Time of Flight Diffraction (TOFD)


Time of flight diffraction (TOFD) is an advanced ultrasonic non-destructive testing method used for inspection of welds.

Time of flight diffraction (TOFD) is one of the most reliable NDT method for pre service and in service inspection of welds. An accurate assessment of welded joints is necessary for stability, safety, integrity for maintaining the reliability of parts.
This ultrasonic method (UT) method has an application in variety of industries like Petrochemical, Oil and Gas, automobile, fabrication and many others.
Major advantage of TOFD (time of flight diffraction) includes: 

  • No shutdown is required.
  • Inspection data is recorded and can be stored digitally.
  • Real time imaging.
  • Fast inspection can be done.
  • All types of weld defects can be detected.
  • Accurate sizing of the discontinuities can be done.

Two probes are placed on the opposite side of the test piece, one probe acts as a transmitter while the other probe acts as a receiver. When there is no flaw is detected the receiver picks up two waves – one wave travels along the surface and other reflects from the backwall. If there is any defect there is a diffraction from the tip of the discontinuities. By calculating the time of flight of the pulse, the depth of the discontinuities can be calculated by trigonometry.

TOFD is often used in conjunction with other NDT method such as PAUT.

Our inspectors are ASNT Level 2 qualified and are highly experienced in using this testing method. Our expertise can help you to ensure that your welded structures and equipments  are in compliance with the industrial codes, standards or customers requirements.
ANDT offers a wide range of NDT methods. Therefore we can provide you with any other  method as well to compliment  TOFD to perform single sided inspection of welds.

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