METHOD AND APPARATUS FOR REPAIRING DAMAGED TUBES

Disclosed is a laser beam welding technique which can be utilized to accomplish clad welding and repair of the internal surface of a tube. The technique uses the addition of filler metal to build up the internal surface of the tube. The apparatus includes a laser energy source connected to an elongated weld head by an optical fiber. The elongated weld head is rotatable and contains a mirror canted at a forty-five (45) degree angle. The laser beam generated by the laser source enters the weld head through a rotary joint, passes through focusing lenses, and is reflected to the interior surface of the damaged tube by the canted mirror. Means are provided to rotate the weld head which causes the beam to travel circumferentially around the interior of the tube. Means are also provided to feed metal fill material to the location where the focused beam contacts the interior surface of the tube. The result is a smooth clad welding repair on the inside surface of the tube which restores the strength of the tube and leaves no crevices for future corrosion attack. In addition, the internal diameter of the tube is very close to the original diameter of the tube thus obviating pressure drop associated with the sleeving type repair and allowing for subsequent repair of the tube at positions beyond the first area of repair.