A method for manufacturing a double-walled tube is provided. The method comprises the extrusion of two tubes wherein one tube is inside the other. A first mold is provided around the outside of the outer tube and a support provided along the inside of the inner tube. Fluid is then injected into the cavity between the inner and outer tubes to mold the outer tube against the first mold.

A shrouded pipe formed from inner and outer pipe sections, the inner pipe section having an outwardly projecting flange joining the outer pipe section, and the outer pipe section having an inwardly projecting flange joining the inner pipe section, an annular volume between the inner and outer pipe sections providing a secondary fluid path. The flanges control axial position of the inner pipe section. By providing one flange which extends radially outwardly and one which extends radially inwardly, assembly is possible of the shrouded pipe by inserting the inner pipe section into the outer pipe section, without modification of the outer pipe section or inner pipe section. The first and second flanges ensure no unwanted contact between the inner and outer pipe sections, and therefore to prevent damage to the primary fluid path. The first and second flanges ensure good load distribution between the inner and outer pipe sections.

A method of manufacturing a shrouded pipe comprising an inner pipe section for providing a primary fluid path and an outer pipe section for enclosing the inner pipe section to provide a secondary fluid path. The method includes opening the outer pipe section by separating first and second longitudinal edges which split the outer pipe section along a longitudinal line, assembling the outer pipe section with the inner pipe section by passing the inner pipe section between the separated first and second longitudinal edges, and closing the outer pipe section by bringing the first and second longitudinal edges together and joining the first and second longitudinal edges together. An advantage of this method is that close manufacturing tolerances can be achieved without a complex or difficult assembly process.

The present double walled grease duct includes a tubular outer shell surrounding a tubular inner liner, wherein a spacer is positioned perpendicular to the walls of the outer shell and the inner liner. The spacer can include a plurality of vertical metal strips extend from a top edge of the spacer to the bottom edge of the spacer, wherein the top edge of the spacer contacts the walls of the outer shell and wherein the bottom edge of the spacer contacts the walls of the inner liner. The metal strips resist the different rates of thermal expansion between the outer shell and inner liner ultimately preventing the collapse of the inner liner under pressure from thermal expansion.

The present double walled grease duct includes a tubular outer shell surrounding a tubular inner liner, wherein a spacer is positioned perpendicular to the walls of the outer shell and the inner liner. The spacer can include a plurality of vertical metal strips extend from a top edge of the spacer to the bottom edge of the spacer, wherein the top edge of the spacer contacts the walls of the outer shell and wherein the bottom edge of the spacer contacts the walls of the inner liner. The metal strips resist the different rates of thermal expansion between the outer shell and inner liner ultimately preventing the collapse of the inner liner under pressure from thermal expansion.

Modular heat insulation, manufactured as separate welded blocks of stainless corrosion-resistant steel, arranged on the pipeline outer surface. The boxes are filled with heat-insulating material and interconnected with quick-acting tension locks. The cover plates shield the block joints. A heat-insulating material being a set of minimum three corrugated or blistered shields is used. These shields are manufactured of stainless corrosion-resistant steel forming enclosed air cavities. The external lining sheets of the adjacent blocks are shorter than the blocks themselves by the size of the cover plates and are installed with a lateral ventilated gap from the external surface of the shield set. The cover plates shall have the shape of mated sections with a multilayer set of corrugated stainless corrosion-resistant steel sheets. The mated sections are quick-acting tension locks, and their cover plates have width overlapping the area of blocks' increased temperature within their joints.

Modular heat insulation, manufactured as separate welded blocks of stainless corrosion-resistant steel, arranged on the pipeline outer surface. The boxes are filled with heat-insulating material and interconnected with quick-acting tension locks. The cover plates shield the block joints. A heat-insulating material being a set of minimum three corrugated or blistered shields is used. These shields are manufactured of stainless corrosion-resistant steel forming enclosed air cavities. The external lining sheets of the adjacent blocks are shorter than the blocks themselves by the size of the cover plates and are installed with a lateral ventilated gap from the external surface of the shield set. The cover plates shall have the shape of mated sections with a multilayer set of corrugated stainless corrosion-resistant steel sheets. The mated sections are quick-acting tension locks, and their cover plates have width overlapping the area of blocks' increased temperature within their joints.

Within examples, a method of manufacturing a double-walled titanium conduit is described. Example methods include stitch welding multiple concentric sheets to form a stitch layer, providing the stitch layer between an inner wall and an outer wall of the double-walled titanium conduit, circumferentially seam welding the inner wall and the outer wall to the stitch layer to create a welded assembly, die forming the welded assembly at temperature and pressure to form inner structures between the multiple concentric sheets according to stitch welding lines and to enable a diffusion bond process among the inner wall, the stitch layer, and the outer wall, and removing the double-walled titanium conduit from the die.

Within examples, a method of manufacturing a double-walled titanium conduit is described. Example methods include stitch welding multiple concentric sheets to form a stitch layer, providing the stitch layer between an inner wall and an outer wall of the double-walled titanium conduit, circumferentially seam welding the inner wall and the outer wall to the stitch layer to create a welded assembly, die forming the welded assembly at temperature and pressure to form inner structures between the multiple concentric sheets according to stitch welding lines and to enable a diffusion bond process among the inner wall, the stitch layer, and the outer wall, and removing the double-walled titanium conduit from the die.

A low temperature fluid dual structure pipe includes: an inner pipe through which a low temperature fluid flows; and an outer pipe externally fitted to the inner pipe with a sealed tubular space therebetween. An inactive gas having a melting point and a boiling point each of which is equal to or higher than a temperature of the low temperature fluid is filled in the tubular space between the inner pipe and the outer pipe. When the low temperature fluid flows through the inner pipe, the inactive gas is liquefied or solidified, and therefore, at least one of a liquefied inactive gas layer and a solidified inactive gas layer is formed on an outer peripheral surface of the inner pipe. As a result, a pseudo vacuum layer that is in a substantially vacuum state is formed in the tubular space.