ARTICLE -  Digital imaging evolution

By David Campos / January 01, 2017

The race to be faster, better, and more efficient is real in the non-destructive testing (NDT) industry, with companies facing the challenge of meeting regulatory restrictions, safety regulations, and fierce competition. To keep a competitive edge, continuous equipment upgrades are a must. The rate of technological advances in a historically slow evolving industry is increasing. Manufacturers of NDT sources and crawler carts have intensified the evolution of their products, making existing NDT fleets less competitive, if not obsolete.

Gamma ray 
Radiography has evolved considerably from the days of using a gamma ray emitting isotope through to today’s highly sophisticated and powerful X-ray sources. Gamma radiography was the original technology used within the pipeline inspection industry; the source would be attached to a projector and emitted to create a radiograph. At the time, the technology was unstable due to technical and safety issues, which produced poor radiographs that took an extremely long time to shoot.
 
Pipeline crawlers
As technology improved, so did the methods in which a radiograph could be created. With the development of safer radiographic X-ray sources, different methods could be employed to position this source at the pipe welds. Using pipeline crawlers, projectors could be centered correctly within the pipe, and the X-ray source could be better controlled to reduce any safety concerns or overexposure. With the latest development of crawler inspection systems, manufacturers such as JME UK can now control and adjust systems from a safe distance, including remote ‘emergency stop’ features and safe recovery options. 
 
Fuel for evolution

Over time, greater restrictions were put in place for storage, transportation, import and export of radioactive isotopes. This, in turn, made them much more difficult to obtain. Due to these restrictions, it was clear that the pipeline inspection industry had to evolve. 

X-rays were seen as the future of pipeline inspection, with this technology having low running costs and no storage issues, unlike a radioactive isotope. Licences for X-ray were much easier to obtain and, more importantly, the source was safe when not in operation due to X-rays only emitting when a current was applied.

Depending on industry requirements, different methods of testing will have their own unique benefits. Radiography stood the test of time and, for decades, is has been the most popular method of weld inspection on new pipelines. 
 
The first leap: oil to gas
A leap in portable X-ray technology was made when cooling shifted from oil to gas. This first significant technological advancement made portable X-ray equipment truly portable. The then oil-cooled X-ray tubes were heavy, cumbersome and required a two man crew or a crane to manoeuvre. Cooling the X-ray tube with gas made them much lighter and easier to manoeuvre. In turn, this made a significant difference in how pipelines were inspected and especially how fast inspection could be conducted, prompting a need to update the inspection company portfolio to keep a competitive edge. 

For pipeline inspection, this too had a noticeable impact. The crawler solutions, which in some cases weighed more than 500 kg when equipped with oil-cooled tubes, now experienced a significant weight reduction, making the workflow much faster and easier. 
 
The second leap: constant potential X-ray 
A second significant leap in portable X-ray inspection came with the implementation of constant potential energy sources. By having constant potential X-ray sources, exposure times were immediately halved. The constant delivery of photons from the X-ray source made these products far superior to their half-wave predecessors. For manufacturers such as YXLON Copenhagen, the transition from oil to gas and half-wave to constant potential was made in one swoop in 1989. Combining a crawler with a constant potential X-ray source was game changing for pipeline inspection. Years on, this technological leap forward has proved to be a key factor in the introduction and success of digital imaging. 

Pipeline inspection has followed the same procedure since the late 80s. It is carried out by attaching an X-ray tube to the pipeline crawler. This is then controlled using an electromagnetic system from the outside of the pipe to ensure the emission point of the X-ray beam is centred on the weld. A single piece of film is wrapped around the weld and a radiograph is produced. Exposure times are easily calculated using the power settings of the X-ray tube and wall thickness of the pipe, giving consistent results.
 
Tube and crawlers evolving as partners
The biggest issues for onsite contractors has always been safety and productivity. Over years of development, crawlers have evolved using higher-grade components and electronics, making pipeline crawler solutions robust for all types of working environments. Manufacturers like JME UK operate in climates ranging from arctic regions to extreme desert heat. Advances have been made and employed to provide equipment that is safe and protected from failure that may be caused by these harsh environments.
 
The third leap: the digital future 
As the whole world moves into the digital age, so does NDT inspection. The reasons for a transition from analog imaging to digital are numerous, and there is no denying technological progress. The quality of defect recognition has now increased by combining digital imaging devices and constant potential X-ray tubes. Digital X-ray inspection has seen considerable development over the past few years, and it is well on its way to replace conventional X-ray film. 

X-ray film has been the preferred imaging medium when inspecting using portable equipment. This is largely because of the low cost of films, but also, when compared to digital flat panels, it has been more suitable for use in challenging outdoor environments.

One of the main benefits of using digital detector technology is that the digital image immediately allows for a possible conclusion to be drawn. Weld defects are detected with greater probability using a digital flat panel detector than with conventional film technology. Other advantages of digital technology include: Significantly shorter inspection times, easier archiving, elimination of chemicals, and post-processing of images.

Constant potential portable X-ray systems can be used with the latest digital detector technology. The integration of detectors combined with portable and mobile products makes such a solution future-proof.

Onsite darkrooms and onsite radiographers are becoming more expensive. The first technology to move away from the standard film was the development of computed radiography, using phosphor plates that replicated film but negate the need for a dark room and chemicals. 

The phosphor plate is wrapped around the weld as it would be if it was traditional film. However, when it comes to developing the image, it is a simple matter of passing the plate through a scanner, which digitizes the image onto a computer and wipes the plate so it can be reused. This, again, saves money on film cost, which can often run into the hundreds of thousands. 

With the image on a computer, it can be inspected instantly onsite with much more accuracy due to complex software. Alternatively, it can be emailed to an offsite radiographer who is able to analyze and negate the need for more personnel cost onsite from a distance.

As we enter the digital era, which is faster, more accurate, and reduces consumable costs to almost zero a crawler and a constant potential panoramic X-ray source can now be used with a digital detector. The detector is attached to the outside of the pipeline and, while the X-ray is being emitted, the detector will navigate around the weld to produce a real-time digital image. As with computerized radiography, the output can be viewed on a computer or emailed offsite, but using digital radiography, the process is much quicker as there is no need to develop a piece of film. There is also the benefit that no plates are needed, and no computed radiography plate scanners are required, cutting costs drastically and saving time. 
 
A competitive advantage
Digital imaging only works with constant potential energy sources. This means that if pipeline crawler manufacturers want to reap the benefits of digital imaging, they have to keep up with manufactures of the X-ray sources who are challenged with optimizing their products to work with digital imaging devices. 

The whole NDT industry is changing. Individual inspection companies are having to revise their inspection equipment and assess whether they have the right equipment to stay competitive. It is safe to say that the digital future has arrived, and inspection companies have to ask themselves if they have a portfolio of competitive equipment that is perfectly integrated with crawler solutions and works seamlessly with digital devices, giving them a competitive advantage with future technology, today. 

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