Ultrasonic Testing (UT) in Belgium
Ultrasonic testing is a high-precision volumetric NDT method that uses the propagation of high-frequency sound waves to detect internal defects and characterise materials. This technique enables the precise location and sizing of discontinuities throughout the full thickness of the material.
What is Ultrasonic Testing?
Ultrasonic testing (UT) is a volumetric non-destructive testing method based on the propagation of high-frequency ultrasonic waves (typically between 0.5 and 15 MHz) through the material under inspection. A piezoelectric transducer (probe) emits ultrasonic pulses that propagate through the component. When the wave encounters an interface (back wall, internal defect, inclusion), part of the energy is reflected back to the transducer, which converts it into an electrical signal. Analysis of the time of flight and amplitude of the echoes enables the determination of the position, size and nature of the detected discontinuities.
Ultrasonic testing offers a unique volumetric detection capability: it enables the entire thickness of the material to be examined, unlike surface methods such as penetrant testing or magnetic particle testing. Conventional techniques use single-element probes with longitudinal waves (normal incidence) or shear waves (angle incidence with a wedge). Advanced techniques such as TOFD (Time of Flight Diffraction) and Phased Array (multi-element ultrasonics) allow for more precise defect sizing and optimised inspection coverage, with the ability to generate cross-sectional images of the material for more reliable interpretation.
LCNDTEST provides technicians certified in conventional ultrasonics and advanced techniques (TOFD, Phased Array). We operate in Belgium and neighbouring countries for weld inspection, detection of internal defects in forgings and castings, as well as ultrasonic thickness measurement. Our state-of-the-art equipment enables us to meet the most stringent industry requirements.
Inspection Methodology
Ultrasonic testing requires careful preparation of the inspection surface: it must be sufficiently smooth and clean to ensure good acoustic coupling between the probe and the component. A couplant (gel, water, oil) is applied to the surface to eliminate air between the probe and the part, as air is a very poor conductor of ultrasound. The ultrasonic instrument is calibrated using standardised reference blocks (V1, V2 blocks, or application-specific blocks) to ensure the accuracy of distance and amplitude measurements.
For weld inspection, the shear wave technique with refraction angles of 45, 60 or 70 degrees is used to detect defects oriented parallel to the weld axis (lack of fusion, longitudinal cracks, lack of penetration). Scanning is performed from both sides of the welded joint to inspect the entire weld volume. The TOFD technique uses a pair of transducers (transmitter and receiver) and exploits signals diffracted by the tips of defects for accurate height sizing. Phased Array enables electronic steering of the ultrasonic beam to perform sectorial scans and generate real-time mapping of the inspected volume.
Each detected indication is evaluated against the acceptance criteria defined by the applicable standards (EN ISO 11666 for steel welds, for example) or by the client specifications. A detailed inspection report is issued, including the inspection parameters, calibration results, defect location and sizing, as well as the acceptance verdict.
Industrial Applications
- Inspection of butt welds and fillet welds on steel, stainless steel and special alloys
- Inspection of forgings (shafts, wheels, flanges) and castings for the detection of internal defects
- Residual thickness measurement on piping, vessels and in-service equipment (corrosion monitoring)
- Inspection of plates and rolled products for the detection of laminations and internal inclusions
- Inspection of pressure equipment and pressure vessels in accordance with ASME and EN 13445 codes
- Advanced inspection using TOFD and Phased Array for precise sizing of critical defects and fitness-for-service assessments
Advantages of Ultrasonic Testing
- Volumetric detection: ability to examine the full material thickness and locate defects at depth
- High detection sensitivity with the ability to accurately size defects (height, length, position)
- No ionising radiation hazard, unlike industrial radiography
- Real-time results enabling rapid on-site decision-making
- Advanced techniques (TOFD, Phased Array) providing cross-sectional imaging and complete results traceability
Reference Standards
EN ISO 17640 • EN ISO 11666 • EN ISO 16810 • EN ISO 16811 • EN ISO 10863 (TOFD) • EN ISO 13588 (Phased Array) • ASME Section V Article 4
Frequently asked questions
Ultrasonic testing is a volumetric non-destructive testing method that uses high-frequency sound waves (typically 0.5 to 15 MHz) to detect internal defects in materials. A piezoelectric transducer emits ultrasonic pulses that travel through the component. When the wave encounters a defect or interface, part of the energy is reflected back to the transducer. By analysing the time of flight and amplitude of these echoes, the inspector can determine the position, size and nature of internal discontinuities.
Ultrasonic testing is extremely versatile in terms of thickness range. It can inspect materials from as thin as approximately 1 mm (using specialised high-frequency probes) up to several metres thick, depending on the material type and the frequency of the transducer used. Lower frequencies penetrate greater thicknesses, while higher frequencies provide better resolution for thinner sections and near-surface defect detection. This wide range makes UT applicable to everything from thin-walled piping to heavy forgings and castings.
Yes, this is one of the principal advantages of ultrasonic testing. Unlike surface methods such as penetrant testing or magnetic particle testing, UT can detect defects located anywhere within the full thickness of the material, including internal cracks, lack of fusion, lack of penetration, porosity, inclusions and laminations. Advanced techniques such as TOFD and Phased Array further enhance the ability to accurately size and characterise these internal defects for engineering critical assessments.