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Research Papers: Design and Analysis

A Method Using Optical Contactless Displacement Sensors to Measure Vibration Stress of Small-Bore Piping

[+] Author and Article Information
Akira Maekawa

e-mail: maekawa@inss.co.jp

Takashi Tsuji

e-mail: tsuji.takashi@inss.co.jp

Tsuneo Takahashi

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

Michiyasu Noda

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

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received April 23, 2012; final manuscript received June 26, 2013; published online October 23, 2013. Assoc. Editor: Spyros A. Karamanos.

J. Pressure Vessel Technol 136(1), 011202 (Oct 23, 2013) (10 pages) Paper No: PVT-12-1047; doi: 10.1115/1.4025082 History: Received April 23, 2012; Revised June 26, 2013

In nuclear power plants, vibration stress of piping is frequently evaluated to prevent fatigue failure. A simple and fast measurement method is attractive to evaluate many piping systems efficiently. In this study, a method to measure the vibration stress using optical contactless displacement sensors was proposed, the prototype instrument was developed, and the instrument practicality for the method was verified. In the proposed method, light emitting diodes (LEDs) were used as measurement sensors and the vibration stress was estimated by measuring the deformation geometry of the piping caused by oscillation, which was measured as the piping curvature radius. The method provided fast and simple vibration estimates for small-bore piping. Its verification and practicality were confirmed by vibration tests using a test pipe and mock-up piping. The stress measured by both the proposed method and an accurate conventional method using strain gauges were in agreement, and it was concluded that the proposed method could be used for actual plant piping systems.

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References

Figures

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Fig. 1

Principle of measuring vibration stress

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Fig. 2

Extrapolation technique to estimate vibration stress at the root section

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Fig. 3

Photograph of the vibration stress measuring instrument

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Fig. 4

Schematic diagram explaining the vibration stress measuring instrument: (a) arrangement for measurement and (b) principle of a contactless displacement sensor

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Fig. 5

Schematic diagram explaining the vibration test: (a) photograph of a vibration unit and (b) measurement locations

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Fig. 6

Actual size mock-up piping: (a) photograph and (b) schematic view

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Fig. 7

Typical vibration stress waveform at measurement interval of 76 mm: (a) upper end and (b) lower end

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Fig. 8

Vibration stress at each measurement location at measurement interval of 76 mm

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Fig. 9

Comparison of vibration stress at the root section (measurement interval: 76 mm)

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Fig. 10

Comparison of vibration stress by the proposed and conventional methods at two measurement intervals: (a) 76 mm and (b) 38 mm

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Fig. 11

Comparison of vibration stress at the root section (measurement interval: 38 mm)

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Fig. 12

Influence of noise on the proposed method: (a) vibration stress σB and (b) vibration stress σo at the root section (measurement interval: 38 mm)

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Fig. 13

Influence of noise on the proposed method: (a) vibration stress σB and (b) vibration stress σo at the root section (measurement interval: 57 mm)

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Fig. 14

Influence of noise on the proposed method: (a) vibration stress σB and (b) vibration stress σo at the root section (measurement interval: 76 mm)

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Fig. 15

Comparison of vibration stress σb measured by the proposed and conventional methods

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Fig. 16

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

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