The maintenance strategy for pipelines of chemical plants has not been established because it requires a large number of inspections and some of them should be carried out at high and dangerous places. In order to establish the rational strategy, it is necessary to develop methodologies to concentrate inspection points on the maximum damaged parts of pipelines. In the case that piping management is carried out, there is a technology which measures the thickness of piping. This paper proposes a method to predict the maximum damaged part, due to erosion-corrosion by use of design and operation information. Then, in this paper, flow analysis is performed using the 3-dimensional heat fluid analysis software FLUENT. The simulation with FLUENT lias been calculated for the piping of the elbow shape to search for the place in the corrosion part where the progress of erosion-corrosion is the fastest in consideration of the influence of shear stress and pressure. As a result, it is clarified that the maximum damaged part can be predicted from design and operation information.