NDT TRAINING CENTER
A brief description of the laboratory ‘s non-destructive testing methods:
Ultrasonic inspection is currently one of the main nondestructive methods for detecting internal defects. Ultrasonic flaw detection methods allow to check welded joints, vessels and high pressure devices, pipelines, forgings, sheet rolled products and other products. Ultrasonic inspection is a mandatory procedure in the manufacture and operation of many essential products.
Compared to other methods of nondestructive testing, ultrasound has important advantages:
- High sensitivity to the most dangerous defects such as cracks and non-cracks;
- Human safety (as opposed to X-ray flaw detection);
- The ability to monitor directly at workplaces without disrupting the process;
- Possibility to test products from various materials, both metals and nonmetals.
The disadvantages of the ultrasonic testing method include the inability to estimate the real size and nature of the defect, difficulties in testing metals with a coarse grain structure due to large scattering and strong attenuation of ultrasound, as well as increased requirements for the state of the tested surface (roughness and undulation).
Penetrant testing is one of the most sensitive methods of non-destructive testing. The method is based on capillary penetration of indicator liquids (penetrants) into surface and through defects. The resulting indicator traces are usually recorded visually. Penetrant methods determine the location of defects, their extent, and surface orientation. Penetrant flaw detection is used when it is necessary to detect small defects to which visual inspection cannot be applied. Penetrant methods are used to test objects of any size and shape made of ferrous and non-ferrous metals and alloys, glass, ceramics, plastics and other materials. Penetrant flaw detection is used during monitoring of essential objects before acceptance and during operation.
The advantages of penetrant flaw detection include ease of inspection and applicability to a wide range of materials. Penetrant flaw detection not only reveals surface or through defects, but also provides valuable information on their location, extent, orientation and shape, which generally facilitates understanding of the causes of these defects.
Among the disadvantages of penetrant flaw detection is the inability to detect internal gaps that do not have an exit to the surface.
Eddy Current Testing.
Eddy current method of non-destructive testing is based on analysis of interaction of external electromagnetic field with electromagnetic field of eddy currents created by excitation coil in electrically conducting object of testing by this field.
Eddy current testing provides the possibility to find defects and evaluate properties of test objects, has a wide range of applications in industry, both in manufacturing of parts and in their repair.
Field of application of eddy current test method: non-destructive inspection of steam turbine blades, heat grooves, axial channel surface of turbine rotors, etc., welded joints, housing equipment, threaded joints, parts of any shape and size of industrial and transport equipment.
The main advantages of the eddy current method are: high sensitivity to microscopic defects that are on the surface, possibility to carry out coating testing, high performance.
Magnetic Particle Testing.
Magnetic flaw detection is a complex of non-destructive inspection methods used to detect defects in ferromagnetic metals (iron, nickel, cobalt and a number of alloys based on them). Defects detected by the magnetic testing include cracks, hair, non-metallic inclusions, non-melting, etc. Defects can be detected if they come to the surface of the article or lie at a shallow depth (not more than 2-3 mm).
Magnetic methods are based on the study of magnetic scattering fields around articles of ferromagnetic materials after magnetization. Redistribution of magnetic fluxes and formation of magnetic scattering fields is observed at defect locations. In magnetic particle testing, particles of magnetic suspension, which have fallen into the zone of action of magnetic field of scattering, are attracted and settled on the surface near places of discontinuities. The obtained indicator patterns are recorded visually or by means of image processing devices.
Advantages of magnetic particle method of nondestructive testing are its relatively low labor input, high efficiency and possibility of detecting surface and subsurface defects. By this method, not only complete gaps are detected, but also defects filled with a foreign substance. Magnetic particle method can be used in manufacturing of parts or during their operation for detection of fatigue cracks, for testing of welded joints.
The laboratory currently uses luminescent magnetic testing with blue light imaging of the results. Application of this method allows to increase reliability of testing and significantly reduce time of test performance.
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