Abstract: A device (20) for installing a tubular junction sleeve inside a pipe (1), having a mandrel (20a) of longitudinal axis (XX) supporting on its surface at least a first peripheral chamber (21) having a wall (21a) that is radially expandable by inflation. The first wall including at least one electrical connector (21b) suitable for being connected to one end of said heater wire. The connector being connected to an umbilical (24) including at least a compressed air feed duct for inflating the first chamber and an electrical power supply duct connected to the electrical connector. The device being characterized in that the mandrel supports on its outer surface a second peripheral chamber (22) having a wall (22a) that is radially expandable by inflation, and also a weld inspection device (23) arranged in the longitudinal direction of the mandrel.