Failure Analysis And Residual Life Assessment Of The Main Steam Pipe

With the steep increase of power needed and complicated mechano -electronic structure, it is important to strengthen failure analysis and precaution. Main steam pipe is one of the key components in a power plant, whose creep capability is defined as design criteria. Undoubtedly, deterioration and damage accumulation occur in high temperature and high pressure. With the consumption of their use, the failure accidents occur more frequently, which will bring threatening to the life of people and the poverties of enterprise. So the failure analysis and the residual life assessment of the main steam pipe become more and more urgent and important. By combining with an engineering practice, the failure pattern, the procedure and the method of failure analysis, the influential factors of service life and the methods of residual life predication of the main steam pipe are investigated systematically in the dissertation. So preventing accident and decreasing damage can be reached.The actualities and development of main steam pipe's failure analysis and residual life predication are analyzed systematically from many engineering failure cases in chapter 1. Thereby the direction and the contents of the research are decided in the research program.The main steam pipe's failure pattern is discussed and analyzed in chapter 2. According to the failure factors, the mechanism, the processes, the critical conditions, the aftereffects etc, the main steam pipe's failure patterns are divided into five types: frangibility, toughness, high temperature, creep, fatigue, The processes and characters of each type is analyzed and summarized.The procedure of the main steam pipe's failure analysis is investigated in detail in chapter 3. In order to obtain the correct judgment of main steam pipe conditions, the studies combined with the engineering practices were carried out. On the basis of the integration, the procedures and the methods of the main steam pipe's failure analysis are constituted. In order to avoid the confusion, the disorder, the repetition, the omission and the limitation, each mechanics is studied in detail.The serious bursting accident of the main steam pipe was analyzed 3by applying the research results above in chapter 4. The main steam pipe has serviced for 12 X 104h in the power plant. Using scanning electron microscope (SEM), X-ray diffraction, optical microscope (OM), mechanical experiments, it is verified that the main reason causing the main steam pipe breaking down were the material and structural defects.The main steam pipe's residual life assessment is investigated in chapter 5. The influential factors of the service life are analyzed. It is pointed out that the creep limit, the rupture limit, the fatigue limit are internal factor, and that the temperature, the stress, the start-failure rate, the modulation are external factor. The residual life assessment methods are formulated under the creep and the creep-fatigue failure patterns. The suitable premise and region of the methods are specified correspondingly. The procedure of the residual life estimation was worked out for the technical management in the power plant.The residual life of the main steam pipe was estimated by using experiments and theoretical calculation in chapter 6. It is concluded that the residual life of the main steam pipe serviced over 10 X104 hours could reach 9 X 104 hours with eliminating the material defects and the structural defects. The summary and expectation in the chapter 7...