Non-destructive testing of welds

By definition, non destructive testing is the testing of materials for surface or internal flaws or metallurgical condition, without interfering with the integrity of the material or its suitability for service.

The technique can be applied on a sampling basis for individual investigation or may be used for complete checking of material in a production quality control system. There are several different methods listed below.


Ultrasonic testing (UT) is a family of non-destructive testing techniques based in the propagation of ultrasonic waves in the object or material tested. This technique is used for the detection of internal and surface (particularly distantsurface) defects in sound conducting materials. In most common UT applications, very short ultrasonic pulse-waves with centre frequencies ranging from 0.1-15 MHz, and occasionally up to 50 MHz, are transmitted into materials to detect internal flaws or to characterize materials. A considerable degree of skill is required to assess the results but this method is useful for thickness and lengths up to 30 feet, and results are instant and detailed.

This is an area of growing innovation with new standards being developed for Guided Wave Testing and Ultrasonic Phased Array Equipment.

Key Standards

BS 9690-1 Non-destructive testing. Guided wave testing. General guidance and principles

BS 9690-2 Non-destructive testing. Guided wave testing. Basic requirements for guided wave testing of pipes, pipelines and structural tubulars

BS EN ISO 17640 Ultrasonic testing. Techniques, testing levels and assessment

BS EN ISO 11666 Ultrasonic testing. Acceptance levels

BS EN ISO 23279 Ultrasonic testing. Characterization of indications in welds.

BS EN ISO 2400 Ultrasonic testing. Specification for calibration block No.1

BS EN ISO 16811 Ultrasonic testing. Sensitivity and range setting

BS EN ISO 16810 Ultrasonic testing. General principles

BS EN ISO 16827 Ultrasonic testing. Characterization and sizing of discontinuities

BS EN 12668-1 Characterization and verification of ultrasonic examination equipment: Instruments

BS EN 12668-2 Characterization and verification of ultrasonic examination equipment: Probes

Radiographic Testing

Xray & Gamma - Industrial radiography is a method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials. This method is useful for thin sections and is suitable for any material. However there are health risks involved.  

Key Standards

BS EN ISO 17636-1 Radiographic testing. X- and gamma-ray techniques with film

BS EN ISO 17635-2 Radiographic testing. X- and gamma-ray techniques with digital detectors

BS EN ISO 19232 Series. Image quality of radiographs

BS EN 16407-1 Radiographic inspection of corrosion and deposits in pipes by X and gamma rays. Tangential radiographic inspection

BS EN ISO 10675-1 Acceptance levels for radiographic testing. Steel, nickel, titanium and their alloys

BS EN ISO 10675-2 Acceptance levels for radiographic testing. Aluminium and its alloys

BS EN ISO 11699-1 Industrial radiographic film. Classification of film systems for industrial radiography

BS EN ISO 11699-2 Industrial radiographic film. Control of film processing by means of reference values

Industrial computed tomography

(CT) scanning is any computer-aided tomographic process, usually x-ray computed tomography, that (like its medical imaging counterparts) uses irradiation (usually with x-rays) to produce three-dimensional representations of the scanned object both externally and internally. Industrial CT scanning has been used in many areas of industry for internal inspection of components. Some of the key uses for CT scanning have been flaw detection, failure analysis, metrology, assembly analysis and reverse engineering applications.

Key Standards

BS EN 16016 Series Radiation methods. Computed tomography: Terminology; Principle, equipment and samples; Operation and interpretation; Qualification

BS EN 14784-1 Industrial computed radiography with storage phosphor imaging plates. Classification of systems

BS EN 14784-2 Industrial computed radiography with storage phosphor imaging plates. General principles for testing of metallic materials using X-ray and gamma rays

Infared thermography

 Infrared thermography, thermal imaging, and thermal video are examples of infrared imaging science. Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum and produce images of that radiation, called thermograms.

Key Standards

BS ISO 10878 Infared thermography. Vocabulary

Magnetic particle Inspection

Magnetic particle inspection (MPI) is a  process for detecting surface and slightly subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys.

Key Standards

BS EN ISO 17638 Magnetic particle testing

BS EN ISO 23278 Magnetic particle testing of welds. Acceptance levels

BS EN ISO 3059 Penetrant & magnetic particle testing. Viewing conditions

BS EN ISO 9934 Series Magnetic particle testing. General principles; Detection media; Equipment (Revision ongoing – publication 2015)

Penetration testing

This method is frequently used for the detection of surface breaking flaws in non-ferromagnetic materials.

Key Standards

BS EN ISO 3452 Series 2013 Penetrant testing. General principles; Testing of penetrant materials; Reference test blocks; Equipment; Penetrant testing at temperatures

BS EN ISO 23277  Penetrant testing of welds. Acceptance levels

BS EN ISO 12706  Penetrant testing. Vocabulary 

Eddy current methods

An electromagnetic NDT Method based on the process of including electrical currents into conductive material and observing the interaction between the currents and the material. Suitable for the determination of a wide range of conditions of conducting material, such as defect detection, composition, hardness, conductivity, permeability etc. in a wide variety of engineering metals.

Key Standards

BS EN ISO 12718 Eddy current testing. Vocabulary

BS EN ISO 15548 Series Equipment for eddy current examination

BS EN ISO 15549  Eddy current testing. General principles

BS EN 1711 2000 Eddy current examination of welds by complex plane analysis

Acoustic emission/Leak detection

Acoustic emission (AE) is the sound waves produced when a material undergoes stress (internal change), as a result of an external force. The technique is used, for example, to study the formation of cracks during the welding process, as opposed to locating them after the weld has been formed with the more familiar ultrasonic testing technique. It is also valuable for detecting cracks forming in pressure vessels and pipelines transporting liquids under high pressures.

Key standards

BS EN 1330-9 Terminology. Terms used in acoustic emission testing

BS EN 15856 Acoustic emission. General principles of AE testing for the detection of corrosion within metallic surrounding filled with liquid

BS EN 15495 Acoustic emission. Examination of metallic pressure equipment during proof testing

BS EN ISO 18249 Acoustic emission testing. Specific methodology and general evaluation criteria for testing of fibre-reinforced polymers

BS EN ISO 18081 Draft for public comment 2014.  Acoustic emission. Leak detection by means of acoustic emission

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