Undoubtedly, the X-ray inspection market has made rapid strides in the field of nondestructive testing. The integration of the latest technologies from the sensors, computers and communication fields has made X-ray inspection systems easy-to-use, safe and fast, all factors which, in the past, limited its adoption for industrial applications. These factors have also broadened the scope of X-ray inspection systems beyond research & development applications and into the realm of in-line production testing. Technological advances in hardware, such as tubes, sources, and detectors, as well as upgrades in software, have all contributed significantly toward improving the user-friendliness and efficiency of X-ray inspection systems.
Probably one of the most talked about trends in the industrial X-ray inspection system market is the evolution to digital radiography (DR). Pick up any magazine or journal on X-ray systems and chances are there will be an article dedicated to this trend and its numerous benefits. It is being touted as the future of industrial X-ray inspection with equipment vendors and industry pundits claiming huge productivity benefits and cost savings. So is it all hype or are we witnessing a genuine shift in the industry? What impact will it have on existing radiography techniques? Does film still have a future?
DR refers to the use of a flat panel detector (FPD), where digital X-ray sensors are used instead of traditional photographic film. In a DR system, the X-ray detector translates the radiation directly into an electrical charge, which is sent to a processing unit that assembles the image. Although the use of digital X-ray for nondestructive applications has been around for decades, unlike previous techniques, the true benefits of digital technologies can be realized by DR. While computed radiography (CR) ushered in the era of digital radiography by simplifying the image archiving and analysis process, improvements related to reduction of workflow steps and productivity were limited. DR eliminates the need for harmful image processing chemicals, with, in addition to the ability to view images immediately on a computer console, greatly improves inspection throughput making DR the ideal inspection tool for manufacturing and production environments.
Integration of TechnologiesDespite the radiographic testing options available to engineers and NDT professionals these days, it is usually a combination of X-ray techniques, depending on workflow, throughput and productivity that produces the optimum results. After having conquered the world of medicine in the 1990s, like most other medical radiography innovations, FPDs was a trend that eventually caught on in the nondestructive testing industry. Although the benefits of adopting FPD technology were well recognized, cost remained a deterrent to wide scale market adoption. These days, however, FPDs are rapidly replacing image intensifiers as the detector technology of choice, particularly for manufacturing and R&D applications. In addition to improving the quality and speed of inspection, DR is also driving other industrial X-ray imaging techniques. The integration of FPDs in CT systems is an important trend in the radiographic inspection market, as it greatly improves the image acquisition time. CT has generally been regarded as an effective yet cumbersome method of inspection with the acquisition of an image taking as long as a few hours. However, with the integration of technologies such as micro/nanofocus tubes, FPDs and improvements in PC processing and software capabilities, the CT market is gaining in prominence as an industrial inspection technology.
According to Chris Damhof, marketing coordinator for North Star Imaging, the success of the two technologies is interrelated. "As a whole, the market is trending toward digital technology, both DR and CT. The continued resolution improvements and increases in scan speed will further the growth of digital technology-especially CT."
Nikon Metrology, formerly known as Metris, specializes in microfocus X-ray inspection systems and has also witnessed an increase in demand for FPDs among its customer base. "We always use FPDs for all our systems except in the electronics inspection market, there it is still imaging intensifiers," said Jos Jans, Nikon Metrology's vice president of marketing. "But now, even in that segment, we are seeing a trend toward flat panels." The company continues to grow its business and client base with its first microfocus turbine blade inspection solution on the market. "The XT H 450 features the world's first 450 kV microfocus source. This enables turbine blade manufacturers to inspect blade wall and web thickness to be measured with 25 µm accuracy," said Jos. "In order to increase inspection productivity without sacrificing resolution i.e. focal spot size, we introduced the "rotating target" option for our 225 and 350 kV sources with the 450 kV source to follow later this year."
Although the aerospace and automotive segments continue to be the biggest adopters of FPD technology due to their high image quality and accuracy requirements, the use of FPDs has broadened, driven by declining costs, making its way into newer applications areas. "Now, almost 100% of full automatic robot systems in the automotive segment are equipped with digital FPDs," says Peter Kramm, YXLON's FPD technology specialist. "And even before that, almost 100% of aerospace applications were using digital FPD. Now, even pipe inspection and standard radioscopy systems for visual inspection are using digital FPD."
Yxlon International, a company recognized for being at the forefront of technology innovation in the field of industrial X-ray inspection, considers the trend toward FPDs in stand-alone as well as CT systems an important part of its long-term growth strategy. "This is a very important growth area for us. In the past, we equipped almost all universal X-ray cabinets with an image intensifier. Since FPDs became more cost-effective and fast, meaning a higher frame-rate," said Kramm. "We were able to use them for radioscopy and so almost 100% of our universal X-ray cabinets were replaced with FPDs."
Yxlon's Y.HDR-Inspect is testament to the company's increased momentum in the digital radiography space. "With the Y.HDR-Inspect we have the best flat panel detector calibration on the market," said Kramm. "We can offer a selected pixel quality to our customers and meanwhile 80% of our universal X-ray cabinets are equipped with a digital flat panel detector and Y.HDR-Inspect."
CT Systems Market-Exploring New Application AreasOne of the most important benefits that digital radiography and FPDs brought to the world of nondestructive testing was improved productivity due its ability to continuously inspect thousands of parts. Integrated with advanced manipulation systems and automatic defect recognition software, the efficiency and productivity of x-ray inspection systems can be further improved.
For CT systems however, production line environments remained an unexplored territory. Lengthy image acquisition times have resulted in end users in cost-driven manufacturing industries to look toward faster and cheaper alternatives. All this, however, is expected to change. "Although industrial CT has been around for many years, it hasn't become widely used until the last 3 to 5 years," says Chris Damhof. "The improvement and increased processing power of computers has been a large factor in the growth of CT. Scans that used to take hours are now being completed in minutes or seconds. This increase in speed has opened the door to new applications, which in turn, have brought in new and somewhat untraditional markets."
These technology advancements have helped companies like Yxlon deliver on its promise of "100% automated inspection at production line speeds." The company range of automated inspection systems include the Y.MU 56, the Y.MU56 Piston and the Y.MU 59, which, when integrated with robotics and the Y.PXV 5000, automated digital imaging system, makes it one of the most effective inline inspection systems in the market. "The robot systems MU56 and MU59 are used by leading car manufactures all over the world. The automatic tire systems for PCR, TBR and OTR are also used by leading suppliers of tires in addition to the automatic and inline wheel inspection system MU231," said Kramm. YXLON is known to offer the best ADR-Software for these different applications. The performance of an ADR-software is measured by the so called "false failure rate," which is normally less than 3% with our systems."
Taking it one step further, North Star Imaging recently released the eXpress-CT system. "This is the first ever inline CT system on the market," Damhof said. The company is keen to tap into the opportunities offered by inline inspection and the productivity gains it is capable of offering. "Another growing opportunity is with in-line CT inspection on the production line. We just launched a product line called eXpress-CT and the current system we are building is the fastest CT system in the world. This system can perform complete CT scans every 6 seconds," he said. With this product, manufacturers can now perform a complete 100% inspection of their product while on the production line at production line speed-something that has never been possible before."
The real change over the last 5 years has been improvements in software capabilities and offerings by companies. North Star Imaging, the leading innovator in the industrial CT inspection systems market in the United States, echoes this opinion. "Historically, CT systems have been relatively difficult to run; the software was confusing and unintuitive," says Damhof. "To solve this issue, we developed our own CT software, efX-CT, which has a 5-step start-to-finish interface. Our software was developed with the user in mind and built to harness all of CT's powerful capabilities into one easy-to-use package."
The growing demand for CT based inspection systems is evident from the slew of product introductions by leading participants across the globe, which has increased awareness among its customer base. Hardware upgrades as well, such as improvements in detector technology and use of microfocus and nanofocus tubes, bodes well for the CT market. "The market is switching from radioscopy to CT and it is increasingly becoming necessary to use a FPD for CT applications," said Kramm of Yxlon International. "The growth of the CT market will boost the market for flat panel detectors
So What Happens to Film?It's easy to forget sometimes, with all the hype surrounding the digital evolution in the nondestructive testing market, that the film-based X-ray market is very much alive and kicking. Since film was first used in the early 1900s for nondestructive applications, it has constantly faced competition from faster, safer and easier alternatives, its primary drawback being usage of hazardous chemicals for processing the image. The biggest advantage that film-based inspection equipment has and the crucial factor that has sustained this market for over 100 years is its low initial investment. Film-based inspection is the perfect alternative for industries that may not have the same financial resources or maintenance budgets as Tier 1 companies. Film is also the logical choice for organizations with low throughput applications that do not justify the purchase of million dollar inspection equipment. Another key factor is the consumer mindset. "The nondestructive testing market is very conservative," says Jans. "Objectively, there is no good reason to stay with film and it will take some time to completely change their procedures. Even though digital technology has been around for a long time, in the minds of the people, digital still has a long way to go, but technically there are no roadblocks." A sentiment echoed by others in the industry. "The rate of technology change in the market is rapid, but the acceptance of utilizing the technology is slow," said Kevin Burton, X-ray department supervisor at Laboratory Testing Inc.
Having said that, the trend toward digital X-ray in undeniable with numerous journals and industry experts presenting findings on DR's cost-effectiveness compared to film in the long run, mainly because reoccurring costs are negligible. For film X-ray, the reoccurring cost of consumables as well as the challenges associated with the storage and disposal of chemicals, a procedure that most customers are more than willing to move away from, are expected to restrain the growth of this market. Among these challenges, however, lower productivity due to lengthy image acquisition and processing time is its biggest drawback. Particularly in such difficult times, productivity and throughput are top concerns of customers, concerns that cannot be addressed effectively by film-based inspection.
Despite its many drawbacks, the industry is unanimous on film's continuing role in the inspection business. "DR will be the main technology in the mid-term but film will play a more niche role," said Yxlon's Kramm. "In my opinion film based inspection will decrease in the near future but for some niches film will be the only possible way to get an X-ray image. But I assume that in 10 years only approximately 5% to 10% of all NDT X-ray images taken worldwide will be done with film."
There are still certain applications where film will continue to play a leading role as an inspection technology. "It seems film-based inspection will continue to decline, but will be used for many years to come due to the versatility and ease of application in the field," says Damhof. "Although becoming less and less frequent, certain markets either still require film-based inspection or have not adopted digital technology as of yet." Field X-ray inspection is subject to challenges, such as harsh environmental conditions, difficult-to-reach inspection areas, and size of objects to be inspected, not optimum conditions for the expensive CT or DR form factors. "North Star Imaging provides systems per our customer's needs, mainly for markets such as casting and aerospace component inspection and field inspections such as pipeline weld examination," said Damhof.
Philadelphia-based, nondestructive testing services company, Laboratory Testing Inc., offers a more optimistic view of the future of film-based X-ray inspection. 100% of X-ray inspection services carried out by the company is film and shows no sign of letting down. "We currently provide only film-based inspection services for X-ray. Currently, I believe film still has a future in industrial inspection. We have not had many requests for digital yet and it has not been a limitation on how much work we've received," said Burton. "The largest percentage of work that we receive is castings. I have noticed a large increase in the number of castings that I radiograph in the last 5 years."