Journal of the Korean Institute of Gas (한국가스학회지)

The Korean Institute of GAS (한국가스학회)
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Residual Life Assessment of mod HP Reformer Tubes Using Surface Replication Methods

표면복제를 사용한 mod HP강 개질로 튜브의 잔여수명 평가에 대한 연구

  • 류형기 (중앙대학교 대학원 기계공학과) ;
  • ;
  • 방효중 (중앙대학교 기계공학과) ;
  • 윤기봉 (중앙대학교 기계공학과)
  • Received : 2021.10.04
  • Accepted : 2021.10.22
  • Published : 2021.10.30
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Abstract

Residual life assessment of reformer tubes of mod HP steel used in the refinery and petrochemical industry were investigated by quantitative metallographic evaluation method. Area fractions of precipitated carbides were measured by using surface replication and its relationship with the remaining life of the tube was investigated. The microstructures of the virgin and other tubes were examined using optical microscopy (OM) for service periods of 1.8, 6.0, 7.2, 8.5, 9.7, and 16.2 years at 950 ℃ and the area fractions of the precipitates were measured by image analysis using ImageJ software. As the area fraction of the precipitates increased, the residual life was decreased accordingly. The results showed that the LMP was the highest in the virgin and the LMP decreased as the service time increased and the residual life decreased. A regressional equation showing the relation between the area fraction of carbides and LMP was experimentally derived. The obtained relationship can be used with the surface replication method for on-site residual life assessment.

정유 및 석유화학산업의 개질로 튜브에 사용되는 mod HP강에 대한 잔여수명의 예측법을 튜브의 표면 금속조직에 석출된 탄화물의 면적분율에 대한 정량적인 평가를 통해 연구하였다. 표면복제법을 활용한 미세조직 분석을 통하여 탄화물의 면적분율과 잔여수명 사이의 관계를 실험적으로 구하였다. 신재(Virgin)와 950 ℃의 개질로에서 1.8, 6.0, 7.2, 8.5, 9.7 및 16.2년 실제 사용한 튜브들을 광학현미경(OM)을 사용하여 관찰하였으며, 석출물의 면적분율을 Image J 프로그램을 이용한 정량적 이미지 분석에 의해 측정하였다. 석출물의 면적분율이 증가함에 따라 잔여수명이 감소하여 서로 반비례하는 결과를 보여주었다. 이 관계를 사용온도와 수명을 결합한 파라미터인 LMP로 나타내면, 신재에서 LMP 값이 가장 높게 나타났고, 사용시간이 증가할수록 LMP가 감소하여 잔여수명이 줄어 듦을 나타내었다. LMP와 탄화물의 면적분율과의 상관관계를 나타내는 관계식을 도출하였다. 도출한 관계식은 현장에서 잔여수명 평가를 위해 표면복제법 적용으로 면적분율을 측정하여 잔여수명을 평가하는데 사용될 수 있다.

Keywords

References

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