Factors affecting the accuracy and resolution of oil casing wall thickness detection

The API standard stipulates that the internal and external surfaces of import and export petroleum casings shall not have folds, separations, cracks, and scars. These defects should be completely removed, and the removal depth should not be less than 12.5% of the nominal wall thickness. Petroleum casing must be fully covered with automatic wall thickness detection. At present, there is an indirect wall thickness measurement method based on the principle of magnetic flux leakage. It is not a method of directly measuring wall thickness, but an indirect method of measuring wall thickness by measuring the information of magnetic field changes caused by wall thickness changes.

Therefore, the magnetic field strength has a great influence on the accuracy and resolution of wall thickness detection, and it is not suitable for online automatic detection. Magnetic ultrasound does not require coupling agents, but it is difficult to excite ultrasound in pipes with uneven surfaces. Industrial ultrasonic phased array probes have high manufacturing costs and complex systems. At present, this kind of equipment rarely appears in our country.

According to the principle of ultrasonic measurement of oil casing wall thickness, the Threeway steel analyzed the focused probe suitable for the automatic detection of oil casing and selected the appropriate focal length and chip size probe to form a full coverage automatic wall thickness detection system. Significant improvement. The design and selection of the probe are very important to the thickness of the tubing and casing. Generally, the sound beam emitted by the circular crystal of the probe has a certain diameter and expands with the increase of the distance. The sound beam is selected to focus locally through the acoustic lens. To increase energy.

After the oil casing inspection is completed, the required thickness detector is completely covered, and the ultrasonic thickness inspection system is installed after the general testing equipment (for example, the magnetic flux leakage inspection system). Under the condition of the parameters, adjust the angle of the probe to determine the rotation speed of the rotating motor and the scanning speed of the oil casing.