AQ-04 Numerical analysis of inspection method of hot spring scale attached to steel pipes in geothermal power plants using electromagnetic vibration
Creators: Ryota Takasugi
Hiroyuki Ikusada
Yuichiro Hosono
Shoutarou Niwa
YonHui Gao
Teruyoshi Sasayama and Yuji Gotoh
Publisher: name: IEEE
Year: 2025

1. Introduction Steam from hot springs flows through the steel pipes at geothermal power plants [1]. In this steel pipe, components in the hot spring accumulate and form solid "hot spring scale," which can obstruct the flow of hot spring steam [2]. This paper proposes a method the pipe is vibrated electromagnetically without contact from the outside, and the thickness of hot spring scale on the inside of the steel pipe is measured from the vibration intensity. The inspection principle is clarified through 3-D FEM electromagnetic vibration displacement analysis considering hysteresis characteristics of the steel pipe. In addition, the results are compared with validation experiments. 2. Inspection model and Results The inspection model shown in Fig. 1 consisted of an actual steel pipe with the hot spring scale and an electromagnetic force vibration device (EFVD), which includes three permanent magnets (PM), an AC excitation coil, a steel plate, and an acceleration sensor (AS). In this inspection method, the static magnetic field from the PM and the eddy currents from the AC excitation coil intersect orthogonally, generating Lorentz force inside the steel pipe. The distribution of this electromagnetic force is calculated by nonlinear electromagnetic field analysis using 3-D FEM with the "Play model" that takes into account for hysteresis characteristics inside the steel pipe. The vibration strength of the steel pipe obtained by the AS inside the EFVD is calculated by displacement analysis using 3-D FEM. Fig. 2 summarizes the vibration intensity versus the thickness of each hot spring scale measured by the AS inside of the EFVD and the results of analysis considering the initial magnetization curve and the hysteresis characteristics of the steel pipe. This figure illustrates that the vibration strength on the steel pipe is decreased when the hot spring scale thickness is increased. The effectiveness of the proposed inspection method was shown by the results of the analysis and the actual measurements, which showed a similar trend.References: [1] K. Wang, B. Yuan, G. Ji, X. Wu, “A comprehensive review of geothermal energy extraction and utilization in oilfields”, Journal of Petroleum Science and Engineering, vol. 168, pp. 635-638, 2018. [2] A. Hagisaka, S. Niwa, S. Shiota, Y. Gao, Y. Gotoh, “Proposal of detection for thickness method of hot spring scale inside steel pipes using vibration”, International Journal of Applied Electromagnetics and Mechanics, vol. 71, no. S1, pp. S483-S491, 2023. [3] T. Matsuo, Y. Osaka, and M. Shimasaki, “Eddy-current analysis using vector hysteresis models with play and stop hysterons,” IEEE Trans. Magn., vol. 36, no. 4, pp. 1172–1177, Jul. 2000.
1. Introduction Steam from hot springs flows through the steel pipes at geothermal power plants [1]. In this steel pipe, components in the hot spring accumulate and form solid "hot spring scale," which can obstruct the flow of hot spring steam [2]. This paper proposes a method the pipe is vibrated electromagnetically without contact from the outside, and the thickness of hot spring scale on the inside of the steel pipe is measured from the vibration intensity. The inspection principle is clarified through 3-D FEM electromagnetic vibration displacement analysis considering hysteresis characteristics of the steel pipe. In addition, the results are compared with validation experiments. 2. Inspection model and Results The inspection model shown in Fig. 1 consisted of an actual steel pipe with the hot spring scale and an electromagnetic force vibration device (EFVD), which includes three permanent magnets (PM), an AC excitation coil, a steel plate, and an acceleration sensor (AS). In this inspection method, the static magnetic field from the PM and the eddy currents from the AC excitation coil intersect orthogonally, generating Lorentz force inside the steel pipe. The distribution of this electromagnetic force is calculated by nonlinear electromagnetic field analysis using 3-D FEM with the "Play model" that takes into account for hysteresis characteristics inside the steel pipe. The vibration strength of the steel pipe obtained by the AS inside the EFVD is calculated by displacement analysis using 3-D FEM. Fig. 2 summarizes the vibration intensity versus the thickness of each hot spring scale measured by the AS inside of the EFVD and the results of analysis considering the initial magnetization curve and the hysteresis characteristics of the steel pipe. This figure illustrates that the vibration strength on the steel pipe is decreased when the hot spring scale thickness is increased. The effectiveness of the proposed inspection method was shown by the results of the analysis and the actual measurements, which showed a similar trend.References: [1] K. Wang, B. Yuan, G. Ji, X. Wu, “A comprehensive review of geothermal energy extraction and utilization in oilfields”, Journal of Petroleum Science and Engineering, vol. 168, pp. 635-638, 2018. [2] A. Hagisaka, S. Niwa, S. Shiota, Y. Gao, Y. Gotoh, “Proposal of detection for thickness method of hot spring scale inside steel pipes using vibration”, International Journal of Applied Electromagnetics and Mechanics, vol. 71, no. S1, pp. S483-S491, 2023. [3] T. Matsuo, Y. Osaka, and M. Shimasaki, “Eddy-current analysis using vector hysteresis models with play and stop hysterons,” IEEE Trans. Magn., vol. 36, no. 4, pp. 1172–1177, Jul. 2000.