Patent ID: 7243409

Claim:
A method of forming a conduit assembly for transporting fluids, comprising the steps of: forming a pair of weldable conduits, each of the conduits being formed by: positioning a tube formed of a material having desirable properties within a pipe formed of a commonly weldable material such that one end of the tube is aligned with one end of the pipe, the tube having an outer diameter slightly less than the inner diameter of the pipe; affixing the tube to the pipe by connecting the aligned ends thereof; and compressing the pipe in a reducing operation so that the inner diameter of the pipe is reduced to a diameter that is less than or equal to the outer diameter of the tube; and positioning the conduits in opposing relation and placing an end of each of the conduits about the respective opposing ends of a coupling for welded interconnection of the conduits, the coupling including: a cylindrical body formed of the same material as the tubes of the conduits, the body having: an outer diameter that is slightly less than the inner diameter of the tubes of the conduits, and a circumferential recess intermediate the ends of the body, and a ring formed of the same material as the tubes of the conduits, the ring being positioned within the recess of the body and having a circumferential stop means for limiting movement of the ends of the body within the respective ends of the conduits by the ends of the conduits abutting the stop means; and at least one circumferential seal intermediate the recess and each of the tapered ends of the body for sealing the interconnected conduits; temporarily affixing the ends of the conduits to one another in the region of the circumferential stop means of the ring; removing the circumferential stop means of the ring to clear an annular pathway for welded interconnection of the ends of the conduits; and welding the ends of the conduits together in the annular pathway.