TOFD and PHASED ARRAY
The Time of Flight Diffraction (TOFD) technique is based on the phenomenon of the diffraction of elastic waves caused by the apices of a discontinuity, and by the examination of radiofrequency signals “the time of flight”. TOFD is a technique that can be applied to both automatic systems and manual systems, especially for the verification of welded joints, often replacing radiographic testing.
This method is supported by ASME Code section 1, section VIII division 1 and division 2, Code Case 2235 and by the standard UNI ENV 583-6.
In phased array technology, the probe contains a series of piezoelectric elements arranged parallel to each other, each of which can be energised independently of the others.
The study and the specific generation of the delays with which the elements are activated generate focal laws to direct and/or concentrate the ultrasound beam to the desired depth and at a very precise angle.
The number and size of each element, probe geometry (base conformation, emission point, etc.) and frequency are the main features of a phased array configuration. The latest generation tools manage over 128 channels, allowing the visualisation of signals which improve real-time image formation, and the accuracy of the defect dimensions.
SGS is the world’s leading inspection, verification, testing and certification company. With more than 97,000 employees, SGS operates a network of over 2,600 offices and lab around the world. In 2017 the SGS Group acquired the CTR srl. SGS CTR Srl performs conventional and advanced NDT. The lab carrying out destructive tests, performs radiographic checks, Failure Analysis, SEM and EDS.