Korean Journal of Air-Conditioning and Refrigeration Engineering (설비공학논문집)

The Society of Air-Conditioning and Refrigerating Engineers of Korea (대한설비공학회)
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A Study on the Oxide Scale of the Long Term Serviced 12%Cr Boiler Tube Steel

장기간 사용한 12%Cr강 보일러 튜브의 산화스케일에 관한 연구

  • Kim, Beom-Soo (Power Generation Lab, Korea Power Research Institute) ;
  • Min, Taek-Ki (School of Mechanical and Nano Mechatronics, Chungnam National University)
  • 김범수 (한전전력연구원 수화력발전연구소) ;
  • 민택기 (충남대학교 기계.기계설계 나노메카닉스공학부)
  • Received : 2011.12.16
  • Accepted : 2012.02.27
  • Published : 2012.03.10
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Abstract

The internal oxide scale of twelve superheater and reheater tubes were tested which were serviced for 30,000~120,000 hours in thermal power plants. The oxide scale was formed in three layers. The Cr-rich area was observed beneath the original metal surface. The hematite ($Fe_2O_3$) phase was formed on the outer surface. The intermediate layer was magnetite ($Fe_3O_4$). The thickness of Cr-rich layer was about half of the total scale. All layers grew during the operation hour of the plant. The thickness of thickest scale was 0.2mm in superheater tubes. This can increase the tube metal temperature about $7^{\circ}C$ more than initial state. $7^{\circ}C$ tube metal temperature can reduce tube life about 30%, but the boiler tube's design margin is big enough therefore it has been analyzed that it would not effect on the life span.

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References

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