Abstract: A process of welding fittings to ends of a double wall pipe comprising forming a first welded joint between an inner pipe and an inner receiver of a first fitting; forming a second welded joint between an outer pipe and an outer receiver of the first fitting; forming a third welded joint between the outer pipe and an outer receiver of a second fitting; and forming a fourth welded joint between the inner pipe and an inner receiver of the second fitting.

Abstract: A fitting for forming a double-walled tube includes an inner fitting having a first inner weld lip, a second inner weld lip, and an inner body extending from the first inner weld lip to the second inner weld lip and having an outer surface with a first threading. The fitting also includes an outer fitting having a first outer weld lip, a second outer weld lip, and an outer body extending from the first outer weld lip to the second outer weld lip and having an inner surface with a second threading that is configured to mate with the first threading.

Abstract: A process of welding fittings to ends of a double wall pipe comprising forming a first welded joint between an inner pipe and an inner receiver of a first fitting; forming a second welded joint between an outer pipe and an outer receiver of the first fitting; forming a third welded joint between the outer pipe and an outer receiver of a second fitting; and forming a fourth welded joint between the inner pipe and an inner receiver of the second fitting.

Abstract: A fitting for forming a double-walled tube includes an inner fitting having a first inner weld lip, a second inner weld lip, and an inner body extending from the first inner weld lip to the second inner weld lip and having an outer surface with a first threading. The fitting also includes an outer fitting having a first outer weld lip, a second outer weld lip, and an outer body extending from the first outer weld lip to the second outer weld lip and having an inner surface with a second threading that is configured to mate with the first threading.

Abstract: Disclosed is a method for constructing a double walled tube assembly, comprising: welding a first axial end of a first tube to a first sub-fitting of a first fitting, sliding a second tube over the first sub-fitting and the first tube, sliding a second sub-fitting of the first fitting over the first sub-fitting such that the first and second sub-fittings are co-axial, welding a first axial end of the second tube to the second sub-fitting, and welding the second sub-fitting to the first sub-fitting. An assembly includes a first fitting that includes a first sub-fitting and a second sub-fitting, a first tube having a first axial end that is welded to the first sub-fitting, and a second tube having a first axial end that is welded to the second sub-fitting, where the first tube is nested within the second tube, where the first sub-fitting is welded to the second sub-fitting.

Abstract: A fitting for forming a double-walled tube includes an inner fitting having a first inner weld lip, a second inner weld lip, and an inner body extending from the first inner weld lip to the second inner weld lip and having an outer surface with a first threading. The fitting also includes an outer fitting having a first outer weld lip, a second outer weld lip, and an outer body extending from the first outer weld lip to the second outer weld lip and having an inner surface with a second threading that is configured to mate with the first threading.

Abstract: A fitting for forming a double-walled tube includes an inner fitting having a first inner weld lip, a second inner weld lip, and an inner body extending from the first inner weld lip to the second inner weld lip and having an outer surface with a first threading. The fitting also includes an outer fitting having a first outer weld lip, a second outer weld lip, and an outer body extending from the first outer weld lip to the second outer weld lip and having an inner surface with a second threading that is configured to mate with the first threading.

Abstract: Disclosed is a method for constructing a double walled tube assembly, comprising: welding a first axial end of a first tube to a first sub-fitting of a first fitting, sliding a second tube over the first sub-fitting and the first tube, sliding a second sub-fitting of the first fitting over the first sub-fitting such that the first and second sub-fittings are co-axial, welding a first axial end of the second tube to the second sub-fitting, and welding the second sub-fitting to the first sub-fitting. An assembly includes a first fitting that includes a first sub-fitting and a second sub-fitting, a first tube having a first axial end that is welded to the first sub-fitting, and a second tube having a first axial end that is welded to the second sub-fitting, where the first tube is nested within the second tube, where the first sub-fitting is welded to the second sub-fitting.