Creep Damage Evaluation of High-Temperature Pipeline Material for Fossil Power Plant by Ultrasonic Test Method

J. Ocean Eng. Technol. 1999;13(2):99-107.

Lee, Sang-Guk;Chung, Min-Hwa;

초음파에 의한 발전소 고온배관재료의 크리프손상 평가

이상국;정민화;

한국전력공사 전력연구원;한국전력공사 발전교육원;

Keywords: Creep Damage, Ultrasonic Test Method, Fossil Power Plant, High-Temperature Pipeline, Sound Velocity, Attenuation

핵심용어: 크리프손상, 초음파법, 화력발전소, 고온배관, 초음파 음속, 초음파 감쇠

Abstract

Boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants are degraded by creep damage due to severe operationg conditions which are high temperature and high pressure for an extended period time. Such material degradation leads to various component failures causing serious accidents at the plants. Conventional measurement techniques such as replica method, electric resistance method, and hardness test method have such disadvantages as complex preparation and measurement procedures, too many control parameters, and therefore, low practicality and they were applied only to component surfaces with good accessibility. In this paper, artificial creep degradation test and ultrasonic measurement for their creep degraded specimens have been carried out for the purpose of evaluation for creep damage which can occur in high-temperature pipeline of fossil power plant. Absolute measuring method of quantitative ultrasonic measurement for material degradation was established, and long term creep degradationtests using life prediction formula were carried out. As a result of ultrasonic tests for crept specimens, we confirmed that the sound velocity decreased and the attenuation coefficient linearly increased in proportion to the increase of creep fractiin(${phi}$c).