Life is linked to liquid transport, and so are vital segments of economy. Pumping devices – be it the human heart, a boiler feeder or the cooling-water pump of a motorcar – are always part of a more or less complex system where pump failure can lead to severe consequences. To select, operate or even design a pump, some understanding of the system is helpful, if not essential. Depending on the appli- tion, a centrifugal pump can be a simple device which could be built in a garage with a minimum of know-how – or a high-tech machine requiring advanced skills, sophisticated engineering and extensive testing. When attempting to describe the state-of-the-art in hydraulic engineering of centrifugal pumps, the focus is nec- sarily on the high-tech side rather than on less-demanding services even though these make up the majority of pump applications. Centrifugal pump technology involves a broad spectrum of flow phenomena which have a profound impact on design and operation through the achievedef- ciency, the stability of the head-capacity characteristic, vibration, noise, com- nent failure due to fatigue, as well as material damage caused by cavitation, - dro-abrasive wear or erosion corrosion. Operation and life cycle costs of pumping equipment depend to a large extent on how well these phenomena and the inter- tion of the pump with the system are understood.