Time-of-flight diffraction (TFOD) also belongs to the category of ultrasonic detection technology. It uses the diffraction wave signal of the defect endpoint in the pipeline or container to detect and determine the defect size. Its structure usually uses a dual probe, one for transmission and one for reception.
Advantages: high defect detection rate and detection accuracy, fast detection speed, low cost, and easy operation. Disadvantages: TFOD is mostly suitable for non-destructive testing of carbon steel and low alloy steel pipes, as well as pipe body butts and container welds. It requires the inspection personnel to have rich experience in image interpretation and it is difficult to characterize the defects.
It is widely used in on-site inspection work, including the installation and manufacturing inspection of pressure pipelines and the inspection of pressure pipelines in use. The standard NB/T47013.10-2015 “Non-destructive Testing of Pressure Equipment” promulgated in 2015 added relevant content of this detection method, providing a standard basis for TOFD detection work.
