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Research Papers

Noncontact Measurement Method of Vibration Stress Using Optical Displacement Sensors for Piping Systems in Nuclear Power Plants

[+] Author and Article Information
Akira Maekawa

Institute of Nuclear Safety System, Inc.,
64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205, Japan
e-mail: maekawa@inss.co.jp

Tsuneo Takahashi

Institute of Nuclear Safety System, Inc.,
64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205, Japan
e-mail: takahashi.tsuneo@inss.co.jp

Takashi Tsuji

The Kansai Electric Power Co., Inc.,
13-8 Goichi, Mihama-cho, Mikata-gun, Fukui 919-1141, Japan
e-mail: tsuji.takashi@e4.kepco.co.jp

Michiyasu Noda

The Kansai Electric Power Co., Inc.,
13-8 Goichi, Mihama-cho, Mikata-gun, Fukui 919-1141, Japan
e-mail: noda.michiyasu@c4.kepco.co.jp

1Corresponding author.

Manuscript received May 15, 2014; final manuscript received November 17, 2014; published online May 14, 2015. Assoc. Editor: John F. P. de Grosbois.

ASME J of Nuclear Rad Sci 1(3), 031002 (May 14, 2015) (10 pages) Paper No: NERS-14-1006; doi: 10.1115/1.4029338 History: Received May 15, 2014; Accepted December 17, 2014; Online May 14, 2015

In nuclear power plants, vibration stress of piping is frequently measured to prevent the occurrence of fatigue failure. A simpler and more efficient measurement method is desired for rapid integrity evaluation of piping. In this study, a method to measure vibration stress in a noncontact manner using optical displacement sensors is presented and validated. The proposed method estimates vibration-induced stress of small-bore piping directly using noncontact sensors based on a light-emission diode. First, the noncontact measurement method was proposed, and the measurement instrument based on the proposed method was developed for the validation. Next, vibration measurement experiments using the instrument were conducted for a mock-up piping system and an actual piping system. The measurement results were compared with the values measured by the conventional method of known accuracy using strain gauges. From this comparison, the proposed noncontact measurement method was demonstrated to be able to provide sufficient accuracy for practical use.

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Figures

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Fig. 1

Principle of measuring vibration stress

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Fig. 2

Proposed extrapolation technique to estimate vibration stress at the root section

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Fig. 3

Principle of an LED-optical displacement sensor

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Fig. 4

Schematic diagram explaining the instrument developed for measuring vibration stress

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Fig. 5

Photograph of the instrument developed for measuring vibration stress

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Fig. 6

Photograph of the mock-up piping system

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Fig. 7

Schematic view of the mock-up piping system

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Fig. 8

Analysis model used for validation of the proposed extrapolation technique

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Fig. 9

Typical time histories of vibration stress

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Fig. 10

Vibration stress at the root section calculated using the proposed extrapolation technique: (a) noise 1 μm, (b) noise 2 μm, (c) noise 3 μm, (d) noise 4 μm, and (e) noise 5 μm

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Fig. 11

Influence of noise on the proposed method: (a) vibration stress σB and (b) vibration stress σO at the root section

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Fig. 12

Dependence of vibration stress obtained by the proposed method on noise and excitation amplitude

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Fig. 13

Dependence of vibration stress at the root section obtained by the proposed extrapolation technique on noise and excitation amplitude

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Fig. 14

Frequency analysis of time histories of strain measured by the conventional method using strain gauges in (a) area B1 and (b) area B2

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Fig. 15

Frequency analysis of time histories of displacement measured by the proposed method in (a) area B1 and (b) area B2

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Fig. 16

Comparison of vibration stress measured by the proposed and conventional methods

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Fig. 17

Comparison of vibration stress at the root section measured by the proposed and conventional methods

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Fig. 18

Comparison of vibration stress at the root section measured by the proposed and conventional methods for small-bore piping in actual plants

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