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Research Papers

An Online Monitoring Technique for Long-Term Operation Using Guided Waves Propagating in Steel Pipe

[+] Author and Article Information
Francesco Bertoncini

DESTEC,
University of Pisa,
L.go Lucio Lazzarino,
Pisa 56122, Italy
e-mail: francesco.bertoncini@gmail.com

Mauro Cappelli

ENEA FSN-FUSPHY-SCM,
Frascati Research Center,
Via E. Fermi, 45,
Frascati 00044, Italy
e-mail: mauro.cappelli@enea.it

Francesco Cordella

ENEA FSN-FUSPHY-SAD,
Frascati Research Center,
Via E. Fermi, 45,
Frascati 00044, Italy
e-mail: francesco.cordella@enea.it

Marco Raugi

DESTEC,
University of Pisa,
L.go Lucio Lazzarino,
Pisa 56122, Italy
e-mail: marco.raugi@dsea.unipi.it

Manuscript received September 29, 2016; final manuscript received June 24, 2017; published online July 31, 2017. Assoc. Editor: Asif Arastu.

ASME J of Nuclear Rad Sci 3(4), 041008 (Jul 31, 2017) (8 pages) Paper No: NERS-16-1118; doi: 10.1115/1.4037204 History: Received September 29, 2016; Revised June 24, 2017

Nondestructive testing (NDT) techniques are widely used as a reliable way for preventing failures and helping in the maintenance design and operation of critical infrastructures and complex industrial plants as nuclear power plants (NPPs). Among the NDT techniques, guided waves (GWs) are a very promising technology for such applications. GWs are structure-borne ultrasonic waves propagating along the structure confined and guided by its geometric boundaries. Testing using GWs is able to find defect locations through long-range screening using low-frequency waves (from 5 to 250 kHz). The technology is regularly used for pipe testing in the oil and gas industry. In the nuclear industry, regulators are working to standardize monitoring and inspection procedures. To use the technology inside an active plant, operators must solve issues like high temperatures (up to more than 300 °C inside a light-water reactor's primary piping), high wall thickness of components in the primary circuit, and characteristic defect typologies. Magnetostrictive sensors are expected to overcome such issues due to their physical properties, namely, robust constitution and simplicity. Recent experimental results have demonstrated that magnetostrictive transducers can withstand temperatures close to 300 °C. In this paper, the GW technology will be introduced in the context of NPPs. Some experimental tests conducted using such a methodology for steel pipe having a complex structure will be described, and open issues related to high-temperature guided wave applications (e.g., wave velocity or amplitude fluctuations during propagation in variable temperature components) will be discussed.

Copyright © 2017 by ASME
Topics: Waves , Pipes , Steel
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References

Figures

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Fig. 1

NDT of a complex pipe structure

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Fig. 2

Amplitude versus distance for a guided wave signal

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Fig. 3

(a) Ni strip, (b) epoxy-bonded strip, and (c) coil placed over the strip

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Fig. 4

(a) Coil placed under insulation and (b) coil placed over the insulation

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Fig. 5

Coordinates used for the cylindrical pipe model

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Fig. 6

First three roots of Eq. (11)

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Fig. 7

Phase velocity cp of torsional modes T(0,1) and T (0,2)between 64 and 128 kHz for a 363.2 × 10−3 m internal diameter, 21.4 × 10−3 m thickness steel pipe with no attenuation: cL = 5960 m/s, cT = 3260 m/s, and ρ = 8000 kg/m3. The cutoff frequency fco of 77.8 kHz, below which the T(0,2) mode is an evanescent wave, is shown with a dashed vertical line.

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Fig. 8

Group velocity cg of torsional modes T(0,1) and T(0,2)between 64 and 128 kHz for a 363.2 × 10−3 m internal diameter, 21.4 × 10−3 m thickness steel pipe with no attenuation: cL = 5960 m/s, cT = 3260 m/s, and ρ = 8000 kg/m3

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Fig. 9

Phase velocity cp of longitudinal modes L(0,1), L(0,2), and L(0,3) between 64 and 128 kHz for a 363.2 × 10−3 m internal diameter, 21.4 × 10−3 m thickness steel pipe with no attenuation: cL = 5960 m/s, cT = 3260 m/s, and ρ = 8000 kg/m3

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Fig. 10

Group velocity cg of longitudinal modes L(0,1), L(0,2), and L(0,3) between 64 and 128 kHz for a 363.2 × 10−3 m internal diameter, 21.4 × 10−3 m thickness steel pipe with no attenuation: cL = 5960 m/s, cT = 3260 m/s, and ρ = 8000 kg/m3

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Fig. 11

Phase velocity cp of flexural modes F(1,i) with i = 1–5, between 64 and 128 kHz for a 363.2 × 10−3 m internal diameter, 21.4 × 10−3 m thickness steel pipe with no attenuation: cL = 5960 m/s, cT = 3260 m/s, and ρ = 8000 kg/m3

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Fig. 12

Group velocity cg of flexural modes F(1,i) with i = 1–5, between 64 and 128 kHz for a 363.2 × 10−3 m internal diameter, 21.4 × 10−3 m thickness steel pipe with no attenuation: cL = 5960 m/s, cT = 3260 m/s, and ρ = 8000 kg/m3

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Fig. 13

Torsional mode greatly exaggerated. In dark, how a one-dimensional (1D) grid of squares is deformed due to the wave passing.

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Fig. 14

Longitudinal mode greatly exaggerated. In dark, how a 1D grid of squares is deformed due to the wave passing.

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Fig. 15

Flexural mode greatly exaggerated. In dark, how a 1D grid of squares is deformed due to the wave passing.

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Fig. 16

Contour plot of the exact solution Eq. (A1) for longitudinal modes L(0,i) with i = 1–4. Since the contour plot uses only a finite number of sample points, the L(0,1) part with f≥2.2×106 is missing.

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Fig. 17

SAFE solution of Eq. (A1) for longitudinal modes L(0,i) with i = 1–4. The L(0,1) mode is completely present, and the part with f≤2.2×106 is coincident with the exact solution.

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