Menu
Time of Flight Diffraction (TOFD) is an advanced ultrasonic non‑destructive testing (NDT) technique used to accurately detect and size defects in welds and critical components. TOFD works by measuring the travel time of ultrasonic waves diffracted from the tips of flaws, providing highly reliable and precise inspections across a wide range of industrial applications.
What is TOFD?
TOFD uses a pair of ultrasonic probes—one transmitter and one receiver—placed on opposite sides of the weld or inspection area.

When ultrasound encounters a crack or defect, the wave energy is diffracted from the flaw tips, and the system calculates the defect’s size and location by analyzing the time of flight of these signals. This technique is widely recognized for delivering accurate, reproducible, and high‑resolution defect sizing.

Key Technical Features

Two ultrasonic transducers (transmitter + receiver) positioned across the weld

Two ultrasonic transducers (transmitter + receiver) positioned across the weld

Detection based on diffracted signals from defect tips

Detection based on diffracted signals from defect tips

Extremely accurate depth measurement using time‑of‑flight calculations

Extremely accurate depth measurement using time‑of‑flight calculations

High‑resolution B‑scan or D‑scan imaging

High‑resolution B‑scan or D‑scan imaging

Capable of sizing flaws with accuracy better than ±1 mm

Capable of sizing flaws with accuracy better than ±1 mm

What TOFD Detects

TOFD is effective at detecting and sizing:

Cracks

Cracks

Lack of fusion

Lack of fusion

Slag inclusions

Slag inclusions

Through‑wall defects

Through‑wall defects

Fabrication flaws

Fabrication flaws

Surface and subsurface discontinuities regardless of orientation

Surface and subsurface discontinuities regardless of orientation

Key Benefits of TOFD

High Sensitivity & Accuracy

High Sensitivity & Accuracy

Provides highly accurate defect sizing and depth measurement, often exceeding the precision of conventional UT and radiography.

Detects All Defect Types

Detects All Defect Types

Can identify cracks, lack of fusion, slag, and other discontinuities independent of orientation.

Fast & Efficient Inspections

Fast & Efficient Inspections

TOFD allows rapid scanning, making it ideal for large weld sections and high‑volume inspection.

Minimal Surface Preparation

Minimal Surface Preparation

Requires little surface cleaning and is less sensitive to uneven surfaces.

Permanent Digital Records

Permanent Digital Records

Stores detailed digital data for defect trending, reporting, and future comparison.

Non‑Radiative Method

Non‑Radiative Method

Safe for use during normal site operations, without the hazards associated with radiography.

Industries Using TOFD
Oil & Gas
Pipelines, tanks, pressure vessels, storage tanks
Aerospace
Engine components, structural welds
Power Generation
Nuclear reactor components, steam turbines
Construction & Infrastructure
Bridges, buildings, heavy steel structures.
Automotive & Manufacturing
Weld quality control

Common Inspection Tasks

Weld inspection and flaw sizing

Weld inspection and flaw sizing

In‑service defect monitoring

In‑service defect monitoring

Fabrication quality verification

Fabrication quality verification

Structural integrity assessments

Structural integrity assessments

Inspection of storage tanks, piping, clad material, and heavy‑wall components

Inspection of storage tanks, piping, clad material, and heavy‑wall components

How the TOFD Process Works

Probe Setup

Probe Setup

Two probes (transmitter & receiver) are positioned on opposite sides of the weld.

Ultrasonic Pulse Transmission

Ultrasonic Pulse Transmission

The transmitter sends a sound wave through the material.

Diffraction at Defects

Diffraction at Defects

When the wave encounters a flaw, it diffracts at the top and bottom crack tips.

Time of Flight Measurement

Time of Flight Measurement

The system measures the time taken for diffracted waves to reach the receiver.

Imaging & Analysis

Imaging & Analysis

Results are displayed in grayscale B‑scan or D‑scan images for accurate flaw interpretation.

Why Choose Our TOFD Services

Certified NDT inspectors trained in TOFD and advanced ultrasonic methods

Certified NDT inspectors trained in TOFD and advanced ultrasonic methods

High‑resolution imaging with permanent digital data storage

High‑resolution imaging with permanent digital data storage

Mobile onsite inspection capability for field and plant operations

Mobile onsite inspection capability for field and plant operations

Fast reporting turnaround with accurate, code‑compliant evaluations

Fast reporting turnaround with accurate, code‑compliant evaluations

Suitable for both fabrication and in‑service inspections

Suitable for both fabrication and in‑service inspections

Contact us at nisalesteam@setsco.com to discuss your project requirements.
Enquire Now