What kind of common pseudo defects may appear in the weld seam inspection of LSAW steel pipe

Common pseudo defect wave in the weld inspection of lsaw steel pipe
1, the instrument clutter: when the instrument is connected to the probe, due to poor performance of the instrument, the sensitivity is set too high, unimodal or multimodal waveform appears on the screen, while when the probe is connected for work, the position of the wave on the screen is fixed. Under normal circumstances, once reducing the sensitivity, the signal disappears.
2, the probe clutter: when the instrument is connected to the probe, a very high pulse amplitude, very broad signal is shown on the screen, regardless of whether the probe contacts the workpiece, it is there and the location is not moving with the probe.
3, coupling agents reflected wave: If the refraction angle of probe is large, and the detection sensitivity is high, then part of these will be converted to the surface wave, this wave is propagated to the forefront of the probe where the coupling agent is accumulated, causing the reflected signal. As long as the probe is fixed, with the loss of coupling agent, the amplitude is slowly decreased and very unstable. If wipe the coupling agent in front of the probe by hand, the signal will disappear.
4, the groove weld surface reflected wave: the trench is formed in the multi-pass welding weld surface. When the ultrasonic sweep the trench, the trench will cause reflection. Identification method: generally lie in the first, secondary wave or slantly behind position, and the characteristic of this reflected signal is not strongly and obtuse.
5,the reflected wave caused by the weld dislocation: as welding seam dislocation, in the first test,  the reflected wave is much like the fillet weld defects within, when the probe is moved to the other side of the detection, there is no reflected wave in a wavefront or horizontal distance measured of the probe is in the weld base metal.