Inner diameter weld metal overlay for the repair of flow accelerated corrosion in power piping

Flow accelerated erosion damage is common in the secondary piping system of nuclear power plants. Typical systems affected are steam extraction, cold reheat, and MSR drain piping. Most of these systems were fabricated using SA106 and similar materials. The susceptibility to erosion has been attributed to the fact that most of the materials used contain little or no chromium. Although very small amounts of chromium (as little as .25%) are needed to significantly reduce the susceptibility to flow accelerated erosion, the most common method for correcting the problem has been to replace the piping components with alloys containing 1.25% to 2.5% chrome. In most plant designs, the system that carries steam from the exhaust of the low pressure turbine to the moisture/steam separator (cold reheat) is fabricated out of thirty-six to forty-eight inch diameter piping components. Replacement of this piping is typically not an option because of its large size and the fact that it is typically located in a very congested area of the power block. This paper addresses a technique which has been used successfully to install an erosion resistant layer of welded material to the inside surface of cold reheat piping. Automatic welding methodology was employed to allow the installation to be performed efficiently and with minimal heat input to the parent metal