DEVELOPMENT OF TECHNOLOGIES FOR DIAGNOSIS OF DEGRADATION IN SERVICE OF STAINLESS STEEL EQUIPMENT IN LNG TERMINALS

摘要

More than 30 years have passed since Tokyo Gas first started using LNG. Key LNG facilities have piping and vessels made from stainless steel, and although their safety is maintained through maintenance work, they are becoming steadily older. Consequently, quantitative assessment of any occurrence of the sorts of corrosion or stress corrosion cracks (SCC) that affect equipment such as stainless steel piping and vessels is essential for long-term maintenance of the facilities, and for reduction in life cycle costs.rnIn order to be able to handle issues such as crevice corrosion occurring in piping support sections, and SCC occurring in piping and similar vessels, Tokyo Gas has developed diagnostic technology with the following characteristics, and is now being used in order to realize effective and efficient maintenance.rn1. Application of ultrasonic testing to enable simple testing without having to remove the support (crevice corrosion inspection system)rn2. Application of ultrasonic testing to enable simple testing of painted equipment without peeling off the paint film (SCC inspection system)rn3. Development of analysis functions enabling 3-D monitoring of corrosion area and depth plotting the results on three axes (common to both systems)rnBy introducing these inspection systems, Tokyo Gas has successfully a remarkable reduction of the labor and costs required for inspection. Since data from diagnosis can be evaluated quantitatively, we can use such data for the evaluation of the remaining working life of the facilities, and make it possible to prolong facility working life.