Transactions of the Korean Society of Pressure Vessels and Piping (한국압력기기공학회 논문집)

Korean Society of Pressure Vessels and Piping (한국압력기기공학회)
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A Study for Flaw Detection of 3/4″ Pipe by Using Guided Wave

유도초음파를 이용한 3/4″ 배관 결함 검출 연구

  • 정우근 (한국수력원자력 중앙연구원) ;
  • 김진회 (한국수력원자력 중앙연구원) ;
  • 천근영 (한국수력원자력 중앙연구원)
  • Received : 2019.04.09
  • Accepted : 2019.06.17
  • Published : 2019.06.30
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Abstract

Unlike the welded pipes in the primary system of light water nuclear power plants being periodically inspected with in-Service inspection program, relatively small pipes with the outer diameter less than 2 inch have not been regularly inspected to date. However, after several failure reports on the occurrence of critical crack-like defects in small pipes, inspection for the small pipes has been more demanded because it could cause the provisional outage of nuclear power plants. Nevertheless, there's no particular method to examine the small pipes having access limitations for inspection due to various reasons; inaccessible area, excessive radiation exposure, hazardous surrounding, and etc. This study is to develop a reliable inspection technique using torsional and flexural modes of guided wave to detect defects that could occur in inaccessible area. The attribute of guided wave that can travel a long distance enables to inspect even isolated range of the pipe from accessible location. This paper presents a case study of the evaluation test on 3/4" small-bore pipes with guide wave method. The test result demonstrates the crack signal behavior and assures possibility to detect the crack signal in a flexural mode, which is clearly distinguishable from the symmetric structure signal in a torsional mode.

Keywords

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Fig. 1 Guided wave Generation in a plate

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Fig. 2 Torsional and longitudinal transducers in a module

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Fig. 3 Wave propagation simulation of torsional mode and flexural mode

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Fig. 4 Reflection from a series of defects

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Fig. 5 Axisymmetric and non-axisymmetric feature

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Fig. 6 Group velocity of 3/4" pipe and frequency Regime

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Fig. 7 Guided wave system for Measurement

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Fig. 8 The geometric of pipe specimen

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Fig. 9 Experimental result of frequency Regime –6

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Fig. 10 Experimental result of frequency Regime +4

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Fig. 11 Experimental result of reverberation technique

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Fig. 12 Amplitude values about depth of the defects

Table 1 Specification of the Specimen

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References

  1. D. N. alleyne and P. Cawley., 1997, " Long Range Propagation of Lamb Waves in Chemical Plant Pipework", Materials Evaluation, Vol. 52, No. 7, pp. 504-508
  2. D.N. alleyne and P. Cawley., 1992, "Optimization of Lamb wave inspection Techniques", NDT & E International, Vol. 25, pp. 11-22 https://doi.org/10.1016/0963-8695(92)90003-Y
  3. P. Cawley, M. J. S. Lowe, D.N. Alleyne, B. Pavlakovic and P. Wilcos., 2003, "Practical Long Range Guided Wave Testing: Application to Pipe and Rail", Material Evaluation, 61(1), pp. 66-74
  4. D.N. Alleyne, B. Pavlakovic, M.J.S. Lowe and P. Cawley., 2001, "Rapid long-range inspection of chemical plant pipework using guided waves" Review of Progress in Quantitative NDE, ed. by D. O. Thompson and D. E. Chimenti (Plenum, NewYork), 20, pp.180-187
  5. Brian Pavlakovic and Mike Lowe., 2001, "A System for Generating Dispersion Curve" user's manual, Version 2.0.11. pp. 20-60