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Assessing the Flaws in Welded Seam of Header of a 300MW Steam Turbine Generator Unit

The flaws such as crack or slag inclusion, in the welded seam of header of a 300MW steam turbine generator unit, were detected by the ultrasonic non-destructive inspection. Based on the crack modeling, the finite element method (FEM) was used to calculate and analyze the displacement field, stress field and stress intensity factors of the cracks under the conditions of warm start, cold start and normal operation, and the residual service life was predicted. Analyzing results showed that these flaws would not bring about primary brittle fracture and propagation of crack was harmless to safe in operation.