Ultrasonic Testing of DSAW Pipe

Keywords:dsaw pipe, ultrasonic testing
In the ultrasonic inspection of dsaw pipe, how to identify and determine the echo is a key issue. The influence of ultrasonic defect signal or non-defect signal and the radius of curvature of the steel pipe on the defect location is analyzed by analyzing the characteristics of the actual ultrasonic testing of the double-sided submerged arc welded pipe weld, including the segregation, inclusions, crack and base metal delamination of the ultrasonic echo signal. This paper summarizes the causes and identification methods of four kinds of pseudo-defective waves, such as the reflected wave of the coupling agent, the reflection wave of the weld surface, the reflected wave caused by the upper and lower dislocation of the weld, and the non-defect wave formed by the weld height or the undercut The accuracy of the defective wave discriminating provides a new idea and direction for the actual ultrasonic testing of the dsaw pipe.

In the ultrasonic inspection of steel pipe welds, due to the characteristics of steel pipe welding process, the oscilloscope screen often in addition to the initial wave and defect wave, there will be some other causes of pseudo-defect echo, these pseudo-defective waves interfere with the defect. The following is the production of four pseudo-defective wave of the causes and identification methods.
(1) Coupling agent reflection wave
The thickness of the coupling layer is theoretically required to be an integral multiple of the radius. The coupling agent is too thick and the fluidity is not good; the thickness of the coupling layer is too thick to accumulate in the front of the probe, and a part of the longitudinal wave reflected from the piezoelectric wafer is converted into a surface wave, causing a reflection signal, Of the coupling agent, the wave will disappear.

(2) Weld surface welding trace reflection wave
This kind of reflected wave appears more in the butt welds of the steel pipe. Due to the deviation of the length of the steel pipe and the cumulative error of the multi-layer structure, the welding width of the part of the steel pipe is too large, and the weld surface is formed by multi-channel welding a road welding marks. When the ultrasonic scan to weld, it will cause weld marks, the reflected wave signal is not strong, slow, generally appear in the first and second bottom wave slightly rearward position. Identification method is to fix the probe fixed, hand dip coupler gently tapping the weld, the wave is gently beating.

(3) The weld caused by the dislocation of the reflected wave
This kind of reflected wave mainly appears in the field butt weld inspection of steel pipe, which is caused by the deviation of the axis when the pipe is connected up and down.

(4) Welds are too high or undercut formed by non-defective waves

When the weld is too high or undercut, it is easy to form corner reflection, the impact of discrimination. ①The method is to calculate the distance of the sound path accurately, according to the data displayed on the display screen, determine the depth of the defect, or the horizontal position to determine whether the defect wave; ② Hand dip coupler gently pat on both sides of the weld, such as the reflected wave signal. There is a beating, then the reflection of the wave is due to the weld height caused by corner reflection, not a defect wave; ③ The use of manual electric grinding on the weld height or scar to be polished and then tested, if the reflection wave disappeared , The reflected wave is a non-defective wave.

dsaw pipe

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