C205 玉形弁下流における流れ加速型腐食の評価 : 2.腐食速度の測定(OS6 流れ加速型腐食)

Abstract

In this study, in order to evaluate the effects of flow field on corrosion rate due to flow accelerated corrosion (FAC), a corrosion rate downstream of the globe valve was measured using the electric resistance method. The valve module had a cage and it was sandwiched between the pipes which had the corrosion sensors. The diameter of these pipe was 50mm, and the temperature of water was controlled within ±1 at 150deg-C. In these measurements, we carried out the two series of measurement. In first series (Run1), we kept flow velocity condition at 4.24m/s. In second series (Run2), we changed flow velocity condition from 4.24 to 5.66m/s. In these results, the distributions of FAC rates downstream of the globe valve were asymmetrical to the center axis of the pipe, and the peak of FAC rate was at 2D downstream from the valve. Increasing the mean velocity from 4.24 to 5.66m/s during the test period, FAC rates of the upper sensor at 2D downstream was increased and the other sensors were not increased. Comparing the measured corrosion rate to the calculated wall shear stress, the distributions of these ratios of downstream / upstream from the valve agreed well.