What factors affect the accuracy and resolution of oil casing wall thickness detection

According to API standards, the inner and outer surfaces of inlet and outlet oil casings must be free of folds, separations, cracks, and scratches. These defects must be thoroughly removed to a depth not less than 12.5% ​​of the nominal wall thickness. Therefore, oil casings must undergo full-coverage automated wall thickness detection. Currently, there is an indirect wall thickness measurement method based on the principle of magnetic leakage. It does not directly measure wall thickness but rather indirectly measures it by measuring the magnetic field changes caused by variations in wall thickness.

Therefore, magnetic field strength has a significant impact on the accuracy and resolution of wall thickness detection, making it unsuitable for online automated detection. Magnetic ultrasonic testing does not require coupling agents, but it is difficult to excite ultrasonic waves in pipes with uneven surfaces. Industrial ultrasonic phased array probes are expensive to manufacture and have complex systems.

Based on the principle of ultrasonic measurement of oil casing wall thickness, oil casing manufacturers have analyzed focusing probes suitable for automated oil casing detection. By selecting appropriate focal lengths and crystal sizes, a full-coverage automated wall thickness detection system has been constructed, resulting in significant improvements within the full coverage range. The design and selection of the probe are crucial to the thickness of the casing. Generally, the circular crystal plate of the probe emits an acoustic beam with a certain diameter, which expands with increasing distance. Selecting the right acoustic beam involves focusing it locally through an acoustic lens to increase energy.

After the casing inspection is completed, the required thickness detector is completely covered. The ultrasonic thickness detection system is typically installed after testing equipment (e.g., a magnetic flux leakage detection system). Under the specified parameters, the probe angle is adjusted, and the rotation speed of the rotary motor and the scanning speed of the casing are determined.