DIAGONOSING AND ESTIMATING METHOD OF CORROSION, FATIGUE AND DAMAGE IN BOILER WATER WALL TUBE

摘要

PROBLEM TO BE SOLVED: To permit the optimum and quantitative evaluation of the degree of damage as well as the remaining life of whole of a boiler water wall tube by a method wherein the depth of corrosion and fatigue crack of a boiler water wall tube is obtained by the linear addition of the advancing speed of fatigue crack and the advancing speed of corrosion or pitting of the boiler including the stopping of the boiler to evaluate the degree of corrosion, fatigue and damage. ;SOLUTION: In a method wherein the degree of corrosion, fatigue and damage of a boiler water wall tube are evaluated to diagonose and estimate it, the depth of corrosion and fatigue crack (aCF) is obtained by the linear sum of the crack advancing speed due to fatigue in high temperature hot-water and the advancing speed of corrosion or pitting of the boiler including them during stopping of the boiler. Then, the degree of corrosion, fatigue and damage of the boiler water wall tube is evaluated. In an empirical formula or a formula I (figure 1), (da/dN) means a fatigue crack advancing speed in high-temperature water, which is obtained from the amplitude of stress, N means the number of times of starting and stopping of the boiler (da/dt) means the advancing speed of corrosion or pitting and (t) means a time (operating time, operating year, stopping time, acid washing time and the like) in regard to the corrosion of the boiler.;COPYRIGHT: (C)1997,JPO