Development of New Field Testing Tools for Geothermal Power Plant Risk Assessment of Corrosion and Scaling

Abstract

We are developing two field testing tools for geothermal power plant risk assessment of corrosion and scaling under NEDO’s “Research and Development of Geothermal Power Generation Technology Program”. The first tool is the portable flow loop corrosion tester. The second one is the Gamma-ray pipe section profiler to measure the scale blockage rate of piping. We are developing the portable flow loop corrosion tester using 1” piping for geothermal single and two-phase flow condition. This tester can be easy to handle by a few workers without a crane and is low cost. The tester can be set up for three corrosion rate measurement methods – ER(Electrical Resistance) Corrosometer®, LPR (Linear Polarization Resistance), and Cylinder coupon exposure tests. The tester can also be set up for any injection systems of acids (H2SO4, HCl, to simulate extreme acidic condition), NaOH (for neutralization) or anti-corrosion/anti-scalant inhibitors. We have already trialed this tester in liquid flow condition (Kakkonda, Iwate) and two-phase flow condition (Okuaizu, Fukushima) in 2016-2017. The basis of the gamma-ray pipe section profiler is to measure the difference of gamma-ray transmission of steel pipe, insulation, geothermal flow, and scale at pipe cross-sections.
We have already trialed this profiler in a reinjection pipeline in Kakkonda steam field and a production pipeline in Okuaizu steam field and compared with visual observations during the regular inspection of each power plant in 2015-2017. This paper shows basis, summary of field tests, estimation of tool accuracy, and issues in the futures of these tools.