1 Scope
This standard specifies test theory, test requirements, test method, standard sample, test equipment, test equipment operation and adjustment, and test result of eddy current test for seamless steel tube and welded steel tube (except submerged arc welded tube).
This standard is applicable to the eddy current test for steel tubes whose outer diameter is not less than 4 mm.
The acceptance level arranged in this standard comes with Level A and Level B (see Table 1 and Table 2).
2 Normative References
Provisions of the following documents, through reference in this standard, constitute provisions of this standard. For dated references, all subsequent modifications (excluding correction contents) or revisions are not applicable to this standard. However, all parties coming to an agreement according to this standard are encouraged to study whether the latest editions of these documents are applicable. For undated references, the latest editions of the normative documents are applicable to this standard.
YB/T 145 "Steel tubes-Measurement method of sizes of standard artificial defect for flaw detection"
YB/T 4083 "Measurement method of comprehensive properties for automatic eddy current flaw detection system for steel tubes"
3 Test Theory
3.1 Eddy current test is based on electromagnetic induction principle. When a steel tube is inserted through a coil energized with A.C. current, the discontinuity (like defect) of steel tube body will result in the change of eddy current field, and the one on or adjacent to the surface has great effect, which cause the change o coil impedance or induced voltage. Above change can indicate the information of tube body or discontinuity.
3.2 The judgment on the test result in this standard refers to the amplitude value comparison on the standard artificial defect and the natural defect display signal. Standard samples are used for setting and calibration for eddy test equipment.
4 Test Requirements
4.1 The eddy current test (inspection) for steel tube is generally conducted after all tube production processing is completed.
4.2 The steel tube eddy current test shall be operated by the personnel holding the eddy current test technology qualification certificate authorized by the related department, and supervised and issued the report by the personnel with level II or higher level qualification certificate designated by the supply party. The test (inspection), if needed, shall be approved by the supply and demand parties.
4.3 The tested steel tube shall straight and even enough, to guarantee the accuracy of the test. Simultaneously, the surface of the tested steel tube shall be free of other substances affecting test; otherwise, it may affect the test accuracy.
