An internal discontinuity of a few tenths of a millimetre, left undetected before assembly, can compromise the tightness of a large-format valve as soon as it enters service. In sectors where the failure of a single component can shut down a plant or put people's safety at risk, non-destructive testing (NDT) is not a check performed after machining, but an integral part of the manufacturing process itself.
This requirement is not new, but the way it is applied has changed substantially in recent years. The evolution of these techniques is transforming both the ability to detect defects and the way they are documented with traceable data, and it is this combination that is beginning to mark the difference between a machining supplier and a technical partner capable of standing behind the integrity of every part it delivers.
From traditional technique to digital inspection
Liquid penetrant testing, ultrasonic testing and magnetic particle testing remain the reference methods for detecting surface discontinuities, thanks to their reliability and low application cost. These are mature techniques, with little scope for disruptive innovation, but they continue to serve as the first quality filter in most manufacturing processes for critical components.
The most visible change is in the inspection of internal discontinuities. Digital radiography is progressively replacing traditional radiographic film: a digital detector replaces the physical film, making it possible to validate the image within minutes rather than hours and to label it and incorporate it directly into the part's quality dossier. This immediacy is not simply a time saving. It reduces the margin for error in the handover of information between inspection and quality documentation, which is particularly relevant when every part must carry a complete, traceable history of its manufacture, from the casting of the material through to the final dimensional check before dispatch.
Verifying repairs: the challenge of welded areas
When a part undergoes a repair or weld build-up process, the subsequent verification must meet a standard equivalent to that applied to the original material.
It is not enough to confirm that the repaired area looks correct. It must be demonstrated that it meets the same dimensional and integrity requirements as the parent material before the part can be accepted, which means combining dimensional inspection with whichever NDT methods are appropriate to the geometry and material of each component. When carried out with precision three-dimensional measuring equipment, this dimensional check makes it possible to document objectively that the repaired geometry conforms to the original drawing, rather than relying solely on a visual inspection of the finish. In large-format parts, this verification takes on an added dimension: the surface area to be inspected is greater, wall thicknesses tend to be higher, and delivery schedules leave no room for repeating checks at the last minute. This is why the sector is increasingly integrating this verification into the manufacturing flow itself, documenting each step as part of the part's quality dossier, rather than treating it as a separate final stage detached from the rest of the process.
Personnel qualification: the variable no technology replaces
None of these techniques adds value if the person interpreting the result is not qualified to do so. Approved welding procedures, in turn, define the conditions under which a repair or weld build-up is accepted on a given project, and serve as the reference point for deciding whether a repaired part can be considered equivalent to a new one. This dual requirement, of qualified equipment and qualified personnel, is what gives the inspection report its legal and technical weight. It also explains why investment in NDT technology only makes sense when matched by an equivalent investment in the training and qualification of the personnel who operate it; without that second element, even the most advanced technology adds no additional assurance about the part being inspected.
NDT as part of ARRI's integrated machining service
At ARRI, NDT control is not managed as an isolated process, but as part of the same continuous flow that integrates machining, welding and dimensional inspection. We apply liquid penetrant testing, ultrasonic testing and magnetic particle testing according to the demands of each project, with qualified personnel working under the specific applicable standard, in sectors where we already work to these standards, such as nuclear and green hydrogen valves, and as a complementary service across the rest of our activity in oil & gas, subsea, cryogenic and desalination applications.
In our repair and weld build-up processes, qualified under the ASME Section IX standard, this integration forms part of ARRI's complementary services. It reduces verification times, improves the traceability of each part, and results in a complete quality dossier delivered to the client alongside each component, without compromising the rigour demanded by any given standard.
This capability is built on more than 30 years of experience in machining valves of all types, a team of 60 professionals and a 3,500 m² facility in Beasain (Gipuzkoa), with the capacity to machine parts of up to Ø2,400 mm and 25 tonnes, all under a quality system certified to ISO 9001:2015. If your project requires a technical partner capable of managing machining, welding, non-destructive testing and dimensional inspection under a single quality system, you can contact the ARRI team through our website.
