Effects of local flow field on flow accelerated corrosion. Corrosion rate in a combination of pipe components

In order to evaluate the effects of a flow field on corrosion rate due to flow accelerated corrosion (FAC), the authors have carried out corrosion rate measurements using the electrical resistance method, measurements of the velocity profile, and numerical analyses for each piping component such as an orifice and a globe valve. In this study, in a case study of the combination of pipe components, corrosion rate measurements were conducted downstream from an orifice with a globe valve located at 14D upstream (D: pipe inner diameter). In the corrosion rate measurement, a test loop operated at high temperature and high pressure conditions was used. The pipe inner diameter was 50 mm, the average velocity was kept at 3.54 m/s and the water temperature was controlled within 150 ± 1℃. In this case, the distribution of FAC rates downstream from the orifice was asymmetrical to the center axis in the circumferential direction of the pipe, and the peak of the FAC rate was observed at 1D downstream from the orifice. In the numerical simulation, in the case with the upstream globe valve, the flow reattachment location was about 1.4-1.8D downstream from the orifice. This reattachment location shifted upstream from 2.5D downstream from the orifice in the case of no valve being attached. It was confirmed that the structure of the flow field changed compared with the case of no valve, and the corrosion rate and its distribution also changed because of the influence from the combination of pipe components. (author)