Time-of-flight diffraction (TOFD) is a non-destructive testing (NDT) method that uses ultrasonic waves to inspect welds and other components for flaws:

TOFD uses two ultrasonic probes, one to transmit and one to receive. The transmitter emits an ultrasonic pulse into the component, and the receiver measures the time it takes for the sound waves to return. TOFD is different from other ultrasonic testing methods because it measures the response time of low amplitude waves that are diffracted by cracks.

TOFD is used to inspect welds, weld overlays, and the heat affected zones of other components like piping, pressure vessels, and storage tanks.

Benefits

TOFD is a sensitive and accurate method that provides a wide area of coverage with a single beam. It’s also more sensitive than standard pulse echo inspections.

History

TOFD originated from tip diffraction techniques that were first published in 1975.

ISO standards

ISO 10863:2011 specifies the application of TOFD to the ultrasonic testing of fusion-welded joints in metallic materials that are at least 6 mm thick.

APPLICATIONS

Weld inspection – Structural / Piping
ToFD in lieu of Radiography Testing (ASME Sec VIII, API 620, ASME B31.3, B31.1)