Nondestructive Creep Damage Evaluation of High-Temperature Pipelines by Ultrasonic Attenuation Measurement and Electric Resistance Methods

J. Ocean Eng. Technol. 1999;13(3):100-107.

Lee, In-Cheol;Kil, Du-Song;Gung, Gye-Jo;Cho, Yong-Sang;Lee, Sang-Guk;

초음파 감쇠 및 전기저항 측정법에 의한 발전소 고온배관의 크리프손상 평가

이인철;길두송;정계조;조용상;이상국;

한국전력공사 전력연구원;한국전력공사 전력연구원;한국전력공사 전력연구원;한국전력공사 전력연구원;한국전력공사 전력연구원;

Keywords: Creep Damage, Attenuation, Electric Resistance, Degradation, Creep Life Fraction

핵심용어: 크리프 손상, 감쇠, 전기 저항, 열화, 크리프 손상율

Abstract

Due to the high temperature and pressure, the materials of pipeline in power plant are degraded by creep damage. So far, many conventional measurement techniques such as replica method, electric resistance method, adn hardness test method for creep damage have been used. Among them, the replica method has mainly been used for the inspection of components. But this technique is restricted to the applications at the surface of the objects and cannot be used to material inside. In this paper, the measuring methods of evaluation by using ultrasonic attenuation and electric resistance for the creep detection of creep damage in the form of cavities on grain boundaries or intergranular microcracks were carried out. Absolute measuring method of quantitave ultrasonic attenuation technique for 1Cr0.5Mo material degradation was analyzed for determining the creep degradation steps using life prediction formula. As a result of measurement for creep specimens, we founded that the coefficient of utrasonic attenuation was increased as the increase of creep life fracton(${phi}c$) and the decreasing rate of wlwctric resistance was also increased.