This paper analyses the clogging behavior of vortex pumps by comparing the characteristics of two impeller designs. The impellers have dissimilar heads and efficiencies; the water was either clear or it contained non-woven textiles. An acrylic casing allowed observing the operation behaviour of the vortex pump while, at the same time, monitoring the data. Principle differences in the clogging behavior of the two impellers could be observed: One impeller outperformed the other in clear water transportation and indeed pumped more of the textiles. However it also lost more of its efficiency and accumulated more textiles declining it as the harder clogging. These results speak against the common approach of designing vortex pumps impellers under clean water operation condition, assuming that the same conditions apply for solid-containing fluids. KEYWORDS VORTEX PUMP, IMPELLER, CLOGGING, EXPERIMENT NOMENCLATURE Q flow rate H head η efficiency ∆Q ratio of the flow rate under clogging to clear water operation ∆H ratio of the head under clogging to clear water operation ∆η ratio of the efficiency under clogging to clear water operation ∆textiles proportion of not-pumped textiles to total amount of textiles

This paper analyzes the clogging behavior of a vortex pump with different impeller designs. The influence of blade outlet angle, blade number, and impeller diameter were tested. Non-woven textiles in different concentrations served as the clogging material. The results suggest that a smaller outlet blade angle, a higher blade number, and a larger impeller diameter allow pumping more textiles. Impellers that were capable of pumping more textiles, however, were less efficient. Overall, pumping textiles causes efficiency losses. However, this could not be only related to increased power consumption. Flow rates under clogging operation were close to the flow rates under clear water operation irrespective of the amount of clogging material and the impellers design. Further, in all tests clogging material accumulated at the suction mouth in the casing.