Abstract: Tube for a cracking plant, comprising an inner tube, a coaxial outer tube and a reinforcement layer intermediate said inner and outer tube, said reinforcement layer having openings or passages through which said inner and outer tube are bonded together.

Abstract: Method for making a tube for a cracking plant, by providing an inner tube, placing a reinforcement about said inner tube, said reinforcement having transverse openings or passages, placing an outer tube coaxially about said inner tube and said reinforcement, bonding together by pressure or fusion welding, said inner tube and said outer tube through said openings or passages in said reinforcement.

Abstract: The invention is related to the integral extrusion of at least two pipes and a common flange to an extruding device and to a flange with at least two pipes integral with said flange. The method is characterized in that said pipes are extruded simultaneously while a common flange is formed at the same time, during which extrusion the material of the starting workpiece (blank), flowing under pressure, is forced, at a certain distance before the beginning of the extrusion openings for the pipes, to flow axially and radially into and through a transient space situated between said openings and the space reserved for the flange.

Abstract: The present invention provides a certain improvement in the method for connecting a pipe to a plate by high pressure welding. This basic method is one in which the pipe is inserted a certain distance into a bore provided in the plate and subsequently the material of the pipe is spread out over the wall surface defining the bore of the plate, under the influence of high pressure and with the aid of a mandrel disposed in the pipe.The improvement provided by the invention basically comprises the steps of positioning within a cooperating punch and die set, the plate with an end section of the pipe inserted into the bore of the plate. The punch and die set have opposed aligned bores accommodating the extension therethrough of the pipe and a mandrel respectively. In addition the punch and die set generally confine the plate at the peripheral edge and opposite sides thereof, and are operable to apply compressive forces to the opposite sides of the plate.