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TOFD

The Time-of-flight diffraction (TOFD) technique is an ultrasonic technique based on a pair of ultrasonic probes in a pitch-catch setup.

The Time-of-flight diffraction (TOFD) technique is an ultrasonic technique based on a pair of ultrasonic probes in a pitch-catch setup. One probe acts as transmitter and emits an ultrasonic pulse that is received by the second probe, the receiver.
Any discontinuity within the coverage of the sound beams will be hit by a sound wave from the transmitter and will generate reflection and/or diffraction waves which are received by the receiver. The received waves are digitized, the analogue amplitude values are transferred into digital values, stored and displayed on the screen as a gray scale image.
When both probes are moved simultaneously, the build-up image is a cross-sectional view of the item under test. With the cursors in the software, dimensions (length and through wall height) of the detected discontinuities can be measured.
TOFD is the most accurate technique for sizing of discontinuities with one of the highest reliabilities of all NDT techniques and can be used as a full replacement for conventional UT or radiographic testing. The main application of TOFD is the examination of welds.

Applications

  • Weld inspection (Pre-service and In-service)
  • Inspection of intermediate welded welds
  • Inspection at elevated temperatures varying from 50°C to over 250°C
  • Detection of root corrosion
  • Detection of cladding disbonding
  • NII, Non-Intrusive Inspection
  • Detection of Hydrogen Induced Cracking (HIC) and Stress Corrosion Cracking (SCC)
  • Detection of High Temperature Hydrogen Attack (HTHA)
Codes and Standards
  • Examination and acceptance criteria according EN-ISO standards
  • Examination and acceptance criteria according ASME code

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