The weldments in PSA adsorbers have been examined by several non-destructive examination (NDE) methods, and then the metallurgical examinations were followed by NDE to confirm the nature of defects. Time of flight diffraction (TOFD), manual ultrasonic testing (UT), and phased array ultrasonic testing (PAUT) were employed to determine the location and size of defects inside of the weldments. Then, many crack-like defects were found in the weldments, and all of them were transverse defects with various sizes and orientations. To understand the nature of crack-like defects, we destructively examined the defects using the metallurgical characterization tools. The defects were found to be in two types: a chevron(1) and a vertical transverse crack. It has been conjectured that the chevron crack was caused by hydrogen during the welding process. And the vertical transverse crack was originated from the small defect that occurred in the weldment during the manufacturing of the vessel. In response to the occurrence of these defects, the effectiveness of manufacturing and in-service inspections was evaluated, and an inspection strategy for aged and future PSA adsorbers has been established. The details of NDE and metallurgical studies and the newly established inspection policy will be discussed in the proceedings.