OVERHEAT DAMAGE DIAGNOSING METHOD FOR BOILER WATER- WALL TUBE

摘要

PROBLEM TO BE SOLVED: To provide a method to efficiently and high-precisely detect the overheat damage portion of a bailer water-wall tube and high-precisely diagnose the degree of damage and a remaining life. ;SOLUTION: (1) Screening of a damage portion and ranking of an evaluation portion are carried out from the oxidation scale thickness of an outer surface on the water-wall tube furnace side. (2) Regarding a portion where an outer surface oxidation scale thickness on the water-wall tube furnace side exceeds a given value, density of a tube inner surface oxidation scale is measured, a portion having a density of 4 g/cm3 or more forms an overheat damage portion. A destructive method (such as a method for measuring a scale amount and a scale thickness) and a non-decretive method (such as, an X-ray CT method and an ultrasonic density method), are given as a method for measuring density of a tube inner surface oxidation scale. (3) An overheat damage portion having density of 4 g/cm3 or more of a tube inner scale is calculated by a method by a method for predicting it from a tube inner surface scale thickness and an overheat supposing time, and an overheat temperature by a method for predicting it from the aforesaid steam oxidation scale thickness. (4) A creep damage rate is calcite from a load stress, calculated from the size (a diameter and a thickness) and the pressure of the water-wall tube, a superheat temperature, an overheat time, and the strength of the material, and a remaining life is diagnosed.;COPYRIGHT: (C)2001,JPO