AXIAL THRUST REDUCING DEVICE FOR PUMPS

摘要

A thrust load reducing device of a pump unit including a pump section (P) having a main impeller (1), a motor section (M) for driving the impeller (1), a thrust disc (7) serving concurrently as an auxiliary impeller located at one end of a motor shaft (4) in the motor section (M) for supplying motor cooling water flowing in circulation to the motor section (M), and thrust bearings (10A, 10B) mounted on an inner surface of the casing (3) in positions in which they are juxtaposed against a front surface of the thrust disc (7) located on its suction side and a rear surface of the thrust disc (7) located on its discharge side, respectively. The thrust load reducing device includes a first fine gap defining member (12) located on the inner surface of the casing (3) and cooperating with an outer peripheral surface of the thrust disc (7) to define therebetween a first fine gap (G1) constituting a passage for a fluid discharged by the thrust disc (7) and returning thereto in return flow.