Centrifugal pump with axially compensated impeller - has axially fixed balance ring behind axially free impeller

摘要

A centrifugal pump has a shaft (2) on which an impeller (1) is keyed (6) to have axial but not rotational freedom of movement. There is a sealing orifice gap (5) between the back of the impeller and the casing and a similar gap (7) at a smaller diameter between the front of the impeller and the casing. There are pressure equallising aperture (4) through the impeller below the blade entry. A balance ring (8) is keyed to the shaft behind the impeller to have neither axial nor rotational freedom of movement. As the impeller (1) moves axially the gap (9) between the equalising openings and the balance ring varies with a resulting variation in pressure which controls the axial movement of the impeller.