Radiography is very common method of inspection utilized for medical and industrial purposes. With technological advancements over the years, different methods of inspection have been introduced and have been classified as radiographic testing, in addition to X-ray. Commonly used to inspect and analyze industrial parts, users are now able to access radiographic testing NDT labs for extensive and accurate part data.
What is Radiography?
Radiography is a method of imaging which uses electromagnetic radiation, usually x-rays, to access internal aspects of a test subject. Radiography is often utilized to analyze the human body, although it is accessible to evaluate industrial parts. Radiography uses the science and theory of radiation to produce images for internal observation. According to Merriam-Webster dictionary, radiography is the process by which radiographs are made (different methods of doing so include X-ray, Computed Tomography, and Ultrasound etc.).
Difference between X-rays and Radiography
X-rays and radiography are often miscommunicated and implied as interchangeable terms. However, X-rays and radiography are not the same in theory or application. X-rays are considered one of the methods undertaken by Radiographic Testing (RT). Although x-rays are a form of radiography, they are not the only method of radiography. Radiography covers a wide range of different types of applications and test methods including Computed Tomography (CT).
Often, X-ray is the term used to describe the resulting image. However, the resulting image is referred to as a “radiograph”, whereas, the process of attaining that radiograph could possibly be X-ray. When x-rays were first discovered, it was an interchangeable term with radiography, as it was the sole method of radiographic testing. Now that multiple different methods are considered radiographic testing, the term “X-ray” can no longer be substituted for radiography.
How Radiography works
Applications of radiography include medical and industrial radiography. For the purpose of this document, focus will be on industrial radiography. Industrial radiography involves exposing a test subject to powerful radiation which penetrates though the subject and reaches a documenting medium. This medium could possibly be an industrial X-ray film or a digital detector.
Low density materials such as aluminum are usually tested with radiography methods, which are based on electrically generated x-rays. Thicker materials with higher density such as steel are commonly tested with radiography methods, which are based on gamma radiation. The resulting image with any x-ray technology is reviewed in gray-scale format. Lower density areas, including areas with defects such as porosity or cracks for example, will appear dark on the resulting image, as more radiation passes through the object, and is captured by the detector panel. Areas with high density material will absorb the radiation and the resulting image will appear, as less radiation will be captured by the detector panel.
Applications of Radiography
Although there are different types of medical and industrial applications, for the purpose of this document, industrial applications will be examined further. There are many different types of industrial application with radiographic testing. All methods of radiographic testing can be utilized for failure investigation applications, analyzing part design and features or simply to inspect internal part structure. These radiographic techniques include the following:
- Film Radiography
- Computed Radiography
- Digital Radiography
When is Radiography necessary?
When a user has a need to investigate internal structure or features of a subject, radiography can be utilized. For industrial purposes, radiography can be utilized during the following stages of a parts life cycle:
- Design and feasibility test
- Prototype verification
- Pre-production inspection
- Production testing
- Pre-service/in-service inspection
- Part sorting
- Failure investigation
- Reverse engineering
Benefits of Radiography
Radiography testing provides many benefits to its users in both medical and industrial applications. Listed below are a few direct benefits of radiography for industrial applications:
- Non-destructive method of inspection
- Cut costs and time relative to other testing methods
- Research & Development guidance and insight
- Full failure investigation
- Part confirmation and verification
- Detect internal flaws and foreign material
Uses of Radiography
Uses of radiography for medical applications cover a broad range of studies that require the visualization of internal parts of the human body, using x-ray based techniques. For industrial applications, radiography can be used in many different ways for different industries:
- Aerospace – Ex. find fatigue in Castings
- Automotive – Ex. Find flaws such as porosity in Piston Head
- Medical Device – Ex. Locate foreign material in medical devices such as an insulin pen
- Packaging – Ex. Find leakage issues in packaged goods
- Consumer Products – Ex. Evaluate wall thickness of a bottled part
- Military & Defense – Ex. Confirm geometry and develop FAI reports for ballistics
History of Radiography & role of Radiographers
In 1895, Professor Wilhelm Rontgen discovered the X-ray. Signifying the “X” with an unknown form of radiation, x-rays became a popular method of inspecting the human body. Radiographs at that time were known as Roentgenograms, and radiographers referred to as Skiagrapher (Ancient Greek for Shadow). Over the years, and with the addition and advancements of new technology classified under radiography, radiographers are also equipped to perform computed tomography, mammography, ultra sound, computed radiography etc.
In order to be qualified to perform such radiographic tests for industrial applications, the American Society of Nondestructive Testing have highlighted standards, examinations and experience required. Classified as NDT level 1, NDT level 2 and finally NDT level 3 with highest authority and qualifications credit to NDT level 3, radiographers must partake in personal certification or employer based certification to perform NDT.