Damage and Residual Life Assessment of Bends for X20CrMoV12.1 Main Steam Pipe after Long-Term Service
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The bent sections from a main steam pipe in a thermal power plant in Shanghai were examined after 165,000 h service at 550 °C under 13.73 MPa pressure. The residual life of the bend sections is determined by evaluation of the service stresses and testing to obtain creep rupture data. Metallographic analysis and tensile, impact, and hardness tests are also conducted. These combined tests show that the properties of the steel deteriorated during service, displaying embrittlement tendencies; the corresponding microstructures exhibit grain boundary weakening and creep damage characteristics. However, considering no evidence of localized damage in the form of creep cavitation or surface cracks was observed in the examined parts, considering the residual life of the bends at service condition, they are adequate for an additional 44,000 h of operation. It is recommended that a health assessment should be taken after 25,000 h service exposure for safety reasons.
KeywordsMain steam pipe Microstructure Finite element analysis Residual life assessment
This work was supported by the National Natural Science Foundation of China under contract no. 50771073 and National Basic Research Program of China under contract no. 2007CB714705.
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