on the performance indicators was evaluated. The experimental results reveal that there is no parameter combination which optimizes the performance indicators simultaneously: the best combination depends on the priority given to each indicator.