Ultrasonic Testing: Flaw Detection, Thickness and Corrosion Mapping

Ultrasonic testing is the principal method for finding what is inside a material, and itmad provides ultrasonic testing for flaw detection, wall thickness measurement, corrosion mapping and lamination testing to ASME V, ASTM, EN, ISO and Australian Standards, by ISO 9712 and ASNT Level II qualified technicians. itmad operates across the Middle East, Asia and Europe. Last reviewed: October 2026.

How it works

A transducer sends in pulse waves, usually between 0.5 and 10 MHz, and the time that each reflection takes to return is measured. Any change in acoustic impedance, whether a flaw, a lamination or a back wall, produces an echo, and the timing of the echo locates it. The method is highly sensitive to embedded planar discontinuities and needs access to only one surface, and it is faster and more economical than radiography, with no radiation source, exclusion zone or film processing.

Applications

Flaw detection (UFD) finds internal discontinuities in welds, castings, forgings and wrought products: lack of fusion, incomplete penetration, cracking, inclusions and porosity. Wall thickness measurement (UTT) gives the remaining wall on pipework, vessels and tanks from the accessible side, without shutting down or opening the system. Corrosion mapping measures thickness systematically across a grid and produces a map of wall loss that shows the pattern of attack and not isolated readings.

Lamination testing (ULT) examines plate and pipe for laminar defects before fabrication, when a lamination found after welding is expensive. Bond and clad testing verifies bonding in clad, lined and bimetallic components, and velocity-based material characterisation supports density and related property determination where the specification requires it.

Techniques

Straight beam probes are used for thickness, lamination and bond testing, where the defect of interest lies parallel to the surface. Angle beam shear wave probes are used on welds, where the fusion faces have to be interrogated at an angle that the geometry does not allow directly. Twin crystal probes are used on thin sections and corroded surfaces, where the near-surface dead zone of a single crystal probe would obscure the result, and technique selection follows the geometry, the material and the flaw type that the specification is concerned with.

Standards applied

Testing is performed to the standard that the contract or governing code calls up, and procedures are established across ASME Boiler and Pressure Vessel Code Section V, Articles 4, 5 and 23; ASTM E164, E114, E2375, A388, A609 and A745; EN 1714, EN 12680-3 and BS EN 10160; and ISO 10543, ISO 11496 and ISO 4386-1. They also cover the Australian Standards AS 2207, AS 2083, AS 2574, AS 1065, AS 2452.3, AS 2824, AS 1101.3, AS 1929, AS 3978, AS 3992, AS 2885.2, AS 1665, AS 1710 and the AS 1554 series, together with API standards, CECT and other national and international standards as specified. That range matters where a project is built to a specification from outside the usual ASME or EN framework, such as Australian Standards on projects with Australian design or ownership.

Limitations

Ultrasonic testing needs coupling to the surface, so surface condition and preparation affect sensitivity. Coarse-grained and highly attenuative materials scatter the beam and reduce penetration, and very thin sections are limited by the near-surface dead zone. A flaw lying parallel to the beam sends back little signal, so welds are examined from several angles and TOFD is used where orientation cannot be assumed. Complex geometry can prevent full coverage, and where that is the case the report says so and does not imply coverage that was not achieved.

Personnel

The technicians hold ISO 9712 and ASNT SNT-TC-1A Level II, with PCN and NAS 410 qualification where the work requires it, and Level III oversight of procedure approval and technique validation. itmad carries out the work on site, in fabrication yards, offshore or at its own premises.

Related methods

If imaged, encoded weld data is needed, phased array ultrasonics provides it, and if the aim is accurate through-wall sizing of a known flaw, TOFD is the more precise method.

What the client receives

A report that identifies each item examined by weld number, line number or drawing reference, with the technique, probe angles and frequencies applied and the standard followed. Calibration records and reference block traceability are included, and indications are recorded with location, depth, length and amplitude. Thickness readings or corrosion maps are provided where that is the scope, with an assessment against the acceptance criteria of the governing code and the technician's qualification level and certification reference.

Frequently asked questions

What is ultrasonic testing and how does it work?

It transmits pulse waves, typically between 0.5 and 10 MHz, into a material and measures the time of flight of the returning reflections. Any change in acoustic impedance, such as a flaw, lamination or back wall, produces an echo, and the timing of the echo locates it.

What are the main applications?

Internal flaw detection in welds, castings and forgings, wall thickness measurement from the accessible side without shutdown, and corrosion mapping across a grid. It is also used for lamination testing of plate and pipe, bond and clad testing, and material characterisation.

What probe techniques are used?

Straight beam probes for thickness, lamination and bond testing, angle beam shear wave probes for welds, and twin crystal probes for thin or corroded sections where the near-surface dead zone would obscure the result. Selection follows the geometry, the material and the flaw type.

Which standards does itmad apply?

ASME Section V Articles 4, 5 and 23, ASTM E164, E114, E2375, A388, A609 and A745, EN 1714, EN 12680-3 and BS EN 10160, ISO 10543, ISO 11496 and ISO 4386-1, and a long list of Australian Standards, with API and other national standards where specified. Procedures are established for these, and others are available on request.

What are the limitations of ultrasonic testing?

It needs surface coupling, coarse-grained materials scatter the beam, and very thin sections are limited by the dead zone. Flaws parallel to the beam return little signal, and where geometry prevents full coverage the report states it.

Why is ultrasonic testing preferred to radiography?

It needs access to only one surface and has no radiation source, exclusion zone or film processing, so it is faster and more economical for most flaw detection. It is also highly sensitive to embedded planar discontinuities.