RadioGraphy Testing Course of NDT

Radiography is used in a very wide range of aplications including medicine, engineering, forensics, security, etc. In NDT, radiography is one of the most important and widely used methods. Radiographic testing (RT) offers a number of advantages over other NDT methods, however, one of its major disadvantages is the health risk associated with the radiation. In general, RT is method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials. The intensity of the radiation that penetrates and passes through the material is either captured by a radiation sensitive film (Film Radiography) or by a planer array of radiation sensitive sensors (Real-time Radiography). Film radiography is the oldest approach, yet it is still the most widely used in NDT.

Principles of Radiographic Testing

In radiographic testing, the part to be inspected is placed between the radiation source and a piece of radiation sensitive film. The radiation source can either be an Xray machine or a radioactive source . The part will stop some of the radiation where thicker and more dense areas will stop more of the radiation. The radiation that passes through the part will expose the film and forms a shadowgraph of the part. The film darkness (density) will vary with the amount of radiation reaching the film through the test object where darker areas indicate more exposure(higher radiation intensity) and liter areas indicate less exposure (higher radiation intensity).This variation in the image darkness can be used to determine thickness or composition of material and would also reveal the presence of any flaws

Advantages

• Both surface and internal discontinuities can be detected.
• Significant variations in composition can be detected.
• It has a very few material limitations.
• Can be used for inspecting hidden areas (direct access to surface is not required)
• Very minimal or no part preparation is required.
• Permanent test record is obtained.
• Good portability especially for gamma-ray sources.

Uses

Industrial Radiography inspection is used to detect features of a component or assembly that exhibit a difference in thickness or physical density as compared to surrounding material. Large differences are more easily detected than small ones. In general, radiography can detect only those features that have an appreciable thickness in direction parallel to the radiation beam. This means that the ability of the process to detect planar discontinuities such as cracks depends on proper orientation of the test piece during testing. Discontinuities such as voids and inclusions, which have measurable thickness in all directions, can be detected as long as they are not too small in relation to section thickness. In general, features that exhibit a 2% or more difference in absorption compared to the surrounding material can be detected. Radiography is more effective when the flaws are not planar.

Applicability

Radiographic testing is used extensively on castings and weldments. Radiography is well suited to the testing of semiconductor devices for cracks, broken wires, unsoldered connections, foreign material and misplaced components. Sensitivity of radiography to various types of flaws depends on many factors, including type of material, type of flaw and product form. Both ferrous alloys can be radio graphed, as can non-metallic materials and composites.

Scope of Radiographic Testing Course

Industrial radiographers, also known as industrial radiography radiation safety personnel or industrial radiography testers, use X-ray and gamma ray technologies to test and inspect metals in engineered or manufactured products, pipes, walls and other materials.

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