5.2.1 Ultrasonic testUltrasonic test shall be carried out after the last heat treatment, preferably onrough machined rings of uniform thickness between ID and OD and free fromprotrusions or score marks.Test shall run from outer circumference as per ASTM 745, using angleprobes. Depth of axial reference notch on OD equal to 3% of ring thicknesscalled up on drawing, 0,5 mm minimum (quality level QA-1). ABB inspectormay decide to use other probe types or repeat the test also from flat parallelfaces to improve resolution, positioning and evaluation of discontinuities.