Radiographic Film Interpretation

What is this method?

Radiography film interpretation test is basically of recording of varying degree of absorption of penetrating radiation by an object. In conventional film radiography, this varying of absorption produces a latent image of object being examined on the film. The film is chemically processed, transforming the latent image into permanent shadow image of internal and external condition of the project. The processed film is called radiograph. The radiograph can be interpreted and thee integrity of the object can be evaluated.

Why is this method?

The major objective of radiographic testing of castings is the disclosure of defects that adversely affect the strength of the product. Castings are a product form that often receive radiographic inspection since many of the defects produced by the casting process are volumetric in nature, and are thus relatively easy to detect with this method. These discontinuities of course, are related to casting process deficiencies, which, if properly understood, can lead to accurate accept-reject decisions as well as to suitable corrective measures. Since different types and sizes of defects have different effects of the performance of the casting, it is important that the radiographer can identify the type and size of the defects. ASTM E155, Standard for Radiographs of castings has been produced to help the radiographer make a better assessment of the defects found in components. The castings used to produce the standard radiographs have been destructively analyzed to confirm the size and type of discontinuities present.

When is this method used?

Although many of the methods and techniques developed over a century ago remain in use, computers are slowly becoming a part of radiographic inspection. The future of radiography will likely see many changes. As noted earlier, companies are performing many inspections without the aid of film. Radiographers of the future will capture images in digitized form and e-mail them to the customer when the inspection has been completed. Film evaluation will likely be left to computers. Inspectors may capture a digitized image, feed them into a computer and wait for a printout of the image with an accept/reject report. Systems will be able to scan a part and present a three-dimensional image to the radiographer, helping him or her to locate the defect within the part. Inspectors in the future will be able to peel away layer after layer of a part to evaluate the material in much greater detail. Color images, much like computer generated ultrasonic C-scans of today, will make interpretation of indications much more reliable and less time consuming.

Roles and responsibilities:

The key function of the radiographic interpreter is to first interpret the radiograph or give meaning to the image produced on the film. The second toto evaluate the condition of the part or determine its worth for serviceability.

Interpretation of radiographs takes place in three basic steps: (1) detection, (2) interpretation, and (3) evaluation. These steps make use of the radiographer’s visual acuity. Visual acuity is the ability to resolve a spatial pattern in an image. The ability of an individual to detect discontinuities in radiography is also affected by the lighting condition in the place of viewing, and the experience level for recognizing various features in the image.

Develop or use new non-destructive testing (NDT) methods such as acoustic emission testing, leak testing, and thermal or infrared testing.