Time of Flight Diffraction (TOFD)
A high-performance NDT technique TOFD can be used to accurately find and size cracks, slag, fusion faults, and other flaws in a welded construction.
Our experts can assist you throughout your testing project and provide you with personalized systems based on your needs.
Weld testing utilizing the TOFD method and data processing using our proprietary software are two of the services we offer. TOFD is a great and widely utilized pre-service and in-service inspection tool that is acknowledged internationally and has defined codes and standards.
How Time of flight Diffraction or TOFD Inspection different from Conventional Ultrasonic Testing..?
The majority of ultrasonic techniques rely on collecting reflections from flaws, even if only from specific flaw aspects. The signals diffracted from the flaw’s extremities are used by TOFD to find cracks (tips). In transmit-receive mode, two angled compression wave probes are used, one on either side of the weld (frequency typically between 2 and 10MHz). The bulk of the thickness is inspected due to the beam divergence, while thicker components can require more than one probe separation. The tip of a crack serves as a secondary emitter that diffuses sound when sound reaches it, sending it in all directions (some in the direction of the receiving probe). Travelling between the transmitter and the receiver is achieved by a “lateral wave” traveling at the same velocity as the compression waves. The distance of the imperfection from the scanned surface can be calculated from the time difference between the lateral wave and the diffracted signal from the flaw. It would be able to resolve the tip diffracted signals from the top and bottom of a flaw if it is large enough in the through-wall (height) dimension, allowing the measurement of the imperfection’s through wall height.
TOFD In service Inspection :
A fairly quick approach of inspecting whole volumes is TOFD. It is most commonly used for the in-service inspection of butt welds in pressure vessels, process pipework, and the petrochemical, nuclear, and oil refining industries Following that, the results are often used in fitness for service (FFS) evaluations in accordance with, for reference, API RP579. (Information on flaw length and height for embedded and surface flaws is required for an FFS assessment of a known flaw. Knowing out the component thickness, the flaw’s orientation in relation to the major stress direction, and whether the flaw’s cross-section is planar are also crucial).