Time of flight diffraction (TOFD)
Time of flight diffraction (TOFD) is a technique that uses two probes in pitch-catch mode.
TOFD was initially developed as a method of accurately sizing and monitoring the through wall height of in service flaws in the nuclear industry.
TOFD is the most effective technique for the location and sizing of flaws in ferritic welds. TOFD uses the diffracted sound initiated from the flaw tips to locate the flaws.
TOFD can detect discontinuities irrespective of their type or orientation.
The benefits of TOFD include:
- rapid scanning speeds;
- accepted alternative to radiography;
- high sensitivity and accuracy;
- computerised electronic data capture and storage gives data retrievability and comparability with historical data; and
- excellent for monitoring weld root erosion, stress corrosion cracking, vessel cladding and hydrogen attack.