Procedure Making & Interpretation of Data as per Procedure or Clients requirements.
PROCEDURE NEED FOR TOFD as perticular job requirements.
1. Chapter 1 – TOFD Introduction & History
2. Chapter 2 – TOFD Vs Other methods
TOFD Signals Signals received
• Lateral wave (LW), subsurface
• Back-wall echo(BW)
• Mode converted ( shear wave echo)
• Diffracted signals from defects
3. Chapter 3 – Physics – Tip Diffraction
Diffraction Mechanism, Effects of Diffraction, Ultrasonic diffraction
4. Chapter 4 – Fundamentals of TOFD
Basic Setup, TOFD Signals, The Lateral wave, Back wall Signal, Diffracted wave - Defect signals,
Mode converted shear signals, Phase - Relationship between waves, ToFD Data Visualization
(A-Scan to B-Scan), TOFD Dead Zones, ToFD Probe angle, Transducer size, Probe frequency
TYPICAL TOFD SETUP, Time of Arrival calculation
5. Chapter 5 – Equipment Setup & Parameters Selection
Probe, Beam spread, Difference in beam spread with respect to frequency, Probe frequency, Probe angle,
Recommended Probe selection parameters for thickness up to 70mm, Probe-Centre Separation (PCS),
Probe-Centre Separation
Settings Gain setting, Time window settings, Time-to-depth conversion (Screen Calibration),
Sensitivity settings, Calibration,
Scanning : Longitudinal scan - Non-Parallel or D-scan or line scan, Limitations
Parallel scan - Lateral, transverse or B-scan, Limitation
Mechanical Scanner
Scan Resolution (Sampling Interval), Parameters for a ToFD Scan
Parameters to be considered in TOFD
Transducer size & Probe frequency
6. Chapter 6 - Errors in TOFD
Errors in the timing
Near Surface errors
Dead zone errors
Resolutions of top and bottom tips
Off-Axis depth error
PCS errors Multiple arcs
Other errors
7. Chapter 7 – Digitization Principles
Key Parameters of digitizer
• Frequency (Digitizer)
• Processor (no. of bits or amount of information that can be handled)
• Averaging
• PRF
• Acquisition Rate
• Soft Gain
8. Chapter 8 – Data Analysis & Sizing
Interpretation and analysis of TOFD images
Assessing the quality of the TOFD image
Identification of relevant indications
Classification of relevant indications
Surface breaking discontinuities
Embedded discontinuity indications
Gain Settings, Missed Scan, Loss of Signa, Effect of thick couplant layer,
Screen Calibration , Lateral wave synchronization, Sizing Techniques,
Height measurements, Synthetic Aperture Focusing Technique (SAFT) ,
TOFD image of surface notch's, TOFD image of opposite surface discontinuity,
TOFD image of opposite surface discontinuity with a larger depth,
TOFD image of a through wall discontinuity, TOFD image of point like discontinuities,
TOFD image of a change in thickness
9. Chapter 9 – Codes & Standards - TOFD
Many national and International standards or European Standards are available :-
EN, ASME, ASTM, AWS, ISO, etc.
10.Chapter 10 – Applications of TOFD
