Heavy rotor forgings, in particular for the power generation market, are highly stressed components and the ultrasonic inspection is the most important method to guarantee a sufficient material quality throughout the volume. This is why more and more heavy rotor forgings have to be inspected using automated inspection systems guarantying a high probability of detection for possible flaws, good documentation as well as highly repeatable inspection. In contrast to manual inspection, automated inspection does not allow for an optimization of a flaw reflection by moving the probe, as the probe is continuously moved over the part surface in distinct scan lines, resulting in a distinct pattern of inspection points. To ensure full volume coverage using overlapping ultrasonic beams from neighboring inspection points, a precise definition of an examination grid is required. To assure that all critical errors are detected, multiple scan directions have to be applied as per VGB-R 504 M [1] to inspect the complete volume, resulting in a high inspection duration. Moreover most of the rotor forgings have a low sound attenuation, resulting in low pulse repetition rates and even longer inspection times. An ideal inspection grid will therefore make sure the full forging volume is covered by the inspection and reduce the inspection duration to a necessary minimum at the same time. Several standards currently specify an examination grid for manual inspection, which are not simply transferrable to automated inspection. This paper presents a solution to this problem, developed by the subcommittee "Automated UT" of the national German society for NDE (DGZfP).

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