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Research Papers: Materials and Fabrication

Simulations and Experiments for the Detection of Flow-Assisted Corrosion in Pipes

[+] Author and Article Information
K. Sathish Kumar

Assistant Professor
Department of Mechanical Engineering,
V.S.B. College of Engineering,
Technical Campus,
Kinathukadavu,
Coimbatore 642 109, India

Krishnan Balasubramaniam

Professor
Centre for Nondestructive Evaluation (CNDE),
Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600 036, India
e-mail: balas@iitm.ac.in

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received September 26, 2014; final manuscript received June 15, 2015; published online August 6, 2015. Assoc. Editor: Kunio Hasegawa.

J. Pressure Vessel Technol 137(6), 061409 (Aug 06, 2015) (10 pages) Paper No: PVT-14-1153; doi: 10.1115/1.4030931 History: Received September 26, 2014

Flow-accelerated corrosion (FAC) is a phenomenon which causes wall thinning of pipes, fittings, vessels, and other components in the metal based piping systems that carry water or water-steam mixture in power plants and refineries. Currently used nondestructive techniques, such as radiographic testing (RT), ultrasonic testing (UT), and pulsed eddy current (PEC) testing in order to determine the remaining wall thickness, are time consuming and not economical. Hence, in this work, the use of the fundamental torsional mode ultrasonic guided wave to detect FAC was investigated using the finite element method (FEM) simulations and that were validated with experiments. The torsional wave was generated by the magnetostriction principle using surface mounted strips made of magnetostrictive Hyperco (FeCo) material that provided the source for the surface tractions required to generate the ultrasonic guided wave. The transient electric field was provided through a solenoid coil wound over the strips and permanent magnets were employed to provide the bias magnetic field. From this work, it was observed that the pulse-echo method is not suitable for the FAC detection because of the insignificant reflections from FAC defect region that could not be effectively detected. The through-transmission method was found to be more suitable for the FAC detection because the amplitude of transmitted signal decreased with increase in radial depth of FAC in both the simulation and experiment.

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References

Figures

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Fig. 1

Reduction in wall thickness of the pipe due to FAC

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Fig. 2

Schematic illustration of the FAC simulation/experiment configuration

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Fig. 3

Schematic illustration of the FAC region

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Fig. 4

Schematic illustration of the: (a) top FAC only and (b) top and bottom FACs

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Fig. 5

Cross section of the mesh at the center of FAC region showing the circumferential location and numbering of the exciting/monitoring nodes, element size, and element type in pipe with the top FAC of 300 mm axial extent, 120 deg circumferential extent, and 3 mm radial depth

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Fig. 6

Snapshots of the fundamental torsional guided wave mode packet interaction with the top FAC of 300 mm axial extent, 120 deg circumferential extent, and 3 mm radial depth at various time instances by the pulse-echo method: (a) the color bar maximum limit at auto scale showing no visible reflection from FAC and (b) the color bar maximum limit at significant lower value showing reflections from FAC

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Fig. 7

Variation of the reflection coefficient of the FAC reflected signal with radial depth for 300 mm axial extent (L/λ = 8.03) and 120 degcircumferential extent FAC

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Fig. 8

Schematic illustrations of type of FAC edges

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Fig. 9

Variation of the reflection coefficient with slope of the FAC edge

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Fig. 10

Snapshots of the transmitted wave packet for various radial depths of the top FAC by the through-transmission method: (a) before FAC region at 376 μs and (b) near the monitoring nodes at 752 μs

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Fig. 11

Variation of the transmission coefficient of the transmitted signal with radial depth for 300 mm axial extent (L/λ = 8.03) and 120 deg circumferential extent FAC

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Fig. 12

Variation of the transmission coefficient of the transmitted signal with axial extent to wavelength ratio, L/λ of the top FAC for various radial depths and 120 deg circumferential extent

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Fig. 13

Variation of the transmission coefficient of the transmitted signal with circumferential extent of the top FAC for various radial depths: (a) 50 mm axial extent (L/λ = 1.34) and (b) 300 mm axial extent (L/λ = 8.03)

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Fig. 14

Variation of the transmission coefficient with slope of the FAC edge

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Fig. 15

Photograph of the FAC experiment setup

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Fig. 16

Axial profile for various radial depths of the: (a) top FAC and (b) bottom FAC

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Fig. 17

Circumferential profile of the top and bottom FACs for a 3 mm radial depth

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Fig. 18

Photograph of the top FAC of 300 mm axial extent, 120 deg circumferential extent, and 3 mm radial depth

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Fig. 19

Time domain transmitted direct signal for pipe without FAC and with top 3 mm FAC at a frequency of 85 kHz

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Fig. 20

Variation of the transmission coefficient of the transmitted signal with radial depth of FAC at a frequency of 85 kHz

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Fig. 21

Variation of the time of flight of the transmitted signal with the temperature for various radial depths of FAC at a frequency of 85 kHz

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Fig. 22

Variation of the transmitted signal amplitude with radial depth of FAC in the simulation and the experiment

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