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Radiographic Testing (RT) is a nondestructive examination (NDE) technique that involves the use of either x-rays or gamma rays to view the internal structure of a component. In the petrochemical industry, RT is often used to inspect machinery, such as pressure vessels and valves, to detect for flaws. RT is also used to inspect weld repairs.

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Compared to other NDE techniques, radiography has several advantages. It is highly reproducible, can be used on a variety of materials, and the data gathered can be stored for later analysis. Radiography is an effective tool that requires very little surface preparation. Moreover, many radiographic systems are portable, which allows for use in the field and at elevated positions.

Types of Radiography

There are numerous types of RT techniques including conventional radiography and multiple forms digital radiographic testing. Each works slightly differently and has its own set of advantages and disadvantages.

Conventional Radiography

Conventional radiography uses a sensitive film which reacts to the emitted radiation to capture an image of the part being tested. This image can then be examined for evidence of damage or flaws. The biggest limitation to this technique is that films can only be used once and they take a long time to process and interpret.

Digital Radiography

Unlike conventional radiography, digital radiography doesn’t require film. Instead, it uses a digital detector to display radiographic images on a computer screen almost instantaneously. It allows for a much shorter exposure time so that the images can be interpreted more quickly. Furthermore, the digital images are much higher quality when compared to conventional radiographic images. With the ability to capture highly quality images, the technology can be utilized to identify flaws in a material, foreign objects in a system, examine weld repairs, and inspect for corrosion under insulation.

The four most commonly utilized digital radiography techniques in the oil & gas and chemical processing industries are computed radiography, direct radiography, real-time radiography, and computed tomography.

1) Computed Radiography

Computed radiography (CR) uses a phosphor imaging plate that replaces film in conventional radiography techniques. This technique is much quicker than film radiography but slower than direct radiography. CR requires several extra steps compared to direct radiography. First, it indirectly captures the image of a component on a phosphor plate, then converts the image into a digital signal that can be visualized on a computer monitor. Image quality is fair but can be enhanced using appropriate tools and techniques (i.e, adjusting contrast, brightness, etc. without compromising integrity). It’s important to know how tools, such as adjusting contrast, effect the image. Care should also be taken to make sure minor defects are not hidden after enhancements are made.

2) Direct Radiography

Direct Radiography (DR) is also a form of digital radiography and very similar to computed radiography. The key difference lies in how the image is captured. In DR, a flat panel detector is used to directly capture an image and display that image on a computer screen. Although this technique is fast and produce higher quality images, it is more costly than computed radiography.

3) Real-Time Radiography

Real-time radiography (RTR), like it’s name suggests, is a form of digital radiography that occurs in real time. RTR works by emitting radiation through an object. These rays then interact with either a special phosphor screen or flat panel detector containing micro-electronic sensors. The interaction between the panel and the radiation creates a digital image that can be viewed and analyzed in real time.

The brighter areas on the image are a result of higher levels of radiation that contact the screen. This corresponds to the thinner or less dense section of the component. Conversely, darker areas are a result of less radiation interacting with the screen and indicate where the component is thicker.

Aside from being able to make the images available more quickly and analyze them in real time, RTR has several other advantages. One being that digital images don’t require physical storage space and thus are easier to store, transfer, and archive than film.

On the other hand, this method has several disadvantages as well. Compared to conventional radiography, RTR has a lower contrast sensitivity and limited image resolution. Images created via RTR often suffer from uneven illumination, limited resolution, a lack of sharpness, and noise. These factors have a major impact on image quality.

4) Computed Tomography

Computed tomography (CT) is a technique that takes hundreds to thousands (depending on the size of the component) of 2D radiography scans and superimposes them to create a 3D radiographic image.

In an industrial setting, CT can be achieved in two ways. In one method, the component to be inspected remains stationary while the radiation source and x-ray detector rotate around the component. This technique is more likely to be utilized for large components. The second method consists of the radiation source and x-ray detector remaining stationary while the component is rotated 360 degrees. This second technique is more useful when the component is small or has complex geometry.

Although this technology is timely, expensive, and requires a large amount of data storage, CT provides highly accurate images, is repeatable and reproducible, and minimizes human error.

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Articles about Radiography
January/February 2022 Inspectioneering Journal

With the advent of digital technology, image processing can be done in digital radiographs which can be used for automated detection and quantification of defects. It is important to know the system's limitations and the probability of detection.

July/August 2021 Inspectioneering Journal

This article illustrates the value of digital radiography as an efficient tool to visualize corrosion and other small bore piping anomalies without disturbing insulation, as well as using PRT in conjunction with UTT to survey small diameter lines.

May/June 2019 Inspectioneering Journal

While planning methods for thickness data acquisition in any Inspection Data Management Program, PRT should be considered as a cost-efficient, effective way to increase the value of your program for small bore piping or any other suitable situation.

Authors: Ryan Baggett
September/October 2018 Inspectioneering Journal

The challenge to find CUI is difficult and one single NDE technique cannot be used to identify it. This remains the case today as we combine NDE techniques to perform CUI assessments. The techniques and strategies commonly used today are summarized...


Nondestructive testing (NDT) careers are on the rise in today’s economy. These fields are constantly advancing, and there is an ever-growing need for technicians, quality assurance specialists and inspectors as infrastructure in the United States...

Authors: Berg Engineering
Partner Content

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July/August 2016 Inspectioneering Journal

The structural integrity of components is controlled by material properties, the presence of flaws, and levels of applied stress. Several factors such as temperature, type of loading, toughness, corrosion resistance, micro-structural stability, cost...


Because radiography involves the use of large amounts ionizing radiation, safety is integral for the technician, the public, and the environment.

March/April 2015 Inspectioneering Journal

This article provides a discussion of a recent inspection performed at a U.S. refinery. Industry HF lines are experiencing piping failures in increasing numbers due to the presence of residual elements entrained within their carbon steel components.

November/December 2014 Inspectioneering Journal

The introduction of PAUT is a challenging effort initially, but can have a very positive impact on your first TAR and become a routine inspection for future TARs. When fully implemented, radiation safety boundaries can be reduced significantly or...

November/December 2014 Inspectioneering Journal

Steam reformers are critical assets for the successful operation of hydrogen, ammonia, and methanol plants. The steam reformer is also one of the most expensive assets in these facilities. Catalyst tubes inside the reformer are one of the most...

Authors: Kelsey Hevner
Partner Content

TEAM’s integrated touch point corrosion program manages all aspects of the integrity process from screening for damage to permanent repair assuring integrity – every time. TEAM’s unique turn-key approach to touch point corrosion integrity...


Over recent years large strides have been made in application, development, and utilization of Digital Detector Arrays (DDAs) in field radiography environments. The use of industrial digital radiography shows benefits of significantly reduced...

Authors: Nick Schmoyer
November/December 2013 Inspectioneering Journal

Over recent years large strides have been made in application, development, and utilization of Digital Detector Arrays (DDAs) in field radiography environments (an application previously limited to film and computed radiography [CR] techniques).

November/December 2013 Inspectioneering Journal

To understand the current non-destructive testing (NDT) world, it is perhaps a good idea to look back at things historically. By doing this, changes which have taken place become apparent, and very soon one can conclude that this is actually quite...

Authors: Jan Verkooijen
September/October 2013 Inspectioneering Journal

The Modulation Transfer Function (MTF) is used in imaging science to assess the reliability of imaging systems to produce different spatial frequency. In digital radiography, it can be used to detect frequency responses of different inspection...

January/February 2013 Inspectioneering Journal

This article is the third of a series of articles that will focus on one critical sub process within a PEIP that is key in managing the integrity of process piping: thickness monitoring programs for internal corrosion. These articles will discuss...

Authors: A.C. Gysbers
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Download Pinnacle's Economics of Reliability Report - Refining to see how reliability is affecting profitability.

November/December 2012 Inspectioneering Journal

Radiography technique is one of the most widely utilized non-destructive methods, used in industry to evaluate the structural integrity or find out the hidden details of an assembled structure. Since this method uses ionizing radiation, it is...

May/June 2012 Inspectioneering Journal

Over the past 100 years, Nondestructive testing has made tremendous advances. New NDT methods have been introduced, while old "tried and true" methods continue to be improved. Although some NDT methods have drastically changed or "evolved" over...

Authors: Jason Butz
November/December 2010 Inspectioneering Journal

Rapid industrial and technological growth throughout the world makes it necessary to develop new materials along with advanced Non-Destructive Testing (NDT) Methods to ensure their quality without premature failures. The complex modern system, where...

July/August 2010 Inspectioneering Journal

CUI (Corrosion Under Insulation) has always been a challenge for plant operators, quality assurance/reliability engineers and equipment owners. It is hard to identify the problem until it has become an emergency situation, often leading to unit shut...

Authors: Santhosh Lukose
November/December 2008 Inspectioneering Journal

A picture is worth a thousand words and thousands of dollars. There are many instances where in-service inspection reports are greatly enhanced by including photographic documentation. Using a conventional high quality 35 mm camera requires...

Partner Content

Whether you decide for a Computed Radiography scanner with flexible imaging plates or a flat panel detector with the fastest imaging, or even combine the advantages of both technologies, DÜRR NDT's innovative systems offer high reliability and the...

January/February 2008 Inspectioneering Journal

Most common radiographic practices for circumferential weld testing are single wall and double wall techniques with certain variations in technique details. Different Codes deal with the number of exposures required and applicability of the...

July/August 2007 Inspectioneering Journal

Degradation of materials with time during service is a common phenomenon for all engineering components. Hence periodic inspection is required to ensure structural integrity and availability for service. During in-service inspection (ISI), wall...

July/August 2005 Inspectioneering Journal

Radiography is the most widely used volumetric examination technique for non-destructive evaluation of components, as it offers the advantage of direct viewing of the flaw image, judging the type of flaw and provides a permanent record. Flaw...

Authors: Sanjoy Das, B.K. Shah
March/April 1999 Inspectioneering Journal

Some Middle Eastern and European operators are now using AE successfully to screen tanks for internal inspection by listening for active tank bottom corrosion, and then grading the tank as high, medium or low need for internal inspection.

Authors: John Reynolds
November/December 1997 Inspectioneering Journal

Radiographic film provides an inexpensive method of ensuring the quality and structural integrity of construction over time. Much of today's analysis being performed with Non Destructive Test (NDT) radiographic film is done visually using light...

Authors: Dave Palmbach
September/October 1997 Inspectioneering Journal

This is the fourth in a series of articles on piping inspection that I'm writing for the Journal. One of the previous ones dealt with improving thickness data taking accuracy with digital ultrasonic methods. This article is a "sister article" that...

Authors: John Reynolds
September/October 1995 Inspectioneering Journal

In May 1995, Omega International Technology, Inc., began testing a new system to measure pipe wall thicknesses using digital radiography (RT) scanning. This new system has the potential for being faster, less labor intensive, and shown improved...

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