ISO 13588:2012 specifies the application of the phased array technology for the semi- or fully automated ultrasonic testing of fusion-welded joints in metallic materials of minimum thickness 6 mm. It applies to full penetration welded joints of simple geometry in plates, pipes, and vessels, where both the weld and parent material are low-alloyed carbon steel.Where material-dependent ultrasonic parameters are specified in ISO 13588:2012, they are based on steels having an ultrasonic sound velocity of (5 920 ± 50) m/s for longitudinal waves, and (3 255 ± 30) m/s for transverse waves. It is necessary to take this fact into account when examining materials with a different velocity.ISO 13588:2012 provides guidance on the specific capabilities and limitations of phased array technology for the detection, location, sizing and characterization of discontinuities in fusion-welded joints. Phased array technology can be used as a stand-alone technology or in combination with other non-destructive testing (NDT) methods or techniques, for manufacturing inspection, pre-service and for in-service inspection.ISO 13588:2012 specifies four testing levels, each corresponding to a different probability of detection of imperfections.ISO 13588:2012 permits assessment of indications for acceptance purposes based on either amplitude (equivalent reflector size) and length or height and length.ISO 13588:2012 does not include acceptance levels for discontinuities.ISO 13588:2012 is not applicable: for coarse-grained metals and austenitic welds; for automated testing of welds during the production of steel products covered by ISO 10893-8, ISO 10893-11, and ISO 3183.