流れ加速型腐食に及ぼす局所流動状況の影響: エルボ管における減肉速度の計測

摘要

流れ加速型腐食(FAC)に及ぼす流れ場の影響について評価するために，著者らはこれまでオリフィス及び玉形弁の下流を対象に，電気抵抗法を用いた減肉速度測定，流速分布測定，数値流体シミュレーションを実施してきた.本研究では，エルボ管を単体で配置した場合を対象に，減肉速度測定を行った.測定には，高温高圧実験ループを用い，試験部は配管内径50mm,管断面平均流速は6.22m/sのち4.98m/sへと実験途中で変化させ，水温は150±1℃以内に制御した.減肉速度分布は，エルボ試験部での減肉速度がその上流部および下流部よりも大きくなった.また，減肉速度はエルボ管の周方向に非対称な分布となり，エルボ管内の背側のほうが腹側よりも大きくなった.%In order to evaluate the effects of a flow field on wall thinning rate due to flow-accelerated corrosion (FAC) ， the authors have carried out wall thinning rate measurements using the electrical resistance method, measurements of the velocity profile, and numerical simulation for each piping component such as an orifice and a globe valve. In this study, wall thinning rates were measured were conducted at an elbow pipe without the orifice. In the wall thinning rate measurement, a test loop operated at high temperature and high pressure conditions was used. The pipe inner diameter was 50mm, and the average velocity was changed during the experiment from 6.22m/s to 4.98m/s. The water temperature was controlled within 150±1℃. The wall thinning rates in the elbow pipe were larger than those upstream and downstream from the elbow pipe. The distribution of wall thinning rates in the elbow pipe was asymmetrical to the center axis in the circumferential direction of the pipe, and the wall thinning rate at the exrtrados of the elbow pipe was larger than that at intrados.