Bypass Retrofit of the Condensate Iron Removal System in a Desulfurization Island and Analysis of Pressure Responses of Wall-Thinned Equipment

Wall thinning caused by residual-steam erosion of the condensate iron-removal vessel and filters in a desulfurization island, together with unclear unloading limits after manual bypass activation, was investigated using two-dimensional axisymmetric models of equivalent wall thinning for the two equipment types. The finite element models were verified by comparing the stress results with thin-walled cylinder theory and by checking their sensitivity to mesh refinement. Gaussian process surrogate models were then used to construct normalized pressure responses and determine equivalent unloading pressures and pressure unloading ratios. The results show that the maximum relative errors in hoop and axial stresses compared with theoretical values are 0.0009% and 0.4149%, respectively. For the local wall-thinning model, the difference in the 95th-percentile equivalent stress between the medium and fine meshes is approximately 0.050%. At the currently recorded minimum wall thicknesses and a thinning-length ratio of 0.10, the equivalent unloading pressures of the condensate iron-removal vessel and filter are 0.5571 MPa and 0.6186 MPa, respectively, corresponding to pressure unloading ratios of 30.36% and 22.67%. The comparison limits determined through this parametric analysis of the two equipment types can provide a basis for bypass operation, maintenance, and subsequent wall-thickness reinspection.