Time of Flight Diffraction (TOFD)
Time of Flight Diffraction (TOFD)
Time of Flight Diffraction (TOFD) is an advanced ultrasonic testing technique used for accurate detection, sizing, and characterization of weld defects. At Assessfie, our TOFD inspections provide precise through-wall sizing of cracks and lack of fusion by measuring diffracted ultrasonic signals from defect tips. This highly reliable method minimizes human interpretation errors and delivers consistent, quantitative results for safety-critical components.
How Time of Flight Diffraction Works
- Two ultrasonic probes are positioned on opposite sides of the weld—one as a transmitter and the other as a receiver.
- Ultrasonic waves propagate through the material and diffract from the tips of defects.
- The diffracted signals are captured and time-of-flight measurements are analyzed.
- Certified TOFD inspectors interpret the data to determine exact defect height, depth, and location, generating a detailed inspection report.
Technologies & Techniques We Use
- Conventional TOFD Weld Inspection
- TOFD with PAUT Combination for Enhanced Coverage
- High-Resolution TOFD Scanning
- Manual and Semi-Automated TOFD Systems
- Advanced Data Acquisition and Imaging Software
- Portable TOFD systems for field and offshore inspections
TOFD Applications in the Oil & Gas Industry
TOFD is widely used across upstream, midstream, and downstream operations where accurate flaw sizing is essential. Typical applications include:
Pipeline Weld Inspection — Girth welds, tie-in welds, and repair welds
Pressure Vessels & Storage Tanks — Shell welds and critical pressure-retaining joints
Structural Steel & Fabrication — Detection and sizing of planar defects
Offshore & Marine Structures — Weld inspection in risers and load-bearing components
Thick-Section Welds — Accurate flaw sizing in heavy-wall components
In-Service Inspection — Monitoring crack growth over time
Weld Repair Verification — Confirmation of defect removal and weld integrity
Standards & Regulations
Our Time of Flight Diffraction services comply with internationally recognized standards and industry codes to ensure accuracy, repeatability, and global acceptance.
International Standards
- ISO 10863 — Application of TOFD for weld inspection
- ISO 15626 — Time of Flight Diffraction technique
- ISO 17640 — Ultrasonic testing of welds
ASTM Standards
- ASTM E2375 — Practice for TOFD examination of welds
- ASTM E2491 — Ultrasonic phased array and TOFD applications
- ASTM E317 — Evaluation of ultrasonic transducers and systems
Industry-Specific Standards
- API 1104 — Advanced ultrasonic inspection of pipeline welds
- API 650 — Weld inspection for storage tanks
- API 570 — In-service piping inspection
- ASME Section V — NDT requirements for pressure equipment
Personnel Qualification Standard
- SNT-TC-1A — Qualification and certification of NDT personnel
