PURPOSE: To prevent abnormal discharge and to make possible the electro-hydraulic expanding method to be applied to setting the pipe to the tube plate, by protruding the insulating cartridge for filling the liquid, out of the tube plate surface, and by protruding the feeder being covered with the insulating tube, out of the tube plate surface.

CONSTITUTION: The inner cylinder 7, constituting the cartridge made of polyethylene, etc., with wall thickness above 2mm, is arranged within the pipe 2 so as to protrude the distance l above 3cm out of the surface of the tube plate 1; and the feeder 11, covered by the insulating tube with wall thickness above 1mm, is arranged so as to protrude the distance L above 5cm out of the surface of the tube plate 1. The switch 13 is closed to supply the electricity; hereby, the energy, discharged from the capacitor 12, instantaneously gasifies the aluminum thin wire 9 within the inner cylinder 7 and the surrounding water 14. This power of explosion is utilized for expanding the pipe 2 which is then tightly set to the tube plate 1. Hereupon, the spark across the feeder 11 and the tube plate 1 is prevented, so that the pipe expanding work is smoothly performed without breaking the inner cylinder 7.