A crack in a welded joint cannot be seen by the eye. It occurs in operation, when the component is already installed and stopping it costs as much as redoing it.
Descoltech's non-destructive testing — in English NDT, Non Destructive Testing — are used to identify internal and surface defects without compromising the part. Ultrasound, radiography, penetrating liquids, magnetoscopy and visual examination, performed by certified inspectors and coordinated with accredited laboratories when the test requires it.
The flaws that matter are not the visible ones. These are the internal discontinuities of the material or the weld seam: cracks, porosity, inclusions, failed fusions. They are born during machining and remain there, silent, until the component works under pressure, temperature or cyclic load. Non-destructive tests are used to find them while the piece is still recoverable.
A failure to melt detected at the factory is resolved by removing the line and re-welding, at the expense of the supplier. The same failure to merge discovered in operation means plant downtime, replacement in the field and an investigation into who accepted that component.
There is no one-size-fits-all control: each method sees some things and is blind to others. Choosing the wrong method does not produce a wrong result. It produces a negative result on a defect that exists.
A report that reports an indication without saying whether it meets the applicable acceptability criteria shifts the problem, not solves it. Our reports indicate what has been detected, how it fits into the reference standard or specification and what consequences it has for the supply, with the consequent operational recommendations. The relationship flows into the technical document management of the order.
Technology alone is not enough: surface preparation, instrument calibration and operator experience all affect the reliability of the result. For this reason, the tests are carried out and interpreted by personnel certified according to the ISO 9712 standard for the specific control method.
We work with manufacturers of components and systems, carpentry and welding workshops, Oil & Gas, chemical and petrochemical companies, energy operators, shipyards and metalworking companies. The roles that contact us are quality managers, QA/QC managers, production managers, engineering managers and project managers.
The one provided for by practice, applied to everything
That an indication has been detected
You are looking for someone to explain the result to you
An extra certificate in the dossier
Audit performed as fulfillment
Chosen based on material, thickness, geometry and expected defect
What was detected, whether it is acceptable according to the specification and what it entails
You already have the operational recommendations and viable options
An element that goes into the decision to accept or reject
With Descoltech non-destructive testing
The most critical defects are often not visible: cracks, porosity, inclusions and non-castings can only emerge when the component is already in operation. Non-destructive testing detects these anomalies before installation, verifying materials and welds without damaging the piece and allowing intervention to be carried out when it is still recoverable.
They are testing methods that detect defects in a material or component without altering its integrity and without affecting its subsequent use. The Italian acronym is CND, the English NDT, i.e. Non Destructive Testing: in international specifications you almost always find the latter. They include surface methods, such as liquid penetrants and magnetoscopy, and volumetric methods, such as ultrasound and radiography. The choice depends on the type of defect sought and the material.
It depends on where the defect may be and the material. For surface defects on carbon steel, magnetoscopy is used; on stainless steels, which are not ferromagnetic, penetrating liquids are used. For internal defects, the choice is between ultrasound and radiography, depending on thickness, accessibility and site constraints. In practice, a visual examination, a superficial method and a volumetric method are combined. The correct combination is often already stated in the project specification.
Ultrasonics identify planar defects well, such as cracks and failed melts, measure thicknesses and do not require interdiction of the area: they can be performed with other processes in progress. X-rays perform better on volumetric defects, such as porosity and inclusions, and produce an objective record that can be stored in the order dossier. The downside is the set-up: it requires access from both sides, a forbidden area and management of the source, with impacts on construction times.
They are advanced ultrasound techniques. The phased array, abbreviated PAUT, uses multi-element probes that electronically orient the beam and return a mapping of the inspected volume, useful on complex geometries. TOFD, or Time of Flight Diffraction, is particularly effective in sizing the height of a defect and following its evolution between one check and the next. They are used especially where radiography is not feasible or where it is necessary to know how large the defect is, not just if there is one.