Small vortexes of air created by the centrifugal force and the rotation are dragged by the vanes from the aspiration toward the drain. There are no parts in contact, thus the blowers do not require routine maintenance but, since the intake air is also used as cooling fluid, they can operate continuously only within certain ranges of pressure. To prevent a damage of the engine it is indeed necessary to install vacuum and pressure limiting valves.
All versions can be used as compressors. If used as a compressor, the output flow is clean and free of pulsations.