Non-Destructive Testing, reference standards
Non-destructive testing (NDT) on welds and on metals does not damage or modify the structures under inspection and it has an important function in our modern industry, because it allows us to qualify a welding procedure on a specific field of validity or in accordance with predetermined criteria.
When the welds and the metallic structures have an impact on our social and economic life, they are subject to rules that assure us safety. The greater the impact of the structures, the more strict the inspections have to be, both in the production and operating process, according to the EN 1090-2.
The NCT, Norme Tecniche per le Costruzioni 2018, requires that inspections on welded joints must be done by personnel appropriately trained and certified according to the UNI EN ISO 9712. The purpose is to identify eventual defects that could compromise the use in safety of the individual piece, to assure the quality of the final product.
The requirement on the inspections on the welds is recalled in many regulatory standards, such as the UNI EN 12062, General rules on the application of NDT on welds.
This standard suggest the best methods to apply, taking into account the materials, the thickness of the metal and the type of joint.
The type of inspections and the entity of the defects that could be found are strictly connected with the acceptability criteria of the UNI EN ISO 5817 “Level of quality of defects on welded joints” and of the 3834 “Requirement on the quality of weld”.
This is the main reason why Non-Destructive Testing are so diffused and regulated.
In order to supply this service, applicable to any kind of industry, we are organised with our own equipment and sensors. The activity is done by certificated inspectors who could operate in any kind of conditions and scenario.
There are two groups of inspection on welds that do not alter the joints:
- Superficial Inspection (visual examination, magnetoscopic testing, colour contrast)
- Volumetric Tests (X-ray examination, ultrasounds examination)
These two typologies allow us to investigate superficial and sub-superficial defects, in the first case, and, internal defects, in the second case.
In order to select the best investigation option for any specific case, it is necessary to have the correct knowledge of the two groups of inspections, of the standards and the experience to identify the best option in terms of costs and in function of the object under examination.
Each type of test presents both advantages and disadvantages. It could be more convenient to adopt one system instead of another, in function of the materials and the inspections. It is frequent to apply complementary investigation methods with the purpose of maximizing the possibility of finding eventual defects on the welds.
The methods are the following:
The visual examination of the welded joints is the most basic and common; it could be possible to use it on the single basic materials and on the final product as well. In addition to this, it is possible to use it on any kind of material. It is executed with an accurate inspection, normally with the naked eye, of the metals and of the joints in order to evaluate the superficial morphological characteristics. It is the cheapest method but also the most subject to errors.
The method with colour contrast allows to identify superficial or emerging discontinuity and it is very effective to detect these types of defects: cracks, porosity and wrappings. It is based on the capacity of a liquid to penetrate on the superficial part of the body of the product; this test permit us to detect easier defects, even if small and not visible with the naked eye.
It is the Non-Destructive Testing that takes advantages from the ferromagnetic properties of the materials to detect discontinuity. The method is based on a common magnet, that presents two poles, that are the beginning and the end of the associated magnetic field.
In the case that there will be discontinuity, there will be a distortion of the magnetic field in correspondence of the point where the material is absent.
Sprinkling the surface with iron particles (or any other ferromagnetic material) on the area where is present the discontinuity, they will tend to agglomerate in correspondence of the perimeter.
This method is very accurate, even for minimal defects, but it has the limit that could be applied on ferromagnetic materials.
The technic that uses X-Ray represents an important method of Non-Destructive Testing, because it does not alter the chemical and physical structure or the mechanical properties of the product and it provides a recording of the result of the inspection.
The possibility of using this method in any phase of the productive process offers a huge advantage in economic terms, because it could assure high quality level in any phase of the entire productive cycle.
This type of test is applicable to any kind of ferrous metals and it is suitable in order to detect eventual discontinuity due to cracks, lack of fusion, waste and porosity. It is based on the assumption that sound propagates on bodies, through the elastic vibrations of the atoms and of the molecules that compose them. The presence of discontinuity alters the path of the sound waves, causing a phenomenon of dispersion.
Every method has a specific standard that provides information about the correct execution and conditions to do the inspection.
Our instrumentation represent the best of the modern technologies in the market and they can assure a very high level of availability and performance.
OUR STRENGHT POINTS
The activities of our team are conducted with the respect of some values such as quality and availability, which represent us. In addition to this, our activities involve professionals regarding interpreting and post-producing data in any sector.
We work independently regarding technical and organisational part. In fact, we have our own equipment, pilots and internal know-how.
This allow us to set the start and the duration of the activities in line with the needs of the customer.
We are able to satisfy any request of the customer, guaranteeing a high level of result in terms of data. We operate on front line since the first phase of planning the mission, until the last phases of elaborating and reporting data.
Eventual special needs of the customer will be considered in function of the necessity of workforce and the programs of investments. Other technical solutions will be managed in accordance with the volume of the contract.