THERMAL FATIGUE CRACK DAMAGE DIAGNOSIS METHOD OF BOILER HEAT TRANSFER TUBE

• Main Author: NAKAO MOTOROKU
• Format: Patent
• Language: English
• Published: 16.08.2007
• Subjects: BLASTING; HEATING; INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; LIGHTING; MEASURING; MECHANICAL ENGINEERING; METHODS OF STEAM GENERATION; PHYSICS; STEAM BOILERS; STEAM GENERATION; TESTING; WEAPONS

PROBLEM TO BE SOLVED: To explain behavior of crack damage in an actual machine by increasing the accuracy of its development and behavior for the crack damage generated by the combination of repetition of thermal stress generated on the outside surface of a boiler heat transfer tube with high-temperature corrosion or high-temperature oxidation. SOLUTION: In this diagnosis method for the degree of damage by an elephant skin-like thermal fatigue crack generated from the outside surface of the heat transfer tube, a stress range coefficient range is calculated based on a thermal stress range and crack depth calculated based on the dimension, temperature variation and the like of the heat transfer tube; a thermal fatigue crack development amount is analyzed based on a thermal fatigue crack development diagram expressing a relationship between the stress range coefficient range and a crack development speed and a thermal stress repeat count; a generation amount of high-temperature scales on the tube outside surface is obtained to evaluate the crack of the scales; the generation amount of oxidized scales on the tube inside surface side is obtained; and the degree of damage of the thermal fatigue crack is diagnosed by incorporating acceleration of the thermal fatigue crack development amount and the scale generation amount on the tube outside surface by the rise of transfer tube metal temperature caused by the scale generation amount on the tube inside surface side. COPYRIGHT: (C)2007,JPO&INPIT