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Pressure Vessel NDT - Eddy Current Testing Technique

It should be noted in the testing process control perspective. (4) defect detection of factors a) calibration block material calibration block material should be close to the workpiece. b) conductive coating layer conductor coating reduces the detection sensitivity and reduce the level of conductivity depends on the conductor. c) non-conductive coating non-conductive coating reduces the sensitivity of detection depends on the probe and the distance between the workpiece, the coating thickness. (Continued on 430) Song Wei et al: Digital Ultrasonic Flaw Detector adjustment and positioning of the probe liquid immersion testing applications workpiece Figure 5 Figure 4BIB2B3B4 transmittance and reflectance of the relationship, B1 of the energy is much larger than A:; F for the Az the reflected wave,[link widoczny dla zalogowanych], A. For the transmission wave, A. Energy is greater than F,[link widoczny dla zalogowanych], F in the steel / water interface reflection and transmission occurs, B2 for the transmitted wave received by the probe surface, B2 on the probe surface, the reflected wave A and A is similar to the formation of B3, B4 and other waves. Therefore, when using immersion testing, if Echo Echo should be on the workpiece surface and bottom echoes, and that means between the B1 and B2 can be the beginning of B1 as a wave,[link widoczny dla zalogowanych], when the B1 in the regulation of all as the previous wave In addition to zero or the beginning of shift, and then adjust the reading speed of sound so that the depth of B2 is consistent with the workpiece size, will be tuned to accurately read between the B1 and Bz the location of the defect wave. 2.2 The liquid layer thickness and probe depth of focus in Figure 5 B2 B3 before painting, but in fact, because the liquid layer thickness and acoustic wave propagation in the liquid and the speed between the workpiece, leading to B2 and B3 of the uncertainty around the position, it is also need to distinguish between the two waves to correctly determine the defect location. Let the liquid layer thickness H, the workpiece thickness H, the liquid sound velocity, sound velocity of the workpiece in the z, with sound propagation in the liquid when the D l, D 2, when used in the workpiece, the instrument preset sound velocity,[link widoczny dla zalogowanych], the probe set Zero itself has been removed, the D l D 2,[link widoczny dla zalogowanych], a fall of a 7Jl \HK calculated a H1 + D for a 2H1 H1 + D for a 2 lH So, when D l> D 2, has once>, that is, H1>, there HB3> HB2, the B3 B2 wave after wave. Conversely if H <when H <HB,, ie B3 wave \When H a moment there HB3 HB2, namely B2 B3 waves and waves coincide. B2 because of a defect in the wave before the wave is, therefore requested B3 B2 wave before the wave can not, or could lead to defects in the B3 wave wave annihilation, but can not correct a defect is discovered, that in determining the thickness of liquid layer which should have H ≥ is a necessary condition for effective discovery of defects. Obviously when the probe line focus testing should be able to cover the entire scope of the workpiece thickness, so thin in the test object, the probe depth of focus in the detection center of the object to be detected object is thick, you may need several different depth of focus of the probe in order to to cover the entire piece, which is when the liquid immersion testing point to note. 2.3 Application of the actual testing, the author was originally set wrong because the water layer thickness, resulting in wave mixing, it is difficult to distinguish. After careful analysis, after adjustment of the water layer thickness, and produced by Nantong Union PXUT a digital detector 360 notebook calibration and testing, testing to successful completion of the work. (Continued on 433) (Continued from p. 416) d) the workpiece shape and geometry of the workpiece region close to the probe and measured the degree of detection sensitivity, complex weld structures (such as fillet weld) should be based on the structure and orientation of possible defects to be detected. e) the angle between the coil and the defects induced current is directional and should therefore be taken to ensure that the current direction and orientation may be perpendicular to the defect and / or parallel. f) the minimum size of defects in ferromagnetic steel eddy current method from 430 * the minimum measured in the weld defect length × deeply lmmX5mm. References: [1] EN1711-20oO, Non-destructiveexaminationofwe1ds-Eddycurrentexaminationofweldycom-plexplaneanalysis [s]. [2] Liu Kai, Yang Wei Shu. Weld coating with rapid detection of fatigue cracks [A]. Eighth annual meeting of NDT in China Proceedings [C]. Suzhou: 2003. [3] Lin Junming, Zhang Kailiang, et al. Rapid detection and weld surface crack depth measurement [A]. Eighth annual meeting of NDT in China Proceedings [C]. Suzhou: 2003.

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