抄録
The objective of the present paper is to propose a method for detecting corrosions on the external surfaces of actual small-diameter pipes by applying angle beam technique using Horizontally Polarized Shear Wave (SH-wave) . The accuracy for measuring the corrosions in the pipes with the nominal diameter of 1∼3 inches, in which artificial flaws have been fabricated is investigated. Furthermore, the measurements in site are carried out and comparisons are made between the measurement results and the actual conditions.
The following results were obtained through these experimental investigations.
(1) The angle beam technique using SH-wave can detect local thickness reduction in the circumferential direction of small-diameter pipes.
(2) The present angle beam technique using SH-wave is not affected by the fluid existed inside the pipes, and the corrosion detection is possible under actual operating conditions.
(3) Although there is no correlation between the depth of the artificial flaw and the signal amplitude, it is shown that the artificial flaws can be detected with high accuracy.
(4) The results of corrosion measurements on the external surface of the actual small-diameter pipes show that corroded parts which are located far from the variable angle probe can be detected and that the reduction rate of the cross-sectional area is greater.
(5) The location of the flaw can be estimated by the angle beam technique using SH-wave even in the case where the corrosion grows.
(6) The present method shown here is an outstanding inspection method for detecting external surface corrosions.
