Failure Analysis of Thermally Stressed Pipelines of Power Plants Operating in the North And Arctic

Abstract

To make various technical objects reliability, it is important to study the material degradation processes and the nature of damage taking into account the operational environment. The nonstationarity of operation modes and the high level of loads under the extreme conditions of the North and Arctic reduce the working life of the thermally stressed elements of power plants. In this regard, an urgent problem is the study of processes and factors affecting the development of high-temperature damage in such elements material. The purpose of the work is to assess the quality, actual state and mechanisms of metal degradation to identify the nature and causes of failures of heating surfaces tubes of boiler plants operating in the low climatic temperatures zone. The techniques used in this article include fractography, metallography, x-ray diffraction, mechanical testing, etc. A developed high-temperature degradation of the metal structure (grain growth, spheroidization of perlite, graphitization) was discovered, indicating that the design temperatures were exceeded (overheating) and reduced the resistance of the metal to the working environment aggressive exposure. The main mechanism of failure is the uneven internal electrochemical corrosion of metal (anodic dissolution processes), the development of which led to the formation of fistulas and emergency depressurization of boiler equipment. The leading role of thermal load as a stimulator of corrosion damage of tubes of boiler units heating surfaces in comparison with the influence of an active corrosive environment has been confirmed. The results of the work can be used to extend the service life of equipment operating at high temperatures and stresses, as well as under the influence of corrosive environments.