What is TOFD?

Time of Flight Diffraction is an Ultrasonic technique developed originally to improve the sizing accuracy of flaws previously detected by other means. Early applications of the technique advanced from solely sizing flaws to applications relying on TOFD for principle detection means, this pioneering technology resulted in major flaws being missed due to poor application and a general lack of understanding by persons operating the equipment.

ndt training in chennai

What are the responsibilities of a individual who is certified to TOFD Level II?

An individual certified to TOFD Level II has demonstrated competence to perform NDT according to TOFD procedures. Within the scope of the competence defined on the certificate, Level II personnel may be authorised by the employer to:

  • Select the TOFD technique for the test method to be used;
  • Define the limitations of application of the testing method;
  • Translate NDT codes, standards, specifications and procedures into NDT instructions adapted to the actual working conditions;
  • Set up and verify equipment settings;
  • Perform and supervise tests;
  • Interpret and evaluate results according to applicable standards, codes, specifications or procedures;
  • Prepare TOFD written instructions
  • Carry out and supervise all tasks at or below level II;
  • Provide guidance for personnel at or below level II, and
  • Report the results of TOFD test


40 hrs of TOFD Level II training covers as per ANSI/ASNT CP-105.

Syllabus specific to Ultrasonic Testing of Welds using Time of Flight Diffraction

Level 2 Specific Theory

  • Flaw sizing with the pulse echo technique
  • Comparison of flaw sizing accuracy for different techniques
  • Angular variation of diffraction signals
  • Effect of change in probe separation and importance of calibration with lateral and back wall signals
  • Change in probe separation
  • Importance of calibration
  • Error due to variations in couplant depth
  • Error due to variations in surface profile
  • Velocity error
  • Index point migration errors
  • Other errors
  • Multiple arcs
  • Procedure writing
  • Equipment and probe checks
  • Equipment checks
  • Screen height linearity
  • Amplitude linearity
  • Time base linearity
  • Probe index emission point
  • Beam angle
  • Beam spread
  • TOFD combined probe delay
  • Sensitivity
  • Resolution
  • Probe checks
  • Material velocity measurement
  • Probe frequency
  • Probe pulse length