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Research Papers: Design and Analysis

Development of Measurement Methods for Vibration-Induced Stress of Small-Bore Piping

[+] Author and Article Information
Akira Maekawa

Institute of Nuclear Safety System, Inc.,
64 Sata, Mihama-cho, Mikata-gun,
Fukui 919-1205, Japan
e-mails: maekawa@inss.co.jp;
maekawa.akira@e3.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

Michiaki Suzuki

Kawasaki Heavy Industries, Ltd.,
1-14-5, Kaigan, Minato-ku,
Tokyo 105-8315, Japan
e-mail: suzuki_m@khi.co.jp

Takeshi Suyama

The Kansai Electric Power Co., Inc.,
13-8 Goichi, Mihama-cho, Mikata-gun,
Fukui 919-1141, Japan
e-mail: suyama.takeshi@b2.kepco.co.jp

Katsuhisa Fujita

Department of Mechanical Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan e-mail: fujita@mech.eng.osaka-cu.ac.jp

1Corresponding author.

2Present address: The Kansai Electric Power Co., Inc., 13-8 Goichi, Mihama-cho, Mikata-gun, Fukui 919-1141, Japan.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received May 28, 2016; final manuscript received April 15, 2017; published online May 26, 2017. Assoc. Editor: Hardayal S. Mehta.

J. Pressure Vessel Technol 139(4), 041207 (May 26, 2017) (8 pages) Paper No: PVT-16-1087; doi: 10.1115/1.4036512 History: Received May 28, 2016; Revised April 15, 2017

The vibration-induced fatigue failure of small-bore piping is one of the common causes of failure trouble at nuclear power plants (NPPs). Therefore, the purpose of this study is to develop the measurement methods of vibration-induced stress for the screening to prevent from fatigue failure mechanism of small-bore piping. First, a measurement method using a single-mass model was introduced, and then, a measurement method using a two-mass model developed as an improved calculation model was proposed. These two kinds of models were validated by vibration tests using mock-up with small-bore branch piping. The results showed that the single-mass model could be used as the coarse screening. Additionally, the two-mass model was found to be suitable to the fine screening due to more accurate measurement of vibration-induced stress. Next, for small-bore piping with typical pattern configurations consisting of several masses and supports, the model considering the supports and the center of gravity being out of pipe centerline was developed and put into practical use. Finally, for the more complex small-bore piping with general piping configurations consisting of many bends, branches, or joints, the method based on the finite element analysis and using the measured values was developed. In the developed method, the differences between the natural frequency and the response acceleration obtained by the measurement and those values calculated using the analysis model are optimized to be enough small, and then, the vibration-induced stress is estimated by superposing the vibration modes of the small-bore piping with the static deformation representing the main piping vibration. In this study, the usability of the developed method was confirmed by the comparison with the numerical results without the measurement error, which were assumed to be the true values. The peak stress induced by vibration frequently occurs at the filet weld part between the small-bore piping and the main piping. The developed methods can be used for various weld geometries although the measurement method using strain gauges cannot be used for such weld parts. The failure possibility by vibration-induced fatigue can be evaluated by comparing the nominal stress measured by the methods in this study with the fatigue threshold stress divided by the stress concentration factor appropriate for the weld geometry.

FIGURES IN THIS ARTICLE
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Copyright © 2017 by ASME
Topics: Stress , Pipes , Vibration
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References

Figures

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Fig. 2

Schematic view of the mock-up

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Fig. 3

Locations of accelerometers

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Fig. 4

Locations of strain gauges

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Fig. 5

Comparison between stresses calculated by Eq. (1) and measured stresses in sinusoidal excitation

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Fig. 6

Comparison between stresses calculated by Eq. (1) and measured stresses in measured wave excitation

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Fig. 8

Comparison between stresses calculated by Eq. (3) and measured stresses in sinusoidal excitation

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Fig. 9

Comparison between stresses calculated by Eq. (3) and measured stresses in measured wave excitation

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Fig. 10

Two-mass model of small-bore piping with typical pattern configuration: (a) straight piping, (b) bending piping (vertical eccentricity), and (c) bending piping (horizontal eccentricity)

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Fig. 11

Procedure to calculate vibration-induced stress in small-bore piping with general piping configuration

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Fig. 12

Typical piping to explain how to measure the vibration-induced stress

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