This European Standard defines the principles for tandem- and LLT -examination for the detection of discontinuities perpendicular to the surface.
The general principles required for the ultrasonic examination of industrial products are described in EN 583-1. A list of symbols and equations is given in EN 583-2.
The tandem- or LLT-examination should be used for the detection of planar discontinuities with distance to the surface greater than 15 mm. This European Standard has been prepared for the examination of metallic materials with a thickness between 40 mm and 500 mm with parallel or concentric surfaces. It can, however, be used for other materials and smaller thickness provided special measures are taken.