Views: 0 Author: Site Editor Publish Time: 2023-06-02 Origin: Site
Radiographic Testing (RT), also known as industrial radiography, is a critical discipline in nondestructive testing. Its primary purpose is to detect macroscopic geometric defects in workpieces. RT includes various methods tailored to specific characteristics, such as X-ray Computed Tomography (X-CT), Computer Radiography (CR), and conventional radiography.
Conventional radiography is widely used in nondestructive testing. It involves using X-rays from an X-ray tube or gamma rays from a radioactive isotope to penetrate the workpiece. Film is used as the recording medium, making it the most fundamental and extensively used technique in radiographic testing. It is an essential component of professional training in this field.
The principle of conventional radiography relies on the penetrative capability of X-rays or gamma rays through materials that are opaque to the naked eye. When these rays expose the film, they stimulate the silver halide in the emulsion layer, resulting in density variations on the film. These variations are caused by differential absorption due to different material densities.
The density differences are manifested as variations in darkness on the developed film, allowing radiographic inspectors to identify the nature and location of defects by observing these differences in darkness.
Conventional radiography is applicable for inspecting welded joints in steel structures using various fusion welding methods. It is also effective for examining cast steel components and, under specific circumstances, detecting fillet welds or other complex structural components.
Conventional radiography offers several advantages. It provides a visual display of defects using film as a recording medium, enabling accurate identification of defect characteristics, quantity, size, and location through film observation. It has a high detection rate for defects with local thickness variations, such as porosity and slag inclusions.
Conventional radiography can detect length and width dimensions at the millimeter and sub-millimeter levels, respectively, or even smaller, with no significant lower thickness limit. It is versatile, working well with various materials like steel, titanium, copper, and aluminum. It is not affected by specimen shape, surface roughness, or material grain size.
However, conventional radiography does have limitations. The detection of crack-type defects is influenced by the angle of penetration and cannot capture thin-layer defects in the perpendicular direction of radiation, such as delamination in steel plates. The upper limit for thickness inspection is determined by the penetrative capacity of the radiation. Conventional radiography is relatively expensive and time-consuming compared to other testing methods. Additionally, it poses health risks due to radiation exposure, requiring proper protective measures.
In conclusion, Radiographic Testing (RT) is a vital component of welded pipe production, ensuring the quality and safety of the final products. Conventional radiography is a widely used and effective nondestructive testing technique for accurately detecting and evaluating defects in pipes. While it has limitations and safety considerations, it remains an essential method in the industry.