On attempting to manipulate or bend a boiler tube some 22 ft. long, sudden failure occurred at what appeared to be a butt weld in the tube. Externally, the weld reinforcement had been ground flush and the entire tube surface painted. Internally, the appearance and width of the heated band suggested that the weld had been made by the oxy-gas process. A lack of root fusion over most of its length was evident. Examination of the fracture faces, which were of crystalline appearance indicative of brittle behavior, indicated incomplete fusion of the weld root. Microscopic examination showed the deposit...