Patent ID: 8118210

Claim:
A method for applying a helical cladding bead to the interior surface of a circularly curved pipe elbow having a first end, a second end, a curved centerline, a center of curvature, and a plane of curvature, said method comprising the steps of: (a) providing an elbow carriage having: a.1 a rotor rotatable about a primary axis; and a.2 an elbow collar mounted to the rotor and radially movable relative to the primary axis; (b) swivelably mounting the first end of the pipe elbow to the elbow collar such that the elbow's plane of curvature will coincide with the primary axis irrespective of the rotational position of the rotor or the radial position of the elbow collar; (c) supporting the second end of the pipe elbow on a steady rest such that the elbow's curved centerline substantially coincides with the primary axis where the primary axis intersects a reference plane transversely perpendicular to the primary axis; (d) providing a weld arm having: a drive end associated with weld arm rotation means for rotating the weld arm about the primary axis; a free end; and a weld head associated with said free end: d.1 said weld arm being configured such that the weld arm can be positioned inside the pipe elbow without physical interference when the elbow is positioned as in step (c); and d.2 said weld arm having weld head linkage means effective to maintain the weld head in a fixed spatial orientation irrespective of rotation of the weld arm about the primary axis; (e) positioning the free end of weld arm inside the pipe elbow with the weld head in close proximity to the reference plane; (f) coordinatedly rotating the rotor and the weld arm in a selected direction about the primary axis, while moving the elbow carriage in a selected direction parallel to the primary axis and moving the elbow collar in a selected radial direction relative to the primary axis, such that the pipe elbow rotates about the primary axis with its center of curvature orbiting around the primary axis in substantial coincidence with the reference plane; and (g) feeding welding wire to the weld head so as to deposit a cladding bead of molten metal on the interior surface of the pipe elbow.