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NDT 101: Radiography, Decoded

June 13, 2012
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From film to digital, here’s what you need to know about one of the oldest NDT techniques.

Unlike conventional x-ray film radiography, digital imaging provides the opportunity for robotically controlled image acquisition. Source: X-R-I Testing


Raise your hand if you’ve used Photoshop before. Many people are familiar with the photo editing software, which is why Brad Kraai, an instructor at X-R-I Testing Training & Consulting (Troy, MI), often introduces digital radiography training this way. Kraai compares the digital radiography process to Photoshop to calm down students who may be apprehensive about learning a new technology.

Radiography itself is not a new technology. It has been employed in nondestructive testing since circa 1920, and it has changed the way that companies inspect a wide variety of industrial components. It has been cited as the first of the modern sophisticated NDT techniques, but it’s still used today as an affordable and versatile test. Now one of the most important nondestructive tests in use today is experiencing an industry-wide shift.

The biggest change is the transition from film to digital. And there’s a reason for the change: digital improves the radiographic process. It’s an exciting time in radiography, experts say, and it’s time to embrace the technology. Kraai, a staff Level 3 consultant and instructor, has been in the NDT industry for more than 25 years. Though adopting a new technology late in your career can be scary, Kraai says he embraced digital because it offers more. “It’s the latest and greatest and we stand behind it,” Kraai says. In the last five years, he has seen an increase in digital radiography applications.

“The revolution is starting,” Kraai says. “As more and more people use that imaging technology and have success with it, word gets out, especially when you consider the volatility of film, which is based on silver and everyone knows how silver has been going crazy lately.”

This revolution has been in the works for a while. Rick Bourdon, X-R-I’s director of NDT Technical Services, has seen digital used since the mid-1990s, and observed its con-tinuous growth in industrial applications. In the beginning, people didn’t understand digi-tal. Both the technology and the training were somewhat weak. Today, the technology is better, computers are faster, and people understand it better, Bourdon says. Digital has come a long ways in these few years.

In addition, ASTM has started to address and prepare new inspection practices for digital radiography. This took some time, as the industry had decades of confidence in film, and understood it well. When digital surfaced, the technology had to demonstrate that it was equal to film-or better. And it is, provided it is used correctly, Bourdon says, though it’s not a complete replacement for film. “It has found its position in life, let’s just say,” Bourdon says. “It’s finally coming into its own.”

Digital radiography generates savings by eliminating X-ray film and associated storage costs. Source: X-R-I Testing

Digital Benefits

So what does digital offer? The radiographer viewing the images will be able to get away from paper and just click on an icon and toolbars, and note what he sees in the image, and automatically populate an inspection report, “which is a beautiful thing,” Kraai notes. “As that progresses more, I think you’ll see more and more applications along that line.”

In his class, he does a lot of comparisons to film, as most people are very comfortable with film. The seasoned film experts know that technology, but it’s time to get on board, Kraai says. A few years ago he knew it was time to investigate digital, however difficult it might be for older NDT staff (including him) to new tricks. After all, “I’m not retiring next year,” Kraai says. And more importantly, he realized digital was a better technology. He had worked a lot in film and was familiar with its many obstacles. It is based on a chemical process, which often requires troubleshooting. This can result in costly night-mares in processing, as well as a lot of maintenance. Though digital radiography also in-volves maintenance, it is more straightforward. The use of film often requires “re-shots” when radiographs are out of tolerance-a considerable waste of materials and labor. A corrected digital image acquisition only involves additional labor.

When problems spring up in film, it’s often a surprise, Kraai says. With digital imag-ing, especially if the process is managed well, operators will perceive problems much faster. “If you compare process control from digital to film radiography, it’s like night and day,” Kraai says. Digital is more quantitative, providing statistics and data from im-age acquisition, whereas film primarily offers visual analysis

Film is Still Here

But even though digital radiography eliminates the chemical process from the inspection method, populates inspection reports, and speeds cycle time, it is not perfect. Though it has its advantages, film does offer benefits as well.

For one, sometimes film can be less complicated. Film radiography has a technique for inspection. Though digital radiography also has established techniques, Kraai says that he has heard the observation that digital requires several techniques: one used to acquire the images and another to evaluate them. A lot more training is needed to evaluate images and learn how to use imaging processing functions. This should include formatted and continuous on-the-job training once the system and image viewing practices are estab-lished and improved to meet requirements.

In addition, film offers tools to check the illuminator, viewer and density, for example, while digital radiographers can apply filters, change contrast and brightness, change the orientation, and digitally manage the image. The process is more complicated. This is when Kraai might compare the image management to Photoshop. Just as the photo edit-ing software can make a person look unrecognizable, bad editing can impair the digital inspection process. Rigid controls are necessary to keep this from happening.

But despite all that, digital does work well. Bourdon suggests, “Don’t look at digital radiography as a drop-in replacement for film; it’s a bigger challenge than that.”

Basically, just try to know what you’re getting into with digital. It is important to train personnel on digital radiography. The more someone uses a technology, the more com-fortable they will be with it, and the more structured the training, the better, Kraai says.

Still, no matter how much training someone receives, it won’t help if they don’t have the right equipment. To be sure you have the appropriate equipment, test it with trial im-aging before purchasing it.

Bourdon notes that potential digital users need to completely review its applications including trials with the radiation devices to be used. Again it is just not a simple drop in replacement for a mature film process. Improper digital system validation is still evident , and potential users need to do their homework prior to procuring a system for the re-placement of film imaging.

But be assured, digital imaging is coming-if not already here-and offers a faster, cheaper and more efficient method of inspection. If you are hiding in the world of analog technology, you may be missing out.

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