To achieve quality control and safety during industrial operations, it is essential to “see through” steel. The ability to see through the invisible defects that may be present inside a pipe or a vessel is a challenge, but a crucial one nevertheless. Although film radiography testing has been proven effective and safe, it is very time-consuming and environmentally costly, and does not always guarantee high-quality images.
Digital radiography testing is one step further, which is based on the application of high-sensitivity detectors rather than film. The efficiency, accuracy, and flaw detection provided by DRT make it a perfect choice for industrial inspection services.
What is Digital Radiography Testing (DRT)?
Digital radiography testing (DRT) is a type of non-destructive testing (NDT) that uses X-rays or Gamma rays to generate a digital image of the interior of a part. Digital radiography testing (DRT) is faster and easier than conventional radiography, which requires chemical processing of film.
With digital radiography testing services, one can see the “DNA” of a weld or casting in action. The technique is widely employed to confirm the integrity of critical equipment without damaging it even at a microscopic level, and is a fundamental part of digital X-ray inspection.
How Digital Radiography Works
The physics behind digital radiography testing (DRT) is equivalent to a medical X-ray, but with different densities. The object being inspected is exposed to radiation; thicker areas (such as solid steel) absorb more radiation, and thinner areas (such as a crack or a bubble) allow more radiation to transmit.
The beam penetrates the object and hits the sensor, where it is converted into an electronic signal that is further interpreted by software to create an extremely sharp black-and-white picture. The inspection of real-time radiography allows for changes in both exposure and positioning on the spot for the highest quality image in a single shot.
Types of Digital Radiography: CR vs. DR
Within the realm of advanced NDT, there are two basic ways to attain a digital image:
1. Computed Radiography (CR)
Computed Radiography is the next step up to digital. It uses a flexible Phosphor Imaging Plate (IP).
- Mechanism: The plate undergoes radiation exposure, followed by scanning by the digital detector that interprets the data into a digital image file.
- Benefit: The plates are flexible; therefore, they are ideal for use in small-diameter pipe welding inspection.
- Keywords: computed radiography, imaging plate.
2. Direct Radiography (DR)
Direct radiography is the most recent technology. It utilizes the use of Flat Panel Detectors (FPD) that are linked to a computer.
- Principle: The picture appears immediately on the computer screen once the beam of X-rays is switched on. No scanning procedure is needed.
- Advantage: Faster and better image quality than CR. It is the quickest of all high-volume manufacturing NDT inspections.
- Keywords: direct radiography, flat panel detector radiography.
Applications of Digital Radiography Testing
Due to its adaptability, DRT is a high-conversion must-have for a number of key industries:
- Oil and Gas Flowlines: Corrosion under insulation (CUI) detection and weld quality inspection in high-pressure flowlines.
- Aerospace Components: Evaluation of turbine blades and composite components for delamination and microcracks.
- Castings and Manufacturing Industries: Porosity and “shrinkage” evaluation of multilayered metal castings before shipping.
- Power Plants: Thin-wall assessment of steam lines and boiler tubes.
- Key Words: weld testing, corrosion testing, radiography.
Benefits of Digital Radiography Testing
The benefits of switching to DRT are efficiency:
- Quicker Inspections: Film development is eliminated, “shot-to-view” time is shortened from hours to seconds.
- Superior Image Quality: Digital images can be easily magnified, amplified, and band-pass filtered to reveal film’s invisible defects.
- Reduced Radiation: Digital images require lower radiation to produce an image because digital sensors are sensitive.
- Digital Archiving: Reports can be sent to the cloud and viewed by a third-party inspector who can approve projects.
DRT vs. Conventional Radiography
| Feature | Conventional (Film) | Digital Radiography (DRT) |
| Processing Time | Slow (Chemical Processing) | Instant / Near-Instant |
| Image Storage | Physical (Bulky) | Digital (Secure) |
| Chemical Waste | Hazardous (Developer/Fixer) | Zero (Green) |
| Sensitivity | Static & Fixed | Variable (Software Adjustments) |
| Overall Speed | Slow | Rapid |
Safety and Compliance in Radiography Testing
Radiation testing has health and safety as its highest priority. A reputed radiography testing company should carefully adhere to:
- Radiation Exposure: “As Low As Reasonably Achievable”
Exclusion Zones: Keeping exclusion zones to safeguard others from harm. - Qualified Technicians: technologists qualified in digital methods – ISO 9712 or ASNT Level II/III.
- Keywords: non-destructive testing company, industrial safety.
How to Choose the Right DRT Service Provider
Many NDT inspection companies have not invested in new digital technology. When looking for a supplier, ask:
- Equipment: Do they have new Flat Panel Detectors (DR) or older CR?
- Software: Do they use software to automatically perform “Gray Scale” analysis, which determines small density changes?
- Experience: Have they done work with your material (inconel, duplex steel, carbon steel, etc.)?
Choose the pros of digital radiography.
Cost of Digital Radiography Testing
The hourly cost of digital radiography testing services is typically higher than that of film, due to the cost of digital detectors. The cost of the project is less, though.
Expert Tip: DRT is faster and generates fewer “retakes” compared to film, so you save on vessel/pipeline downtime and man-hours, and can expect to save 20-30% on the overall cost of the inspection project.
Future Trends in Digital Radiography
The industry is moving fast as NDT technologies are applied:
Machine Vision: Analytics that can show a defect in a weld, increasing accuracy.
Remote Inspection: Information is sent from a distant pipeline location to an auditor half a world away for review.
Battery-Powered X-ray Units: Lower-power, lightweight x-ray sources to enable DRT in the most confined offshore spaces.
Conclusion: Accurate Inspection with DRT
Digital radiography testing (DRT) is revolutionising safety in the industrial sector. With its improved resolution, real-time output, and a safer work environment, it has almost made film-based solutions redundant for today’s infrastructure. For those looking to maintain asset integrity and increase efficiency, DRT is not an innovation; it’s a must-have.
To get help with digital radiography testing, contact us now.
Frequently Asked Questions (FAQ)
Q1. Is DRT as good as film for thin-wall?
Ans: Yes. In many cases, it is more accurate. The digital image can be enhanced (contrast and brightness) to increase the “Probability of Detection” (POD) over still film images.
Q2. Can DRT see through insulation?
Ans: Absolutely. In fact, this is a main application in the oil and gas industry. It can “see” pipe wall thinning without the costly stripping of insulation.
Q3.Is there any waste from DRT?
Ans: No. A key advantage of DRT is that it does away with the silver chemicals and metals used in conventional film processing.
Q4. How long does the digital detector data last?
Ans: Premier Flat Panel Detectors are built for industrial environments, but are susceptible to radiation damage. If well-shielded, they can endure thousands of exposures.