| 摘要 |
PROBLEM TO BE SOLVED: To highly accurately evaluate a damage of a part which is difficult to evaluate by a nondestructive test, particularly, a fine particle area thermally influenced by welding, by applying a damage ratio of a weld part obtained by a stress analysis to a damage evaluation by a nondestructive test. SOLUTION: A plurality of stub pipes 13 are welded to a secondary superheater exit header 1. A welded part becomes a stub pipe base weld part 12. A material of a damage evaluation part A which is a fine particle area thermally influenced by the welding is, e.g. fire STBA28. A drive time of a boiler at a damage evaluation diagnosis is approximately 8500 hours. Through a stress analysis with the use of the finite element method, a creep damage rate of the part A is 38.5% and that of a stub pipe parent material part (part B) is 27.3%, and a damage ratio is 1.4:1. A hardness at the parent material part (part B) is actually measured. The creep damage rate obtained by a nondestructive inspection method from the measured value is 35%. When the damage ratio 1.4 is applied, the creep damage rate of the fine particle area thermally influenced by the welding is evaluated and diagnosed to be 35%×1.4=49%.
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