The difference in theories and characteristics of AUT and MUT use in practice for the offshore structures (platform, jacket, subsea pipeline) are analyzed in details. On the basis of analysis, operation process for various conditions was proposed. In accordance with practical project the judgment of discontinuities in weld streams and associated criteria were studied and compared. The study has certainly positive significance for improving precision and efficiency of ultrasonic test used for offshore structures and helping to explain the test results are well-founded.
Ultrasonic inspection is one of the main nondestructive test (NDT) methods to ensure the quality of offshore steel structure weld streams. Along with the development of ultrasonic technology, automatic ultrasonic test (AUT) method was excogitated which includes zone discrimination, linear scan, phased array-UT, time-of-flight diffraction systems etc. The AUT has great technical improvement in both theory and operation process, comparing with manual ultrasonic test (MUT) and is becoming the more popular ultrasonic test method. In this paper, differences between AUT and MUT such as theory, judgment of flaw in weld stream, applied characteristics are analyzed. On basis of the study, directive conclusions for the UT method used in practice on offshore structure are given.
Ultrasonic is the wavy spread of its vibration through elastic medium. In terms of the ultrasonic technique use for weld stream flaw detect, it depends on reflection or other effect on wave produced by the defect in weld stream. The things detected are all elastic materials composed of particles get together with elasticity. On these basis sound wave theory and piezoelectricity, electric and sound signal can conversion from each other by wafer. Probe defined as the sonic beam transmitter includes straight type (detecting with vertical wave) and slantwise type (detecting with transverse wave).