Time of Flight Diffraction (TOFD)
Typical application
TOFD is commonly applied for:
• Weld inspections in pressure equipment
• New build fabrication inspections
• Detection and sizing of planar defects
• Inspection of thick-section welds
• Complementary use with PAUT
TOFD is frequently used where defect height measurement is critical.
Suitable inspection scenarios
TOFD is commonly applied for:
• Weld inspections in pressure equipment
• New build fabrication inspections
• Detection and sizing of planar defects
• Inspection of thick-section welds
• Complementary use with PAUT
TOFD is frequently used where defect height measurement is critical.
Not suitable / limitations
TOFD is not suitable for:
• Very thin materials
• Complex weld geometries
• Near-surface defect detection
• Coarse-grained materials
Limitations include:
• Reduced sensitivity to surface-breaking defects
• Requires access on both sides of the weld cap
• Skilled setup and interpretation required
• Typically used alongside PAUT
Safety considerations
TOFD is commonly applied for:
• Weld inspections in pressure equipment
• New build fabrication inspections
• Detection and sizing of planar defects
• Inspection of thick-section welds
• Complementary use with PAUT
TOFD is frequently used where defect height measurement is critical.
Description
Time of Flight Diffraction (TOFD) is an ultrasonic inspection technique that detects defects by analysing diffracted ultrasonic signals generated at flaw tips. Unlike conventional UT or PAUT, TOFD does not rely on reflected signals, making it particularly effective for accurate defect sizing. TOFD provides quantitative through-wall defect information.
Pros
Pros Cons
ConsAdvantages in the right context:
• Accurate defect height sizing
• High probability of detection for planar defects
• Quantitative inspection results
• Radiation-free
• Excellent repeatability
Limitations to consider:
• Limited near-surface sensitivity
• Requires experienced interpretation
• Less effective on complex geometries
• Often not used as a standalone method
• Surface condition influences results
Disclaimer
Information on this page is indicative and context-dependent.
TOFD does not replace applicable codes, standards or engineering judgement.
Inspection planning, procedure qualification and acceptance decisions remain the responsibility of the asset owner and inspection professional.