Nondestructive Examination of Ferromagnetic Tube Using Magnetic Saturation Eddy Current Technique

자기포화 와전류기법에 의한 자성 튜브 비파괴검사

  • 이희종 (한국전력공사 전력연구원 비파괴평가센터) ;
  • 조찬희 (한국전력공사 전력연구원 비파괴평가센터) ;
  • 송석윤 (한국전력공사 전력연구원 비파괴평가센터) ;
  • 지동현 (한국전력공사 전력연구원 비파괴평가센터) ;
  • 정지홍 (한국전력공사 전력연구원 비파괴평가센터)
  • Published : 2008.10.30

Abstract

The tubes in heat exchanger are typically made from copper alloy, stainless steel, carbon steel, titanium alloy material. type-439 ferritic stainless steel is ferromagnetic material, and furnish higher heat transfer rates than austenitic stainless steels and higher resistance to corrosion-induced flaws. Ferritic stainless steel can typically be found in low-pressure(LP) feedwater heaters and moisture separator reheaters(MSRs). LP feedwater heaters generally utilize thin wall type-439 stainless steel tubing, whereas MSRs typically employ a heavier wall tubing with integral fins. Service-induced damage can occur on the OD(outside diameter) surface of type-439 ferritic stainless steel tubing which is employed for MSRs tubing, and the most typical damage mechanism is vibration-induced tube-to-TSP(tube support plate) wear and fatigue cracking. The wear has been reported that occurs mainly on the OD surface. Accordingly, in this study, we have evaluated the flaw sizing capability of magnetic saturation eddy current technique using magnetic saturation probe and flawed specimen.

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