Axial pump

An axial-flow pump moves liquid along the shaft axis with a propeller-type impeller, giving high volume flow at low head. It suits ballast transfer, main sea water cooling, and dock dewatering, where a ship must shift large quantities against a few meters of head. Head per stage is low, often under 10 meters, while flow can reach thousands of cubic meters per hour. The pump is a dynamic, not positive-displacement, machine: head falls as flow rises along its characteristic curve, and it must be primed because it cannot draw a dry suction. Specific speed is high, the marker that separates axial from radial designs.