PSI - Issue 48

Evgeniia Georgievskaia / Procedia Structural Integrity 48 (2023) 310–317 Georgievskaia / Structural Integrity Procedia 00 (2019) 000 – 000

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7. Recommendations for ensuring the safe and secure LSS operation Based on the results of the calculation and experimental work, recommendations were developed to ensure reliable and safe operation of the LSS during the inter-maintenance period, aimed at minimizing the severity of crack formation, including incidental one, and at identification of appearing cracks in their early development stages. Firstly, these are technological recommendations for recovery repairs upon detecting LSS cracks, aiming at reoccurring crack quantity reduction. Secondly, these recommendations are for LSS inter-overhaul inspection by HPP personnel during equipment operation and short shutdowns for periodic routine maintenance, allowing identification of cracks in their early development stages. Thirdly, LSS structure reinforcement through the installation of additional inclined stiffeners. Fig. 5 shows the reinforcement scheme proposed for the LSS structure and static stress change schedule along the junction line between the central part with LSS spokes before and after installing reinforcing stiffeners during nominal HU operation. Fig. 6 shows the relative dynamic stress distribution field before and after installing reinforcing stiffeners (on the same scale). Maximum static and dynamic stresses in both structures are achieved directly below the butt beam. According to the data provided installing reinforcing stiffeners allows for decreasing local stresses by approximately 1.8 times. This solution has already been implemented in one HPP unit and has proved to be effective. a b

Fig. 5. LSS structure local stresses reduction. (a) LSS structure reinforcement scheme; (b) static stresses along the junction line between the central part with LSS spokes during nominal HU operation before and after reinforcement a b

Fig. 6. Relative dynamic stress distribution field (intensity). (a) before installing reinforcing stiffeners; (b) after installing reinforcing stiffeners

8. Conclusion Conducted research leads to the following conclusions: