Digital radiography has opened up new horizons in non-destructive materials testing and there is still plenty of potential, especially if we look at the results of the last 10 years and follow the development of digital radiography in other application areas. Medical science has made major technological breakthroughs in recent years, and these advances are filtering down to other industries, including non-destructive testing. The cutting edge of innovation is clearly the direct digital imaging system for X-ray materials testing, the DDA (digital detector array).
The purpose of this article is to present the business benefits of this new technology in the context of other technologies on the market, highlighting the application areas where digital radiography can be used to make non-destructive material testing processes much more efficient.
Exponential development in radiography
Of all the non-destructive materials testing techniques, X-ray testing is the best example of exponential progress: it has been 100 years since X-rays were first used in science, and for a very long time only analogue imaging systems were used by materials scientists. Thanks to the rise of digitisation, the last 10-20 years have seen the emergence of phosphor plates, where it is now possible to digitise the results secondarily, but it is only in the last decade that primary imaging systems have appeared in science that can also perform direct digitisation, so that images can be evaluated in 1-2 seconds.
Originally used mainly in the military and medical industries, the instrumentation has been fine-tuned and optimised for non-destructive testing processes by specialist manufacturers over the last 5 years. This is the DDA (digital detector array), or direct digital X-ray imaging system.
However, the competitive advantages of a new technology can only be truly recognised and exploited if it is put into context and benchmarked against other technologies on the market.
Comparison of X-ray materials testing technologies
The direct digital imaging system is still less known in the Hungarian market, and is therefore often confused with the phosphoscopic version of digital radiography. Moreover, as is the case with the introduction of cutting-edge technologies, the Hungarian market is characterised by excessive caution and mistrust: fear of the unknown rather than the novelty of the new, and therefore customers stick to the familiar analogue imaging system in cases where DDA would be a more efficient solution.
We want to dispel doubts and bring innovation a little closer to those who are too new to this technology. To do this, however, it is essential to look at the other toolboxes, depending on the DDA.
Traditional radiography with analogue film
Operational principle: The test piece is placed between the radiation source (X-ray or gamma) and the detection unit. The detection unit is a film in a light-tight package. The radiation is fixed on the film and the exposure time is determined by the local absorption and the thickness of the material.
Field of application: It is excellent for detecting bulk defects, and the radiation penetrates steel, aluminium and other metals.
Benefit: In dangerous, hard-to-reach places where it would be risky to deploy DDA's valuable, innovative imaging system, analogue may be a better choice. Alternatively, there are material testing jobs where the use of analogue film is explicitly required.
Disadvantage: Developing and documenting images is time-consuming, not tailored to the pace of the modern world, and environmentally polluting, with materials scientists having to spend long hours between chemicals to develop the images. Furthermore, this workflow prevents testing and evaluation from taking place in parallel, wasting valuable time for both the client and the materials testing company.
Digital radiography with phosphor sheet
Operational principle: Alongside DDA, CR (computed radiography) is the most common form of digital radiography. It can be used with X-ray equipment in the same way as analogue radiography, but requires a phosphor plate or image plate to store the radiation signal, which is scanned by a special laser optics after exposure. This is followed by photocopying, signal amplification and digitisation.
Field of application: Ideal for efficient non-destructive material testing of pipe welds.
Benefit: It's faster to get results and more environmentally friendly, because there are no chemicals, no film costs and up to thousands of images can be captured on a phosphor plate over its lifetime, because the image plate can be erased and reused at the end of the scanning process.
Its advantage over the DDA is that it gives faster results than the rigid DDA flat panel when field testing medium diameter steel pipe fittings - because the phosphor sheet can be wrapped around the pipe.
Disadvantage: Compared to DDA, it is still a much more time-consuming process, in terms of preparation, digitisation and documentation.
Computed tomography (CT): pinpoint accuracy
Operational principle: In the case of tomography, a thin, planar X-ray beam is shone through the object being examined. A detector placed behind the object detects where and how much of the beam has been absorbed along a line. The object of the scan is shown broken down into imaginary slices.
Field of application: In addition to medicine, non-destructive material testing is also a major use of CT scanning. It is excellent for the geometric inspection of complex components.
Advantage: It is used to take extremely precise pictures. In conventional X-ray imaging, objects of larger size and higher density obscure smaller ones, while industrial CT eliminates these by using projections from multiple directions.
Disadvantage: Because of its precision, it takes longer than DDA and stationary testing, so it is not suitable for testing tasks where mobility and rapid deployment are required.
Direct digital radiography: lightning-fast imaging
Operational principle: Images are captured using a multilayer flat panel, which converts and transmits the information extracted from the radiation passing through the test piece to the image processor in a few seconds.
Field of application: It offers the greatest competitive advantage in the OK/NOK testing of mass-produced products, such as automotive components. Here, rapid deployment and mobility are of paramount importance, as well as fast imaging, evaluation and documentation.
Sometimes, an unsafe product that has accumulated due to an unexpected failure needs to be quickly tested to get the system back up and running. Until a clear decision is made, no delivery will be made. This puts the supply chain at risk. Currently, DDA is the fastest and most reliable way to do this, with minimal downtime for suppliers - because until the cause of the production disruption is resolved, the OK/NOK status of the backlogged workpieces is decided.
Advantage: Access to images that can be analysed in seconds, so scanning and analysis can be done at the same time, revolutionising the scanning process, and it is a mobile, easy-to-move device.
Disadvantage: As mentioned above, the flat, rigid panel is not the ideal choice for the field inspection of medium diameter steel pipe welds, and CT X-ray examination can provide a more detailed image. It is also important to note that DDA is an expensive device, has a high entry threshold and is not yet widespread in the market, so if it is not used properly or fails for other reasons, the repair time is not 1-2 days, but can take weeks. For an OK/NOK test, this is a serious disadvantage. It is therefore worth taking a cautious approach to innovation and preparing for the unexpected by buying more equipment.
How can innovation become a competitive advantage?
Direct digital radiography serves innovation and progress when it is seen not just as a tool but as a system optimised for the task. In this way, it becomes a toolbox that transforms the entire operation of the company. It is never the technology tool that drives innovation, it is not the tool that gives the competitive advantage, but the systemic approach that permeates the operation of a non-destructive testing company, from the development of testing technology to the motivation of testing personnel.
The real competitive advantage is therefore based on a systemic and practice-oriented approach to innovation. Innovation and new technologies always stem from a real problem, and therefore each material testing task must be considered in context, as innovation will only really deliver business value if the toolbox is optimised for the task. It is therefore worth considering the following three aspects:
- Mobility of the system
The manoeuvrability of the instrument system is an important test aspect, affecting the efficiency of the materials testing process, as time is saved by rapid deployment. This is key in non-destructive material testing, where a defect in the part under test can become a fatal flaw if not detected in time. Of course, there is also a justification for fixed systems if the inspection task requires it. The point is that mobility is an important issue to clarify when investing in technology
- The way of imaging
Detail, speed of imaging, documentation and sustainability are important considerations in the selection of a device system. It is also worth mentioning the difference between static and dynamic imaging. In static imaging, radiation is received, processed and displayed in a linear, spaced-apart time, whereas in dynamic imaging, real-time display and evaluation are possible, and the difference between photography (static) and film (dynamic) is best illustrated by the difference between the two imaging modes. In direct digital radiography, both imaging modes can be used, depending on whether a static or dynamic DDA panel is used.
- The level of customisation
Mobile DDA systems, ready-made screening booths, have a modular design, similar to a boxed software, they can be customised for multiple inspection tasks, but only to a certain extent, with a few module variations. In contrast, fully task-specific systems are optimised for a single inspection task, taking into account all its characteristics, with units built specifically for the task: for example, an assembly line inspection of a series-produced shaped product of a specific plant, with robot arms, an auxiliary building, an assembly line, a fault detection target software, possibly supported by artificial intelligence, built for the task.
In our email course, we will elaborate on the above-mentioned aspects and the systemic approach that innovation can take to ensure real business advantage and long-term competitiveness for both the materials testing and the client company.
New horizons in direct digital radiography
Visible results are always achieved where the most attention and energy is focused, in the field of non-destructive materials testing, and this is clearly the imaging system and its improvement in direct digital radiography, where pre-breakthrough experimental stage technologies have been developed that could put the approach to non-destructive materials testing on a whole new footing.