PURPOSE: To restore assembly in an optimum condition of a pump shaft easily in a short time by providing a space restricting screw means in an upper end part of the pump shaft, and setting an upper end of the space restricting screw means to height, where it is brought into contact with a lower end of an electric motor shaft, in a condition that an axial directional position of the pump shaft is optimized relating to the electric motor shaft.

CONSTITUTION: A space restricting screw means 30 is mounted to an upper end of a pump shaft 41. That is, a restricting bolt 31 is screwed into an internal thread part 41a provided in an upper end part of the pump shaft 41. In a setting up work site, a mechanical seal 19 and an impeller or the like are replaced, and reassembly after repair is performed such that the pump shaft is tightened and connected by a bolt by lifting the pump shaft 141 to a position, where a head part of the restricting bolt 31 is brought into contact with a lower end of an electric motor shaft 2, and by fitting semi-cylindrical parts 20a, 20b of a box-shaped shaft joint 20 to both shaft end parts. In this way, an axial directional position relating to the electric motor shaft of the shaft 41 is restored to an optimum position of plant assembly.