To provide a multi-stage motor pump capable of minimizing the outside diameter of the pump as much as possible without making a passage structure complicated.
In this multistage motor pump which introduces treated fluid discharged from an impeller 14 on a first stage and flowing to one side in an axial direction into an impeller 15 on a second stage as a flow in the other direction, a discharge side pump casing 3 in which the impeller 15 on the second stage is accommodated inside is provided. The discharge side pump casing 3 has first opening parts 51 to 54 which make the treated fluid flow to one side in the axial direction, a second opening part 57 which introduces the flow in the other direction into the impeller 15 on the second stage, and passage walls 60 to 63 for forming a plurality of volute passages 55, 56 which introduce the treated fluid discharged from the impeller 15 on the second stage to the outside in the radius direction.
IIJIMA KATSUJI
MAKINO TSUTOMU
UEI KEITA
