API standards stipulate that the inner and outer surfaces of import and export oil casings shall not have folds, separations, cracks, or scars. These defects should be thoroughly removed, and the removal depth should not be less than 12.5% ​​of the nominal wall thickness. Oil 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 leakage. It is not a method to directly measure the wall thickness, but a method to indirectly measure the wall thickness by measuring the magnetic field change information caused by the wall thickness change.

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

According to the principle of ultrasonic measurement of oil casing wall thickness, oil casing manufacturers analyzed the focusing probes suitable for automatic detection of oil casing, selected the appropriate focal length and wafer size probes to form a full-coverage automatic wall thickness detection system, and made significant improvements in the full coverage range. The design and selection of the probe are crucial to the thickness of the oil casing. Generally, the sound wave beam emitted by the circular crystal sheet of the probe has a certain diameter and expands with the increase of distance. The sound wave beam is selected to focus locally through the acoustic lens to increase the energy.

After the oil casing inspection is completed, the required thickness detector is completely covered. The ultrasonic thickness detection system is generally installed after the test equipment (for example, magnetic flux leakage detection system). Under the conditions of the parameters, adjust the angle of the probe, and determine the speed of the rotating motor and the scanning speed of the oil casing.