CONTACT US
MY SIDEIUS
teceurolab logo

Non-destructive testing on welding

Non-destructive testing (NDT) of welds includes a range of inspection methods used to assess the integrity and quality of welded joints without causing any damage to the material. These non-destructive techniques make it possible to detect both internal and surface defects that could compromise the mechanical performance of the joint, and ultimately the reliability of the entire structure.

With these weld checks, it is possible to validate the welded product reliably, ensuring compliance with international standards and industry regulations and ensuring durability and safety of components and systems.

REQUEST INFORMATION

Types of non-destructive testing on welds

Non-destructive testing of welds is the first key step in weld product validation, as it allows the quality of the weld to be verified without compromising the integrity of the component.
Nondestructive testing of welds falls into two broad categories: surface methods, which detect defects surfacing or near the surface, and volumetric methods, which investigate the component deeper instead.
The main surface methods include the visual method (VT), the earliest form of nondestructive inspection, which involves direct observation of the joint, often using optical instruments. We then find inspection with liquid penetrant (PT), ideal for highlighting cracks and surface porosity even on nonferromagnetic materials, and the magnetoscopic method (MT), which uses magnetic fields to highlight surface or shallow discontinuities in ferromagnetic materials.
Other surface and subsurface methods include Induced Currents (ET), a check that uses the principles of electromagnetism to detect defects and discontinuities in conductive materials; the Leak Detection (LT) method, which involves detecting leaks or leaks of gas or liquids through a joint, container, or system, verifying the integrity and tightness of the system without damaging it; Thermography (TT), a technique that uses infrared radiation emitted by materials to measure and visualize the distribution of surface temperatures, allowing the detection of defects, discontinuities or anomalies without direct contact; Strain Gauging (ST), a technique that uses strain gauges (strain gauges) or optical systems to measure the local deformations of a material or structure under load, allowing the evaluation of stress distribution and detection of anomalies without damaging the component. Or Acoustic Emissions (AT), which consist of detecting and analyzing elastic waves (ultrasound) generated spontaneously within a material or structure when it is subjected to mechanical stress. These acoustic waves are produced by phenomena such as crack growth, localized plastic deformation or internal movement, and are picked up by piezoelectric sensors applied to the surface of the component.

Volumetric methods, on the other hand, include ultrasonic inspection (UT), which uses sound waves to detect and locate even very small internal defects with great precision, and the radiographic method (RT), which uses X-rays or gamma rays to visualize internal defects such as porosity, lack of fusion, or inclusions.

Difference between destructive and nondestructive testing on welds

The fundamental difference between nondestructive and destructive testing for weld inspection lies in the integrity of the part examined at the end of the test. In fact, while nondestructive testing does not damage the tested component, which can then be used in operation if it conforms, destructive weld testing involves breaking or altering the specimen to assess its mechanical properties and material microstructure.
Among these weld tests, the most common are mechanical tests such as tensile, bend, and resilience tests, and metallographic tests such as hardness tests and macro/micrographs, which are useful for checking the strength, ductility, toughness, internal defects, and microstructure of the material. The two types of weld testing are equally important and not mutually exclusive: when subjecting a component to weld quality control, it is necessary to be able to verify both its surface and volume integrity, using nondestructive testing, and the mechanical and metallographic properties of the joint, thus using destructive methods.

Reference standards for ndt checks on welds

Non-destructive testing of welds must comply with international standards that define the required test methods, acceptability criteria and quality levels, so that uniformity is guaranteed in the processes of verification and safety of welded products, regardless of the area of application.
Among the main industry standards are some general standards, such as UNI EN ISO 5817, which defines 3 quality levels for steel joints (B,C,D) and the maximum size of detected discontinuities, and UNI EN ISO 10042, a reference for quality levels of imperfections in aluminum alloy joints.
Each nondestructive testing method then has specific normative references. For visual examination (VT), the reference standard for welded joints is UNI EN ISO 17637. For the magnetoscopic (MT) method, UNI EN ISO 17638 defines the general principles, while UNI EN ISO 23278 circumscribes the acceptability criteria (1,2,3).
For the liquid penetrant (PT) method, on the other hand, UNI EN ISO 23277 is taken as the reference for acceptability criteria. The radiographic method (RT) has UNI EN ISO 17636-1 for film radiography and UNI EN ISO 17636-2 for no-film radiography as reference for general principles. For acceptability criteria (levels 1,2,3), UNI EN ISO 10675-1 for steel welded joints and UNI EN ISO 10675-2 for Aluminum welded joints are followed. Finally, the ultrasonic (UT) method follows UNI EN ISO 17640 for the general principles of the method, UNI EN ISO 11666 for acceptability criteria and UNI EN ISO 23279 for the characterization of discontinuities on welds.
An important role is also played by UNI EN ISO 17635, which correlates the quality levels given in ISO 5817 with the requirements of other specific standards.
Other international references, beyond the UNI EN ISO series, areASTM E1032, which governs the radiographic examination of industrial film welded joints, and AWS D17.1, devoted to welding specifications for aerospace applications.

Are ndt tests on welds mandatory?

In many regulated industries, nondestructive testing of welds is in fact a mandatory safety requirement. The need for NCDs depends on the type of plant or product, the applicable technical regulations, and the contractual conditions required by the customer. Mandatory weld ndt inspections, for example, in these cases:
  • Aerospace and automotive: the quality of welded joints is subject to mandatory testing, often to specific standards such as AWS D17.1 for aerospace.
  • Construction and infrastructure: CNDs are required to verify the quality of welds in buildings, bridges, tanks, and load-bearing metal structures
  • Rail sector: mandatory ndt on welding of bogies, tracks and critical components
  • Oil & Gas and Energy: pipelines, pressure vessels, exchangers, and process plants require systematic NDT checks to prevent risks of leaks or accidents.
  • Pressure systems and boilers: European legislation (PED – Pressure Equipment Directive) provides for nondestructive testing as a compliance requirement for CE marking.

In all these cases, nondestructive testing of welds is an indispensable step in product certification and plant commissioning.

Do you need to verify the integrity of your welds with nondestructive testing?

REQUEST INFORMATION

The support of TEC Eurolab

Relying on TEC Eurolab for nondestructive testing of welds means being able to count on a qualified partner with decades of experience. Our technicians certified according to UNI EN ISO 9712 can perform all the main NDT methods – visual, liquid penetrant, magnetoscopic, ultrasonic, radiographic and tomographic – both in the laboratory and on site, directly at the customer’s premises. In addition to performing nondestructive testing on welds, we are able to support the client with regard to the entire welding certification pathway, from personnel certification to qualification of welding processes and quality management system in welding, thus being able to offer a complete service designed on specific needs.

FAQ - CND on welds

What is meant by nondestructive testing on welds?
Nondestructive testing on welds refers to a type of test that allows the integrity and quality of a weld to be verified without damaging the part, and detecting the possible presence of surface or internal defects.
The main CND methods on welds are visual examination (VT), liquid penetrant (VT), magnetoscopic method (MT), ultrasound (UT), radiography (RT), and industrial computed tomography (CT). The first three are surface methods, while the last three are volumetric methods.
Non-destructive testing keeps the tested part intact and assesses the presence of defects throughout the component. Destructive testing, on the other hand, breaks or alters the test specimen to check its mechanical properties or study the microstructure of the welded joint.
Only technicians qualified and certified according to UNI EN ISO 9712, working in accredited laboratories or directly at the customer site, can perform nondestructive testing on welds.
NDT checks on welds are mandatory in regulated industries such as aerospace, construction, railroad, oil & gas, and in the pressure equipment (PED) field.
The main standards governing nondestructive testing of welds include: UNI EN ISO 5817, UNI EN ISO 17637 (VT), UNI EN ISO 17638 and 23278 (MT), UNI EN ISO 23277 (PT), UNI EN ISO 17636 and 10675 (RT), UNI EN ISO 17640, 11666 and 23279 (UT), as well as American standards such as ASTM E1032 and AWS D17.1.
Duration depends on the method and complexity of the part: from a few minutes (visual inspection) to several hours. The frequency of inspections varies according to industry regulations, contract requirements, and the maintenance plan for the part.

Do you want to activate a nondestructive testing program on your welds?

Request information
(max size 10 Mb - allowed formats pdf, doc)