Nondestructive testing means without damaging or does not affect the tested object using performance, do not harm is detected objects under the premise of internal organization, the use of material internal structural abnormalities or defects caused by heat, sound, light, the change of the reaction, such as electric and magnetic, by means of physical or chemical method, with the help of modern technology and equipment, to the specimen surface and internal structure, properties, status and defect type, nature, quantity, shape, location, size, distribution and its changes for inspection and testing method. NDT is an indispensable and effective tool for industrial development, which reflects the industrial development level of a country to a certain extent. The importance of NDT has been recognized, mainly consisting of four types: radiographic test (RT), ultrasonic test (UT), magnetic powder test (MT) and liquid permeation test (PT). Other non-destructive testing methods include eddy current test (ECT), acoustic emission test (AE), thermal image/infrared (TIR), leakage test (LT), ac field measurement technology (ACFMT), magnetic flux leakage test (MFL), far field test (RFT), ultrasonic diffraction time difference (TOFD), etc.
Non-destructive – means that no parts are lost except for the removal of nonconforming products while the test results are obtained. Therefore, the test scale is not limited by the number of parts, both sampling inspection, and when necessary general inspection. As a result, more flexibility (general inspection, sampling can be) and reliability.
repeatability– that is, different test methods can be used simultaneously or successively for the same part, And the same test can be repeated. It is also a non-destructive benefit.
Dynamic – this means that nondestructive inspection methods can be used to test the parts in use, and the cumulative impact of the product’s running time can be examined in due course. Therefore, the failure mechanism of the structure can be identified.
Stringency — refers to the stringency of non-destructive testing technology. First, special instruments and equipment are needed for NDT.It also requires specially trained inspectors to operate according to strict procedures and standards.
The Divergence of test results – different testers may differ on the test results of the same specimen. Especially in the ultrasonic inspection, the same inspection project to be completed by two inspectors. A consultation is needed.
Generally speaking, NDT is characterized by non-destructive, mutual tolerance, dynamic, strict and divergent test results.
Drawing is the most basic technical data used in production and also the basis of processing and inspection.Especially in the technical requirements of drawings, the quality grades of raw materials, parts, products, specific requirements and the need for nondestructive testing are often specified.
Production enterprises often need to implement relevant standards, such as enterprise standards, industry standards, national standards, international standards and so on. These are the guiding documents for product processing and, naturally, for the implementation of NDT. In a specific standard, often specified inspection object, inspection method, inspection scale and so on.
Various technical documents issued by the production process department, such as process procedures, inspection CARDS, product inspection reports, repair orders, etc. Sometimes additional or changing testing requirements, etc.
Special inspection requirements for certain products, quality control provisions, and sometimes more detailed emphasis should be given to particular attention in an order contract.
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