Design and development of robotic scanning device mechanism for accessibility and stability of self-magnetic leakage field technique for boiler tube inspection at power plants


In a power plant, a primary concern regarding unplanned shutdown is failure of the boiler and its components, for instance the boiler tube. Boiler tubes are an important element in boilers as water and steam are channelled to drive the turbine. Boiler tubes are usually fabricated from carbon steel with high strength. They operate under pressure and thermomechanical loading. The application of advanced heat resistance and special alloy steel materials still do not solve tube leaking or burst tube problems. Hence, periodical inspection of boiler tube condition after prolonged service is needed to prevent any tube failure. The method and equipment used to check the boiler tube condition also need to be informative and easy to use. If possible, the inspection should be carried out without incurring excessive costs and, at the same time, it should produce no kind of pollution in the surrounding area. Over the years, non-destructive testing (NDT) has been used at power plants to assess the condition of the boiler tubes and identify defects. In an effort to further enhance these activities, TNB Research is focusing on the development of robotic systems to assist in the existing inspection process, which can also minimise the manual operation and the effects of the human factor in the context of labour-intensive or dangerous work and also in inaccessible environments. This paper describes the robotic mechanism systems developed by TNB Research, in collaboration with Universiti Tenaga Nasional for boiler tube inspection using a scanning sensor device in the application of the self-magnetic leakage field (SMLF) technique. The robotic systems are designed to work in an environment close to room temperature when the boiler is offline. The lab test results of developed prototypes indicate that the robotic systems are almost ready for further on-site applications. The developed robotic systems are proven to assist in optimising the current inspection process, increase work efficiency and reduce the overall inspection time.