The technique known so far includes the following: the continuous movement of the flaw detector fitted with an acoustical-electrical transducer along the pipe wall, the generation of ultrasonic oscillations by the acoustical-electrical pulse transducer, the non-contact transmission of ultrasonic oscillation pulses through the medium pumped to the pipe wall, the excitation of ultrasonic oscillations inside the pipe wall, the reflection of ultrasonic oscillations from the inhomogeinities of the pipe wall, the transmission of reflected ultrasonic oscillations from the pipe wall to the acoustical-electrical transducer, the registration of reflected ultrasonic oscillations and the identification of the nature, size and location of defects detected on the pipe wall.

The technique to be patented is based on the use of Lamb’s waves. (Lamb, Willis Eugene, an American physicist, the 1955 Nobel Prize winner, G.Ch.).

This technique differs from the one known so far in that for the non-contact transmission of ultrasonic oscillation pulses generated by the acoustical-electrical transducer to the pipe wall, and for the reception of the ultrasonic oscillations reflected from the inhomogeinities of the material of the pipe wall and their transmission to the acoustical-electrical transducer, a solid-state waveguide is used whose acoustical characteristics match those of the pipe wall, and that, during diagnostics, the waveguide is moved equidistantly with regard to the surface of the pipe wall.

While ultrasonic oscillations are transmitted to the pipe wall, first a Lamb’s wave is induced in the waveguide, then a narrow beam of that Lamb’s ultrasonic wave oriented along the waveguide and synchronized with the Lamb’s wave inside the waveguide is formed in the pipe wall.

Then, while ultrasonic oscillations reflected from the inhomogeinities of the wall material are being transmitted to the acoustical-electrical transducer, the inverted ultrasonic Lamb’s wave is scanned by the waveguide and a synchronous ultrasonic Lamb’s wave, whose amplitude and frequency response is similar to that of the inverted Lamb’s wave in the pipe wall, is generated in the waveguide, then the parameters of Lamb’s wave in the waveguide are recorded by the acoustical-electrical transducer.

The patent describes the following modifications of the proposed technique.

1. One of the modifications provides for the use of a rigid metal strip as a waveguide whose thickness is equal to that of the pipe wall.

2. Another modification uses a rigid metal strip bent spirally as a waveguide.

3. This modification differs in that the beam of the ultrasonic Lamb’s wave in the pipe wall is directed at an angle of a = 70-90^о to the longitudinal generatrix of the pipe wall.

4. The technique’s next modification’s specific feature is that the narrow beam of Lamb’s waves is formed with the beamwidth of its radiation pattern lobe equal to b = 20-30 ^о.

Apart from this, the patent describes the technique’s modifications in which one and the same acoustical-electrical transducer or self-contained acoustical-electrical transducers is/are used for generating ultrasonic oscillation pulses and recording ultrasonic oscillations reflected by the defect.

Also described is a variant that makes use of several waveguides each of which has such an angular displacement with respect to the previous one that there is an overlap of the tangent projections of the radiation pattern lobes of the adjacent ultrasonic beams.

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