Method for Detecting Thread Defects in Casing

Casing pipe thread detection sensor mainly by the magnetizer and magnetic detection probe composed of two parts. According to the structural characteristics of the oil pipe thread area, there are two kinds of end detection magnetization method and two kinds of probe scanning mode. The magnetization method has two kinds of external magnetic field and magnetic field magnetization. The scanning mode of the element is mainly axial and circumferential. In the axial scanning mode, the Hall element is evenly distributed in the circumferential direction and is scanned in the axial direction of the crest of the oil jacket thread. The Hall element can measure the X-direction component of the magnetic field, or the Y-direction component of the measured magnetic field. And because the oil casing thread area is 1:16 of the taper, therefore, the detection element in the scanning process, you can always close to the crest of the casing thread in the direction of the diagonal to scan, can also be along the axis parallel The direction of the line to scan. In the circumferential scanning mode, in order to avoid the influence of the thread thread on the detection signal, the detection element must be scanned along the circumferential direction along the direction of the thread, but because the pitch and the pitch of the oil jacket thread are not too large, The impact of the oil, the detection element is difficult to accurately along the thread direction of the oil casing to scan, and along the circumferential scan of the detected signal must be wireless or slip ring connection to enter the follow-up processing circuit, so the probe scan Method is susceptible to interference, the detection signal is not very stable, it is also very difficult to achieve.

The above two kinds of magnetization and two kinds of probe scanning method can achieve four different discrete magnetic flux leakage detection methods:(1) magnetic field of the coil outside the magnetization, magnetic induction components along the axial scanning of the far-field magnetic field detection.(2) magnetic field of the coil outside the magnetization, magnetic induction components in the direction of the circumferential thread scanning far field magnetic field detection.(3) Open magnetic flux leakage detection method in which the magnetic yoke is magnetized and the magnetic induction element is scanned in the axial direction.(4) Open magnetic flux detection method in which the magnetic yoke is magnetized and the magnetic induction element is scanned in the direction of the circumferential thread.

It is difficult to scan the magnetic induction element along the circumference of the oil jacket thread, so the experiment mainly adopts the first (1) and (3) kinds. To

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