Safety evaluation of urea reactors containing defects was studied based on acoustic emission examination and subsequent dissection. First, acoustic emission examination was conducted in the process of pressure testing during the hydro test and the existed defects of the urea reactor were detected and comprehensively evaluated. Second, the dissection results of the multilayer urea reactor confirmed that the acoustic emission source locations were heavy weld radial expansion cracks. Third, crack stress intensity factors were calculated in accordance with the finite element analysis results and actual crack sizes which were acquired during urea reactor dissection. Based on the crack stress intensity factors, the remaining life of the multilayer urea reactors can be estimated during the acoustic emission testing process in accordance with the acoustic emission source location appearance pressures.

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