TIME OF FLIGHT DIFFRACTION (TOFD)
Welding flaws can compromise the welded structure’s stability and integrity. When it comes to testing welds, Time of Flight Diffraction (TOFD), high-performance non-destructive testing (NDT) technique, provides accurate detection and sizing of cracks, slag, and lack of fusion in true wall direction, allowing you to access the vessel’s life. We will be with you throughout your testing project and will provide you with tailored solutions. Weld testing using the TOFD technique, data processing, and report preparation using the developed software are all part of our capabilities. We believe that using our TOFD inspection service will result in significant time savings throughout the life cycle of new construction and replacement projects.
It is an excellent and widely accepted pre-service and in-service inspection tool that is recognized internationally, with defined codes, standards, and acceptance criteria available for its use.
How ToFD Works?
ToFD is an ultrasonic testing innovation that consists of two probes. One will serve as a transmitter, while the other will serve as a receiver. Instead of recording the ultrasound reflected by defects, it detects the diffraction of sound waves emitted by the tips of defects.ToFD inspection provides precise data on the length and height of defects. ToFD, unlike other testing methods, can detect flaws regardless of their orientation.
TOFD differs from conventional pulse-echo ultrasonics in that it is a non-amplitude-based technique that relies on diffracted energy rather than reflected energy. TOFD, on the other hand, uses time-based, low energy, diffracted signals from the tips of flaws to measure and image the flaw’s exact or absolute position and size. The technique employs two probes, a transmitter and a receiver, which are normally placed on either side of the weld joint or area to be examined. Because the technique is not amplitude-dependent, as in conventional ultrasonics, it is not constrained by probe location to flaw orientation, poor coupling, uneven or changing material surfaces, and so on. TOFD also employs only the longitudinal wave, allowing mode converted signals to be screened out, simplifying flaw characterization and positioning. The scan data is collected in ‘raw’ form and digitized in RF format (‘A’ Scan).
- Higher probability of failure detection compared to conventional procedures such as radiographic testing (RT) and ultrasonic testing (UT) .
- Reduced costs, as TOFD inspections can take place on-site alongside production work during the day shift.
- No logistical difficulty as in the case of radiographic testing.
- Quick results, as inspection time is not as highly affected by material thickness as it is in the case of radiographic testing.
- Material examinations and inspections are possible even to temperatures exceeding 400°C.
- Reduced risk of company liability thanks to documented safety standards.
- Well qualified operators.
- Certified inspectors in accordance with the TOFD certification program based on ISO 9712 (former EN 473).