Vertical shaft pump

摘要

A vertical shaft pump to be disposed in a pump pit comprises a pump casing having a suction opening, and an impeller disposed in the pump casing below a position corresponding to the lowest water level in the pump pit below which the pump starts to suck air through the suction opening during operation. A series of intake ports are provided in the pump casing below the impeller with equal intervals in the circumferential direction of the pump casing. These intake ports act to introduce atmospheric air into the pump casing through intake pipes when the pressure at the intake ports is lowered below the atmospheric pressure.