Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Failure Analysis of Stress Reliever in Heat-Transport Pipe of District Heating System

  • Cho, Jeongmin (Department of Materials Science and Engineering, Chungnam National University) ;
  • Chae, Hobyung (Department of Materials Science and Engineering, Chungnam National University) ;
  • Kim, Heesan (Department of Materials Science and Engineering, Hongik University) ;
  • Kim, Jung-Gu (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Kim, Woo Cheol (R&D Institute, Korea District Heating Corp.) ;
  • Lee, Soo Yeol (Department of Materials Science and Engineering, Chungnam National University)
  • Received : 2022.06.29
  • Accepted : 2022.06.30
  • Published : 2022.09.02
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Abstract

The objective of the present study was to perform failure analysis of double-layered bellow (expansion joint), a core part of stress reliever, used to relieve axial stresses induced by thermal expansion of heat-transport pipes in a district heating system. The bellow underwent tensile or compressive stresses due to its structure in terms of position. A leaked position sufferred a fatigue with a tensile component for decades. A cracked bellow contained a higher fraction of martensitic phase because of manufacturing and usage histories, which induced more brittleness on the component. Inclusions in the inner layer of the bellow acted as a site of stress concentration, from which cracks initiated and then propagated along the hoop direction from the inner surface of the inner layer under fatigue loading conditions. As the crack reached critical thickness, the crack propagated to the outer surface at a higher rate, resulting in leakage of the stress reliever.

Keywords

Acknowledgement

This work was supported by the research funds of Korea District Heating Corporation.

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