Ultrasonic testing (UT)

UT involves introducing an ultrasonic wave into the material by means of a probe, and then recording and analysing the reflected signals. The character and position of the echo make it possible to identify any discontinuities inside the component. The method is used, among other things, to inspect welds, castings, forgings, sheet metal, bars, machine components and pressure components, when a volumetric quality assessment is required.

UT very effectively detects cracks, lack of penetration, lack of fusion, slag inclusions, gas pores, laminations and rolled-in laps. With the right choice of probes and scanning techniques, discontinuities perpendicular to the beam can be detected and – with advanced techniques – also those with less favourable orientations

Ultrasonic waves are not transmitted through air, so in order to effectively introduce the beam into the material, adequate acoustic coupling must be ensured at the point where the ultrasonic beam enters the tested material. The tested surface should be smooth and free of any contamination, paint or weld spatter.

In many applications, yes – UT provides a volumetric assessment of welded joints without the need for ionising radiation, which simplifies work organisation and safety. However, in some cases (e.g. very complex geometry, thin walls, regulatory requirements) radiography remains the reference or mandatory method, so the decision should be based on the requirements of standards and the client’s specification.

One limitation is the minimum required thickness of the tested component. In addition, UT testing is difficult to carry out on components with complex geometry and usually requires appropriate surface preparation to ensure good contact with the probe. Test effectiveness can also decrease for materials that strongly attenuate or scatter ultrasonic waves (e.g. austenitic weld structure, grey cast iron).

Yes, in accordance with the guidelines of standard PN-EN ISO 17640. The standard describes manual ultrasonic testing techniques for welded joints at least 8 mm thick, for materials with low attenuation of the ultrasonic beam.

Yes – UT uses mechanical (sound) waves rather than ionising radiation, so it does not require protective zones or special radiological procedures; however, compliance with standard health and safety rules and correct equipment operation is always necessary.

Not always – despite high sensitivity to volumetric defects, UT may not detect very fine surface cracks or certain types of discontinuities; therefore, in practice we combine UT with surface methods (PT, MT) and, where necessary, with RT, PAUT or TOFD, in accordance with the requirements of standards and risk analysis.