At least two spacers in an elongated shape is provided between an internal pipe and an external pipe along the center line of a double pipe. In the cross section of a bent portion as viewed in a direction along the center line of the double pipe, the first spacer is located inwardly relative to the center of the double pipe with reference to the radial direction of the bent portion. The second spacer is located outwardly relative to the center of the double pipe. When a straight line that passes through the center of the radius of the bent portion and through the center of the double pipe is taken as a reference line at least either one of the first spacer or the second spacer overlaps the reference line.

The invention relates to a process for producing a multilayer pipe (1) from a tubular element having a metallurgical bond comprising at least one outer pipe (10) of metallic material and one inner pipe (20) of metallic material arranged within the outer pipe, the inner surface of the outer pipe (10) being mechanically bonded to the outer surface of the inner pipe (20) at least in parts of their interface, in which, in a production line, the tubular element is simultaneously heated and drawn, wherein each portion of the tubular element is submitted to heating by induction and then to hot-drawing, wherein the tubular element is drawn with a mandrel located therein. Through this process, the existing mechanical connection between the pipes is trans-formed in a metallurgical connection. The invention also relates to a multilayer pipe (1) produced for this process, wherein the outer pipe (10) is made of a carbon manganese steel alloy and the inner pipe (2) is made of a corrosion-resistant alloy.

A method of making an annular component includes forming sheet feedstock into an annular shape disposed about a central axis; and bonding one portion of the feedstock to another portion of the feedstock using ultrasonic welding, so as to fix the annular shape.

A super-long thermal insulation steel jacket pipe and a machining process for making such a pipe are provided. The pipe is designed to exhibit good thermal insulation performance and corrosion resistance. An annular cavity of the pipe is in a vacuum state, and the pipe is internally provided with a support frame and filled with a phase change material. When the pipe is used for underground energy exploitation, temperature in a working steel pipe in the pipe can be effectively kept unaffected when external temperature decreases. The steel jacket pipe has long service life, and can greatly reduce costs of exploitation of petroleum and/or of an underground heat source, such as by reducing a heat loss in exploitation.

A pipe body, wherein the pipe body (10) has a welded portion (11) at both ends of the pipe body, aligned in a widthwise direction of the pipe body (10). The thickness of the welded portion (11) decreases gradually from the inside to the outside of the pipe, and an outer end of the welded portion (11) is located at a center portion of the pipe body (10) in a thickness direction. The configuration of the welding structure enhances the strength of the welded portion of the pipe, so that the pipe will not crack easily when it is reworked by flaring or bending, thus having high reworkability. In addition, a pipe (100) made of the pipe body (10) and a method of making the pipe (100) are disclosed.

Herein a metallic tube portion is disclosed. The metallic tube portion comprises a connection element. The connection element comprises a protruding portion of a metallic outer tube of the metallic tube portion and a housing member. The housing member is welded to the protruding portion and at least a further portion of the metallic outer tube and/or a portion of a metallic inner tube. A signal line extends at least partially through the connection element.

Method for manufacturing a composite tube having at least one double-layered portion with an annular outer layer of a first alloy and an annular inner layer of a second alloy provides a base component of the second alloy, having a central through-hole and an externally threaded section, provides an outer component of the first alloy, having an internally threaded section configured to engage with the externally threaded section, forms a tubular work piece by mounting the outer component around the base component such that the internally threaded section is in engagement with the externally threaded section, and hot works the work piece so that a metallic bond is formed between the threaded sections while the mechanical interlock is maintained, and so that the work piece is elongated and its outer diameter is reduced, thus forming a composite tube.

The invention relates to a long tubular pipe comprising an outer tube, an inner fluid-transporting tube mounted in the outer tube, and a separating member designed to transmit bending efforts between said outer tube and said inner tube when said outer tube is bent, the separating member comprising means for the longitudinal passage of fluid between the inner tube and the outer tube, the separating member comprising a first edge and a second edge together defining an assembly slot, the first edge and the second edge respectively comprising a first connecting element and a second connecting element designed to cooperate mechanically on the outer periphery of the inner tube.

A method of manufacturing a tube is provided. The method includes: selecting a core pipe having a thickness that is initially less than a desired thickness of the tube; and building-up an outer layer over an exterior surface of the core pipe via additive manufacturing so as to increase the thickness of the core pipe such that the thickness of the core pipe is equal to the desired thickness of the tube.

A method for manufacturing a composite tube having at least one double-layered portion with an annular outer layer of a first alloy and an annular inner layer of a second alloy, comprising: providing a base component (301) of the second alloy, having a central through-hole and an externally threaded section (302), providing an outer component (401) of the first alloy, having an internally threaded section (402) configured to engage with the externally threaded section, forming a tubular work piece by mounting the outer component around the base component such that the internally threaded section is in engagement with the externally threaded section, hot working the work piece so that a metallic bond is formed between the threaded sections while the mechanical interlock is maintained, and so that the work piece is elongated and its outer diameter is reduced, thus forming a composite tube.