Time of Flight Diffraction (ToFD)

TOFD is an ultrasonic testing technique that measures diffracted waves to accurately size and locate defects. It is particularly effective for detecting and characterizing cracks, weld defects, and other discontinuities.
Time of Flight Diffraction (ToFD) uses an ultrasonic pulse to find and detect flaws in welds along with weld overlays and the heat affected zones of other components.


• TOFD defect detection does not depend on the defect orientation, in contrast to the pulse. Planar defects and cracks, which are not perpendicular to the measured surface can be detected. When Engineering Critical Assessment (ECA) is applied, only the relevant defect must be cut, thereby preventing needless repairs which could harm the integrity of the weld. Results are immediately available with a permanent record. Defect height can be exactly determined.

What defects/indications can it detect?

• Corrosion or thinning (known as ‘thickness gauging’).
• Inclusion/laminations.
• Internal planar defects (such as lack of fusion).
• Cracks and voids.

Commonly used to test

• Storage tanks.
• Pressure vessels.
• Clad materials. environments.
• Piping.
• Structural steel.


• More reliant on a clean/smooth surface.
• Material thickness (A minimum material thickness may be required when inspecting welds).
• The weld must be feasibly accessible from both sides.
• There is a dead zone for defect detection under the surface.

Alternative inspection methods

• Radiography (RT).
• Ultrasonic Testing (UT).
• Phased Array Ultrasonic Testing (PAUT)