Device for stopping a leak in a straight portion of a heat-exchanger tube

A device for stopping a leak in a straight portion of a heat-exchanger tube, wherein said device comprises an axial mandrel of material having good electrical conductivity on which are engaged metal washers of revolution having a conical profile and separated by cylindrical insulating pastilles, an insulating head fixed at one end of the axial mandrel and an insulating support mounted at the end opposite to said head, a threaded portion of said mandrel being passed freely through said support and adapted to cooperate with a nut which is applied against the support and serves to exert on the conical washers an adjustable initial compressive stress such that the outer peripheral edges of said washers are applied against a thin cylindrical lining sleeve which is coaxial with the mandrel, the external diameter of said sleeve being smaller than the internal diameter of the tube in which the leak to be stopped is located, means for introducing the support within the lining sleeve and then introducing the sleeve within the tube in order to place said sleeve opposite to a region which includes said leak, means for subjecting the mandrel aforesaid to an axial displacement with respect to said support so that the conical washers are compressed to a maximum extent and thus undergo a change from a conical profile to a more flattened profile so that each washer exerts on said lining sleeve a radial force which applies said sleeve in intimate contact with said tube along a number of circular lines corresponding to the number of washers, and means for passing an electric current successively through the mandrel, the washers, the lining sleeve and the tube in order to joint said tube and said sleeve by means of resistance welds formed along said circular lines.