Evaluation on local wall thinning of Piping due to liquid droplet impingement by coupled analysis of corrosion and flow dynamics

In order to avoid unexpected pipe failures caused by liquid droplet impingement, a new evaluation methodology is proposed. Features of the methodology are: (1) adopting a concept of local corrosion: (2) considering chemical properties of flowing water and steam in pipes, focusing on pH: (3) considering alternating abrasion and growth of oxide layers on base metal which possibly accelerates wall thinning: and (4) considering residual stress in oxide layers formed on base metal of the pipe wall analogous to zirconium oxide formed on zirconium. From results obtained by the methodology, it is concluded that thinning rate is controlled mainly by alternating abrasion and growth of oxide layers in the range of low pH, while in the range of high pH, thinning rate is affected mainly by direct dissolution of iron. (author)