Development of flow-accelerated corrosion prediction method (2) Modeling and validation with thinning rate profile data

摘要

A series of study is presented to develop a prediction method for pipe wall thinning in power plants in order to improve the maintenance management for piping system. In the first report, experiments for flow-accelerated corrosion (FAC) of carbon steel specimens were conducted and basic data of FAC rate were obtained by setting temperature from 50 to 150 ℃ and pH from 7.0 to 9.8 as main parameters. As this second report, the experimental data of FAC rate were compared with the prediction method. Effective mass transfer coefficient correlation was proposed and implemented into the prediction method considering combining effect of local average and turbulent velocity in the near-wall region calculated by computational fluid dynamics (CFD) simulation code. Fairly good agreement was confirmed between experimental and predicted FAC rate profile, quantitatively. Continuously, prediction method was applied to actual power plant piping systems, and some elbow components were chosen for evaluation in detail. Comparison of measured and predicted FAC rate also showed good agreement with data mostly evaluated conservatively in sense of maintenance management. As a whole, presented FAC prediction method including effective mass transfer coefficient was confirmed to predict measured FAC rate data of power plant pipe component with fairly good accuracy and reasonable conservatism, at least for the subjected temperature and pH conditions.