Time of Flight Diffraction (TOFD)

Time of Flight Diffraction is an advanced ultrasonic inspection technique used primarily for accurate detection and sizing of cracks and planar defects. TOFD relies on the diffraction of ultrasonic waves from crack tips, enabling precise measurement of defect height and location.

TOFD is widely recognized for its reliability, accuracy, and reduced operator dependency, making it a preferred technique for inspection of critical welds.

Why TOFD Is Required

Accurate sizing of cracks is essential for integrity assessment and fitness-for-service decisions. TOFD helps address challenges such as:

• Reliable detection of planar defects

• Accurate through-wall sizing of cracks

• Reduced subjectivity compared to conventional UT

• Requirement for high-confidence inspection data

TOFD provides consistent and repeatable results.

Scope of Inspection

TOFD is applicable to:

• Welded joints in pipelines and piping

• Pressure vessels and storage tanks

• Structural welds

• Thick and safety-critical components
  

Inspection Methodology

TOFD inspection follows a structured approach.

Development of inspection setup based on component thickness.

Placement of transmitter and receiver probes on either side of the weld.

Encoded scanning along the weld length.

Recording of diffraction signals from crack tips.

Analysis of TOFD data to determine defect size and location.

Engineering interpretation and reporting.

Tools and Techniques

TOFD inspection is supported by:

• TOFD probe configurations

• Encoded ultrasonic scanners

• Advanced signal analysis software
  

Key Benefits

• High accuracy in crack sizing

• Reliable detection of planar defects

• Reduced operator dependency

• Strong input for fitness-for-service evaluations

• Improved inspection confidence
  

Industries and Applications

TOFD is widely applied in oil and gas pipelines, refineries, petrochemical plants, power generation, fabrication yards, and EPC projects.

Time of Flight Diffraction provides precise and reliable inspection of welds and critical components. By enabling accurate defect sizing, TOFD supports informed integrity decisions and safe asset operation.