Time of Flight Diffraction (TOFD) method of Ultrasonic inspection is a very sensitive and accurate method for nondestructive testing of welding defects. Testing with the TOFD method is only applied by continuously moving the probe pair along the weld seam, while in traditional UT techniques the probe must be also moved perpendicular to the weld seam.  Depending on the equipment the scan is performed either manually or by use of an automated manipulator.  In any case a computerized data evaluation is necessary.

Benefits:

Completely Non Destructive
Rapid and simple linear scanning
Detection of small and large defects are very accurate including planar shape and sharp edges defects (cracks)
Detection is independent of defect orientation
Sizing is not dependent on amplitude of the signal
100% raw data recording – second opinion is possible without doing secondary inspection
Superior inspection reliability
Defect height can be exactly determined. 
Dependable propagation monitoring
Offline analysis
Simple data storage
The inspection results are immediately available, as is a permanent record and a permanent print as longitudinal or transversal projection of the weld is available.