Reversible centrifugal pump

Abstract

A centrifugal pump capable of rotating in a normal direction while enabling a fluid to flow in a normal direction and rotating in a reverse direction while enabling the fluid to flow in the reverse direction without having its pumping efficiency dropping to a lower level in a reverse rotation mode than in a normal rotation mode. The pump includes two pump casings each having an inlet and outlet portion extending tangentially of each pump casing and connected together through an intermediate casing to provide a unitary structure in which the two pump casings are located concentrically in face-to-face relation, and an impeller having a helical blade extending axially from one zone in one pump casing into another zone in the other pump casing for rotation along the center axis of the pump. The impeller has a minimum outer diameter at the center of its center axis and includes portions each flaring in one of axial opposite directions in the form of a cone. The impeller has an outer periphery cooperating with an inner periphery of the intermediate casing to define a small clearance therebetween. The inlet and outlet portions of the two pump casings are arranged such that when the two pump casings alternately act as a suction casing at the time of normal rotation and reverse rotation, the influx direction of the fluid through the inlet and outlet portion of the pump casing acting as a suction casing is opposed to the direction of rotation of the impeller means.