Time-of-Flight Diffraction (ToFD)
Time-of-Flight Diffraction (TOFD) is an advanced ultrasonic testing technique for inspecting welds and critical components. It provides accurate information about the location and size of internal indications.
What is Time-of-Flight Diffraction (ToFD)?
Accurate detection and sizing of internal indications
Time-of-Flight Diffraction (TOFD) is an advanced Non-Destructive Testing (NDT) method based on ultrasonic waves. It uses two probes positioned on opposite sides of a weld. One probe transmits ultrasonic waves while the other receives the signals diffracted from the tips of an indication.
Unlike conventional ultrasonic testing, TOFD does not rely primarily on reflected signals from a defect. Instead, it detects diffracted sound waves generated at the edges of an indication. By measuring the travel time of these signals, the location and dimensions of an indication can be determined accurately.
TOFD is particularly effective for detecting and sizing weld discontinuities such as cracks, lack of fusion and inclusions. The inspection data is recorded digitally and can be visually analysed and reviewed.
Benefits
- Accurate sizing of indications, including their length and depth
- High probability of detection (POD) for relevant weld discontinuities
- Digital inspection data for analysis, reporting and future reference
Used in these markets:
TIME-OF-FLIGHT DIFFRACTION
TOFD inspection
TYPICAL APPLICATIONS
Typical applications of TOFD
Time-of-Flight Diffraction is commonly applied for the inspection and sizing of weld discontinuities in critical components and structures.
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Performance overview
Strengths and limitations of Time-of-Flight Diffraction
Strenghts
- Accurate information about indication length and depth
- High probability of detection for relevant defects
- Digital recording and visual representation of inspection data
- No harmful ionising radiation
- Suitable for a wide range of materials, including plastics such as HDPE
- Can be used for material thicknesses from approximately 5 to 200 mm
- Can be performed without interrupting production in suitable applications
- Suitable for elevated-temperature inspections in specific applications
Limitations
- Requires access for positioning the probes on both sides of the weld
- Probe placement and surface condition can influence inspection quality
- Requires qualified and experienced personnel for data acquisition and interpretation
- Geometry and weld configuration can affect the inspection results
- Near-surface indications can be more difficult to detect and evaluate
- Suitable inspection procedures and calibration are required for reliable results
Cases
Proven in practice
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Making sure heavy lifting gear meets the highest standards
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Frequently Asked Questions
Questions about this service?
Time-of-Flight Diffraction provides accurate information about the location and size of internal weld indications. Our experts can advise whether TOFD is suitable for your inspection requirements.
See also
Related products & services
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Radiographic Testing (RT)
Radiographic Testing (RT) reveals internal indications and discontinuities that cannot be detected by visual examination alone. Reliable inspections support quality control, safety and asset integrity.
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Phased Array Ultrasonic Testing (PAUT)
Fast and detailed inspection of complex geometries
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Ultrasonic Testing (UT)
Uses high-frequency sound waves to detect internal defects and measure material thickness without damaging the component.
